The Home Machinist!

There are probably quite a few people reading this forum who are almost beginners when it comes to CNC. Would some you more experienced guys share some basics with us? CNC Conversion 101.

How would you go about converting a lathe or milling machine to CNC? I don’t want to buy a machine today and discover later that it was a dead end.

Is there a good website on such conversions? What’s the best book on the topic?

Can the converted mill/lathe still be used for manual operation? Which mill would you choose: a BP clone or something a bit more robust? What are the basic components? I am under the impression that normal DRO scales are used to sense position. Is that correct? Then stepper motors turn the “handles”? Do the stepper motors connect directly to the controller, then the controller is cabled to the computer, or are there more components in between?

If these questions are too ignorant and elementary, then just tell me to “bug off.” But I believe that someday I would like to upgrade to CNC, and would like for whatever machinery I purchase now to be compatible with such an upgrade.

I am in awe of the enormous reservoir of knowledge on Chaski, and I really appreciate the patient generosity of those who share it.

--Bob

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--Bob

Gorton NC mill converted to manual to be converted to CNC.

I'm not a CNC expert, but have looked quite extensively into some of the builds.

Two sites come to mind, G0602 and G0704. That guys is quite knowledgeable on CNC conversions of the inexpensive Chinese machines and has provided a good deal of information.

My understanding is that you will usually replace the lead screws with ball screws. The motors are programmed to turn a set amount - there is no DRO feedback. This seems to be a problem if the machine crashes, the motors go unsynced and you loose position, but otherwise not an issue.

The basic system runs PC -> controller -> motor driver -> motor.

_________________
Standards are so important that everyone must have their own...
Logan 10x24 Lathe, RF-30 Mill, 20 Ton Press
Disclaimer: I'm just a guy with a few machines...

When I search G0602 and G0704 I get Grizzly part numbers. Am I missing something? Perhaps someone has converted those two particular machines to CNC?

Bob

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--Bob

Gorton NC mill converted to manual to be converted to CNC.

wubbleyou wubbleyou wubbleyou dot gee zero six zero two dot com

http://www.G0602.com

etc...

Or. if you're using Google, it's usually the second link...

Yes, those are the model numbers for Grizzly small mill and lathe.

_________________
Standards are so important that everyone must have their own...
Logan 10x24 Lathe, RF-30 Mill, 20 Ton Press
Disclaimer: I'm just a guy with a few machines...

NO FEEDBACK....

not hardly.

Even with steppers, you can have feedback, and my personal preference is that you always SHOULD have feedback so that you know where you are, not just walking out 'blindly'.

Many machines run without feedback, but I have never built one that didn't.

Feedback can be in terms of incremental or absolute encoder on motor / lead-screw, or glass scale elsewhere on axis that gives true position, not 'calculated' from screw turns.

This means you don't have to worry about accumulated deviation (important on BIG machines).

Can you run a converted machine with handles? - yes you can, assuming you leave the handles on and have a way to easily de-power the axis drivers without shutting down other desired functions.

What machine?

Something this is big, rigid, sturdy, without way wear -> and one you can get ball-screws for.

You can never have too much travel.

Also, something that allows you to use a tool-holder that you use to remove / install tools without having to constantly reset the offsets.

Working with R8 collets and a CNC machine is OK if there is no alternative, but boy is it a PITA.

Bill:

Thanks for your response. Perhaps I should warn you that every good answer provokes a new question. Sorry.

I have noticed in quite a few posts lately, a disenchantment with R8s, even though that seems to be the "industry standard". Is there an emerging concensus on a better one, or does each machinist have his own favorite?

"Big and sturdy" is also a recurring theme. I'm kinda leaning towards possibly Cincinnati or Gorton. They seem to be pretty price competitive with Budahport machines.

As to feedback, it would seem logical that the more direct and the closer to the tool, the better--true? Would that mean that the DRO is the preferable source? [I suspect many machines would have DROs before conversion?]

Are there "kits" for conversion, or is each case a "roll your own?"

Thanks again for your "feedback".

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--Bob

Gorton NC mill converted to manual to be converted to CNC.

MOST cnc machines (designed as such) have some sort of quick change holder that allows you to change tools without having to reset origins. go with what you can afford and fits the machine.

Which Cinci? Don't know much about Gorton except name.

Feedback - no, not correct. Glass scales are best because they feedback actual tool / table motion. My CNC here at home has encoders on lead screws, and for what I want, it is just fine. In a more industrial environment, with larger motion and bigger loads, I would go scales.

If ways are worn, and being 'away' from the tool is an issue, you should not be using the machine.

I always roll my own, and tend toward industrial controllers (FAGOR is my cost-effective favorite), but there are lots of windows / PC based systems out there.

I would PERSONALLY stay away from any that actually USES Windows to control the motion. Windows for an interface is fine, but actually controlling the motion - no thanks.

The Gekko systems seem quite popular.

I meant no DRO feedback. Most stepper/servo motors will have encoders or similar means of feedback, but some just run on blind faith. I agree that absolute linear positional feedback is the best, but it did not seem all that common for home retrofits...

I've read about folks trying to use a standalone DRO for feedback, and it does not work well enough because the communication from the DRO to the controller is too slow. In my limited observations, position is typically displayed within the control software, however it is received.

My long term CNC plan (dream) would be to keep a DRO on the machine, but intercept the position from the linear encoders before they go to the DRO (thinking that would just make manual operation easier).



As always, the sky is the limit...and that would be lesson #1 - open your wallet. I was looking at complete CNC conversion kits for a table-top mill and they price around 4 grand, using servo motors.

I guess the Grizzly machines are too small for your interest.

_________________
Standards are so important that everyone must have their own...
Logan 10x24 Lathe, RF-30 Mill, 20 Ton Press
Disclaimer: I'm just a guy with a few machines...

why no DRO feedback?

There is no reason why you cannot have a scale connected to a DRO while the CNC runs.

I admit, it is silly since the machine controller tells you where the machine is, but nothing excludes it.

Mostly because of Post #5
http://www.cnczone.com/forums/benchtop_ ... er_sw.html



It might be. I was considering using the machine with the controller off. I had also considered a much simpler CNC system with a small microcomputer without a display at all. The DRO would provide position and a hand controller would allow machine driven control. Programs could be loaded as one-off programs and executed from the microcomputer - the microcomputer would be interfaced with another PC system that would host the design software, converted to a machine control program, and uploaded to the micro... I thought I could hack into and use the existing power feeds for the drive motors, but that idea seems too arcane and fundamentally flawed. It seemed good on paper - I mean a micro would replace the human behind the knobs, and the micro does not err and thinks much quicker...

_________________
Standards are so important that everyone must have their own...
Logan 10x24 Lathe, RF-30 Mill, 20 Ton Press
Disclaimer: I'm just a guy with a few machines...

you can always MDI in linear motion, at a feed rate and you basically have a motor driven single axis machine at a known, solid feed rate.

This is easy on the FAGOR controls - which is one reason why I use them.

MDI?

_________________
Standards are so important that everyone must have their own...
Logan 10x24 Lathe, RF-30 Mill, 20 Ton Press
Disclaimer: I'm just a guy with a few machines...