If you were to get a mill and convert it to CNC, what would you get?

[kb58]

Buy one as close to the desired end result as you can. Broken is okay, but if it's already CNC, that makes it Much easier to get it running fairly quickly and inexpensively - as these things go.

[automatedingenuities]

You have had some good responses here but I was in that same boat, trying to decide which machine to purchase. I took the route of buying a PM940 and am slowly converting it to CNC, with linear rails on the X axis, Y and Z maybe to come in the future.

One of the biggest reasons I didn't go with a scrapped CNC is spindle HP. My electrical requirements required me to have a spindle HP 3HP and lower. Most of these machines that are scrapped are 10,15, 30 HP machines, often requiring 3 phase power etc. Sure you can change the spindle motor to something smaller but then you may not have the power to drive an endmill at 250ipm into steel. Yes you will likely have more rigidity with a premade CNC, but still taking the lighter cuts due to spindle power.

Of course amongst all things it's what are you looking to get out of it. If your intent is to mill an 8 inch cube for return on investment purposes then your focus should be on getting the tooling to mill the 8 inch cube not making the machine to do it. On the flip side if you want to test your engineering skills and design and make your vision come to reality, go with a manual milling machine, add linear rails, bt30 3 HP spindle, auto lubrication, coolant and wash down, full enclosure, custom atc, etc, and once all that is done, then your fork out your services to get the money you put in back.

Just my two cents...

[EastMemphis]

@automatedingenuities - Thanks for the information on that. Have you converted a PM940 to CNC? I have the same restriction on power. Single phase 220. I'm not looking to become a milling shop. I build custom auto parts and accessories for exotic cars (and other things) so my volume is low and my margins are high.

[automatedingenuities]

@automatedingenuities - Thanks for the information on that. Have you converted a PM940 to CNC? I have the same restriction on power. Single phase 220. I'm not looking to become a milling shop. I build custom auto parts and accessories for exotic cars (and other things) so my volume is low and my margins are high.

I'm slowly working on my conversion. Doing a few changes from a buy a ballscrew kit and replace leadscrew with ballscrews type conversion.

I have bought linear rails for my X axis and plan to invert the mill table and bolt it down to my Y axis so that the mill table only moves front to back. I will mill off the dovetails (which will be facing up) and install linear rails. I'll then attach a new t slot plate to the linear rails. This should increase rigidity of the machine and give it a more traditional VMC look and feel.

I also have welded a new head together from 1" steel and bought a 3hp 8000rpm BT30 spindle with pneumatic drawbar release so I can replace the old gear driven head.

Closed loop steppers on all 3 axis and the Z will have a closed loop steppers with brake. Everything will be controlled by centroid acorn of course.

I've attached a picture.

I think in your case building a CNC machine would be fun if you want the challenge, but you already have a market so buying a machine could be worth it too.

[EastMemphis]

@automatedingenuities - I'm looking for less of a challenge and more of a bolt together. I see on the PM website that a third party offers a complete kit including clearpath drives for the PM940. Cost wise, the PM940 and the kit together are in the sweet spot of my budget.

I appreciate sending me down this path. It looks very promissing.

[kb58]

If/when I do a manual mill-to-CNC conversion, I'll retain the knobs and handles so that quick one-off jobs can still be performed. Many conversion kits I see do away with the handle which is a no-go-in my mind, detracting from versatility and flexibility.

[automatedingenuities]

@automatedingenuities - I'm looking for less of a challenge and more of a bolt together. I see on the PM website that a third party offers a complete kit including clearpath drives for the PM940. Cost wise, the PM940 and the kit together are in the sweet spot of my budget.

I appreciate sending me down this path. It looks very promissing.

Yes ArizonaCNC kits. That's the kit I have for the PM940. It is a really high quality kit.

Your going to have to compromise some things if you go with a complete bolt together kit. As others mentioned, rigidity, speed, depth of cut, enclosure etc are things you may have to sacrifice, but overall you will be able to accomplish your goal.

[automatedingenuities]

If/when I do a manual mill-to-CNC conversion, I'll retain the knobs and handles so that quick one-off jobs can still be performed. Many conversion kits I see do away with the handle which is a no-go-in my mind, detracting from versatility and flexibility.

That often makes things difficult. You may have to use linear encoders so the motors can track the positions, and you would have to disengage the motors to move the machines manually. Some steppers motors have dual shafts so you can drive the motors with a handwheel, but the motor would still be required to be disengaged and unless the motors have built in encoders you will have to add some.

What alot of people do instead is they use conversational programming or use a pendant. You can think of CNC like power feeds on all axis of a milling machine, the CNC ability makes it much easier and accurate, plus you effectively have the DRO for the positions.

In my opinion it would be worth it to learn conversational programming for the simple jobs or use a pendant or even learn a bit of gcode so you can make the machine do what you want versus keeping the hand and jog wheels.

[EastMemphis]

@automatedingenuities - I'm going to look deeper into the ArizonaCNC system and the PM 940. That looks to be good for me. I'm an engineer, not a machinist so no manual handles will be just fine.

The pendant is a great addition. I went for 10+ years without one on my CNC and the day I got it, I thought "What the heck have I been doing all these years?" Great tool to add to the arsenal.

[tblough]

That often makes things difficult. You may have to use linear encoders so the motors can track the positions, and you would have to disengage the motors to move the machines manually. Some steppers motors have dual shafts so you can drive the motors with a handwheel, but the motor would still be required to be disengaged and unless the motors have built in encoders you will have to add some.

What alot of people do instead is they use conversational programming or use a pendant. You can think of CNC like power feeds on all axis of a milling machine, the CNC ability makes it much easier and accurate, plus you effectively have the DRO for the positions.

In my opinion it would be worth it to learn conversational programming for the simple jobs or use a pendant or even learn a bit of gcode so you can make the machine do what you want versus keeping the hand and jog wheels.

This is easily handled with an AllIn1DC or Oak and servos - no additional encoders needed. Just push a button on the operator interface to disable the motors and you can crank the handles all you want with the same manual feedback of the original machine.

While I agree that everyone should learn G-Code and Intercon, MANY things are much faster with manual operations. I challenge anyone to face off a saw cut end on a piece of stock using g-Code, Intercon, or pendant faster than I can do it using the handwheels on my machine.