Re: [Emc-users] Gear cutting setup on low-cost HF mill??
Have you heard of openDog, the open source hardware robot quadruped? A google for open source robot dog brings up it and some others people are working on. Boston Dynamics has been a big inspiration. Now when do we get open source bipedal robots? On Thursday, March 11, 2021, 12:58:00 PM MST, Chris Albertson wrote: THanks, all for you advice. I think the best way to get a small ring gear is to buy one. What I'm doing is a design-study to find out the best kind of reduction system. Timing belts are very easy to use but sun/planet gears are far more compact. I want to make a machine, using machine-tool terminology it will be a 12 axis system where every axis is rotary. Using robotic terminology it will be a quadruped where each leg has 3 degrees of freedom. My goal is to design something that can be made for under $100 per axis ($1,200 total cost) This is actually possible but performance is poor. I want both the < $100 cost and excellent performance. I think it can be done by using motors from quadcopter drones and then using a reduction drive of 6 or 8 to 1. Harmonic and cycloidic reduction drives are to slow 6:1 or 10:1 should work. The only way to know which design is best is to do multiple designs and test simple prototypes. One of the options is gears. ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gear cutting setup on low-cost HF mill??
> Harmonic and cycloidic reduction drives are to slow > 6:1 or 10:1 should work. My first robot arm used 9:1 3d printed cycloidal gear boxed (plus 3:1 motor to gearbox pulley reduction). Cyclodial ratios can be made small with less teeth/lobes and larger pins. I'm not sure if that makes them any stronger, or more efficient. At the end of this video is a graph that shows how various parameters effects cycloid design - https://youtu.be/CJyCcXob0c8?t=49 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gear cutting setup on low-cost HF mill??
Rotary broaching is a process used to quickly cut internal ring gears. On Thursday, March 11, 2021, 6:21:08 AM MST, andy pugh wrote: On Thu, 11 Mar 2021 at 13:05, wrote: > I believe that wire EDM is the usual way to make small quantities of internal > (ring) gears. It seems possible that one might imitate a mini-Fellows by > moving the z-axis up/down to shave the gear. Bear in mind that the Fellows system still generates the gear. The cutter and the blank both rotate, in the proportions of their ratio. You can get away with only one accurate rotary axis if you interpolate the other. (but you would need to modify the rotation of the rotating axis) I have considered making a slotting head for my mill, and probably would have done so by now were it not for the fact that if I did do that, it would need to be a CNC-rotated slotting head for just this purpose. ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gear cutting setup on low-cost HF mill??
On Thu, 11 Mar 2021 at 19:58, Chris Albertson wrote: > Using robotic > terminology it will be a quadruped where each leg has 3 degrees of freedom. > My goal is to design something that can be made for under $100 per axis > ($1,200 total cost) This is actually possible but performance is poor. I > want both the < $100 cost and excellent performance. I think it can be > done by using motors from quadcopter drones and then using a reduction > drive of 6 or 8 to 1. There might be some ideas here: https://hackaday.io/project/157812-3d-printed-robot-actuator -- atp "A motorcycle is a bicycle with a pandemonium attachment and is designed for the especial use of mechanical geniuses, daredevils and lunatics." — George Fitch, Atlanta Constitution Newspaper, 1912 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gear cutting setup on low-cost HF mill??
I realize that water jet capability has improved over the years but is it really up to accurately cutting a M0.5 internal gear? I have made somewhat coarser ring gears by using a 0.03125 diameter endmill and cutting as a 2.5D job in 5mm Delrin. -Original Message- From: Gregg Eshelman via Emc-users Sent: March 11, 2021 1:39 PM To: Enhanced Machine Controller (EMC) Cc: Gregg Eshelman Subject: Re: [Emc-users] Gear cutting setup on low-cost HF mill?? Could have it water jet cut on a machine with a tilting head for kerf angle compensation. Water jet cutters tend to make the exit side of the cut slightly wider so a 2 axis tilting head can push all that to the waste side. On Thursday, March 11, 2021, 3:15:07 AM MST, andy pugh wrote: Cutting internal teeth isn't something that can be done with a hob _or_ an involute cutter. You need a Fellows gear shaper, or at least to find a way to set up the equivalent on your CNC mill. https://youtu.be/72YgpVF4O7g I don't think it is impossible, with the cutting tool in the rotary axis, circularly interpolating around the blank. It might be simpler to order one wire-spark eroded for a one-off or a stock part from HPC or similar. ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gear cutting setup on low-cost HF mill??
> Not sure if anyone mentioned, spiral hobs will not work unless your hob can > be tilted to the required angle of the hob cutter. Even for straight teeth, > it's at least 1.5�. Wouldn't it be easier in the home workshop to just tilt the rotary table holding the work piece up 1.5 degrees? ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gear cutting setup on low-cost HF mill??
THanks, all for you advice. I think the best way to get a small ring gear is to buy one. What I'm doing is a design-study to find out the best kind of reduction system. Timing belts are very easy to use but sun/planet gears are far more compact. I want to make a machine, using machine-tool terminology it will be a 12 axis system where every axis is rotary. Using robotic terminology it will be a quadruped where each leg has 3 degrees of freedom. My goal is to design something that can be made for under $100 per axis ($1,200 total cost) This is actually possible but performance is poor. I want both the < $100 cost and excellent performance. I think it can be done by using motors from quadcopter drones and then using a reduction drive of 6 or 8 to 1. Harmonic and cycloidic reduction drives are to slow 6:1 or 10:1 should work. The only way to know which design is best is to do multiple designs and test simple prototypes. One of the options is gears. ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gear cutting setup on low-cost HF mill??
On Thu, 11 Mar 2021 at 19:29, Jon Elson wrote: > Bridgeport made an adapter to turn their mill into a mini > shaper for this purpose. A "slotting head" Many mills had them available as an accessory. (Including my Harrison) it basically makes them into a slotter, rather than a shaper: http://www.lathes.co.uk/rothley/ -- atp "A motorcycle is a bicycle with a pandemonium attachment and is designed for the especial use of mechanical geniuses, daredevils and lunatics." — George Fitch, Atlanta Constitution Newspaper, 1912 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gear cutting setup on low-cost HF mill??
On 03/11/2021 12:39 PM, Peter Hodgson wrote: Could you not make a broaching cutter mounted in the quill and cnc broach one tooth at a time with the stock mounted on a rotary table? That's a slow version of the custom gear cutter and right angle drive. Bridgeport made an adapter to turn their mill into a mini shaper for this purpose. Jon ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gear cutting setup on low-cost HF mill??
Oohh that looks like fun! Phil T. The Feral Engineer Check out my LinuxCNC tutorials, machine builds and other antics at www.youtube.com/c/theferalengineer On Thu, Mar 11, 2021, 2:18 PM andy pugh wrote: > On Thu, 11 Mar 2021 at 19:11, Feral Engineer > wrote: > > > > As a side note, fanuc, Mitsubishi and the other big names have a > dedicated > > hobbing function that synchronizes the linear and rotary axis based on > > number of teeth, module, pitch diameter, tooth angle... Bunch of factors. > > The LinuxCNC version is a bit more homespun: > http://wiki.linuxcnc.org/cgi-bin/wiki.pl?Hobbing > > -- > atp > "A motorcycle is a bicycle with a pandemonium attachment and is > designed for the especial use of mechanical geniuses, daredevils and > lunatics." > — George Fitch, Atlanta Constitution Newspaper, 1912 > > > ___ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gear cutting setup on low-cost HF mill??
On Thu, 11 Mar 2021 at 19:11, Feral Engineer wrote: > > As a side note, fanuc, Mitsubishi and the other big names have a dedicated > hobbing function that synchronizes the linear and rotary axis based on > number of teeth, module, pitch diameter, tooth angle... Bunch of factors. The LinuxCNC version is a bit more homespun: http://wiki.linuxcnc.org/cgi-bin/wiki.pl?Hobbing -- atp "A motorcycle is a bicycle with a pandemonium attachment and is designed for the especial use of mechanical geniuses, daredevils and lunatics." — George Fitch, Atlanta Constitution Newspaper, 1912 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gear cutting setup on low-cost HF mill??
As a side note, fanuc, Mitsubishi and the other big names have a dedicated hobbing function that synchronizes the linear and rotary axis based on number of teeth, module, pitch diameter, tooth angle... Bunch of factors. I can upload documentation on these functions if anyone wants to read about it but can't supply the actual logic, it's embedded in the macro executor. Phil T. The Feral Engineer Check out my LinuxCNC tutorials, machine builds and other antics at www.youtube.com/c/theferalengineer On Thu, Mar 11, 2021, 1:31 AM Chris Albertson wrote: > I'm looking for advice on gear cutting. I've got a low-end harbor freight > mill with a 4th axis added (actually a rotary table) and I want to cut some > module 0.5 spur gears. I know that the smaller the gear the more precision > is required.These need to be as strong as possible too. They need to > survive impact loads. What's the best kind of steel to buy that gives a > combination of machinability on a small mill and strength. I'll buy either > a set of involute cutters or a commercially made hob in 0.5 size. > > Given my setup, a HF mill and manual (non-CNC) HF mini lathe which would > have the best result, a hob or an involute cutter? > > The really hard part that I don't know how to do is a ring gear. I can't > figure out how to cut internal teeth. I might just buy these if they > can't be machined. > > If this works I need about 60 total gears plus all the ones I used for > testing > > Yes I can 3D print these but plastic would not be strong enough. > > -- > > Chris Albertson > Redondo Beach, California > > ___ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gear cutting setup on low-cost HF mill??
Not sure if anyone mentioned, spiral hobs will not work unless your hob can be tilted to the required angle of the hob cutter. Even for straight teeth, it's at least 1.5°. Usually, I do this with a dedicated live tool that has an adjustable angle or a mill turn machine (DMG Mori NT/NTX series machine). You can get a cutter made up to cut the profile, but it's one tooth at a time and very slow. Phil T. The Feral Engineer Check out my LinuxCNC tutorials, machine builds and other antics at www.youtube.com/c/theferalengineer On Thu, Mar 11, 2021, 1:31 AM Chris Albertson wrote: > I'm looking for advice on gear cutting. I've got a low-end harbor freight > mill with a 4th axis added (actually a rotary table) and I want to cut some > module 0.5 spur gears. I know that the smaller the gear the more precision > is required.These need to be as strong as possible too. They need to > survive impact loads. What's the best kind of steel to buy that gives a > combination of machinability on a small mill and strength. I'll buy either > a set of involute cutters or a commercially made hob in 0.5 size. > > Given my setup, a HF mill and manual (non-CNC) HF mini lathe which would > have the best result, a hob or an involute cutter? > > The really hard part that I don't know how to do is a ring gear. I can't > figure out how to cut internal teeth. I might just buy these if they > can't be machined. > > If this works I need about 60 total gears plus all the ones I used for > testing > > Yes I can 3D print these but plastic would not be strong enough. > > -- > > Chris Albertson > Redondo Beach, California > > ___ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gear cutting setup on low-cost HF mill??
One method is to make a multi-tooth straight hob with teeth that have flat sides. On each pass it does a full cut on the tooth or gullet on the center line of the gear and partial cuts to the teeth and gullets above and below. That makes a faceted approximation of involute teeth. If you have the patience and calculate things right you can make the teeth smoother by raising or lowering the hob and changing the gear rotation to hit the high spots between the first pass cuts. Or just buy the one cutter from a set of eight 0.5 MOD cutters and cut one tooth at a time to the full smooth profile. Each cutter is made for a specific range of numbers of teeth. IIRC they provide the best fit near the middle of their ranges. Or you could build your own gear hobbing machine. https://www.collegeengineering.co.uk/product-category/castings/gear-hobbing-machine/ On Wednesday, March 10, 2021, 11:31:35 PM MST, Chris Albertson wrote: I'm looking for advice on gear cutting. I've got a low-end harbor freight mill with a 4th axis added (actually a rotary table) and I want to cut some module 0.5 spur gears. I know that the smaller the gear the more precision is required. These need to be as strong as possible too. They need to survive impact loads. What's the best kind of steel to buy that gives a combination of machinability on a small mill and strength. I'll buy either a set of involute cutters or a commercially made hob in 0.5 size. Given my setup, a HF mill and manual (non-CNC) HF mini lathe which would have the best result, a hob or an involute cutter? The really hard part that I don't know how to do is a ring gear. I can't figure out how to cut internal teeth. I might just buy these if they can't be machined. If this works I need about 60 total gears plus all the ones I used for testing Yes I can 3D print these but plastic would not be strong enough. ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gear cutting setup on low-cost HF mill??
That’s basically Andy’s idea to simulate a fellows gear shaper by interpolating the tooth form. It’s probably the easiest way if you can work out the math and lock the quill rotation. And grind the appropriate size cutter. Matt > On Mar 11, 2021, at 1:39 PM, Peter Hodgson wrote: > > Could you not make a broaching cutter mounted in the quill and cnc broach one > tooth at a time with the stock mounted on a rotary table? > > Pete > >> On 11 Mar 2021, at 18:06, Greg Bernard wrote: >> >> This doesn't address the op but it is intriguing: >> https://www.igus.com/info/3d-printed-gear >> >>> On Thu, Mar 11, 2021, 11:14 AM andy pugh wrote: >>> On Thu, 11 Mar 2021 at 17:08, Jon Elson wrote: Or, with a mini right angle drive attached to the machine quill. >>> >>> Though to do that you would have to make your own convex involute cutters. >>> >>> >>> -- >>> atp >>> "A motorcycle is a bicycle with a pandemonium attachment and is >>> designed for the especial use of mechanical geniuses, daredevils and >>> lunatics." >>> — George Fitch, Atlanta Constitution Newspaper, 1912 >>> >>> >>> ___ >>> Emc-users mailing list >>> Emc-users@lists.sourceforge.net >>> https://lists.sourceforge.net/lists/listinfo/emc-users >>> >> >> ___ >> Emc-users mailing list >> Emc-users@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/emc-users > > > ___ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gear cutting setup on low-cost HF mill??
Could you not make a broaching cutter mounted in the quill and cnc broach one tooth at a time with the stock mounted on a rotary table? Pete > On 11 Mar 2021, at 18:06, Greg Bernard wrote: > > This doesn't address the op but it is intriguing: > https://www.igus.com/info/3d-printed-gear > >> On Thu, Mar 11, 2021, 11:14 AM andy pugh wrote: >> >>> On Thu, 11 Mar 2021 at 17:08, Jon Elson wrote: >>> >>> Or, with a mini right angle drive attached to the machine quill. >> >> Though to do that you would have to make your own convex involute cutters. >> >> >> -- >> atp >> "A motorcycle is a bicycle with a pandemonium attachment and is >> designed for the especial use of mechanical geniuses, daredevils and >> lunatics." >> — George Fitch, Atlanta Constitution Newspaper, 1912 >> >> >> ___ >> Emc-users mailing list >> Emc-users@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/emc-users >> > > ___ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gear cutting setup on low-cost HF mill??
Could have it water jet cut on a machine with a tilting head for kerf angle compensation. Water jet cutters tend to make the exit side of the cut slightly wider so a 2 axis tilting head can push all that to the waste side. On Thursday, March 11, 2021, 3:15:07 AM MST, andy pugh wrote: Cutting internal teeth isn't something that can be done with a hob _or_ an involute cutter. You need a Fellows gear shaper, or at least to find a way to set up the equivalent on your CNC mill. https://youtu.be/72YgpVF4O7g I don't think it is impossible, with the cutting tool in the rotary axis, circularly interpolating around the blank. It might be simpler to order one wire-spark eroded for a one-off or a stock part from HPC or similar. ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gear cutting setup on low-cost HF mill??
This doesn't address the op but it is intriguing: https://www.igus.com/info/3d-printed-gear On Thu, Mar 11, 2021, 11:14 AM andy pugh wrote: > On Thu, 11 Mar 2021 at 17:08, Jon Elson wrote: > > > Or, with a mini right angle drive attached to the machine quill. > > Though to do that you would have to make your own convex involute cutters. > > > -- > atp > "A motorcycle is a bicycle with a pandemonium attachment and is > designed for the especial use of mechanical geniuses, daredevils and > lunatics." > — George Fitch, Atlanta Constitution Newspaper, 1912 > > > ___ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gear cutting setup on low-cost HF mill??
On Thu, 11 Mar 2021 at 17:08, Jon Elson wrote: > Or, with a mini right angle drive attached to the machine quill. Though to do that you would have to make your own convex involute cutters. -- atp "A motorcycle is a bicycle with a pandemonium attachment and is designed for the especial use of mechanical geniuses, daredevils and lunatics." — George Fitch, Atlanta Constitution Newspaper, 1912 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gear cutting setup on low-cost HF mill??
On 03/11/2021 12:28 AM, Chris Albertson wrote: The really hard part that I don't know how to do is a ring gear. I can't figure out how to cut internal teeth. I might just buy these if they can't be machined. Internal teeth need to be cut with a gear shaper, or specialized gear hobbing machine. Or, with a mini right angle drive attached to the machine quill. Jon ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gear cutting setup on low-cost HF mill??
On Thu, 11 Mar 2021 at 13:05, wrote: > I believe that wire EDM is the usual way to make small quantities of internal > (ring) gears. It seems possible that one might imitate a mini-Fellows by > moving the z-axis up/down to shave the gear. Bear in mind that the Fellows system still generates the gear. The cutter and the blank both rotate, in the proportions of their ratio. You can get away with only one accurate rotary axis if you interpolate the other. (but you would need to modify the rotation of the rotating axis) I have considered making a slotting head for my mill, and probably would have done so by now were it not for the fact that if I did do that, it would need to be a CNC-rotated slotting head for just this purpose. -- atp "A motorcycle is a bicycle with a pandemonium attachment and is designed for the especial use of mechanical geniuses, daredevils and lunatics." — George Fitch, Atlanta Constitution Newspaper, 1912 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gear cutting setup on low-cost HF mill??
I believe that wire EDM is the usual way to make small quantities of internal (ring) gears. It seems possible that one might imitate a mini-Fellows by moving the z-axis up/down to shave the gear. At least some high volume small ring gears are made of sintered metal. I don't know your application but have you considered commercial ring gears? Many electric drills/screwdrivers use a planetary gear train. Also, Chinese gearhead motors may be a cost-effective way to get the needed parts. -Original Message- From: andy pugh Sent: March 11, 2021 5:12 AM To: Enhanced Machine Controller (EMC) Subject: Re: [Emc-users] Gear cutting setup on low-cost HF mill?? On Thu, 11 Mar 2021 at 06:31, Chris Albertson wrote: > What's the best kind of steel to buy that gives a combination of > machinability on a small mill and strength. I will concur with Marcus, when making starter gears for the Ner-a-Car I used EN8. EN8 is the old name (ie, before 1970) name for 080M40 In turn 080M40 is similar to US 1039, 1040, 1042, 1043, 1045 > Given my setup, a HF mill and manual (non-CNC) HF mini lathe which > would have the best result, a hob or an involute cutter? You can only hob if you can set the hob spindle at an angle to the gear axis. Hobbing should give a perfect profile at any tooth count, but it more difficult to arrange. You definitely can hob on a mini-mill, though. https://youtu.be/ZhICrb0Tbn4 > The really hard part that I don't know how to do is a ring gear. I can't > figure out how to cut internal teeth. Cutting internal teeth isn't something that can be done with a hob _or_ an involute cutter. You need a Fellows gear shaper, or at least to find a way to set up the equivalent on your CNC mill. https://youtu.be/72YgpVF4O7g I don't think it is impossible, with the cutting tool in the rotary axis, circularly interpolating around the blank. It might be simpler to order one wire-spark eroded for a one-off or a stock part from HPC or similar. -- atp "A motorcycle is a bicycle with a pandemonium attachment and is designed for the especial use of mechanical geniuses, daredevils and lunatics." — George Fitch, Atlanta Constitution Newspaper, 1912 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gear cutting setup on low-cost HF mill??
On Thu, 11 Mar 2021 at 06:31, Chris Albertson wrote: > What's the best kind of steel to buy that gives a > combination of machinability on a small mill and strength. I will concur with Marcus, when making starter gears for the Ner-a-Car I used EN8. EN8 is the old name (ie, before 1970) name for 080M40 In turn 080M40 is similar to US 1039, 1040, 1042, 1043, 1045 > Given my setup, a HF mill and manual (non-CNC) HF mini lathe which would > have the best result, a hob or an involute cutter? You can only hob if you can set the hob spindle at an angle to the gear axis. Hobbing should give a perfect profile at any tooth count, but it more difficult to arrange. You definitely can hob on a mini-mill, though. https://youtu.be/ZhICrb0Tbn4 > The really hard part that I don't know how to do is a ring gear. I can't > figure out how to cut internal teeth. Cutting internal teeth isn't something that can be done with a hob _or_ an involute cutter. You need a Fellows gear shaper, or at least to find a way to set up the equivalent on your CNC mill. https://youtu.be/72YgpVF4O7g I don't think it is impossible, with the cutting tool in the rotary axis, circularly interpolating around the blank. It might be simpler to order one wire-spark eroded for a one-off or a stock part from HPC or similar. -- atp "A motorcycle is a bicycle with a pandemonium attachment and is designed for the especial use of mechanical geniuses, daredevils and lunatics." — George Fitch, Atlanta Constitution Newspaper, 1912 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gear cutting setup on low-cost HF mill??
On 2021-03-11 06:28, Chris Albertson wrote: What's the best kind of steel to buy that gives a combination of machinability on a small mill and strength. I would be inclined to try EN8T which is a machinable steel with some tensile strength that can easily be hardened afterwards, using an oxy-acetylene torch. Or the even better EN40T, which is tougher and more ductile. The T denotes that it is supplied in the hardened and tenpered state, but it machines very nicely. I hagve used EN40T in the lathe and the mill, and it gives a good finish without much difficulty. I have used EN40T for making replacement parts for a large hydraulic bender for stainless steel pipe, where the steel was roughly cone-shaped and was used by being forced into a set of hardened 'fingers' to swage the end of a pipe, so it was highly stressed and subject to wear. I didn't do any heat treatment - that was to be done by the owner of the machine (although I am not convinced they bothered). Marcus ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gear Cutting
Hi Kirk, One of the main reasons I want to try to generate gears and, particularly, pinions is the great problem I have in trying to make working pinion cutters small enough for the watches I work on. I could get cutters made but, as you have said, a different one is required for each individual pinion or small subset of wheels and, at a cost of 50+UKP ($100) each, any repair using more than one of them would probably become uneconomic. This is compounded by the fact that most of the watches I work on are more than 200 years old and their wheels and pinions were hand cut or made with 'home-made' cutters which do not comply to any current standards. So, if the watch is to run properly, I have to try to match the size and shape of the original teeth exactly and no currently obtainable commercial cutter has exactly the same form as these old wheels and pinions. Consequently, even where I have a cutter which is very close to size, I usually end up having to hand finish the profile of each tooth by filing and polishing - a very tedious and lengthy process. :-( My wheels and pinions are cycloidal and not involute and have radial flanks to the leaves with a rounded or ogival top so that, in my case, the cutting can be in two stages - the straight radial flanks and the rounded tops. However, I think that the basic process should be the same whatever the tooth profile - maybe mine would just need an additional step to move the cutter a bit in Y before starting the rounded tops to the leaves whereas an involute would need the curve generated from the start. The big problem making a cutter is all down to the size and the difficulty in measuring and working to exact tiny dimensions. The 5-leaf pinion I need to make at the moment has a flat in the bottom of the tooth spaces of just 0.2mm width and a tooth depth of 0.45mm or thereabouts. Have you ever tried to get accurate measurements across sloping faces at this scale?? ;-) I have used my little cnc miller to successfully make cutters but it usually takes a couple of goes at least and it is a problem to get relief on the cutting edges. My idea for generating the pinions - (which are one-offs and not multi productions, therefore the time involved in making them is of no consequence) - is to use tiny grinding disks like the thin cut-off disks they sell for Dremels but thinner ( dentists use ones of 0.2mm thickness ) and grind the blank to shape. I have used this technique to grind small shafts and it works fine provided the speed of the disk is high and the feed is slow. I was actually very surprised how well the disks worked and after half an hour's grinding, the disk was still virtually the same size as when I started. So, if I can just work out the way to compose a G-code file with the multiple loops, I think the idea is well worth a try. Maybe for your purposes, you could consider using a similar idea by finding a supply of larger grinding disks - angle grinder cut-off disks maybe? -- Best wishes, Ian Ian W. Wright Sheffield UK The difference between theory and practice is much smaller in theory than in practice... -- Best wishes, Ian Ian W. Wright Sheffield UK The difference between theory and practice is much smaller in theory than in practice... - Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://sourceforge.net/services/buy/index.php ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gear Cutting
We should talk one day, I work with Chris Lowe at Richards of Burton, and have made a cnc to cut gears here, I still use a Safag for the really small stuff though. I want to do profile work for escape wheels, verge and normal. Dave Caroline archivist on the #emc IRC channel on freenode - Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://sourceforge.net/services/buy/index.php ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gear Cutting
Ian W. Wright wrote: One of the main reasons I want to try to generate gears and, particularly, pinions is the great problem I have in trying to make working pinion cutters small enough for the watches I work on. It just seems to me that if you have a CNC machine of any type, you should be able to cut a master tool for the form required. Then, that tool could cut the gear teeth directly, and reduce a 5 hour job to 15 minutes! Even if you only have a mill, you can mount a disc on the spindle and a lathe-type tool in the vise, and make a gear cutter by laboriously following the tooth profile. Then, you could cut radial slots to form the cutting teeth, harden it, and you'd have a pretty professional gear cutter for any tooth profile you need. Jon - Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://sourceforge.net/services/buy/index.php ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gear Cutting
On Fri, 2008-06-13 at 09:40 +0100, Ian W. Wright wrote: ... snip The big problem making a cutter is all down to the size and the difficulty in measuring and working to exact tiny dimensions. The 5-leaf pinion I need to make at the moment has a flat in the bottom of the tooth spaces of just 0.2mm width and a tooth depth of 0.45mm or thereabouts. Have you ever tried to get accurate measurements across sloping faces at this scale?? ;-) ... snip I have used my little cnc miller to successfully make cutters but it usually takes a couple of goes at least and it is a problem to get relief on the cutting edges. My idea for generating the pinions - (which are one-offs and not multi productions, therefore the time involved in making them is of no consequence) - is to use tiny grinding disks like the thin cut-off disks they sell for Dremels but thinner ( dentists use ones of 0.2mm thickness ) and grind the blank to shape. I have used this technique to grind small shafts and it works fine provided the speed of the disk is high and the feed is slow. I was actually very surprised how well the disks worked and after half an hour's grinding, the disk was still virtually the same size as when I started. So, if I can just work out the way to compose a G-code file with the multiple loops, I think the idea is well worth a try. Do you have pictures of your setup? Maybe for your purposes, you could consider using a similar idea by finding a supply of larger grinding disks - angle grinder cut-off disks maybe? -- Best wishes, Ian My original concept was to use generic tooling and have the CNC magic do the custom shapes. It's turning out that there is no generic tooling that will work. So a compromise of being able to easily make generic tooling with basic shapes may be the way to go. I was thinking that the generic tooling would do the roughing and your Dremel style disks would do the finish work on the mesh areas. The roughing tools would be like slot saws, only with side relief, so the sides could take light cuts. You would still need a set consisting of square cutters for square bottom roots and half rounds for radiused roots. Different widths in round and square cutters would also be needed, but they should be easy enough to make, so you make them when you need them. I am thinking that regrinding end or face mill inserts might be the way to go. A small insert would be easier to get the proper geometry on. The first rough cuts would be a slot across the gear face for the right and left root corners. Then, in my setup: http://www.wallacecompany.com/machine_shop/gear_cutting-2b.png the A axis would be rotated a little, the Z would come up a little to match the first tangent of the curve. Y could stay the same if the cutter doesn't touch the opposite gear curve, otherwise it can be adjusted for clearance. Then the slot is cut. Since we a roughing, six or seven tangents may be all that are needed. The X sweep will always be the same, the coordinates of the tangent point can be derived by a drawing program, so you would have six or seven loops that increment Y, Z and A which can be mirrored for roughing the opposite gear face on the back side of the setup. These two loops would be run for each tooth by incrementing A by a constant. A gear with a few teeth should be managable to g-code by hand and could be a model for a software utility. The tips of an involute gear could use the same method with an standard end mill (shown in violet in the link above). The tips of a cycloidal gear should already be done. So, at this point, we have a rough gear. Since the cutting load would be light, I think a Dremel style diamond disk would work. The roots should not need to be touched, so only the side of the disk will be used, which is good because I don't think the circumference is meant to be used anyway. The same method of sweeping X on tangents could work for finishing but allot more tangents would be needed. I think sweeping A and incrementing X might make a smoother profile and I think my CAM has a five axis processor so the g-code should not be a problem. Either way, with sweeping X or A the key is to derive the tangent points of the mesh area (30 or 40?) and looping those points a gazillion times. If this system could work, the only semi-custom tooling would be the face mill inserts. A standard surface grinder would make square inserts. Adding an A axis might do the half-round inserts. I suppose you could cut a large number at one time. Darn, now I have to buy a surface grinder. Another thought comes to mind, could wire EDM be used to cut very small gears and pinions? -- Kirk Wallace (California, USA http://www.wallacecompany.com/machine_shop/ Hardinge HNC/EMC CNC lathe, Bridgeport mill conversion, doing XY now, Zubal lathe conversion pending Craftsman AA 109 restoration Shizuoka ST-N/EMC CNC) -
Re: [Emc-users] Gear Cutting
snip Another thought comes to mind, could wire EDM be used to cut very small gears and pinions? /snip I know I've seen someone take a rotary tool similar to a Proxon (beefy dremel type) and true out the spindle and cut his collets using EDM and they were fairly small. So I don't see why doing gears - as long as they are straight cut - couldn't be done with EDM. My .02x10^-10 YMMV Greg Michalski www.distinctperspective.com - Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://sourceforge.net/services/buy/index.php ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gear Cutting
Idea is ok but Dremel stuff is in no way suitable for the scales that Ian Wright or us need when cutting watch pinion sizes. The positional accuracy needed to get a good form to the result is also a problem. Involute form is easy as a hobbing action and generation is possible but not for cycloidal form. On 6/13/08, Kirk Wallace [EMAIL PROTECTED] wrote: On Fri, 2008-06-13 at 09:40 +0100, Ian W. Wright wrote: Another thought comes to mind, could wire EDM be used to cut very small gears and pinions? yes I have seen .2 module pinions made as examples by Davall gears in the UK also I know a company in the States using Laser to cut internal gears for a freefall height meter Dave Caroline - Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://sourceforge.net/services/buy/index.php ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gear Cutting
On Fri, 2008-06-13 at 13:17 -0500, Jon Elson wrote: Ian W. Wright wrote: One of the main reasons I want to try to generate gears and, particularly, pinions is the great problem I have in trying to make working pinion cutters small enough for the watches I work on. It just seems to me that if you have a CNC machine of any type, you should be able to cut a master tool for the form required. Then, that tool could cut the gear teeth directly, and reduce a 5 hour job to 15 minutes! Even if you only have a mill, you can mount a disc on the spindle and a lathe-type tool in the vise, and make a gear cutter by laboriously following the tooth profile. Then, you could cut radial slots to form the cutting teeth, harden it, and you'd have a pretty professional gear cutter for any tooth profile you need. Jon A full gear tooth profile cutter is only accurate for the particular involute gear you are cutting. If you change any parameter, you have a different profile. It's worse with cycloidal gears because the mating profile is different, even when all parameters match (or so I have read so far). The problem is that gear cutting seems to be like house painting, 80% of the work is in preparing the surface and the rest is painting, and preping one house doesn't make the next one any easier. It would be nice to have a system where it takes 10 or 20% of the project effort to make the tool, or 50%, and have a tool left over to use on the next project. The more I think about using face mill inserts and a CNC four axis surface grinder, the more I think you could have it both ways. It would be almost as easy to make a full tooth form cutter as it would be for a semi-generic cutter. It seems to depend on where you prefer to develop the g-code. -- Kirk Wallace (California, USA http://www.wallacecompany.com/machine_shop/ Hardinge HNC/EMC CNC lathe, Bridgeport mill conversion, doing XY now, Zubal lathe conversion pending Craftsman AA 109 restoration Shizuoka ST-N/EMC CNC) - Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://sourceforge.net/services/buy/index.php ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gear Cutting
On Fri, 2008-06-13 at 20:29 +0100, Dave Caroline wrote: Idea is ok but Dremel stuff is in no way suitable for the scales that Ian Wright or us need when cutting watch pinion sizes. I just used the Dremel term to describe a type of abrasive disk, because most people are familiar with Dremel tools. I believe that appropriate abrasive disks should be available. Maybe a steel or carbide disk with diamond coating. The positional accuracy needed to get a good form to the result is also a problem. Involute form is easy as a hobbing action and generation is possible but not for cycloidal form. It's too bad that hobbing is not an option for most people. It would be nice to have a hob machine, but it's hard to justify if you don't make gears every day. (Which came first, the gear hob machine or the gears to make the gear hob machine?) On 6/13/08, Kirk Wallace [EMAIL PROTECTED] wrote: On Fri, 2008-06-13 at 09:40 +0100, Ian W. Wright wrote: Another thought comes to mind, could wire EDM be used to cut very small gears and pinions? yes I have seen .2 module pinions made as examples by Davall gears in the UK also I know a company in the States using Laser to cut internal gears for a freefall height meter Dave Caroline - Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://sourceforge.net/services/buy/index.php ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gear Cutting
Jon Elson wrote.. It just seems to me that if you have a CNC machine of any type, you should be able to cut a master tool for the form required. Then, that tool could cut the gear teeth directly, and reduce a 5 hour job to 15 minutes! Even if you only have a mill, you can mount a disc on the spindle and a lathe-type tool in the vise, and make a gear cutter by laboriously following the tooth profile. Then, you could cut radial slots to form the cutting teeth, I'm sure you are right Jon but look at my tag line The only way I have so far made a successful pinion cutter as as in the last of the links in Kirk's post of the 12th. i.e. make a form tool for the radius of the tooth top, turn a disk with this cutter, drill an array of holes in the disk, cut slots into the holes and then bend the teeth back to get relief on them before hardening and tempering. This method works but has two major potential problem areas - if all the teeth are not exactly like and bent back by exactly the same amount, the cutter will not cut on all the teeth and, more importantly, there is a significant chance of the teeth going out-of-flat during the bending back process and by warping in hardening. However, I have made this method work although it took me a whole day to get a good working cutter. Even with cnc and a pretty tight machine as I have, its still easy to get errors of a few thous. when making a profiled disk cutter less than 3/8 diameter and about 1/32 thick and that error is then a significant percentage of final size and can have a serious effect on the action of the resulting gear. I will, however, give some though to what you say and it may be possible to make maybe a 4 or 5 tooth cutter by generating relief with the form tool. At the moment my machine is our of action as I had problems with the electronics and so I am taking the opportunity to rebuild my controller so as to tidy things up a bit and add in a couple of extra features I want... -- Best wishes, Ian Ian W. Wright Sheffield UK The difference between theory and practice is much smaller in theory than in practice... - Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://sourceforge.net/services/buy/index.php ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gear Cutting
Greg Michalski wrote: snip Another thought comes to mind, could wire EDM be used to cut very small gears and pinions? You bet! For hair-thin wheels and intricate escapement profiles, they are the way to go. Of course, wire EDM is a whole other domain, and you can't buy a $500 Chinese wire EDM machine like the desktop mills. I wish we could get Robert Langlois to come down and show his stuff at the CNC Workshop. I met him years ago at NAMES, and he was working on some incredible stuff even back then. Jon - Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://sourceforge.net/services/buy/index.php ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gear Cutting
On Thu, 12 Jun 2008 00:38:02 -0500, you wrote: Kirk Wallace wrote: Has anyone tried cutting gears with something similar to this arrangement? http://www.wallacecompany.com/machine_shop/Gear_Cutter-1b.png I was thinking a slot saw (gray disk) could be used, centered on the gear shaft(violet). The gear tooth form could be followed with Y while rotating the gear (bronze color) and incrementing X on each gear rotation until the width of the gear is complete. Or successive passes in X and incrementing Y and A could make a complete tooth so that one gear rotation would complete the gear. Slot saws aren't very stiff and don't side cut, so some other cutter would be needed. Part of my thinking is that I would like to avoid special cutters like those needed for normal gear cutting. In theory, this can be done. A thin slitting saw would deflect too much to get an accurate tooth profile. You can buy gear tooth cutters and run them like this, and it will go much faster, which is still fairly slow. http://www.jeffree.co.uk/Pages/cnc-wheel-cutting-engine.htm I've seen that in operation and used it at a show here in the UK, it's not slow, gear cutter rpm was about 2500 rpm and you can stuff the cutter through the blank full depth - I guess feed was about 100 ipm. On thin brass blanks, I reckon it takes no longer than 1 second a tooth. Steve Blackmore -- - Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://sourceforge.net/services/buy/index.php ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gear Cutting
I do not know much about CNC operation but need to ask a question about the operation similar to this gear cutting. Machinery's handbook (20th) describes how to construct an involute on page 288. I read this as the involute is the length of a line tangent to the circle, equal to the cord of the circle part. Why do we not just calculate this in a spread sheet and plug it into G code? R = radius of gear angle goes from 0 to 90 degrees Angle /rad is angle in radians Xc and Yc are points on the radius of the circle where the cord is tangent to the circle length of cord is the length of the cord around the circle X Y Are points on the involute This is what you want the cutter to be. x mily mil are used to add to a G0 line to make the G code R =0.75 ANGLEangle/RADXcYCLENGTH OF CORDX Y x mil y mil 0 0 0.750 0 0.750 750 0 1 0.02 0.750.01 0.01 0.750 750.11 0 2 0.03 0.750.030.03 0.750 750.46 0.01 3 0.05 0.750.040.04 0.750 751.03 0.04 4 0.07 0.750.050.05 0.750 751.83 0.09 5 0.09 0.750.07 0.07 0.750 752.85 0.17 6 0.1 0.750.080.08 0.750 754.1 0.29 7 0.12 0.740.09 0.09 0.760 755.580.46 8 0.14 0.74 0.1 0.1 0.760 757.280.68 370.650.6 0.450.48 0.890.06 890.4564.56 380.660.59 0.460.5 0.90.07 897.2569.78 390.680.58 0.470.51 0.90.08 904.1375.25 881.540.03 0.751.15 1.180.711177.39709.34 891.550.01 0.751.17 1.180.731177.92729.55 901.570 0.751.18 1.180.751178.1750 This seems so simple to me. I know that I need to adjust for cutter size and also for root, pitch and outside diameter of the gear. And, I have not run a formal analyze of my math. What am I missing? I may have to turn the spread sheet into a text doc and then add the x mil and y mil column's to a G0 column but that seems trivial to me. As I say, What am I missing? Thanks, My problem is I can't get the computer to wiggle the parallel port. I'm working on it, and I will get it sometime. bill Jacobs - Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://sourceforge.net/services/buy/index.php ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gear Cutting
On Thu, 2008-06-12 at 08:31 +0100, Steve Blackmore wrote: ... snip http://www.jeffree.co.uk/Pages/cnc-wheel-cutting-engine.htm I've seen that in operation and used it at a show here in the UK, it's not slow, gear cutter rpm was about 2500 rpm and you can stuff the cutter through the blank full depth - I guess feed was about 100 ipm. On thin brass blanks, I reckon it takes no longer than 1 second a tooth. Steve Blackmore What I am proposing is a little different. The machine above uses a cutter that cuts one complete gear tooth form that matches the pitch and diameter for the gear being made. Theoretically, each gear diameter and pitch needs to have a custom cutter, but sometimes one cutter can be used for a few different gear diameters within the same pitch class. So if you cut allot different gears, you will need allot of expensive cutters. I want to use the same style cutter, except it will cut a simple radiused groove with a radius slightly smaller than the smallest radius in the gear tooth form. The cutter would be used like a ball end-mill to follow the tooth shape. I would only need a cutter for each pitch. It might even be possible to have indexable tooling. -- Kirk Wallace (California, USA http://www.wallacecompany.com/machine_shop/ Hardinge HNC/EMC CNC lathe, Bridgeport mill conversion, doing XY now, Zubal lathe conversion pending Craftsman AA 109 restoration Shizuoka ST-N/EMC CNC) - Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://sourceforge.net/services/buy/index.php ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gear Cutting
Steve Blackmore wrote: On Thu, 12 Jun 2008 00:38:02 -0500, you wrote: In theory, this can be done. A thin slitting saw would deflect too much to get an accurate tooth profile. You can buy gear tooth cutters and run them like this, and it will go much faster, which is still fairly slow. http://www.jeffree.co.uk/Pages/cnc-wheel-cutting-engine.htm I've seen that in operation and used it at a show here in the UK, it's not slow, gear cutter rpm was about 2500 rpm and you can stuff the cutter through the blank full depth - I guess feed was about 100 ipm. If you do it on a horizontal mill with arbor supported at both ends, you can do it like that. 2500 RPM certainly wasn't an HSS cutter in a steel gear blank. On thin brass blanks, I reckon it takes no longer than 1 second a tooth. You can't do that as the gear blank willl fold up. So, you need some discs on the side to support it. For moderately thin gears the support might be made slightly under the tooth root diameter, for really thing clockwork gears, the support discs probably need to be full tip diameter. Jon - Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://sourceforge.net/services/buy/index.php ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gear Cutting
On Thu, 2008-06-12 at 01:51 -0700, Kirk Wallace wrote: On Thu, 2008-06-12 at 08:31 +0100, Steve Blackmore wrote: ... snip http://www.jeffree.co.uk/Pages/cnc-wheel-cutting-engine.htm I've seen that in operation and used it at a show here in the UK, it's not slow, gear cutter rpm was about 2500 rpm and you can stuff the cutter through the blank full depth - I guess feed was about 100 ipm. On thin brass blanks, I reckon it takes no longer than 1 second a tooth. Steve Blackmore What I am proposing is a little different. The machine above uses a cutter that cuts one complete gear tooth form that matches the pitch and diameter for the gear being made. Theoretically, each gear diameter and pitch needs to have a custom cutter, but sometimes one cutter can be used for a few different gear diameters within the same pitch class. So if you cut allot different gears, you will need allot of expensive cutters. I want to use the same style cutter, except it will cut a simple radiused groove with a radius slightly smaller than the smallest radius in the gear tooth form. The cutter would be used like a ball end-mill to follow the tooth shape. I would only need a cutter for each pitch. It might even be possible to have indexable tooling. Here is my latest scenario for making gears with generic (almost) tooling: http://www.wallacecompany.com/machine_shop/gear_cutting-2b.png After roughing, the raduised slot cutter (blue) would sweep X (pointing towards the viewer) and increment A (gear rotation) for a short period until the root radius is formed. The the flat bottom (South face) of the slot cutter would be used to cut the critical mesh area (between the inner gray circles) by incrementing A and Z (North direction of picture). The remaining tip radius could be done with a tool change to an end-mill, again sweeping X and incrementing A and Z. Now I just need to build a rotary axis for my mill to see if the plan will work. -- Kirk Wallace (California, USA http://www.wallacecompany.com/machine_shop/ Hardinge HNC/EMC CNC lathe, Bridgeport mill conversion, doing XY now, Zubal lathe conversion pending Craftsman AA 109 restoration Shizuoka ST-N/EMC CNC) - Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://sourceforge.net/services/buy/index.php ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gear Cutting
On Thu, 2008-06-12 at 03:45 -0400, W. Jacobs wrote: I do not know much about CNC operation but need to ask a question about the operation similar to this gear cutting. Machinery's handbook (20th) describes how to construct an involute on page 288. I read this as the involute is the length of a line tangent to the circle, equal to the cord of the circle part. Why do we not just calculate this in a spread sheet and plug it into G code? This would be handy, but having a way to automated the g-code would be good. The more g-code way-points you can create the smoother the curves will be. But getting enough by hand would be difficult. R = radius of gear angle goes from 0 to 90 degrees Angle /rad is angle in radians ... snip 1.180.731177.92729.55 901.570 0.751.18 1.180.751178.1750 This seems so simple to me. I know that I need to adjust for cutter size and also for root, pitch and outside diameter of the gear. And, I have not run a formal analyze of my math. What am I missing? The more I learn about gears the more I don't know. It seems that some people have built careers on studying gear shapes. I may have to turn the spread sheet into a text doc and then add the x mil and y mil column's to a G0 column but that seems trivial to me. As I say, What am I missing? Fortunately, I found that my CAD/CAM (Synergy) software has a gear utility that makes the creation of gear forms and tool paths fairly easy. Thanks, My problem is I can't get the computer to wiggle the parallel port. I'm working on it, and I will get it sometime. bill Jacobs If you want to share your machine configuration and problem symptoms, someone here may be able to help. For the interested student, here are some links I have collected so far: http://en.wikipedia.org/wiki/Involute http://mathworld.wolfram.com/Involute.html http://www.metalwebnews.com/howto/gear/gear1.html http://www.engineersedge.com/gear_pitch_chart.htm http://www.roymech.co.uk/Useful_Tables/Drive/Gears.html http://en.wikipedia.org/wiki/Involute_gear http://en.wikipedia.org/wiki/Gear http://en.wikipedia.org/wiki/Image:Gear_words.png http://en.wikipedia.org/wiki/Leonhard_Euler http://www.smallparts.com/products/descriptions/gss.cfm http://www.csparks.com/watchmaking/WheelCutting.html OT: http://www.hobartwelders.com/weldtalk/showthread.php?t=30595 -- Kirk Wallace (California, USA http://www.wallacecompany.com/machine_shop/ Hardinge HNC/EMC CNC lathe, Bridgeport mill conversion, doing XY now, Zubal lathe conversion pending Craftsman AA 109 restoration Shizuoka ST-N/EMC CNC) - Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://sourceforge.net/services/buy/index.php ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gear Cutting
Here is an interesting gear link: http://www.cadquest.com/books/pdf/gears.pdf -- Kirk Wallace (California, USA http://www.wallacecompany.com/machine_shop/ Hardinge HNC/EMC CNC lathe, Bridgeport mill conversion, doing XY now, Zubal lathe conversion pending Craftsman AA 109 restoration Shizuoka ST-N/EMC CNC) - Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://sourceforge.net/services/buy/index.php ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gear Cutting
Kirk Wallace wrote: Has anyone tried cutting gears with something similar to this arrangement? http://www.wallacecompany.com/machine_shop/Gear_Cutter-1b.png I was thinking a slot saw (gray disk) could be used, centered on the gear shaft(violet). The gear tooth form could be followed with Y while rotating the gear (bronze color) and incrementing X on each gear rotation until the width of the gear is complete. Or successive passes in X and incrementing Y and A could make a complete tooth so that one gear rotation would complete the gear. Slot saws aren't very stiff and don't side cut, so some other cutter would be needed. Part of my thinking is that I would like to avoid special cutters like those needed for normal gear cutting. In theory, this can be done. A thin slitting saw would deflect too much to get an accurate tooth profile. You can buy gear tooth cutters and run them like this, and it will go much faster, which is still fairly slow. Jon - Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://sourceforge.net/services/buy/index.php ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
