New Refurb of a Practical CNC

[Sawdust Steve]

Sawdust Steve Build Thread
This build thread is related to a 4’ x 4’ extruded frame CNC I bought at an auction. It was in a university and used to cut foam for wind tunnel testing. It sat in a back corner since 2008. It is rack & pinion with an odd part of the design in that it only has one stepper on the Y axis with a driveshaft to the other side for the pinion.

This build is being done in stages. First is to replace the WinCNC controller with Acorn. Depending on its performance, I may change it over to a spindle. Final stage may be to upgrade the R&P to Avid hardware, I have a quote in process.

Stage 1. I’ve already connected my Acorn with a Gecko G540 to the machine to verify a sign of life and it was successful. All the wiring was on a card table alongside the CNC.

I saw Marty’s build log on a ZenBot with a G540 and ordered the case he used. Serious help to my talents. Also ordering the Omron G3N-220B relay he used for router power control.

First question: Can someone give me the link to schematic for attaching the relay to the Acorn to use M2/M3 in the gcode? I did look.

Steppers are NEMA 23. I’m replacing the 161-ounce steppers with 380-ounce from Avid. The CNC was wired with Molex and the steppers I have ordered will come with DB9. So, I am replacing the Molex with DB9.

The CNC must have been in an adjacent room from the controller since all the cables are at least 12’ longer than needed for a control box on the machine. For cutting foam that could make sense. They are 22 gauge and I plan to keep them after shortening them.

Update coming after case and steppers arrive next week.

Steve.

[cnckeith]

hello.

All Acorn schematics are here.
https://www.centroidcnc.com/centroid_di ... browse.php#

overall generic system schematic
https://www.centroidcnc.com/dealersuppo ... 010.r3.pdf

generic VFD (m3/m4)
https://www.centroidcnc.com/dealersuppo ... 009.r3.pdf

[Gary Campbell]

Having done a few Practical refurbs, thumbs up to replacing the spindle rack gear and the wimpy cross shaft.

[Sawdust Steve]

Having done a few Practical refurbs, thumbs up to replacing the spindle rack gear and the wimpy cross shaft.

What replacement of the spindle rack gear did you find the least machining? I'm considering Avid Nema R&P 34 parts, but some machining will be needed on the Practical end plates to mount the Avid mechanism correctly. Also thinking of putting the R&P mechanisms on the outboard of frame.
Steve.

[Gary Campbell]

Not sure on your question, but I am able to do all my own machining, so I don't buy mfgr parts

[Sawdust Steve]

Parts arrived and I started assembly of the control box. My prime references are Marty's pictures from his ZenBot g540 build and the S14979 schematic drawing for Acorn/G540. I'm using an Automation Technology case and Automation Direct SSR. I used 18 gauge for all wiring that was not 120 v and 12 gauge for 120 v. I could be less than a day before smoke or motion. Still need to change stepper motor connectors from Molex to DB9, mount control box and hook up computer. I have already done a bench test with the Acorn and computer.
Q1) I could not find a schematic for a simple SSR to turn the router on/off m3/m5. I wired the control side to the Acorn relay strip. Is that right?
Q2) There is a fuse on the case. I could not see a fuse in any schematics. How do I use it?
Q3) After building I noticed that I had put some of the 120 AC cabling in a position that the ethernet cable lays or crosses them. See View 1 picture. Do I need to reroute the AC cabling?
Q4) The box has slots for ventilation. Can I cover them with breather mesh to keep dust out?
Q5) I'm using the stepper power supply line input terminals to feed all 120 parts. Is that adequate or do I need to add a terminal buss.
Steve.

[Gary Campbell]

Q1: 24v com to the neg side of the SSR and 24+ thru a relay set to SpinFWD to the pos side
Q2: use fuses or breakers to protect wiring and devices. They go inline on the power feeds
Q3: separation is always better
Q4: I like sealed boxes with a fan and filter
Q5: I use power distribution blocks into multiple breakers rated for each device

[Sawdust Steve]

UPDATE: All wiring in the box was done, new steppers mounted, wiring from the machine was cleaned up/connected and motion achieved without smoke. I used the calculator to get the distance very close, will get out the dial indicators shortly.

Some comedy was created.
1) The home switches were time consuming until I figured out which schematic to use. Embarrassing to admit since they are only SPST.
2) In removing the spade terminal from the 120 v output to reroute wires the ground terminal pulled out. Not repairable, need new one.
3) New steppers came with molded DB9 connectors, machine had Molex squares. I cut off the Molex squares and soldered on DB9 only to figure out there wasn't any female threads for the molded DB9. Current fix is short computer standoffs so each side can thread in. Are there DB9 female with included fasteners?

Comedy over, now for some Acorn questions.
A) The CNC came with a Tool Height mounted to the frame. I've never been a fan of them. It is a simple SPST switch two wire output. Is that compatible with Acorn? If so, is it the same as home switches? (I've been a G92 with 1-2-3 block person.)
B) I have an AutomationDirect SSR for router power (M3/M5). It calls for 3-32vdc input. Can this be controlled directly from the Acorn board or do I need an intermediate relay?

Non-Acorn question, but hope for some guidance from builders. The CNC has an Acme leadscrew for the Z axis. Its 1/2" diameter and 9" of thread. What is a reasonable expected IPM for it with a 380 oz stepper and PC7518 router? Looking at the original WinCNC ini file it was set for 50 IPM with the original 161 oz steppers.

Steve.

[Sawdust Steve]

I had to step away for couple weeks. Three weeks ago I was successful in moving all axis in gcode of a simple rectangle. Today I wanted to reconfirm sign of life today and failed. First I tried a file I found was way larger than 50b, since I want to confirm life before the license. I then tried running one of the Acorn files "Boss Control Panel" that came on the install. Only 26 KB just a small panel.
I don't have a Z axis home switch yet, which gave me problems trying to start the program, went in the wizard and set it for manual.
I'm getting a "325 Limit: job cancelled" and "907 X axis travel exceeded" after line N130 which I only see a small negative direction move.
I started the file about 10" both X and Y from any contact.
Steve.

[Nigelo]

You need to reset your WCS #1 to valid coords.

Your report shows X soft limits as Minus 0 and Plus 48.0 whereas WCS #1 has an X origin of Minus 0.40388. It therefore follows that your Job's X move of Minus 1.2025 will exceed the X negative limit by 0.79862.

Hope this helps