New PM-940V

Hi,

I have one of the last PM 940M CNC machines that I think PM sold. I purchased it around the fall of 2017. I live in Pittsburgh, PA and so have been to PM facility several times. So, if you have questions about how my machine is constructed maybe I can help. I might even has some thoughts on things not to do! One of my findings is that with the motor, housing, gears, oil, etc the head is too heavy for the stepper to hold when powered down. I figure it weights in at about 250#s or so. So the Z-axis stepper needs to be bigger than is actually required to move the assembly up and down. I think this is really due to the fact that the Z-axis lead screw is too long for the mountings that it uses. Maybe your belt drive system will not be so heavy! Since you have it all apart maybe you could just weight the parts and let me know how heavy it is?

It came with some version of n-motion controller and code for a Mach3 setup. It has worked fine for me, but I know a some folks are frustrated by not having decent documentation on the Chinese n-motion. Earlier I posted the owners manual, which contains some circuits including the spindle motor control. It has a Delta VFD which seems to be decent and pretty standard. Attached is a photo of the spindle motor. Similar to yours. I will say the cooling fan is pretty loud!
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Dave
 
Hi B2, Yes, the motor looks similar. I haven't run it yet but may hook it up on the floor just to see how it runs. I'll try to weigh some of the parts while it is still apart.

I finally got it all apart, including the Z lead screw. I decided to paint it so I started to strip everything. Fortunately, there is not much painted area. They used more bondo than I expected. The column has pretty much a full skim coat of bondo over the entire surfaces. The Z axis saddle has up to 1/16" in some places to fair it out. When I get it all stripped, I'll decide how much I will put back on. They must have a full team of bondo guys in the factory.
 
So looks like it is a vector motor based on the nameplate, i.e. 2-200 Hz motor rating. It would appear the base speed on the motor is 50 Hz based on the r/min of 1390. I use a timer on my blower so it shuts off, with a TENV motor it is not an issue. As far as the bondo......
lipstick_on_a_pig_1.jpg
 
Hi P
Yes, Bondo everywhere. You are also going to find that the castings are not great material. The steel is very porous. I found that when I went to drill and tap the column that the casting just sort of broke down into sand. Not a nice clean hole at all. You'll not find any thing like a steel cut, chips nor pigtail cuttings. Just sandy particles. So if you want to tap into it I suggest you use an undersized drill for the tap. You can do it successfully but you need to take care. I took my very large CNC electronics cabinet off of the back of the column and made new holes on the side of the column and in the steel cabinet and mounted it by the side so that I could open the doors from the front.

mksj, Love that PIG!
Also the picture I posted is of my 940M motor not P's motor. His photo was of the fan motor part so I do not know if his motor is exactly the same as mine. Mine does not have a separate motor lable for the fan part. I would have to go back and look, but I do not think the fan motor was running on 3 phase. I have never found the spindle motor to get all that hot unless I am running it under a heavy cutting load for a long time. Then it does get hot even with the fan on. I could probably put the fan on a small mechanical thermal switch but have just never bothered to do so.

Dave
 
I am moving along on the CNC conversion for my PM-940V. As I stated above, I divided to refinish the mill while I had it apart. While I think it will look good when I am done, I am not sure it is worth it. It is taking quite a bit of effort to do this. In order to get a decent finish on the cast iron parts, the factory puts a skim coat of body putty over the entire thing, in some places almost 1/8" thick. To do this right, I had to remove and redo the skim coat prior to painting. Th following pictures show the raw base casting with the body putty removed.

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And the column before and after painting.

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I should have the ArizonaCNC conversion kit in about 2 weeks and I can start to put it back together.

I have also been working on the control system with a Centroid Acorn CNC board and should have that done about the same time.
 
It's looking great. Keep posting please.
 
davidpbest said:
It's looking great. Keep posting please.
Click to expand...

I blame you for all the extra work I am doing to repaint the mill :) Looking at all your beautiful repainting work on your mill and lathe got me into this. Joking of course, but if it comes out anywhere as nice as yours I'll be happy.
 
I'm moving along with my CNC conversion. I have most of the mill repainted and ready to put back together when I receive the conversion kit. In the meantime I have almost completed the new CNC control system based on a Centroid Acorn board. So far I have the Acorn controlling the VFD for spindle speed and direction at least as far as I can tell without the motor hooked up. Next step is to hook up a servo and see how that goes. This is how it looks so far.

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Next step is to put the panel in the enclosure and work out all the cable connections.
 
That is so awesome! Keeping an eye on this. Do you have pictures of the mill after the paint?
 
A little more progress. This is how the control board looks inside the enclosure. My biggest issue right now is figuring out where to mount the enclosure. It weighs around 78 lbs so it needs a fairly sturdy mounting location. The original enclosure was mounted on the back of the mill column but that requires too much space behind the mill so the door can open. It will probably have to go beside the base somehow.

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All the cables going to control board including the control panel, drive cables, limit switches , etc. will have Molex connectors mounted on panels on the side of the enclosure. The Clearpath drives use Molex connectors to I just stuck with them for everything else. If I change something and need new holes, I can replace the panel and not end up with extra hole in the enclosure. I will have these panels cut and labeled by Front Panel Express and will install as shown here:

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,
 
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