[4]

My PM-940 CNC Modifications

[3]
[10] Like what you see?
Click here to donate to this forum and upgrade your account!

cut2cut

H-M Supporter - Silver Member
H-M Supporter - Silver Member ($10)
Joined
Dec 21, 2016
Messages
194
Likes
30
#1
I've been slowly making modifications to my turnkey Precision Mathews PM 940 CNC mill with the Variable speed motor option since it arrived in January 2017

So far I don't have a lot of time testing the changes I've made, so I can't say for certain if they are wise or not, but a number of people have been asking about various things so I thought I'd start a separate thread rather than Hijack the other one.

Ok, so here she goes with just the bare facts which I'll outline in further detail later on and update this post as more things are changed out or modified.

1 ) Spindle, drive train and Motor "upgrade"
Removed Spindle Gear Box completely
Replaced with Belt and Pulley
Replaced Spindle Motor ( has encoder built in )
Requires Better spindle bearings

2 ) Control hardware and software
Removed the nMotion USB controller
Replaced with the Mesa 7i76E ( E stands for Ethernet ) controller
Replaced Mach 3 with Linux CNC control software ( required with Mesa controller )

Future :
3 ) "Power" Drawbar

4 ) Servo motors

5 ) Enclosure

6 ) Other cool stuff, hopefully ! lol

Each section will have a parts list and links to where I got them.

Cheers,

Jake
 

cut2cut

H-M Supporter - Silver Member
H-M Supporter - Silver Member ($10)
Joined
Dec 21, 2016
Messages
194
Likes
30
#2
Part 1 ) Spindle , Gear train and Motor "upgrade"

I used quotes around the word "upgrade" because I have yet know if its an vertical move, or lateral ! :)

For instance, the Motor probably doesn't produce more HP but it appears to be better quality and also has an encoder for better speed control with an appropriate VFD. Depending on the speed control ( VFD ) the encoder can be used as feedback for the VFD to help maintain speed more consistently, and also should maintain better torque. I believe the Delta VFD-E that comes with the PM940 CNC VS has this capability with an optional card, but I am not sure. I also bought , but have yet to use, a Durapulse VFD with a feedback card. So far, its collecting dust due to time constraints mostly. The Delta seems to be working pretty well after someone on this forum suggested settings that match this particular motor better than the default settings that the VFD comes with.

april 15 2017 edit
[ So, I should go into more detail about the spindle bearing upgrade. You need a large press to remove the spindle bearings and put it all back together with the new AC bearings, Also, you need a bearing puller to remove the standard bearing race(s) (this is a tricky step because there isn't much lip for the puller to access).
The AC bearings do not have a separate bearing race like the standard bearings, so when you assemble it, it has to be pressed into each part in a logical order or it will put stress / harm the new ball bearing and/or races. The upper bearing on the inner bearing surface (of the spindle itself) can either be cooled and the bearing warmed to allow the bearing to be seated, OR you can do what I did which was create a slip fit for the inside of the upper bearing by turning the spindle on a lathe with a bit of sandpaper to buff it down a small amount. The problem with this approach is you could introduce some runout by creating too much of a slip fit. Also if you aren't consistent you may make your spindle "seat" out of round. My greatest worry is that I'd take too much off and certainly this would result in increased runout. Even a slight amount of heat (created by the sanding process) would throw off the measurement and could cause you to keep sanding due to heat expansion. If I were to do it again I'd have some way to cool the spindle after each session of sanding it ( with 1000 grit sandpaper and slightly warm the bearing before testing bearing fit after each attempt at sanding more off. Its a bit tedious but worth the extra concern, imho. ]

There is more detail needed and I will add more detail but don't have time right now. ZZZZ... sleep is calling me. However I am providing a parts list for those that just don't care about details and live dangerously :) Note that items with double asterisk ( ** ) need and will get more detail.

Here is the motor I used:
http://dealerselectric.com/145THTR15540.asp

The AC bearings for the spindle :
qty 1 - VXB Brand 7207C P5 High Precision Angular Contact Bearing 35x72x17 ABEC-5
qty 1 -VXB Brand 7206C-P5 7206C P5 High Precision Angular Contact Bearing 30x62x16 ABEC-5

Pulley ( 2 to one ratio )
**qty 1 : 5.6 inch 10 groove J - Profile pulley
http://www.ebay.com/itm/291936349578?ul_noapp=true
( requires some of the head case to be modified for this pulley to fit inside the gearbox cavity )
** Taper bushing not listed yet... it depends on your motor shaft size ...)
** 2.8 inch 12 groove J profile PULLEY
http://www.ametric.com/p-18443-12j281108.aspx

** taper bushing for 2.8 inch pulley for 28mm spindle ID
http://www.ametric.com/p-13391-110828.aspx
( requires some thin shim as spindle OD is slightly less than 28mm )
( requires a key to be fabricated to go in spindle grooves so Pulley isn't only a friction fit )

** Ametric brand BELT -10 ribs Micro V J groove
http://www.ametric.com/p-30298-260j10.aspx
( the Ametric belt is what I used, but I believe an 8 groove GoodYear brand one is better after some people on this forum suggested the good year brand over Gates, which I think is what Ametric sells, possibly ) McMaster Carr has GoodYear brand :
** 9003K89 Ultra-Flexible J-Section V-Belt 8 Bands, Trade Size 260J8, 26.3" Outer Circle
( could be a bit bigger than the Ametric one... hard to say if its too large. I have one coming so I'll be able to try it and update this )

Cheers,
Jake

note, the motor mount plate is just temporary, something sexy will be made when I decide on how to configure a double pulley arrangement.
IMG_1881.jpg
 

rodjava

Registered
Registered
Joined
Jan 25, 2017
Messages
37
Likes
21
#3
Jake,
For servos, check out DMM Technology at http://www.dmm-tech.com/

This a true plug and play, complete servo system and the pricing is not bad.

I have the 4 axis AC servos on my cnc router and they setup and work perfectly.
You can ask and read more at cnczone.com.

Btw, thank you for sharing your upgrades. I might do the same in the future.


Rod
 

cut2cut

H-M Supporter - Silver Member
H-M Supporter - Silver Member ($10)
Joined
Dec 21, 2016
Messages
194
Likes
30
#4
Jake,
For servos, check out DMM Technology at http://www.dmm-tech.com/

This a true plug and play, complete servo system and the pricing is not bad.

I have the 4 axis AC servos on my cnc router and they setup and work perfectly.
You can ask and read more at cnczone.com.

Btw, thank you for sharing your upgrades. I might do the same in the future.


Rod
Hey Rod,
I am considering the Clearpath servos but I'll check these out too. Thanks ! I really really like that my pulley and belt spindle is whisper quiet now... would be cool to have the benefits of a closed loop and also they are whisper quiet too !
And while we are on the subject of quiet, one of the reasons I switched out the motor was the one I got doesn't have a fan at all and doesn't need one either !, so its way more peaceful when the machine is on, but not cutting.
Cheers,
Jake
 

phazertwo

Active Member
Registered
Joined
Dec 31, 2016
Messages
176
Likes
98
#5
Any more updates on this? I'm very interested in the spindle motor setup, mine makes enough noise to drive you nuts while it's running.

PZ
 

pburgh

H-M Supporter - Sustaining Member
H-M Platinum Supporter ($50)
Joined
Dec 14, 2017
Messages
78
Likes
10
#6
Jake,
I just got the PM-940 CNC with the nMotion card. Still getting my feet wet with the original config. I'm going to be switching it to a Centrod Acorn controller. What models of the Clear Path motors are you looking to use for the X, Y and Z axes? Also, what are your plans for the power draw bar? Thanks,
Regards,
Doug
 

megaplow

Still have 10 fingers
Registered
Joined
Dec 14, 2017
Messages
22
Likes
1
#7
2 ) Control hardware and software
Very excited to see how this goes. I would like my whole shop to use the same control technology. If all goes well on your end, I will follow your lead and then do the same to the laser.
 

cut2cut

H-M Supporter - Silver Member
H-M Supporter - Silver Member ($10)
Joined
Dec 21, 2016
Messages
194
Likes
30
#8
I really haven’t done much with the mill as I haven’t had projects in the last 6 months. So I haven’t felt compelled to upgrade to servos or much of anything. Sadly, it appears Linux cnc really has stalled in development as far as I can tell so I can’t say it’s ever going to be plug and play. The best options are probably Masso or it appears the Acorn ? I have no experience with either but they seem to be a decent alternative to Mach 3.

Jake
 

phazertwo

Active Member
Registered
Joined
Dec 31, 2016
Messages
176
Likes
98
#9
Were you able to get Linux CNC running at all? I was actually hoping to start installing it this week and see if I could get it running correctly.

I was assuming that the last release of LinuxCNC (July 2017) was good enough that they didn't need any more tweaking. If it's not cutting the cheese that's a serious bummer. Acorn looks cool, but I liked the idea of open source...

PZ
 

cut2cut

H-M Supporter - Silver Member
H-M Supporter - Silver Member ($10)
Joined
Dec 21, 2016
Messages
194
Likes
30
#10
Were you able to get Linux CNC running at all? I was actually hoping to start installing it this week and see if I could get it running correctly.

I was assuming that the last release of LinuxCNC (July 2017) was good enough that they didn't need any more tweaking. If it's not cutting the cheese that's a serious bummer. Acorn looks cool, but I liked the idea of open source...

PZ
Yes, I have Linux cnc working mostly . It’s just not perfect ( has its own flaws ) and in my experience will be difficult and very time consuming to install the proper version for the controll hardware you need and then to setup. You would need an alternate controller as the nMotion is Mach3 only. This required a fair bit of re-wiring of the control electronics and a very specific install of Linux cnc with the appropriate kernel, etc. This took me quite a lot of energy and left a lot to be desired as open source has a lot of dead ends too. If you like a challenge or have a good Linux background already, you could go with Linux cnc. If you want to use your mill sooner than later, i’d suggest trying a Masso. However, I don’t have a Masso either so it’s tough for me to say that is the best alternative or not. Good luck !
 

phazertwo

Active Member
Registered
Joined
Dec 31, 2016
Messages
176
Likes
98
#11
Hmmmm... I did some looking at the Acorn, which looks like a decent setup, however I want a true real-time system (which it looks like you can do with LinuxCNC). Also the Acorn lacks a 5th axis, which honestly I'll probably never have/use, but I really don't want to limit myself.

I JUST now for the first time googled Masso... Looks like it cost lots o' the monies... but you don't need a PC to go with it and judging by that fact it's likely running real time. And it's 5 axis capable, and I don't have to have an additional PC... Defiantly need to do more research on it (guess I know what I'm doing with my lunch break today...)

I have very little patience for things that are finicky/unreliable and I bought the mill to be able to make parts for other projects not so much to be a project itself. If spending ~$600 on a controller gets me up and running, it will be money well spent... after all I have bulldozer parts that need makin'

PZ
 

megaplow

Still have 10 fingers
Registered
Joined
Dec 14, 2017
Messages
22
Likes
1
#12
I was looking into all in one purpose build systems, like the CNC4940. They look cool, but the price tag... geez!
 

megaplow

Still have 10 fingers
Registered
Joined
Dec 14, 2017
Messages
22
Likes
1
#13
Just ordered my 7I76e... wish me luck!
 

cut2cut

H-M Supporter - Silver Member
H-M Supporter - Silver Member ($10)
Joined
Dec 21, 2016
Messages
194
Likes
30
#14
Last edited:

pburgh

H-M Supporter - Sustaining Member
H-M Platinum Supporter ($50)
Joined
Dec 14, 2017
Messages
78
Likes
10
#15
The Acorn is their entry level controller. They have 2 other DIY cards, and they are pricier. But they will do a lot more. I'm going to start out with the Acorn and move up from there as i want more features. The nice thing is that the Centroid software is the same for all models. So there is no learning curve there. Also, i briefly talked to Matt about the Acorn and he said he liked the Centroid software as he's used it before. Says it's very robust. Guys are starting to post more about the Acorn card and a guy just posted a setup using Lead Shine yesterday. Here's the link:

He has alot of other good videos too.

Here's a good comparison between Clear Path and DMM.

I was leaning towards Clear Path until i watched this video. Sam has some other good videos. He puts a lot of good info into them. After watching this one, i'm leaning towards the DMM solution. Also, the Clear Path folks weren't very helpful when i called. I guess they don't want to waste too much time on one offs. I hope DMM is better.

Too many decisions.... But i decided that i don't want to waste my time learning Mach. I fired up my mill to make sure everything moves and runs the way i expect, but i'm going to switch to the Acorn card for now since i already purchased it. Still trying to decide the best option for a power drawbar.
 

cut2cut

H-M Supporter - Silver Member
H-M Supporter - Silver Member ($10)
Joined
Dec 21, 2016
Messages
194
Likes
30
#16
The Acorn Centroid looks like a great solution. I may get one and convert over as it’s likely going to provide all that I need for $265 + $100 for the pro software. Looks great and shouldn’t be hard to convert over. Only thing that could be tricky is the wiring for the vfd ( controlling direction ) as far as I can tell. Thanks for suggesting it!
Way easier than Going the Linux cnc route.
I suppose the only possible negative is that it’s running windows that theoretically could introduce crashes and maybe timing errors. That’s hopefully not an issue.

Jake
 
Last edited:

phazertwo

Active Member
Registered
Joined
Dec 31, 2016
Messages
176
Likes
98
#17
Acorn does look nice... but it's lacking the real-time that I'm hoping for... and in order to give it linear encoder feedback (which I would really like to do some day) you have to upgrade to one of their higher end controllers which look like they only work with nice servo systems (as in not step and direction).

I really want 3 things in a controller:
  1. Real-time processing (Most of my current problems would be fixed in a real-time system... I think)
  2. Capability of 5 axis (probably never make it to 5 axis but I like to dream big)
  3. Capable of tracking spindle speed, AND having an encoder on each axis
And yeah, cheap would be nice too AND if they can do it in a package like the Masso that doesn't need a PC to go with it :eagerness:

I guess in reality I need to look at my bank account and remind myself that I'm a hobbyist, not a pro...

PZ
 

phazertwo

Active Member
Registered
Joined
Dec 31, 2016
Messages
176
Likes
98
#18
Also, after more lunch reading, I cannot find anywhere that the Acorn accepts a MPG... Am I just missing this?
 

cut2cut

H-M Supporter - Silver Member
H-M Supporter - Silver Member ($10)
Joined
Dec 21, 2016
Messages
194
Likes
30
#19
Yes, currently no MPG it appears however they say TBA for a USB MPG, so maybe there is hope.
Assuming TBA means “ to be announced”
 

phazertwo

Active Member
Registered
Joined
Dec 31, 2016
Messages
176
Likes
98
#20
Yeah, I wonder if it will be compatible with the current board... hopefully just a firmware update and not buy a new board.

Also, looks like the software won't run on my windows 2k pro machine :rolleyes:

PZ
 

cut2cut

H-M Supporter - Silver Member
H-M Supporter - Silver Member ($10)
Joined
Dec 21, 2016
Messages
194
Likes
30
#21
For anyone that is upgrading their PM 940CNC from the supplied nMotion controller ( for Mach3) to the 7176e ( for use with linuxcnc ) here is the wiring schematic that my brother made for me. Its been a bit since i got it up and going, so I don't recall the details but hopefully it is of some help. Assuming the wiring on yours is the same as my PM940CNC that I got January 2017 with the Delta VFD.
Best Regards,
Jake

PastedGraphic-1 2.png
 

phazertwo

Active Member
Registered
Joined
Dec 31, 2016
Messages
176
Likes
98
#22
Been doing a ton of research on different controllers. Stumbled across this as a good solution for no MPG for Centroid Acron:

In all my searching, I think I've come to the conclusion that Centroid Acorn is the way to go. Masso is also a good option and probably easier to setup, but Centroid builds industrial gear... they know exactly what they are doing. Also, I can upgrade my mill computer, buy the card and software for about the same price as the Masso... So the cost is kinda a wash.

PZ
 

cut2cut

H-M Supporter - Silver Member
H-M Supporter - Silver Member ($10)
Joined
Dec 21, 2016
Messages
194
Likes
30
#23
Been doing a ton of research on different controllers. Stumbled across this as a good solution for no MPG for Centroid Acron:

In all my searching, I think I've come to the conclusion that Centroid Acorn is the way to go. Masso is also a good option and probably easier to setup, but Centroid builds industrial gear... they know exactly what they are doing. Also, I can upgrade my mill computer, buy the card and software for about the same price as the Masso... So the cost is kinda a wash.

PZ
Previously you mentioned that the Acorn wasn't realtime vs LinuxCNC. Did you resolve that it wasn't an issue since it has an onboard motion control CPU so it shouldn't incur any loss of "timing" ? I looked around for any comparisons on the subject and couldn't find any, which is why I'm asking. I do think the Acorn looks great and the company has been around the block a few times so they probably are putting out a good well thought out product and at great price point. I think Precision Mathews should consider using this as a controller, IMHO.

Thanks,

Jake
 

pburgh

H-M Supporter - Sustaining Member
H-M Platinum Supporter ($50)
Joined
Dec 14, 2017
Messages
78
Likes
10
#24
Hey Guys, good to hear that your onboard with the Acorn. Hopefully you see this post. If you're going to go this route, you'll want to purchase the board and upgrade to the pro software now before jan 3 2018. They are going to be raising the price of the card and software. There is a post on the Centriod Acorn forum that I read today about it. I'll be posting some info to the forum about the 940 and the setup to be sure that i'm looking to make this change from the nMotion to the Acorn without any issues. So, keep an eye out for it and you'll probably get some questions answered too. Also I found info that they are developing a driver for a wireless MPG they are testing now (might already be good to go). Something I discovered going into this is that i'm going to have to purchase a 5vDC power supply for the LeadShine drives. Looks like the 5vDC is provided by the nMotion now. Well, here we go. I'm going to craft the initial post now. Hopefully this is helpful to everyone.
 

cut2cut

H-M Supporter - Silver Member
H-M Supporter - Silver Member ($10)
Joined
Dec 21, 2016
Messages
194
Likes
30
#25
Hey Guys, good to hear that your onboard with the Acorn. Hopefully you see this post. If you're going to go this route, you'll want to purchase the board and upgrade to the pro software now before jan 3 2018. They are going to be raising the price of the card and software. There is a post on the Centriod Acorn forum that I read today about it. I'll be posting some info to the forum about the 940 and the setup to be sure that i'm looking to make this change from the nMotion to the Acorn without any issues. So, keep an eye out for it and you'll probably get some questions answered too. Also I found info that they are developing a driver for a wireless MPG they are testing now (might already be good to go). Something I discovered going into this is that i'm going to have to purchase a 5vDC power supply for the LeadShine drives. Looks like the 5vDC is provided by the nMotion now. Well, here we go. I'm going to craft the initial post now. Hopefully this is helpful to everyone.
Thanks for the heads up Pburgh!
I'm haven't counted up the number of ins and outs to see if the Acorn has enough for the 940cnc.
Please leave a link here pointing to your post there, so we don't have to hunt for it.
Cheers,

Jake
 

cut2cut

H-M Supporter - Silver Member
H-M Supporter - Silver Member ($10)
Joined
Dec 21, 2016
Messages
194
Likes
30
#27

pburgh

H-M Supporter - Sustaining Member
H-M Platinum Supporter ($50)
Joined
Dec 14, 2017
Messages
78
Likes
10
#28
Thanks Jake, that would be great. I was looking at some posts in the Acorn forum. I searched on Precision Matthews and there is a post in there of a guy who fried his VFD. I don't want to do that, so i'm a little apprehensive. They didn't give me a manual on the VFD and I have to get the info on the one that's in there. Did you get a manual with yours? I'm a little annoyed at the lack of info that came with this unit. Even though they are priced better than most of what's out there it's still a lot of money for something with such poor info. I was looking at a Grizzley unit to try to get an idea on how to connect the coolant pump and I was impressed by how well the documentation was setup. Do you know if the nMotion card provides 5vDC? I didn't see anything on the schematic or in the cabinet that generates 5v.
 

cut2cut

H-M Supporter - Silver Member
H-M Supporter - Silver Member ($10)
Joined
Dec 21, 2016
Messages
194
Likes
30
#29
My PM940CNC came with a DVD for the Delta VFD-E however, you can get the manual here :
http://www.delta.com.tw/product/em/.../manual/DELTA_IA-MDS_VFD-E_UM_EN_20150302.pdf

Yeah, I have yet to connect the coolant pump.... but coincidently I intend to wire it up tomorrow. If you have any pointers, I'd appreciate it. It should be simple but if I remember right, its not clear cut.

I think you are right, it appears to me the 5v to the stepper drives are provided by the nMotion card itself via wire 055.
We can probably use a USB cable/charger for an iPhone as the 5v source. So its not a huge hurdle.
Screen Shot 2017-12-22 at 10.03.49 PM.jpg
Jake
 
Last edited:

pburgh

H-M Supporter - Sustaining Member
H-M Platinum Supporter ($50)
Joined
Dec 14, 2017
Messages
78
Likes
10
#30
Thanks for the info on the VFD Jake. I didn't get much with the mill. I got the manual in a binder with the schematics and breakdown of parts, and I got a usb thumb drive for the nMotion card with the config xml file for Mach, the driver dll for Mach and a watered down version of the the nMotion manual and that's all.

As far as the coolant pump, Matt told me to connect the wires to one of the terminals with the capacitor leads and the one terminal without the capacitor leads. See the pic below. I connected mine with the hot legs on the terminals with the red arrows and the ground on an obscure threaded hole in the pump case where the green arrow is pointing. I'm embarrassed to say that I used to be a construction electrician and I've hooked up my fair share of all kinds of motors, but I've never run into a peckerhead that is setup like this one. The Chinese nomenclature for how they label their terminals threw me off. And the ground is very close to the one terminal so be careful of the clearance. I haven't tested this yet, but that's how I set mine up. Hope this helps.
 

Attachments

[6]
[5] [7]
Top