Harrison M250 CNC Acorn retrofit

[Fishface]

Hi All,
I have just purchased a Harrison M250 CNC and i'm going to retrofit an Acorn and AC servos for the Anilam Crusader 2 controller and DC servo motors.


I have started to strip out the controller, encoders and servos (SEM MT30s). My first problem is the spindle encoder which is an Anilam L25G-1000-ABZ-7406R-SPT02-S, it is a thousand line encoder so it should work with the acorn. Does anyone know the pin outs for this encoder, The controller board isn't marked although the wires are colour coded. It is a 6 pin cannon connector marked ABCDEF. I am expecting A, B, Z, Grnd & +V but I have no idea what order they are in.




I am currently trying to work out what AC servos and drives to buy. The SEM Servos have 75mm Pitch circle diameter, most of the AC servo drives have a 110mm PCD. Is this standard? Can you get AC servos that are direct replacements for the SEM Mt30s?

Any help is much appreciated

Regards Pat

[Petel]

I'm just finishing a similar conversion on a M300. I re-used the Anilam 1000 line encoder (different part no. to yours) and put it through a single ended to differential converter - seems to work OK https://www.cnc4pc.com/c72-differential ... river.html

If it helps the Anilam encoder wire colours were Black=Gnd Red=+5v Blue=Z White=A Green=B

I used AC servos - these needed new mounting plates (laser cut steel) and the original mounting plates recessing to suit.

[Fishface]

That's super useful thank you.

I have traced the wires on the old controller and I am sure that I have a Red +V and Black Common with a green case earth. That should mean I don't fry it working out which Pins are ABZ at least. I don't have an oscilloscope but I think I should be able to work it out by connecting to CNC12 without damaging anything. I do have some wiring diagrams for the controller but they aren't very clear.




Thanks for the link to the differential converter, I hadn't got far enough to consider how to convert from simple logic so that's a real help!

Interestingly the X and Y axis has discreet encoders, I haven't taken the covers off the servo motors yet but I was expected to find the encoders in the servos. I know that they can have servo encoders and axis encoders but I had assumed that the controller was pretty primitive and only has the three encoders. Is this the same as the original setup on the M300?

What AC servos did you use? There seems to be an endless choice so any recommendation would be welcome.

[Petel]

I can't remember what the old servo setup was - SEM units with encoders and tachos I think? I did not take much interest as I planned to use more modern units from the start.

I used the generic Chinese AASD type AC servos, a 90ST-M02430 and a 90ST-M04025. The pulleys dropped straight on. I was given a recommendation for a supplier on Aliexpress called BST Automation - seems a lot of guys in the UK use them for drives and rails etc.

[Fishface]

I managed to find a super helpful company here in the UK called encoders UK who were able to tell me the pin outs for the Anilam L25G-1000-ABZ-7406-SPT02 encoder

A – A signal
B – B signal
C - +V
D – 0V
E – Shield
F – Z signal

This will save me a huge amount of pfaffing and prevent me from damaging anything!

Thanks for the AC servo recommendation this is very useful information. I do have one question though. The shaft length on my SEM DC servos is 45mm (42mm effective length when mounted) The 80ST and 90ST AC servo motors are 35mm, which will equate to an effective length of 32mm when mounted. I have a mounting ring on the original servos which is circa 2mm thick but that still means the shaft length is 8mm short. How do people overcome this? Do you use an offset boss on the pully wheel, or are there AC servo motors with 45mm shafts that I am missing? Sorry if I am being daft.

[cnckeith]

I managed to find a super helpful company here in the UK called encoders UK who were able to tell me the pin outs for the Anilam L25G-1000-ABZ-7406-SPT02 encoder

A – A signal
B – B signal
C - +V
D – 0V
E – Shield
F – Z signal

This will save me a huge amount of pfaffing and prevent me from damaging anything!

Thanks for the AC servo recommendation this is very useful information. I do have one question though. The shaft length on my SEM DC servos is 45mm (42mm effective length when mounted) The 80ST and 90ST AC servo motors are 35mm, which will equate to an effective length of 32mm when mounted. I have a mounting ring on the original servos which is circa 2mm thick but that still means the shaft length is 8mm short. How do people overcome this? Do you use an offset boss on the pully wheel, or are there AC servo motors with 45mm shafts that I am missing? Sorry if I am being daft.

https://centroidcncforum.com/viewtopic.php?f=63&t=921

[Fishface]

I was going to try using a differential encoder and see how I get on I can always change the encoder later if it doesn't work very well.

Right now I'm trying to work out where to get ac servo motors with 45mm shafts or how to use the ac servos with 35mm shafts.

[Petel]

No need to find 45mm shafts: Cut out the existsing aluminium mount plates (t=15mm) and insert new steel mounting plates (t=6mm) to the front of the mount. The steel plates allow you to add the new servo PCD.

This moves the servo forward in the mount by ~ 9mm and leaves the end of the shaft in the right place - reuse the origonal pulleys.

PM me if you would like the drawings.

[Fishface]

Hi Petel,
I have been trying to send you a PM for a couple of weeks now without any joy. They just sit in my outbox. Drawings would be super helpful if we can work out how to share!

Regards Pat