CNC mill conversion questions

This forum is dedicated to those Hobbyists Interested in CNC machining in their home shops. (Digital Read Outs are also topical, as is CAD/CAM as it relates to CNC)

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hanermo
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Re: CNC mill conversion questions

Postby hanermo » Wed Sep 10, 2014 4:33 am

Yes, I´ve used linuxcnc.
The closed loop argument is complete bs.

Yes .. it can be done, with special hw. The sw loop is far too slow for real use.
No .. it cannot be done easily and well. Docs are scarce.

There are some arguments for linuxcnc. The closed loop is not one of them.
Inputting servo position is NOT accurate positioning as the motion control train introduces error.

Using the CSMIO, and servos, you are always guaranteed servo positioning.
You can adjust your servo error parameters to whatever accuracy you want.
Its also possible to fit glass scales with the CSMIO (differential input) for accurate machine co-ordinate input.
Suitable scales are about 1000€.

Again, doing better than commercial machines (50-100k VMCs) is easily done, at significant cost in better servos.
But first you need to make a more rigid machine.

When I sold 65 industrial VMCs at 73.000€ avg, each, we put secondary closed loop ie glass scales, on 2.
Out of avg 5000 machines sold by us in the past 20 years, about 2% had them (statistical fact).

Std servos on commercial machines (all of them, in general) deliver +/- 2.5 microns repeatability and accuracy.
This is the common spec on most industrial machines, until you go into ultra-high range like spinner lathes and some Mori Seiki high end machines.
Haas, Leadwell, etc etc all spec 2.5+/- microns.

My step size on new industrial lathe will be 4000 steps x 2:1 ratio / 5 mm screw rise = 0.625 microns.
This delivers around 1 micron real world resolution and better than 2 microns repeatability.

A 400 W AC brushless servo system is 290€, fwiw.
The better servos start at 690€, or so. (More parameters, sw setup, 220V, etc).

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GlennW
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Re: CNC mill conversion questions

Postby GlennW » Mon Sep 15, 2014 7:15 am

Thanks for all of the very helpful replies!

Still cogitating all of this, as I don't look foreword to PC control after using the Dynapath.
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!

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Marty_Escarcega
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Re: CNC mill conversion questions

Postby Marty_Escarcega » Mon Sep 15, 2014 7:39 am

Glenn Wegman wrote:Thanks for all of the very helpful replies!

Still cogitating all of this, as I don't look foreword to PC control after using the Dynapath.


For a hobby machine Mach3 is fine (I think its still quirky)
For an advanced hobby machine, I like Flashcut much better.

You might look at speaking with Dynapath to see what your options our. You might be money and TIME ahead to repair or upgrade your Dynapath control.

Marty
"Jack of all Trades, Master of None"

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GlennW
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Re: CNC mill conversion questions

Postby GlennW » Fri Oct 17, 2014 7:21 am

I have decided to ship the "brain" in for evaluation to see just what the issue might be. If it's not too bad, I would much rather have the controller repaired.

The shop was about a hundred degrees inside the day it failed and the cabinet was hot to the touch. The previous owner of the machine said the controller would shut down from heat after a couple of hours of use in an air conditioned shop and had added another fan in the cabinet. He said it helped, but they ended up running it with the cabinet door open to keep it cool.

If it is repairable, I will from now on cool the electronics cabinet using a small portable air conditioner via a duct.
Glenn



Operating machines is perfectly safe......until you forget how dangerous it really is!

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Marty_Escarcega
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Re: CNC mill conversion questions

Postby Marty_Escarcega » Fri Oct 17, 2014 9:40 am

Likely a good idea. Hopefully not too bad. Keep us posted.
Marty
"Jack of all Trades, Master of None"

redneckalbertan
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Re: CNC mill conversion questions

Postby redneckalbertan » Fri Oct 17, 2014 6:55 pm

Heat is a huge killer of electronics. The air conditioner is a good idea, be mindful of condensation.

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GlennW
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Re: CNC mill conversion questions

Postby GlennW » Sat Jul 11, 2015 9:03 am

Since I hardly ever use the machine, I finally got around to shipping the entire controller and power supply out to see what it might need to get it running again.

I was expecting a phone call with a damage report, but instead got a phone call wanting my CC info and UPS shipper number to get it back to me! It seems that the processor had a massive failure so an updated processor board was installed and a few extra features added that I'll most likely never use, as they are Conversational related and I don't do Conversational programming.

Powered it up yesterday, and it runs!

Now I'll work on the cooling issue a bit.
Glenn



Operating machines is perfectly safe......until you forget how dangerous it really is!

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DICKEYBIRD
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Re: CNC mill conversion questions

Postby DICKEYBIRD » Sat Jul 11, 2015 10:10 am

A good choice methinks and one that will save you a ton of time & misery trying to reinvent the wheel.
Milton in Tennessee

"Accuracy is the sum total of your compensating mistakes."

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GlennW
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Re: CNC mill conversion questions

Postby GlennW » Sat Jul 11, 2015 10:19 am

I really have no interest in PC control at all or doing a conversion. Couldn't stand the thought!

I have a friend that converted a similar machine to PC control and he pulled his hair out for months getting it to operate properly, and his business is electronics and wiring.
Glenn



Operating machines is perfectly safe......until you forget how dangerous it really is!

hanermo
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Re: CNC mill conversion questions

Postby hanermo » Sat Aug 29, 2015 7:18 am

1. Its really hard to build a "real" cnc machine.
2. Its really hard to build a good retrofit.
3. Both are quiet expensive,

Ignoring realities 1-3. is not likely to be a good strategy, imho, ime.

There is a big divergency between reality and desires, mostly common when people want to "save money" and re-use old hardware.
Time and money can be traded for each other, but you are unlikely to do so better than someone who works at it, all day, every day, and has industrial tools at their disposal.

Thus, often expectations and realities collide, and retrofits fail because people give up.
Mostly, imo, because they
1. started with wrong expectations
2. started with wrong hw & (or) sw
3. the hw makers have very poor documentation.

Its very much easier to re-fit everything with all new hw and sw, from the same providers, with support in a clear, comprehensible language.
Its also cheaper, if your time is worth anything.

The electronics are NOT the problem.

The problem is that the sw, plugins, and hw all have bugs.
All have incompatible features.
All have missing features, sometimes crucial.
All have FUD.

Very few people have experienec with 3 or more motion controllers, both main sw controllers linuxcnc and mach3/4, and industrial hw and sw.

Thus, most people will mix and match the above, to create wildly optimistic and inaccurate statements / fantasies, further muddling the issue.

The controller makers dont state, for example;
CSS working on lathe ? With servos ? Sure ? To what resolution/speed ?
Rear toolpost working on lathe ? With compensations ?
Screw mapping working ?
Threading ? With step/dir spindle ? With slaved axes ? How many slaves ? Rigid tapping ? To what speed ?

How is handled ..?
-homing
-slaving axes
-probing
-rigid tapping (with what limitations)

Just to make some simple examples.
I have experience with linuxcnc, mach3(3000+ hours), industrial machines (100+ machines), steppers (5+ driver types), servos (4+ types), fwiw ..

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Marty_Escarcega
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Re: CNC mill conversion questions

Postby Marty_Escarcega » Sat Aug 29, 2015 8:20 am

GlennW wrote:Since I hardly ever use the machine, I finally got around to shipping the entire controller and power supply out to see what it might need to get it running again.

I was expecting a phone call with a damage report, but instead got a phone call wanting my CC info and UPS shipper number to get it back to me! It seems that the processor had a massive failure so an updated processor board was installed and a few extra features added that I'll most likely never use, as they are Conversational related and I don't do Conversational programming.

Powered it up yesterday, and it runs!

Now I'll work on the cooling issue a bit.


Thanks for the update Glenn. I hope it was fairly reasonable all things considered. Glad you are back up and running.
Marty
"Jack of all Trades, Master of None"

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GlennW
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Re: CNC mill conversion questions

Postby GlennW » Sat Aug 29, 2015 10:49 am

Hello Marty,

It all worked out quite well in the end.

I have two machines that are equipped with this same type controller, so it's nice and simple that way.

Thanks!
Glenn



Operating machines is perfectly safe......until you forget how dangerous it really is!


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