# Wanting To Go Cnc



## DvCnewt (Sep 18, 2015)

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


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## jbolt (Sep 18, 2015)

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


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## DvCnewt (Sep 19, 2015)

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


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## jbolt (Sep 19, 2015)

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


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## JimDawson (Sep 19, 2015)

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.


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## dave2176 (Sep 20, 2015)

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


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## DvCnewt (Sep 20, 2015)

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


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## compsurge (Sep 27, 2015)

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.


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## DvCnewt (Sep 28, 2015)

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.


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## TomS (Sep 28, 2015)

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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## compsurge (Sep 28, 2015)

The PM-45 CNC has a hardened ways option as well. There are a few members on this forum that have one and seem to be pretty pleased with it.

http://www.hobby-machinist.com/threads/pm45-cnc-owners.21107/
http://www.hobby-machinist.com/threads/pm-45m-cnc-setup-and-configuration-with-mach3.21179/


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## Flammable_Solid (Sep 28, 2015)

I am looking at a Taig unit that is ready to go to learn CNC on.  A lot less than a Tormach and less confusing than a conversion and doesn't require you to already have other machines to build parts for the retrofit.


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## Former Member - WoodNDust (Sep 28, 2015)

DvCnewt said:


> 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.



I too am looking at getting a mill to convert to CNC.   Where on the PM site can I find the PM-940 CNC version?


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## DvCnewt (Sep 28, 2015)

The PM-940 CNC is not on the website, but is suppose to have all the same options that are available on the PM-45.

I just put a deposit down to hold one for me today!


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## compsurge (Sep 28, 2015)

Flammable_Solid said:


> I am looking at a Taig unit that is ready to go to learn CNC on.  A lot less than a Tormach and less confusing than a conversion and doesn't require you to already have other machines to build parts for the retrofit.



If the Taig suits your needs and you are aware of its limitations, it is a great little machine.

I regularly use a Taig and find it does a great job on small parts. If it was my money, I would put  towards a larger, more capable machine because the parts I use it for (high school robotics team) run into the maximum work envelope and horsepower limitation fairly often. For the money, you could potentially be well into a G0704 purchase and most - if not all - of the conversion parts.




DvCnewt said:


> The PM-940 CNC is not on the website, but is suppose to have all the same options that are available on the PM-45.
> 
> I just put a deposit down to hold one for me today!



Excellent! I somehow misread your post as "there is also the PM-45" instead of "there is a PM-940 CNC."

Can't wait for pics! Do you know if it is set up for anti-backlash double ball nuts?


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## DvCnewt (Oct 1, 2015)

Don't know if it is set up for anti-backlash double ball nuts. 

Will be sure to take pics when it arrives.  Check going out tomorrow.


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## markba633csi (Oct 3, 2015)

I was also looking at a Taig since it is very low cost and can do (apparently) some serious cutting. It's not a Deckel but for an introduction to CNC it looks like a great starter machine.  It has an alloy table, not steel or cast iron, with steel gib strips underneath.  I think the head is alloy too, that's how they reach such a low price point.
Mark S.


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## compsurge (Oct 3, 2015)

markba633csi said:


> I was also looking at a Taig since it is very low cost and can do (apparently) some serious cutting. It's not a Deckel but for an introduction to CNC it looks like a great starter machine.  It has an alloy table, not steel or cast iron, with steel gib strips underneath.  I think the head is alloy too, that's how they reach such a low price point.
> Mark S.



I think the Taig-provided 1/4HP motor is the limiting factor. I've taken some cuts that the machine seemed mechanically able to perform, but the motor just didn't have enough power to carry out the cut. I plan on upgrading the motor with a newly acquired DC treadmill motor. I don't know what your definition of serious cutting is, but it will handle plastics at max RPM and max feed rate with a 1/4" end mill with at least a 1/8" depth of cut. Aluminum is entirely different in my experience, but I think it should be capable of some intermediate cuts at a decent feed rate (with 2D adaptive clearing, I would expect 8-12 IPM at 1/8" DoC at 6500rpm with a 1/4" carbide ZrN coated 3-flute end mill/ or whatever recipe equates to about 0.001" chipload per tooth).

The Taig is basically built with a body made of steel tubing. The spindle housing is aluminum, as is the table. The box ways are steel and the gibs are brass. The saddle appears to be cast and machined - I think it is aluminum. On the Z-axis, the head is mounted to an aluminum mount that rides on a precision ground plate.

The mill I use has a TB6560 3-axis eBay board. It works ok, but it would not be my first choice and the modifications that are on CNC-Zone are good to do. You will want to install limit switches and an E-stop. When you do your motor selection, get a large (>230 oz-in) Z-axis motor if possible. I do not like how the Taig spindle motor is controlled by a light switch. It should be controlled by the host software via the control board and a solid state relay at the very least. This is a simple modification to do and can be performed with the TB6560 eBay board.


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