Re: [Emc-users] More cbn headaches

[Chris Albertson]

On Sun, Jul 5, 2020 at 3:33 AM andy pugh  wrote:

>
> You say this a lot, but I have never heard anyone else say it. What is
> your source?
>

THis might be a "Chemistry 101" question.  It should be easy enough to
figure out except that I last studied this stuff in the last 1970s

We all know that burning carbon produces a lot of heat.  The chemical
equation is
C + O2 --> CO2  -394 kJ / mole

The corresponding equation of aluminum is
4Al + 3O2 --> 2Al2O3  -1676 kJ/mole
Aluminum produces more heat per mole than carbon and also more heat per
gram than carbon.   It would make good fuel except for combustion stops
once the oxide layer is formed.

Next, I looked up the specific heat of aluminum.  It is very close to 1.0
kJ / (Kg K).  So it only takes 1 Joule to heat one gram of aluminum one
degree K.

So there is plenty of energy and the metal is also easy to heat.  But what
we don't know is the fraction of aluminum that is oxidized.   You could
figure this out if you had a good enough scale and could collect all the
chips.  We could see how much mass the chips gained from the added oxygen.



-- 

Chris Albertson
Redondo Beach, California

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Re: [Emc-users] More cbn headaches

[Jon Elson]

On 07/05/2020 08:55 PM, Gregg Eshelman via Emc-users wrote:
That was my clue that I was never going to light a smith 
wrench anywhere near mag.
If you've ever seen a magnesium engine or transmission case 
burn, it is quite a show.
And, when the fire department doesn't have foam in their 
truck, the only thing they have is water.
LOTS of water will put out burning magnesium, but will cause 
a white-hot explosion at first, the firemen have to have the 
high temperature suits to get away with it.


I've seen a VW microbus go up, and they only had one tiny 
foam can. The foam knocked it down for a few seconds quite 
nicely, but then when they hit it with water it looked like 
a 4th of July display gone wrong!


Jon


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Re: [Emc-users] More cbn headaches

[Gregg Eshelman via Emc-users]

There are ways to make magnesium very hard to burn. NeXT did it to the cases on 
their computers. https://simson.net/ref/1993/cubefire.html
I assume that laptop computers with magnesium cases use similar alloys.
Mongoose BMX bicycles back in the 80's did a sneaky thing for their factory 
team. Their production wheels were die cast aluminum. But in the dead of night 
they cast and machined a run in pure magnesium. Quite tricky to not end up with 
their wheel casting plant and machine shop on fire. Didn't bother getting 
inspection or permits etc for working with molten magnesium because it was a 
one off to make wheels for company use.

On Sunday, July 5, 2020, 7:08:36 AM MDT, Gene Heskett 
 wrote:  
 On Sunday 05 July 2020 06:30:13 andy pugh wrote:

> On Sun, 5 Jul 2020 at 07:05, Gene Heskett  wrote:
> > quicker because alox is the 2nd hardest abrasive we have.
>
> No, that's CBN, second after diamond.
>
> > That, and if
> > cutting dry, the heat of oxidation of the chip coming off is 98% of
> > the heat generated.
>
> [citation needed]
>
> You say this a lot, but I have never heard anyone else say it. What is
> your source?

Almost any src discussing the properties of alu.  It is a very active 
metal, oxidizing (burning IOW) in microseconds behind the passage of a 
cutting edge that exposes the bare metal to the oxygen in our air. This 
process continues at a rapid rate until a layer of oxide has been made 
that protects it by covering the surface with an oxide coat that must be 
cut by the next oncoming tool edge.  The rate of burn slows until the 
oxide, which is also a perfect insulator, has reached a thickness to 
withstand around 50 volts, I've read about a millisecond by which time 
it takes additional chemical help to get to its best withstand of about 
400 volts. Coloring of this oxide coat, commonly called anodizing, takes 
place at this time also.
Getting something, almost anything, to coat that bare alu as the cutting 
edge passes, slows this burn rate and prolongs the life of the cutting 
tool by many times as it reduces the oxide the tool has to cut again 
with the next passing edge.

Because its colorfull as it burns, and can be colored  by contaminates, 
its powdered form is commonly used in fireworks made for aerial 
displays.  The fireworks delayed explosives are used as an igniter. That 
and magnesium which generally are the brighter whiter ones.  The trick 
for the fireworks experts is to have it all burned before it gets to the 
ground and starts a real fire.

Back in the middle 50's, in Iowa City, we burned up a mercury outboard 
motor block, on purpose as part of a welding class I took, doing it on 
some very poor condition sidewalk 50 feet away from the welding shop on 
the front of a vacant lot. The shop owner had a string of military 
welding certs in his wallet, and first showed us that mag can be welded 
with a smith wrench, aka acetylene torch, and put the stuff knocked out 
of that big 6 block back in place that an errant con rod had knocked 
out.  And once we had looked at the work, he said "and this is what 
happens if you aren't carefull" and lit that block up. Took it about 20 
minutes to burn and made to good sized pit in the ground doing it. But 
the local fire dept had to be restrained for dousing it with water when 
they arrived like the 7nth cavalry, which the magnesium would have 
loved, creating a much larger pit from the explosion. So they did the 
next best thing and wrote him up. But he'd planned that show in advance 
and by the time the court date rolled around, the pit had been filled 
and a brand new sidewalk the length of that block had been graded and 
poured, pix of which got the cite laughed out of court, the city was 
glad to get that 40 yo sidewalk fixed at no cost to them.  That was my 
clue that I was never going to light a smith wrench anywhere near mag.  
The smoke is not healthy to start with.  
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Re: [Emc-users] CAM grinder- What harware

[Leonardo Marsaglia]

Have you considered external offsets for this? I have had moderate success
turning low lift cams with this feature.

I'm preparing the retrofit of a cylindrical grinder with LinuxCNC to
achieve camshaft and crankshaft grinding. With external offsets you don't
need a really precise servo spindle. A normal and well reduced VFD driven
spindle could be used and the X axis will follow the rotation.

The obvious problem I had is that to achieve good results with the lathe I
need a live tool to allow for lower spindle rpms. I'm working on that and
soon I should have a live tool to mill the cams.

With this approach you can use pretty simple g code and you only need a hal
component to feed the external offset as the spindle turns. By the way, the
cam data must be hard coded inside the component, I guess it could be fed
in by some method by I didn't get there yet.

Here are some tests I've been doing.

https://youtu.be/KzEPyKZ6Xjo

https://youtu.be/xjBXa6RHSPQ

Leonardo Marsaglia

El dom., 5 jul. 2020 20:24, Forums  escribió:

> I'm getting to the point where I need my own camshaft grinder.
>
> The question I have is the G-code. The grinder has 2 basic components, a
> rotary operation to turn the cam and a linear movement to move the grinding
> head. For simplistic sake, say the G-code is 360 deg with the
> corresponding X
> travel.  Say we start with a blank round cam. In each revolution of the
> cam,
> the grinding wheel has to step in an amount till it gets to final size.
>
> This can be done with and If and Else statement.
>
> I was looking at some of the Chinese CNC controllers which are cheap and
> stand
> alone and as this is a simple job, would be a good option but I have not
> been
> able to find one that has logic in the G-Code.
>
> I don't think feedback is required and step and direction would be fine for
> this project. It would need constant recalibration as the wheel wears. My
> question is, what would be a suitable bit of hardware to run LinuxCNC. Is
> the
> PI up to this as yet ?
>
> Thanks Wallace.
>
>
>
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>

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[Emc-users] CAM grinder- What harware

[Forums]

I'm getting to the point where I need my own camshaft grinder. 

The question I have is the G-code. The grinder has 2 basic components, a
rotary operation to turn the cam and a linear movement to move the grinding
head. For simplistic sake, say the G-code is 360 deg with the corresponding X
travel.  Say we start with a blank round cam. In each revolution of the cam,
the grinding wheel has to step in an amount till it gets to final size. 

This can be done with and If and Else statement.

I was looking at some of the Chinese CNC controllers which are cheap and stand
alone and as this is a simple job, would be a good option but I have not been
able to find one that has logic in the G-Code.

I don't think feedback is required and step and direction would be fine for
this project. It would need constant recalibration as the wheel wears. My
question is, what would be a suitable bit of hardware to run LinuxCNC. Is the
PI up to this as yet ?   

Thanks Wallace.  



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Re: [Emc-users] 2.9.0 Jerky jog

[N]

> On Sun, 5 Jul 2020 at 14:07, N  wrote:
> >
> > Are currently using version 2.9.0 pre something. G0 move work smoothly but 
> > jogging is jerky, anyone else here made same experience?
> 
> How are you jogging?

Jogging speed is high, have a small toy motor on desktop behind me then I test 
software, it is less noticable then speed is turned down to rather slow speed I 
expect is used for jogging. It still sometime turn up in "vel" field, small 
spike rather seldom, as number is very even and stable I do not think it come 
from feedback and is calculated before sent to hardware

> This is new in 2.9:
> joint.N.jog−accel−fraction IN FLOAT
> http://linuxcnc.org/docs/devel/html/man/man9/motion.9.html


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Re: [Emc-users] 2.9.0 Jerky jog

[N]

> On Sun, 5 Jul 2020 at 14:07, N  wrote:
> >
> > Are currently using version 2.9.0 pre something. G0 move work smoothly but 
> > jogging is jerky, anyone else here made same experience?
> 
> How are you jogging?

Keyboard. sim seems OK. Running against hardware and it sometimes show up in 
the "vel" field so I guess it happen within Linuxcnc before sent to hardware 
but are not totally sure.

> This is new in 2.9:
> joint.N.jog−accel−fraction IN FLOAT
> http://linuxcnc.org/docs/devel/html/man/man9/motion.9.html


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Re: [Emc-users] 2.9.0 Jerky jog

[N]

> On Sun, 5 Jul 2020 at 16:02, N  wrote:
> 
> > > What have you changed since it last worked properly?
> >
> > Nothing, except some automatic update from [AXIS] to [JOINT] in .ini file.
> 
> When you say "nothing" do you really mean "a major upgrade from
> LinuxCNC 2.7 to LinuxCNC 2.9?"

Actually from 2.8 to 2.9 but I made no change to configuration.


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Re: [Emc-users] 2.9.0 Jerky jog

[andy pugh]

On Sun, 5 Jul 2020 at 16:02, N  wrote:

> > What have you changed since it last worked properly?
>
> Nothing, except some automatic update from [AXIS] to [JOINT] in .ini file.

When you say "nothing" do you really mean "a major upgrade from
LinuxCNC 2.7 to LinuxCNC 2.9?"

-- 
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


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Re: [Emc-users] 2.9.0 Jerky jog

[N]

> On Sun, 5 Jul 2020 at 15:02, N  wrote:
> 
> > > How are you jogging?
> >
> > Ordinary keryboard, it have worked a lot better before.
> 
> So, cursor keys?
> 
> There have been some changes to incremental jogging, but I don't know
> if anything has changed with continuous jogging.
> 
> What have you changed since it last worked properly?

Nothing, except some automatic update from [AXIS] to [JOINT] in .ini file.


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Re: [Emc-users] 2.9.0 Jerky jog

[andy pugh]

On Sun, 5 Jul 2020 at 15:02, N  wrote:

> > How are you jogging?
>
> Ordinary keryboard, it have worked a lot better before.

So, cursor keys?

There have been some changes to incremental jogging, but I don't know
if anything has changed with continuous jogging.

What have you changed since it last worked properly?

-- 
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


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Re: [Emc-users] 2.9.0 Jerky jog

[N]

> On Sun, 5 Jul 2020 at 14:07, N  wrote:
> >
> > Are currently using version 2.9.0 pre something. G0 move work smoothly but 
> > jogging is jerky, anyone else here made same experience?
> 
> How are you jogging?

Ordinary keryboard, it have worked a lot better before.


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Re: [Emc-users] 2.9.0 Jerky jog

[andy pugh]

On Sun, 5 Jul 2020 at 14:07, N  wrote:
>
> Are currently using version 2.9.0 pre something. G0 move work smoothly but 
> jogging is jerky, anyone else here made same experience?

How are you jogging?

This is new in 2.9:
joint.N.jog−accel−fraction IN FLOAT
http://linuxcnc.org/docs/devel/html/man/man9/motion.9.html

-- 
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


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Re: [Emc-users] More cbn headaches

[Gene Heskett]

On Sunday 05 July 2020 06:30:13 andy pugh wrote:

> On Sun, 5 Jul 2020 at 07:05, Gene Heskett  wrote:
> > quicker because alox is the 2nd hardest abrasive we have.
>
> No, that's CBN, second after diamond.
>
> > That, and if
> > cutting dry, the heat of oxidation of the chip coming off is 98% of
> > the heat generated.
>
> [citation needed]
>
> You say this a lot, but I have never heard anyone else say it. What is
> your source?

Almost any src discussing the properties of alu.  It is a very active 
metal, oxidizing (burning IOW) in microseconds behind the passage of a 
cutting edge that exposes the bare metal to the oxygen in our air. This 
process continues at a rapid rate until a layer of oxide has been made 
that protects it by covering the surface with an oxide coat that must be 
cut by the next oncoming tool edge.  The rate of burn slows until the 
oxide, which is also a perfect insulator, has reached a thickness to 
withstand around 50 volts, I've read about a millisecond by which time 
it takes additional chemical help to get to its best withstand of about 
400 volts. Coloring of this oxide coat, commonly called anodizing, takes 
place at this time also.
Getting something, almost anything, to coat that bare alu as the cutting 
edge passes, slows this burn rate and prolongs the life of the cutting 
tool by many times as it reduces the oxide the tool has to cut again 
with the next passing edge.

Because its colorfull as it burns, and can be colored  by contaminates, 
its powdered form is commonly used in fireworks made for aerial 
displays.  The fireworks delayed explosives are used as an igniter. That 
and magnesium which generally are the brighter whiter ones.  The trick 
for the fireworks experts is to have it all burned before it gets to the 
ground and starts a real fire.

Back in the middle 50's, in Iowa City, we burned up a mercury outboard 
motor block, on purpose as part of a welding class I took, doing it on 
some very poor condition sidewalk 50 feet away from the welding shop on 
the front of a vacant lot. The shop owner had a string of military 
welding certs in his wallet, and first showed us that mag can be welded 
with a smith wrench, aka acetylene torch, and put the stuff knocked out 
of that big 6 block back in place that an errant con rod had knocked 
out.  And once we had looked at the work, he said "and this is what 
happens if you aren't carefull" and lit that block up. Took it about 20 
minutes to burn and made to good sized pit in the ground doing it. But 
the local fire dept had to be restrained for dousing it with water when 
they arrived like the 7nth cavalry, which the magnesium would have 
loved, creating a much larger pit from the explosion. So they did the 
next best thing and wrote him up. But he'd planned that show in advance 
and by the time the court date rolled around, the pit had been filled 
and a brand new sidewalk the length of that block had been graded and 
poured, pix of which got the cite laughed out of court, the city was 
glad to get that 40 yo sidewalk fixed at no cost to them.  That was my 
clue that I was never going to light a smith wrench anywhere near mag.  
The smoke is not healthy to start with. 

Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.
 - Louis D. Brandeis
Genes Web page 


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[Emc-users] 2.9.0 Jerky jog

[N]

Are currently using version 2.9.0 pre something. G0 move work smoothly but 
jogging is jerky, anyone else here made same experience?


Nicklas Karlsson


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Re: [Emc-users] More cbn headaches

[andy pugh]

On Sun, 5 Jul 2020 at 07:05, Gene Heskett  wrote:

> quicker because alox is the 2nd hardest abrasive we have.

No, that's CBN, second after diamond.

> That, and if
> cutting dry, the heat of oxidation of the chip coming off is 98% of the
> heat generated.

[citation needed]

You say this a lot, but I have never heard anyone else say it. What is
your source?

-- 
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


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Re: [Emc-users] Can't get chuck inside -- finally inside

[N]

On Sun, 21 Jun 2020 16:36:19 +0100
andy pugh  wrote:

> On Sun, 21 Jun 2020 at 16:11, N  wrote:> 
> >
> > Looking closer on chuck and slit, to long and wrong shape. Neither of them
> > fit with tool changer. I tried ISO40 (DIN2080) so now is the question if I
> > should try BT40 (JIS B6339) or SK40 (DIN69871) or both.
> 
> 
> There is a risk of damaging the petal clamp if a pull-stud of the wrong
> angle is used. I think you need to take the washer stack and petal clamp
> out see what you have.

Tried to figure out but failed and tried anyway. There are small oily marks not 
scratching the metal, from the edge a bit inwards so I guess angle is correct.

> But one alternative might be to form modelling clay around a stick on the
> end of a holder with no pull stud, to see what shape it pushes the clay in
> to.

Tried with wheat dough but replaced salt in receipt with oil as I think machine 
oil is better for machine than salt due to corrision, did not get it to work. 
Tried to grip the end of a cable and that did not work either, could see no 
marks at all.

> (And then when the clay gets stuck in the petals you have no choice but to
> strip it all down for inspection)
> 
> It might be easy. On my home-made drawbar the entire thing just lifts out:
> https://youtu.be/pxrzJ_KfcQ0?t=23

Removed from top, there is some kind of oil cylinder releasing tool but failed 
to get further down , a pin sticking out not possible to move, guess there is a 
spring somewhere further down.


I tried anyway and think angle is OK. For some reason touch off did not work in 
the Y direction in version I had, tool running in air behind part which was 
really annoying then I at last get it inside. Tried new version then I got back 
to office and there it works in simulation so I am pretty sure touch off will 
work once I get back to workshop with an updated version.


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Re: [Emc-users] More cbn headaches

[Gene Heskett]

On Saturday 04 July 2020 21:12:57 Jon Elson wrote:

> On 07/04/2020 04:26 PM, Gene Heskett wrote:
> > IIRC no sparks, 200 or so revs, could just barely hear it touching,
> > peeled two strips down to the alu about 1/4" wide. Not at all
> > impressed. Up to that point, I was watching a very thin cloud of
> > steel dust drifting away in the work light and figured it would get
> > to where it should be in about half an hour.  I wound up doing it on
> > the bench grinder with a glass of water to keep from burning my
> > fingers.
>
> Unless you are whetting the edge on a scalpel, no need to
> use diamond to shape a lathe tool.
>
> A coarse alumina wheel will do a fine job.
>
> Jon
>
That depends on how long you want that edge to last. On a wood plane 
iron, nothing compares to the edge that 12,000 grit rouge wheel leaves. 
I touch it up about yearly, and a touch is all it needs. On a piece of 
3/8 HSS tool steel cutting alu, that mirror like finish goes away much 
quicker because alox is the 2nd hardest abrasive we have. That, and if 
cutting dry, the heat of oxidation of the chip coming off is 98% of the 
heat generated.  The heat from the chip sliding off the top of the tool 
is nothing compared to the heat generated by the rapid burning of the 
freshly cut alu surface, both on the bottom of the chip as the airborn 
oxygen attacks it, and on the workpieces freshly exposed surface. If you 
can put the work in a dry nitrogen atmosphere, you can machine alu at 
20x faster rates, and the swarf still won't burn you until its flown 
thru a couple foot of normal air. Water, delivered as a mist, possibly 
with other contaminants, even though its 2 parts oxy, is harder for the 
alu to oxidize rapidly than plain dry air.  And if directed at the back 
edge of the tool, can easily extend the life of a carbide tool by 5 to 
20x, depending on how fast you can get the alu wet behind the passage of 
the cutting edge. Microseconds count. So high pressure air pushing that 
mist is the key, not so much the quantity of water or mix delivered. As 
an experiment 20 years back, I had to make bearing spacer block to move 
a blower bearing out of the groove cut in the shaft by 50 years of its 
spinning in the fafner eccentric collar. About an inch thick and 5" 
square, I rigged a mister using safflower oil, all this on the only mill 
I had at the time, the teeny little hf I had cnc'd. Took about 4 hours 
working on a block bandsawn from a 7"x7"x24" of solid alu I'd found at 
one of our recycle places and stolen for a 40 dollar bill.  And misted 
about 3 oz of oil.  That block never got warm. But with that much oil in 
the air, I couldn't see the 16 foot length of the shop building and my 
lungs complained for several days.  Its still under that bearing today, 
but that whole 1956 transmitter was turned off forever at midnight June 
30, 2008.

Proving to me that keeping airborn oxygen away from the alu makes 
machining it much easier. But making that environment was harder than I 
thought. And hard on the human involved. I can certainly see why 
machining centers pump coolant by the hundreds of gallons peer hour, 
unless you get legionaires growing in the sump, much easier on the 
humans nearby.

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Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.
 - Louis D. Brandeis
Genes Web page 


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