Plastic works because it is a "mini" mill. I would use metal for a larger industrial sized machine. But even if you are making a cast iron part, make the pattern on a 3D printer.
On Mon, Jun 14, 2021 at 8:04 PM John Dammeyer <jo...@autoartisans.com> wrote: > Thank you for posting that. > So in the places where I'd make a pattern and cast from scrap aluminium > you 3D print the part. > Very nicely done! > John > > > -----Original Message----- > > From: Chris Albertson [mailto:albertson.ch...@gmail.com] > > Sent: June-14-21 7:44 PM > > To: Enhanced Machine Controller (EMC) > > Subject: Re: [Emc-users] Spindle Control > > > > On Mon, Jun 14, 2021 at 9:43 AM John Dammeyer <jo...@autoartisans.com> > > wrote: > > > > > Have you any photos of the 3D printed motor mounts etc? Direct drive > or > > > belt driven? The 3Nm implies size 23 so I'll guess direct drive. > > > John > > > > > > > THis shows X and Y. https://youtu.be/wupYP2NNsXI?t=33 > > > > This shows the Z axis. On this machine the nut spins on a non-rotating > > ball scew https://youtu.be/tlMTksuOuZQ?t=27 > > This is a render of some z-axis parts https://a360.co/3zrzIwB > > > > Note that in the two above videos I am used 3D printed timing belts. At > > first I did this as a joke but they actally work for almost an hour with > is > > long enough for testing to see if you have the right size belt. It is > > just plane old PLA printed 100% solid. All the timing pulleys are > printed > > but have steel hubs and steel set screws. > > > > Here is an interactive 3D model you can look at. This versionhas some > > alignment issues but by using the "eplode" button and slider you can look > > at the parts and rotate them to see all sides https://a360.co/2TxOscU > > > > "Universal PWM spindle speed control device" (don't laugh, it works.) > > https://a360.co/2N95AiL > > > > > > > > > > > > -----Original Message----- > > > > From: Chris Albertson [mailto:albertson.ch...@gmail.com] > > > > Sent: June-14-21 8:41 AM > > > > To: Enhanced Machine Controller (EMC) > > > > Subject: Re: [Emc-users] Spindle Control > > > > > > > > Yes, I thought about reverse engineering the spindle motor > controller and > > > > fitting it with a conector for external PWM input but my goal with > this > > > CNC > > > > conversion was to try and do the lowest cost and easiest possible > > > > conversion and document it. So at every decision point I take the > > > simplest > > > > route that costs the least and most importantly, they anyone reading > my > > > > instructions could follow. As soon as I suggest modifying a > controller > > > > board, I've lost 90% of the machinists who might be following my > > > > instructions. > > > > > > > > To that end I've 3D printed almost all the parts needed for CNC > > > conversion. > > > > People usually use metal but the stepper motors I use only only > > > produce > > > > less them 3 Newton meters of torque. The the maxim force the motor > > > mounts > > > > will ever see is 3 Newton meters. I don't need cast iron for that, > > > plastic > > > > works. My goal is to do the complete conversion including motors > and a > > > > ball screw all for under $400 with an assembly time of no more then > one > > > day > > > > of work, not counting the time needed to print the parts. I looks > like > > > > I'll meet these goals. > > > > > > > > I use a dial indictor to measure deflection under load of the plastic > > > parts > > > > and there is one part on they-axis that needs to be redesigned into > the > > > > more organic-looking shape with compound curves. I find this is the > > > > "secret" for making strong 3D printed parts, It is the same reason > car > > > > fenders don't bend, even though that are made with thin sheet > metal, It > > > is > > > > the compound shape. Printed parts are like that, they are made of a > > > thinn > > > > skin of solid plastic over a light foam-like core and all the > strength is > > > > in the skin. Flat slabs of printed plastic are not very strong or > > > ridgid. > > > > > > > > I does not impress me much that someone can build a CNC milling > machine > > > for > > > > $10,000 and 6 months of work. Anyone can do that. What I want is > "under > > > > $400 and one day". After about three attemps I'm getting closer to > > > that. > > > > When I get there I'll write it up on the web and publish the design > > > files. > > > > > > > > So, back to my spindle speed controller. This device will literally > > > > replace the knob on the pot and cost about $6 to make. > > > > > > > > > > > > > > > > On Sun, Jun 13, 2021 at 11:09 PM Gregg Eshelman via Emc-users < > > > > emc-users@lists.sourceforge.net> wrote: > > > > > > > > > How old is that mill? Those Chinese mini mills and lathes have had > PWM > > > > > spindle motor controllers for many years. I used to have a Grizzly > mini > > > > > lathe with a low 3 digit serial number, probably from the first > batch > > > they > > > > > imported. I was at least the 3rd owner and I had to fix a lot of > > > issues, > > > > > both original and from prior owner abuse. One fix was resoldering > one > > > end > > > > > of a big resistor on the primitive and very noisy motor controller. > > > > > You can buy a new PWM motor controller and potentiometer to > upgrade. > > > > > > > > > http://benchtopmachineshop.blogspot.com/2017/01/mill-speed-controller.html > > > > > On Sunday, June 13, 2021, 2:30:15 PM MDT, Chris Albertson < > > > > > albertson.ch...@gmail.com> wrote: > > > > > I have a Harbor freight mini mill with the dumbest possible > spindle > > > > > control. The mill comes from the factory with a variable resistor > to > > > > > control speed. My idea was to connect a variable resistor to a $5 > > > model > > > > > airplane servo. So the PWM output from LinuxCNC drives the servo > and > > > the > > > > > servo turns the pot which controls the spindle motor. I would > never be > > > > > able to do rigid tapping with this setup. > > > > > _______________________________________________ > > > > > Emc-users mailing list > > > > > Emc-users@lists.sourceforge.net > > > > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > > > > > > > > > > > > > > -- > > > > > > > > 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 > > > > > > > > > -- > > > > 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 > -- Chris Albertson Redondo Beach, California _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
