DIY heavy duty PM-833 CNC conversion

[buzzfab]

I am still waiting for the ballscrews to arrive but I finally made a decision about motors.

I ordered Leadshine EL8 EtherCAT drivers and ELM2 motors, these are their newest lines and have 23bit optical encoders with inline battery.
The frame size I went with is 80mm, X/Y motors are 750 watt but the Z is a 1000w with built in holding brake.

These will be a major upgrade from the old DC servos i have on hand and the wiring will be so much easier and neater with the EtherCAT.
The drivers even have some I/O ports for limit switches, homing, estop buttons and even specific highspeed ports for a probe input but they can be use for other things aswell. This means one could get away without any other costly controller boards like MESA cards even though I own a few already.

anyway... more waiting

Eric

 

[Aukai]

WAAAAAY over MY head.

 

[buzzfab]

I figured I would post the prices quoted to me from Leadshine as of yesterday (March 10 2023)

EL8-EC1000F - EtherCat 1000w driver ($458)
ELM2H-1000LA80E - 1000w motor with holding brake and 23bit optical encoder ($398)
EL8-EC750F - EtherCat 750w driver ($408)
ELM2H-0750LA80F - 750w motor with 23bit optical encoder ($278)
CABLE-BMAH3M0-124-TS - 3 meter encoder cable with battery ($39)
CABLE-RZSH3M0-114-TS - 3 meter power cable for motor with brake ($25)
CABLE-RZH3M0-114-TS - 3 meter power cable for motor without brake ($19)

These motors can also be run off their mid range EL7 Series drivers which are very capable but with a few less features and I/O ports which run about $60 cheaper per driver.

Eric

 

[B2]

@buzzfab

Nice planning, protos and photos.

Leadshine as of yesterday (March 10 2023)

My PM940M VS CNC came with Leadshine steppers. They seem to be ok, but a bigger one on top might be helpful to hold the heavy head when powered down. They are older fashioned kind .... just steppers with external drivers. Did you consider the ClearPath motors, Victor NY, near Rochester NY area. https://teknic.com Several other HMs have used them in there CNC conversions.

Good luck.
Dave L.

 

[buzzfab]

I looked at every brand of AC servo I could find over the last year, If money was no object the EtherCAT version of the Panasonic MINAS 6 series would be my top choice. Delta A2 Series is very nice also. I live 10 minutes from DMM-tech and have been there numerous times because of a retrofit i did a while back. They are local (for me) and super helpful so they should be the choice I went with but my problem with them is they couldn't provide me with pricing for EtherCAT models. they have them listed in there DYN5 series but its new and they were not production ready at time. they also lack a 80mm 1000w version where most other companied make one. The recently released EL8 series from Leadshine actually has more features, a better encoder, built in STO, and oil sealed ip67 rated motors as standard while other companies charge more for these options. Clearpath was further down on my list to be honest.

We will see how they work but I don't have any worries as these are pretty much 3 generations newer and more powerful than the ones "thisoldtony" uses on his MAHO conversion. The ones he uses have been discontinued for a while but for some reason they are still being sold at automationtechnologiesinc. I had to contact Leadshine directly via email to purchase the ones I wanted

Eric

 

[buzzfab]

The ballscrews arrived today and from initial inspection they do not looked warped or scratched and are very shinny. The ballnuts take a bit of effort to move by hand but still turn very smooth with no crunching noises or anything. I can't wait to get these on the machine. I guess I have everting needed for the mechanical side of the build so if I can find some time I will get on it.




I am definitely getting excited.
Eric

 

[buzzfab]

After a few reprints of my prototype parts I have finished the X axis. Here is a short video of what it looks like.

video

The stock Y leadnut is attached to the saddle with one M8 screw. My design uses a second M8 bolt to attach the ballnut to the saddle casting. The threaded hole already exists so no new drilling was required. The ballnut can travel the full length of the screw, it can move all the way to the front until the ballnut touches the casting and the same with the back. I have no real way of measuring the distance yet to give exact numbers yet.

When I ordered the ballscrew for the X I knew it was a little long but and had the machined end for a support bearing. I know I could have ordered it with an unfinished but I figured I would just cut it to the size I needed on the bandsaw at work. It ended up being easier than I thought and managed to cut it relatively easily by hand with a hacksaw and used a flap disc to clean it up. I took a bit more time because I didn't want to heat it up but it went pretty smooth.




I had to cleaned up a rough section base casting where the cut end of the ballscrew was rubbing with a grinder, it now has like 0.5mm clearance. I will paint over the exposed iron before I am done so it doesn't start to rust.



Up next is the Y

Eric

 

[buzzfab]

My day job and side business have gotten in the way of making any progress on the conversion this week but I will be back at it in a few days. It is real tight fitting the 25mm ballscrew under the bed but I am happy to say that it does fit without any modification to the castings. It is tricky to get in because it has to be install with the bed on the machine, this also means that the screws cant be tightened with a allen key because there is not room for it. Instead I replaced the M8 socket head cap screws with a pair of grade 12.9 m8 hex bolts which allows for tightening with a 13mm box wrench.

On a different subject kinda.. At some point down the line I am wanting to build a carousel style ATC for 12 tools using the tormach TTS holders. While I was laying in bed last night thought of a pretty simple design so I wanted to get it in CAD while it was on my mind. This morning I spent a bit of time in Fusion360 and whipped this up. This is only the first part but its a start so now I can back burner the idea and get on with my life.

60mm motor direct drive, with a 3304 double angular contact bearing.




Eric

 

[buzzfab]

I figured I would do a bit more on the ATC design while sitting around this morning so I drew up the plate for the 20mm linear rails to mount on.


I have about 5 feet of extra HGR20 rail I can cut up and a pair HGW20-CC carriages floating around so I figured I should use them in the design. To move the carousel toward and away from the spindle I see a lot of people are using a pneumatic cylinder. It looks like a decent design but I think I will go a different route and use a Gates PowerGrip timing belt, pulley and stepper/servo.

I wonder if a 40mm 100w servo motor would be powerful enough? anyone have any thoughts? will this design even work?

Anyway I am getting distracted again and need to focus back on the conversion.

Eric

 

[Harlech]

All of my bearings arrived today. Japanese made NSK TAC series which are specifically designs for ballscrew supports. I could have just gotten some no name Chinese angular contact bearings for like $3 each on Ebay but I find that usually you get what you pay for.
Some info here... nsk-tac-bearings.pdf
Or even more here... CAT. No. E1254 SUPER PRECISION BEARINGS

View attachment 438780
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Now I am just waiting for the ballscrews to arrive. I've got a tracking number but it seems like they haven't actually shipped yet.
Hopefully they don't take too long, I can't move forward until they arrive.

Eric

Out of curiosity, what was the butcher's bill on your new bearings?