Build log: Emco Compact 5 CNC Acorn conversion

[AcornFanBoy]

Hi there! I'm pretty new here, and definitely a rookie hobbyist machinist. I've been dreaming about owning a lathe for as long as I can remember, and in March 2018 I finally bit the bullet and bought a small Emco Compact 5 CNC lathe from a school that had had it sitting unused for a couple of decades. The lathe was in very good condition; I wasn't able to see almost any wear on it. Even the Plexiglas chip cover has its cover film intact. However all CNC electronics were based on 80's tech, and even though it worked properly, I very soon decided to do something about it. I don't remember how I found Centroid, but as soon as I started reading about Acorn I abandoned all Mach and LinuxCNC ideas and slowly started gathering components for an Acorn upgrade.

This thread will be the build log for my Acorn project.

Components so far:

• Emco Compact 5 CNC lathe

• 6 position tool changer

• Centroid Acorn ($325)

• Centroid CWP-4 wireless pendant ($258)

• Meanwell S-25-24 24DC power supply (bundled with Acorn)

• KBSI-240D rev D signal isolator (115€) (bundled with KBIC-240 that's not going to be used)

• KBPB-225 (8901G) adjustable speed control DC drive with brake and reverse ($85)

• 2 x Teknic ClearPath CPM-SDSK-2311S-EQN servos ($654)

• 2 x Teknic ClearPath CPM-CABLE-PWR-MS120 Power Cable ($38)

• 2 x Teknic CPM-CABLE-CTRL-MU120 Controller Cable ($46)

• Teknic IPC-3 Power Supply ($213)

• Lenovo ThinkCentre M93p Tiny, i5-4570T, 256G SSD, 8GB RAM, wlan (220€)

• Acer T232HL 23" Full HD touch screen (120€)

This is where the saga begins: the Emco Compact CNC 5 in its original condition.

I had to play with the original CNC controls. Neat, but very slow and error prone to program.

I'm a sucker for cool gadgets which explains why I went for the Acorn route, but also the über-overkill ClearPath servos. I know it's absurd to have that fancy motors in such a tiny lathe, but I know I'm going to enjoy integrating and using them. And who knows, perhaps I'll end up upgrading the lathe itself, and then I can move the servos to the new one...

Gathering bits and pieces...

I thought removing the old control cabinet would be as easy as removing four screws from the sides. Wrong! There is a band of silicon between the cabinet and the lathe bed. Using a hot air gun, wedges and a hacksaw blade I was able to cut the glue and finally detach the electronics (which by the way are very beautifully assembled. You can definitely tell this is an Austrian machine).

If someone else is going to attempt the same, this is how it was glued.

And here we have the cabinet. It is for sale, btw.

The very first component I replaced was the Z-axis motor. Stock motors are steppers, but the ClearPath was a drop-in replacement as both had 6mm shafts. I'm going to replace the transmission at some point, but for now I'm using original pulleys and pinions. There are a ton of videos about ClearPath servos, and I'm not going to go into details, but let me say they were easy to configure. The USB interface and configuration software is very intuitive, and it made easy to test run the mechanics after the servo motor was mounted.

I started this project in March, but last weekend I finally had enough spare time to really start playing around with the electronics. I've been running the servos with Acorn on a desk, but that was more or less "IT stuff" which I'm good at. Electronics on the other hand are not really my strong suit, which may explain why I hadn't started integrating the spindle motor controls earlier. The KBSI-240D signal isolator seemed simple enough, but no matter what I did the output gave a static 13.7 volts. After a while and to my utter frustration I noticed that the unit I had bought off the eBay was missing nine components that were very cleanly and carefully cut away. Since I didn't want to wait for another signal isolator to arrive, I started collecting information about the missing components. Luckily there are a lot of pictures of the unit in google, but I almost gave up before I finally found a picture where I was barely able to read (or guess) the markings from a TO-92 packaged regulator. I was happy to find out that all of the missing components were available in a local components store, and after a bit of soldering I had a working unit again. Yay!

After reading the KBSI-240D manual for a couple of times I wired it to the Acorn, configured min and max spindle speeds in CNC12, and started measuring output voltages from the isolator while changing spindle speed from the CNC12's interface. At this point I didn't know how the old DC motor would behave, but I guessed 0.5 volts as the minimum output and 9 volts for the max as defined in the motor controller manual.

For the actual DC motor drive I'm using KBPB-225, which is a reversing and braking model. It is identical to KBCC-R, but this was cheaper, so I bought it. I definitely wanted a drive with a reverse for rigid tapping and whatnot. From manufacturer's site: "The KBPB is a compact version of the KBCC “R”-suffix control. The APRM is mounted directly to the rear of the KBMM speed control. A built-in Barrier Terminal Block and its small size make the control ideal for installation where space is at a premium. The KBPB is equipped with a built-in dynamic brake resistor, Accel/Decel trimpots and provision for AC line and armature fusing. This control provides functions identical to that of the KBCC-R. A 5K ohm remote potentiometer is included. Patented."

Setting up the KBPB seems to be pretty similar to other KB drives. By DC motor is 440W (0.6hp), so I chose a 1/2 hp HorsePower Resistor, but I also have a 3/4 hp resistor just in case. Because this was a preowned unit, I set the six trimpots to factory default positions. I run out of time tonight, and wasn't able to tune the settings at all, but at least I was able to run the motor using Acorn even with those default settings. In lower speeds the motor stopped briefly before picking up more speed; perhaps this has something to do with my start delay setting.

This is it for now for the first post. Not much information so far, but this is intended to be a start for the thread. I'm happy to hear your comments and suggestions while the project goes on

[ScotY]

Nice! Looking forward to seeing your progress!

[AcornFanBoy]

Here is a video showing the problem I'm having with the motor drive. With low speeds the motor starts, kind of stops and immediately continues to rotate. Well, have a look at the video to get the idea. With higher speeds it's running smooth. I'm sure this will be an easy fix by adjusting ACCEL, MIN and CL trimpots in the speed controller. Off to buy a tach...

https://youtu.be/ZRxEUJ9oz6I

[martyscncgarage]

Here is a video showing the problem I'm having with the motor drive. With low speeds the motor starts, kind of stops and immediately continues to rotate. Well, have a look at the video to get the idea. With higher speeds it's running smooth. I'm sure this will be an easy fix by adjusting ACCEL, MIN and CL trimpots in the speed controller. Off to buy a tach...

I got kind of confused. Are you using new signal isolator and new speed control or used and or repaired Ebay stuff?

I've been down that road and won't do it again. Buy known new components. I know hobbyists have tight budgets, but the budgets get BLOWN when you BLOW up components (Acorn?) trying to save some money. (Please don't ask me how I know this, roached the spindle analog output on Acorn with a VFD that didn't behave as expected. You must use the SIGNAL ISOLATOR on your DC Controls!)

Disconnect the analog signals from Acorn. Put a meter set to DC on those outputs, I don't know what you set your spindle speed range to in Acorn Wizard Spindle Setup, but just for testing's sake, set it 0 to 1000 max. Then use MDI and call M3 S1000 and note the voltage on your volt meter. Should very close to 10VDC. Call S500, should be at or near 5VDC. Call S250 should be at or near 2.5VDC. Acorn outputs should be quite steady.

Anything after that is your motor control setup.

Marty