Another PM940-CNC-VS Thread...

The guys on the Centroid board got me sorted out in short order. Turns out that the way I had it set, it was looking for a tool height setter on the same input... Changed the input for the tool height setter (which doesn't exist) to a open input, and we're rocking.

I've been probing, and it's freaking life changing. Setup takes about half the time... Centroid provides some free probing routines with my Pro license, and with the next update of the software they are giving the Pro license access to all probing routines, so it should get even faster when I have those!

The fun was short lived though, as during a spring pass on the first part I made after getting everything running again, the spindle dropped to 500 RPM, even though the control was still calling for 6k RPM. Opened up the cabinet and the spindle servo drive was flashing an error code that turned out to be "hall sensor error." While this servo motor *was* very nice, it was a pain to setup. Even running on the table I couldn't get it to run super smooth at higher RPMs, and since it had no auto tuning it was a long process to get it to where it was okay. I decided to go back to the original 2hp motor and Delta VFD that came with the machine. If anyone remember the wood motor mount, well it saved the day again. I was able to machine the new motor mount for the original motor with it, and it worked great. Unfortunately I was working fast because I had a paying job that needed to get out the door, so no pics. I dumbed the new motor mount down quite a bit, and got it to work well enough with my existing PDB design. After all that, I actually like this setup much better. It hums at 5k RPM max, and is MUCH smoother than the old servo motor. Makes me wonder if that hall sensor was bad all along? Also, a note for the other 940CNC-VS guys out there, I changed the Delta VFD to sensorless vector control. It seems to make a nice difference down low, time will tell how the motor likes it, but it's running nice and cool. I actually disconnected the electric fan on top because I was sick of listening to it. Even after 20 min straight of spindle time, running a 3/8 EM hard, it was only warm to the touch.

I got the paying job off the mill and started the stand-offs for the PDB. They came out quite nice, I've been running the machine hard and it really seems to be doing a good job. I cut the 3/4" 6061 place at full depth, 0.075" step over and 0.004 IPT. At 5K rpm I think that was 60IPM. Spindle didn't even slow down, and she just ate it. Did a 0.010" finish pass at 0.001IPT with a repeat pass, and the parts came out about the best I've seen off this machine! You can also see the motor mount in the background.

IMG_20200501_194355 by Phazer Two, on Flickr

IMG_20200501_194400 by Phazer Two, on Flickr

IMG_20200501_194437 by Phazer Two, on Flickr

Next up, I bought a 3" 3 Jaw chuck off Amazon. I'm going to make mounts to bolt it to the table. Should make Round parts much easier!
IMG_20200430_120731 by Phazer Two, on Flickr

IMG_20200430_121053 by Phazer Two, on Flickr

For $88, with Prime shipping, I couldn't say no. It also came with a set of OD jaws, which look like they would clamp on ~3" stock. Hoping it will let me knock out the round parts I need to make for the PDB faster than working in the vice.

PZ

Parts used:
 
Last week I made the sub plate and standoff for the 3 jaw chuck.

The sub plate was easy, a few though holes and a few counterbored through holes on the back side. I wish I would have used something more robust than 0.5" MIC 6 plate. You'll see why a bit later.

Milling the stand off was a little more interesting. I made it out of a 3x4 piece of scrap alluminum I picked up at the scarp yard years ago. No idea what flavor it is, but I would guess it's 6061 T6, since that is what most aluminum is. It cut great. I forgot to take a pic of side one, which would be the side that is bolted down to the subplate. I than flipped it and bolted it to the sub plate and finished the top while it was assembled. Originally I had it at ~3" tall, but decided that was too tall, and made it 2". In the end, I think it will be getting even shorter to maximize rigidity. Here is a video that shows the roughing cut that reduced it from 3" to 2". 0.990"DOC x 0.04" WOC at 60ipm for a total of dang closet to 2.37 cubes/min.

Click link for vid...

VID_20200508_205355
by Phazer Two, on Flickr

Notice that I have some chatter in the X axis. When I made this same cut on side one, in the vice, I had no chatter at all. I am going to say that is the fault of the sub plate being too thin, and the bolts being too far away from the chuck itself. I will just have to baby parts in it for now, as PDB is absolute top priority right now.

And the finished assembly.

IMG_20200510_090423
by Phazer Two, on Flickr

The whole point of this, is to make it easier to make the round parts I need for my PDB, since I don't have a lathe. I have a chunk of 1045 I found in a scrap bin that I was hoping to turn into the top hat, so I decided to chuck it up and see how she goes... Didn't go awesome. I was using a 0.5" 4 flute carbide end mill. I would much rather use a 0.375" 5FL EM for this, but beggars can''t be choosers. I had to go VERY slow, and while it wasn't chattering it didn't sound great. I also got some interesting vertical facets, which I believe are due to the 4 flute end mill noting having more than one flute engaged causing a vibration/resonance in the system. If anyone has a good line on 0.375" 5FL EM's let me know! In the mean time, I think I am going to double the LOC and half the WOC to see if I can get more than one flute engaged...

FYI, this was 20 min worth of milling to get to this point, and while the 0.5" 4FL is not chipped, it's now very dull.

IMG_20200510_090441
by Phazer Two, on Flickr


Till next time,
PZ
 
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