PM932 CNC Build

[jbolt]

Is that the 6" table from Wholesale Tools? I just got one in December.

Putting the motor mount on it and getting it running is fairly close to the top of my To Do list. I have motor mounts I made for the Hoss Phase 1 conversion and was hoping one of them would be useful.

I haven't even looked for a way to take it apart, yet, so no idea of dimensions or anything.


Bob

It is a Phase II rotary table I got from Enco. Mounting a stepper to it was straight forward.

The tricky part was finding a 4th axis Mach3 post processor for HSM Works. Most Mach3 3-axis post processors are 4th axis ready but it is disabled in the code.

 

[SheffS4]

Hello Jay,

Thanks again for the design files, I'm the guy who's planning to do the DMM-Tech conversion.

Do you have any return coolant drains on the table itself? If not, how do you deal with the t-slots filling with coolant?

 

[jbolt]

The table has one drain outlet on the right rear. I run high volume coolant so it overwhelms the drain anyway. That does not matter with the enclosure.

Sent from my SAMSUNG-SM-G900A using Tapatalk

 

[SheffS4]

Got it, thanks. I'm running some temporary flood for some manual steel cutting for now with strategically placed catches and flexible hose.

Are you using set screw style couplers for your steppers? DMM-Tech recommended keyed couplers but i'm struggling to find a good option. The set screw style is by far the most common it seems.

That chip pan is so nice, I think I'm gonna have to go to a local sheet metal fab shop for a quote to make one. What gauge sheet metal did you use?
.

 

[jbolt]

Got it, thanks. I'm running some temporary flood for some manual steel cutting for now with strategically placed catches and flexible hose.

Are you using set screw style couplers for your steppers? DMM-Tech recommended keyed couplers but i'm struggling to find a good option. The set screw style is by far the most common it seems.

That chip pan is so nice, I think I'm gonna have to go to a local sheet metal fab shop for a quote to make one. What gauge sheet metal did you use?
.

To maximize the use of flood coolant you need volume and pressure to evacuate the chips from the cutter. My first coolant system was a small pond pump and a 5 gal bucket. worked okay but with the high volume system my finishes are much better. I highly recommend Koolrite 2290 coolant. This is by far the most home shop user friendly and machine friendly coolant I have used so far.

I'm using set screws on the couplers. What I do for round shaft motors is replace the set screws with pointed set screws and drill a mating detent in the shaft. Never had an issue done that way. I also add a second set screw the each end of the coupler at 90 deg from the other. If you motor shafts have flats use cup point set screws on the flat, no detent needed. If my stepper shafts had key-ways I would broach a key-way into a coupler.

The chip pan is .060 aluminum. I have a buddy who does outside sales for a shop that has a laser cutter and large press brake. He cut and bent the pan pieces for me for the cost of materials.

 

[SheffS4]

Yeah I gave up on the flood coolant for now and am sticking with my koolmist setup until I can get a proper chip pan.

Thanks for the tip on coolant type, I got some microsol 685 that I purchased a little while ago for now. Should last a while considering I'm not using it right now lol

I will need to get / make a broaching tool for the pulleys / couplers.

How is your Fabco air cylinder working out? Looks like it'll do 3349 lbs with 90psi. Working well for your TTS with no pullout? I saw you mention you were considering an electric drawbar, like the one that Novakon sells. Seems pretty straightforward except I'm not sure how they handle the torque setting. Are you still considering this option?

 

[jbolt]

Yeah I gave up on the flood coolant for now and am sticking with my koolmist setup until I can get a proper chip pan.

Thanks for the tip on coolant type, I got some microsol 685 that I purchased a little while ago for now. Should last a while considering I'm not using it right now lol

I will need to get / make a broaching tool for the pulleys / couplers.

How is your Fabco air cylinder working out? Looks like it'll do 3349 lbs with 90psi. Working well for your TTS with no pullout? I saw you mention you were considering an electric drawbar, like the one that Novakon sells. Seems pretty straightforward except I'm not sure how they handle the torque setting. Are you still considering this option?

I like the pneumatic drawbar on this mill since I have air for mist and a air nozzle for clearing chips and coolant. I have a DIY electric on my HD drill press since it has no air near it and I don't plan on bringing it there. The 3-stack air cylinder woks okay but it is just barely enough for most things. I can get pullout with larger end mills and aggressive feeds. I plan to replace it with a 4 stack cylinder ay some point.

 

[SheffS4]

Thanks Jay.

I compared some numbers (cost/force) of the Fabco cylinders and the 4" bore 4 stack will give you the best bang for your buck in that price and force range. I will be going the same route.

Going with RM2505 ballscrew on Z, would you still feel the need to support the bottom of the ballscrew with a thrust bearing? I ran some ballscrew critical speed and column strength calculators and it doesn't seem necessary.

Also is there a reason you chose to use a thrust bearing instead of a BF / FF support? Was greater axial load handling without any radial loading your goal?

 

[jbolt]

Thanks Jay.

I compared some numbers (cost/force) of the Fabco cylinders and the 4" bore 4 stack will give you the best bang for your buck in that price and force range. I will be going the same route.

Going with RM2505 ballscrew on Z, would you still feel the need to support the bottom of the ballscrew with a thrust bearing? I ran some ballscrew critical speed and column strength calculators and it doesn't seem necessary.

Also is there a reason you chose to use a thrust bearing instead of a BF / FF support? Was greater axial load handling without any radial loading your goal?

I chose to support the Z ball screw because I was uncomfortable hanging the weight of the head off the end of the ball screw shaft with a cheap 1/4" wide nut that is retained by a crappy set screw. The thrust bearing supports the shaft and takes most of the hanging load. I'm not an engineer and my concern may be unfounded but I have built (and broken) enough stuff over the years (some designed by engineers) to be cautious. There are other builds out there that do not have an end support or constraints that are working fine so far. Seems like cheap insurance to me but YMMV.

How is the build going?

 

[SheffS4]

Fair point, I wouldn't trust a set screw that much either. I got a brake on my Z axis servo for safety so I should probably support the bottom of the leadscrew. I'll consider my options.

I'm still in the gathering parts and over-researching everything as I always do stage. All I have so far is DMM-Tech servos, drivers, and a Meanwell RSP-1600-48 from work. Just about to finalize the ballscrew order with Chai after laughing hysterically at a quote from Nook. It looks like all the measurements on your machine are the same as mine so far, which is a PM932-V-PDF so I may just order the same length screws as you spec'd.

I have a MB2 BoB (looks really nice, I look forward to using it), Ethernet Smoothstepper, and china special tool setting probe (SK-66B) on the way. Need to look into my delta VFD that came with the machine and see what options I have to control it. Went with ModBus last time. Works great but was a bit of a headscratcher trying to set it up.

This will be my 3rd CNC electronics build, first mechanical conversion though. I should probably start a thread and stop taking over yours! My workshop is very small and not very nice to photograph though lol. I'm still not sure how I'm going to do the machining on the saddle as this is my only mill, will probably need to call on some help.