View Full Version : Retrofitting on a budget

Odin M Yggdrasi
08-06-2013, 09:12 AM
I've got a Bostomatic 14/40 here currently being controlled using a Fagor 8025M CNC, and am looking at the possibilities for retrofitting it a second time to utilize a PC-based solution, ideally using a solution like Mach3 or EMC2.

The biggest snag I have found so far is that the existing amplifier hardware uses +/- 10V DC input. Replacing the amplifiers and DC servos would likely push the cost of the retrofit out of what the budget for this project allows, so I need to come up with a solution that works with what is there.

It is a four axis mill, the usual XYZ and then a 3 jaw rotary parallel to X and controlled currently via W.

All four axis have that +/- 10v DC input, and use the standard ABZ type 5v encoders, I believe they are 625 lines per turn on 4 pitch ballscrews.

Spindle control isn't as much of an engineering problem, as it uses 0-10v DC reversing by relay- that amplifier also supports RS485, which I might try to use on it.

Ideally I would like to use an arduino or similar device to keep the servo loop closed in hardware instead of relying on the PC, making it so that the PC merely tells the machine where to move and how to get there, and the machine does the rest at a far higher response rate than having the PC control it directly would be able to.

My problem is what hardware can I use in between to get the required voltages for driving the amplifiers. The existing machine does have a 24v DC rail that I might be able to use a motor driver with, but I am not certain of the wiring of that.

Has anyone attempted a conversion like this before? What solutions would work, trying for a total project cost of less than $500. I do have enough programming experience to write the required micro-controller software for this to work.

08-06-2013, 10:22 AM
Use LinuxCNC and they have a nice plugin for the Mesa line of boards that will give you the needed analog output. Might not make it in under the $500 budget but it should be under $1000.


Odin M Yggdrasi
08-06-2013, 12:07 PM
Little more digging into the existing hardware revealed a tag on the main XYZ amplifier- it has the following info:

Model 124HLB90-3L
Part Number 152-4683-034

If anyone knows where I can get information on this amplifier, it would help with resolving the technical details of this project. It's entirely possible that it isn't limited to +/-10v for control.

4th axis is a Westamp type, I already have the documentation for that.

Someone familiar with Mach3 recommended a CS Labs, CSMIO/IP-A for this application, although it looks to me like all that does is IO processing- it will not maintain the servo loop by itself and requires a PC attached for the purpose.

08-07-2013, 09:31 AM
the mesa 5i25 + servo interface daughter board is $239. 6 axis interface (+/-10v and diff/ttl encoder interface) + 48 i/o and expandable.


James Newton
08-07-2013, 03:23 PM
If you don't mind soldering, our THB6064AH drivers and 4 axis board should work. It is also designed to be used with an Arduino. The total cost should be around $150 for the electronics, not including stepper motors or power supply.

Odin M Yggdrasi
08-07-2013, 06:24 PM
Soldering is no problem. I'm alright with making custom PCBs as well, and might do so if needed to make this work right.

It's going to be driving the existing amplifiers and interfacing with a PC that will cause problems. Most homebrew CNC projects use stepper motors and don't seem to have feedback, while this has the original closed loop servos that require +/- 10v for direction and speed as well as ABZ signalling rotary encoders.

So far my only solution for the amplifier problem is to get some op-amps capable of bipolar operation, run them from the +/- 15V DC tap of the Westamp amplifier, and then drive that by filtering down the Arduino's PWM outputs or using a quad DAC driven by SPI.

$150 total cost is about what I have in mind, but it has to work with the original amplifiers and servos.

Gimme a little bit to go find a pic of what this machine looks like. It has a 39" X travel, and 14" travel on the Y and Z. Cast iron the whole way on the original boxways. I convinced it up to 150 inches per minute a couple years ago, and it might have a little more if I can keep the servo loop stable.

02-26-2015, 01:22 PM
If you are ever interested in selling your Bostomatic, I have a customer who'd be interested.

02-26-2015, 05:14 PM
Maybe Look at granite Devices , General mechatronics and linuxcnc i Used that combo to retrofit an Bridgeport 412 i read at granite that they can drive via Voltage maybe that helps

04-05-2015, 09:44 PM
Fagor 8025 T are very good control, if it work I shouldn't change it.

Carlos Cabrera