Pm-940m-cnc (pre-assembled)

[TomS]

Hi Tom,

My machine is using the nMotion board as the control board. I believe this came in the newer versions of the PM-940-CNC.

I have no experience with the nMotion board but let's see if we can make it work. Here's a few suggestions that you can try. Keep track of the changes you make so you can revert back to the original configuration if necessary.

1. On the nMotion Status and Config screen lower left corner there are check boxes for homing switches. Put a check in the X, Y and Z boxes and see what happens.

2. In Mach3 configuration Inputs screen change the Port# to Port 1.

3. Your limit and home switches are connected to Pins 1 thru 6 on your controller. Mach 3 recognizes pins 10 thru 13 and pin 15 as inputs. It appears your switches are not wired in series so you don't have enough input pins available for all your switches. You can wire them in series then connect them to two of your input pins (one pin for limits and one for homing), then change Mach3 configuration to reflect the pin numbers you are using.

Let me know how this works out.

 

[TomS]

Anything to report?

 

[qualitymachinetools]

Thank you so much for the replies Tom, hopefully that will get him going! I really need to get a machine set up again so I keep up on them like you guys do, I rarely get to run anything anymore.

 

[TomS]

Thank you so much for the replies Tom, hopefully that will get him going! I really need to get a machine set up again so I keep up on them like you guys do, I rarely get to run anything anymore.

My pleasure. It's my way of giving back to this forum.

 

[chocadile]

Hi Tom,

Sorry I went dark for a little while, I've had other things occupying my time here at work. We are a small shop and the Mill has been a side project for us. I am now getting some more time to focus on the Mill set up. Thank you for the input it's greatly appreciated. My responses are under you suggestions.

I have no experience with the nMotion board but let's see if we can make it work. Here's a few suggestions that you can try. Keep track of the changes you make so you can revert back to the original configuration if necessary.

1. On the nMotion Status and Config screen lower left corner there are check boxes for homing switches. Put a check in the X, Y and Z boxes and see what happens.

When I attempt to check those boxes in the configuration screen, The check will appear when I click the box. Then quickly the check will disappear. The boxes will not remain checked.

2. In Mach3 configuration Inputs screen change the Port# to Port 1.

I gave this a try, when changing my Port# to Port1 my limit and home switches do not work at all. In the diagnostics screen the light will no longer come on when the switches are being actuated. I did this for only the home switches Returning the Port# to Port2 show all switches lighting up in the diagnostics screen when actuated.

3. Your limit and home switches are connected to Pins 1 thru 6 on your controller. Mach 3 recognizes pins 10 thru 13 and pin 15 as inputs. It appears your switches are not wired in series so you don't have enough input pins available for all your switches. You can wire them in series then connect them to two of your input pins (one pin for limits and one for homing), then change Mach3 configuration to reflect the pin numbers you are using.

Re-wiring the switches is definitely intimidating for me. Not something I've done before but, willing to give it a try. My only concern is from what I've read on the forum, it seems other users have had success without having to rewire the home/limit switches. My other concern is modifying the machine and doing something that can't be reversed. I guess returning the switches to the current set up shouldn't be to difficult if wiring them in series doesn't pan out?

Let me know how this works out.

Thanks again Tom

 

[TomS]

Hi Tom,

Sorry I went dark for a little while, I've had other things occupying my time here at work. We are a small shop and the Mill has been a side project for us. I am now getting some more time to focus on the Mill set up. Thank you for the input it's greatly appreciated. My responses are under you suggestions.



Thanks again Tom

I've read what I could find on this forum and it appears your switch wiring is correct. Without a manual it's hard for me to understand what's causing your problems and searching the net there is virtually no information out there. So at this point I'm at a loss. You may want to PM these two other PM-940 CNC owners PhazerTwo and cut2cut and get a dialogue going with them. They appear to have worked through some of the problems you are facing.

Probably not what you want to hear but many others have replaced their nmotion controller with a more mainstream controller. I have a PM-932 that I converted and recently changed out my electronics with a PMDX-126 breakout board, a Warp 9 ethernet smoothstepper and PMDX-107 spindle control board. This setup work flawlessly.

 

[Skookum]

I've been trying to figure out the 940m cnc and it's been strange. The steppers are getting VERY hot after only ~20 minutes running. I checked the stepper drivers and they're set to 10000 steps per revolution, but I only get accurate movement when I set mach3 to 8000 steps.

Also, loading gcode that contains arcs (G02, G03) results in incorrect shapes being drawn and cut.

I feel like I should be blaming the nmotion controller, but if anyone has some tips, I'd really appreciate it.

 

[phazertwo]

I've been trying to figure out the 940m cnc and it's been strange. The steppers are getting VERY hot after only ~20 minutes running. I checked the stepper drivers and they're set to 10000 steps per revolution, but I only get accurate movement when I set mach3 to 8000 steps.

Also, loading gcode that contains arcs (G02, G03) results in incorrect shapes being drawn and cut.

I feel like I should be blaming the nmotion controller, but if anyone has some tips, I'd really appreciate it.

First question: When was your machine received, and can you post a pic from inside the cabinet? I know there has been some changes and we have seen these changes even in machines that were all received in 2017. Not a bad thing, they're just making improvements.

Mine, and from what I remember others with 940 CNC's as well, came setup for 8000 steps/rev. I would assume that you have DM860H drives, so your dip switches should be set like this for 8k steps/rev.

Hope this helps.

If you have any video or pics of the machine making the "incorrect shapes" that would be helpful. My gut says that you are missing steps but who knows.

Also what CAM software are you using, and what post processor?

PZ

 

[Skookum]

First question: When was your machine received, and can you post a pic from inside the cabinet? I know there has been some changes and we have seen these changes even in machines that were all received in 2017. Not a bad thing, they're just making improvements.

Mine, and from what I remember others with 940 CNC's as well, came setup for 8000 steps/rev. I would assume that you have DM860H drives, so your dip switches should be set like this for 8k steps/rev.

Hope this helps.

If you have any video or pics of the machine making the "incorrect shapes" that would be helpful. My gut says that you are missing steps but who knows.

Also what CAM software are you using, and what post processor?

PZ

Got it late 2017, maybe November or December. The spindle also seems to be underpowered compared to an older version of the 940 that a colleague has.

Using Vectric Aspire, and so far the only post-processor that works there is 'Plain G-Code', trying to use 'Mach 2/3 Arcs' results in incorrect curves.

Spent all day today messing with steps, got it moving nicely now, but I bet there still will be the problem with arcs.

For reference, I set the drivers to 20,000 pulses/rev and I think Mach3 is set to 100,000 steps per unit.
I also lowered the amperage.

After a 90 minute job, the steppers only reached a max temp of about 65C, compared to 80C after 20 minutes.

I'll post more tomorrow and some pictures of the errors I see.

 

[phazertwo]

20k steps/rev is A LOT! My drives are set to 1600 and 2000 would be the max that I would go. At 2000 steps/rev, each step is 0.0001" linear movement of the table. At 20k steps/rev your table is moving 0.00001" per step.... or one, one-hundred-thousands of an inch... Which is an insane number, especially considering the run out on the spindle bearings is only rated at like 0.0015" or 150 x larger than your step distance.

Also, just to run 100IPM your going to need 166khz/axis. I can't imagine that the nMotion/M3 handles that well. I would try bumping it down to 2k steps/rev and give it a shot, that essentially reduces the load on the nMotion/M3 by 10. Also, stepper motors get hot, I have never measured mine so I don't know how hot they get, but they feel toasty. Due to the nature of a stepper, heating will always be an issue.

Is there a reason you are not using Fusion 360 for CAM?

PZ