G0704 CNC AC Servo Rebuild (Picture Heavy)

Marardoso, you are really turning that G0704 into a Diamond. thanks for continuing to share the journey.
 
Thanks! Having a lot of fun with it, especially now that everything works. Haven't had much shop time lately but still plugging along.
 
Totally an aside, but I found a seller on eBay offering "Super Precision" .0002 TIR ER20 collets for $0.99 each :D

So knowing full well that these would be absolute junk I bought a few of each size, $25 in total. I figured I'd see what I could get and return the bad ones since they don't meet the specs. Just got them in the mail and I'm testing them in my best collet chuck for runout.

They all have really bad burrs from the slitting operation, but those flake off with a fingernail scrape. so far 30-40% are in the .0004 to .0008 TIR range and the rest are complete garbage with the worst reading .0085" TIR (you can visually SEE the runout!). I saved the "decent" ones in a bin for emergency use and I marked all the junk ones to be trashed/returned.

In all I ended up with 9 moderately good collets for $25. If you have patience I guess you could go this route, but I wouldn't recommend it.

https://www.ebay.com/itm/1-2-SUPER-...e=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649
 
Upgraded to Mach 4 build 4162 last night without incident. I moved all my serial and servo scripts into two modules which are loaded when you open Mach 4. The benefits of this are that you get to use a "class" in your programming, and that the screen load script doesn't have a ton of functions just hanging around (makes it hard to read).

My serial module contains 5 functions and my servo module contains 28. I went through the list of available serial commands for the drive and created a Mach 4 interface to any of them that I thought might ever be used. Easy to add more in the future.

I made a special function mcServo.SpindleLoad2Reg() which queries the servo drive for the torque consumption averaged over 100ms and copies the data into a global register. I will probably do some math to convert the torque to power since the torque curve drops a bit past 3800rpm. The function is called from the PLC script 10 times per second. I added a bar gauge to the spindle section of the screen which reads the global register and displays the real time torque on the spindle (roughly analogous to load). The gauge fills up with green to 100%, yellow to 150% and red to 200%. In reality, the register goes up to 250% but I didn't feel like having it go that high since I won't be machining in the red. The refresh is pleasant to watch and it is very responsive to me twisting the spindle nose.

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After I took pictures, I also added a spindle orient button and a text display for the motor temperature. I would love to add some thermocouples to the spindle bearings, but this is good enough for now.

I think having a good understanding of the spindle load will help me fine tune my toolpath settings.
 
In preparation for a prototype job that I recently started on, I ran a test part on my CNC using the spindle as a lathe (tools clamped in the vise). Unfortunately I cannot post any pictures from the job directly, but I will try to get some of the setup in general.

I have never used MasterCam lathe and was concerned about the learning curve to generate the code necessary. It took me less than 30 minutes to generate the geometry and toolpaths, modify a post processor to output in radius mode, and post code ready to run. The machine axes are all already in the correct setup (Z and X are the same as a real lathe, as well as their directions) and the Y axis can be used to adjust tool centerline or index to a new tool. Instead of using tool offsets to change tools, a new work offset is defined for each tool and the G54-59 call is placed in the code where a toolchange would occur.

I have purchased a Thinbit grooving tool to make all of the grooves on the part and I am excited to see how it works.
 
Long time without a post, but I just finished up a prototype job that required me to use the mill as a CNC lathe with tools ganged in a vise. Machine worked great! As mentioned above, one of the tools I picked out was a Thinbit Groove N' Turn to do some narrow slotting in the parts. This worked great and I was amazed by the quality of a name brand tool.

I also opted to do all of the CNC turning (in 304 SS) with a CCGX32.50 insert for Aluminum. The workholding rigidity was pretty poor due to the shape of the part, so I wanted to keep the cutting forces very low. It actually worked great and left near mirror surface finishes. DOC was only .005 and that easily formed a chip and never rubbed. Tool life was very low (about 5 parts per edge) and still left good finishes but would audibly begin to chatter. At $6 an insert from Shars this was very economical. Maybe I could have found a fancy superfinishing insert for SS, but these got the job done quick and easy.

Getting married in 11 days so probably won't be in the shop for a little while. Can't say I can complain :)
 
macardoso said:
Long time without a post, but I just finished up a prototype job that required me to use the mill as a CNC lathe with tools ganged in a vise. Machine worked great! As mentioned above, one of the tools I picked out was a Thinbit Groove N' Turn to do some narrow slotting in the parts. This worked great and I was amazed by the quality of a name brand tool.

I also opted to do all of the CNC turning (in 304 SS) with a CCGX32.50 insert for Aluminum. The workholding rigidity was pretty poor due to the shape of the part, so I wanted to keep the cutting forces very low. It actually worked great and left near mirror surface finishes. DOC was only .005 and that easily formed a chip and never rubbed. Tool life was very low (about 5 parts per edge) and still left good finishes but would audibly begin to chatter. At $6 an insert from Shars this was very economical. Maybe I could have found a fancy superfinishing insert for SS, but these got the job done quick and easy.

Getting married in 11 days so probably won't be in the shop for a little while. Can't say I can complain :)
Click to expand...
Congrats on the upcoming nuptials! Maybe adapt the spindle to dispense icing for cake decorating? Or CNC the bride and groom on top of the cake? Or add a 4th axis to the mill (wouldn't that be a fantastic wedding present) so you can engrave a nice ring? Enjoying your string.

Bruce
 
Thanks Bruce! I haven't done much by way of wood working, but I'm thinking a CNC'd hardwood ring box would make a nice birthday present (it is a month after the wedding).
 
Also this past job was the destroyer of tools (I've never worked in stainless before)

The following were added to the graveyard:
  • 1 - CCMT Insert (cut above centerline)
  • 3 - CCGX inserts (worn edges, fine by me)
  • 1 - M3.5x0.6 tap (stuck in the part)
  • 1 - 3mm carbide ball endmill (CNC crash due to code error)
  • 1 - carbide center drill (fed too fast)
  • Chipped the edge off my parting tool (reground)
Fortunately the $16 Thinbit inserts made it through unharmed!
 
You may have mentioned this in a previous thread, but what air cylinder are you using, and what size bellevilles?
 
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