Wanting To Go Cnc

D

DvCnewt

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Sep 16, 2015
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Hey guys,

New member here and I have a few questions.
I would like to get a small cnc mill for at home but not sure which route I should go. I don't want something big like a knee mill right now. Looking at something that is turnkey or try to retrofit. I think I would enjoy the challenge of doing it myself but I currently don't have any machines at home besides a small drill press.
What machines would be useful to do a conversion? Thinking along with the mill, a rotary table would also come in handy? A lathe?
Looking to keep cost no more than $10k if possible.

David
 
What do you want to do with the mill?

For turnkey the Tormach mills are popular and have good reputation and support.

Several of us here have done conversions. You can look at the SX3 size mills or the larger RF45 clone mills. Look in the "Build Logs" for several of those conversions. Lots of good information.

I converted a PM932 (RF45 clone). I used the mill manually to make the parts for the conversion. It does require tearing down parts of the mill to get measurements and then reassembling to make the parts. Depending on how the motors are mounted a lathe might be handy but not totally necessary.

I have about $6K into my stepper based mill including semi-enclosure, flood & mist coolant systems, one-shot oiler system, power drawbar and belt drive with computer controlled variable speed.

Jay
 
The mill would be used for aluminum most of the time.

I have looked at the Tormach mills, but the cost seems to go over my budget.

Looking at the PM-940M because of the extra travel, which I think would be nice to have. The problem I have is worried about trying to move and set it up due to the weight. I guess would need a crane / hoist of some sort.

Did you need a rotary table for the mill? Seem like would need something to make larger dia. hole cutouts.

Will check out some of the build threads. Thanks

David
 
I have a 6" rotary table that I have probably used a dozen times in the last 8 years. I did not use it for the mill conversion. Currently it is slated to become a 4th axis for the cnc mill. The largest hole I had to bore for the mill conversion was roughed out with a hole saw and finished with a boring head.

Jay
 
I think I have used my rotary table twice in the last 8 years. It's one of those nice to have things, and one of those things that you need when you need it. I have two, an 8 inch and a 6 inch, one of which will become the 4th axis on my mill when I get to it.

As far as a CNC goes, doing a retrofit on any mill can be a lot of fun. Your budget is realistic, so you can look at a reasonably heavy machine. Also look at the used machines available, many times you can get a good CNC machine with a bad controller for a pretty good price. Doing a controls retrofit is the easy part. Shouldn't take more than a week or so to be up and running.
 
I use my rotary table a lot. Wouldn't want to be without one. Just got a spin indexer that will be used a lot as well.
Dave
 
That's good to know that a rotary table would not be necessary. I like the idea about using hole saw and then finish boring.
Don't want to buy something that wouldn't need after mill was converted, unless planning to add 4th axis as suggested.

David
 
I'd look at a retrofit of a PM-940 with hardened ways, a PM-45 CNC, or the Tormach PCNC440/770/1100. You could also get a G0704 and retrofit it with Hoss's plans or buy a retrofit kit and ballscrews off eBay.

For the CNC conversion, you will likely need large drill bits for starting the bores for the ballscrew holes and bearing pockets. I would get a used Criterion boring head (2 inch) off of eBay versus a new imported head of the same price (I have a Shar's boring head and will be replacing it).

For a conversion project, most of the work involved is the continuing cycle of disassembly, measurements, and reassembly of the machine. I made models in CAD and 3D printed several iterations of parts to test fit and compare dimensions. It has been a huge learning process and I am much more comfortable in machine design as a result. My current machine conversion should be wrapping up this week.

You don't have a working envelope described, so this will help determine what other suggestions we can provide.
 
I don't have a specific item in mind to make on the mill. But I do know you can never have enough travel.

I was looking at the Charter Oak 12z originally, but I have since checked with Precision Matthews, and Matt has recommended the PM-940 w/ hardened ways if going to retrofit.
He also says that the mill can be purchased already CNC like the PM-45. I am seriously considering going this route. Now to decide if I want the 4th axis option.
 
The 940 came out soon after I got my PM-932 (since converted to CNC). Had I known I would have waited and got the 940. Not complaining as the PM-932 is a nice machine and does everything I'v asked it to do.

Tom S
 
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