I have an Excello 3 axis CNC knee mill with a Centroid CNC4 controller. It came running perfectly from an auction and I have been using it for years. The mill and controller were built in 1991 so things were a little dated.
I grew tired of the non-graphical interface and command line operation. Luckily the 286 computer that handles the communication with the proprietary Centroid CNC4 computer gave up the ghost. After requiring more than 20 minutes to boot for 6 months it began to freeze up while the programs were running. That was bad.
Dead 286 computer.
This is the part I was attempting to machine when the Centroid controller decided to stop responding to commands. So, a great reason to update an obsolete system.
I tried to see how to reuse the Centroid driver boards and such for a while. I gave up after discovering that the proprietary computer was partly on the computer board and partly on the driver boards. Time for some new electronics.
The mill uses 8 amp steppers for each of the three axis. I decided to reuse the steppers but throw everything else away.
I got 4 Chinese drivers with a breakout board off ebay. The drivers are the DM860A. The were originally described as 7.8 amp drivers. After I ordered them the vendor contacted me and said they were 7.2 amp. And he gave me a discount for the order. Later I learned that the drivers were 7.2 amp max and 5.6 amp RMS. Turns out Centroid rated their drivers the same way and the drivers are pretty much the same as what I had before. I am using a 80 VDC power supply from Antek. At 80 volts and 10 amps it is probably overkill. I tested the set up with some 8 amp steppers from the scrap bin.
I gutted the power box on the old mill for a place to install the new electronics.
Tried to layout the new power panel on the computer. It was only good for giving me a warm fuzzy that there was enough volume for everything. Too much effort for the payback involved.
This is a schematic of the power and control system. It is a little outdated as some changes were made during assembly.
A clean blank panel to layout the components on!
The components were laid out on the panel. My son Michael wired up everything for me and then we tried it out with the 8 amp spare steppers. It worked first time out of the box!
Got the panel mounted in the power box of the mill. Cut some holes in the box for fans.
Hooked up everything and got it running. Not quite as quickly done as the bench test.
I am using LinuxCNC on an older PC running Ubuntu 8.04. The computer has a single processor and the LinuxCNC included on the 8.04 distribution is built to run a single. Newer versions are available for multiple processor computers. The computer talks to mill via the parallel port to the breakout board in the control panel.
I have used LinuxCNC with the ORAC CNC lathe for several years and it is much nicer than the 1991 software.
The software was installed and the mill parameters calibrated. The adapter was remachined using LinuxCNC.
Part turned out nice and I get to watch the backplot on the screen as things are machined now.
Things not yet complete:
Forced air cooling to the drivers amplifiers is required. Currently this shroud is cardboard as I await a 3D printed shroud from our developing 3D printer capability.
This is what the fan shroud will look like after it is printed.