Control system for Harrison M250 CNC

[AdrianW]

Just get a cheap and cheerful Hyangyung one on Ebay. £100 ish and sorted. There is a guy on ebay, near me, selling good quality encoders for circa £45.

Cheers - those VFDs look like great value. Do you have a link for the guy selling encoders? The minimum recommended spec is 8000p/r (seems excessive?) and even the 2000p/r ones I've found are in the hundreds of quid.

[m_c]

Cheers - those VFDs look like great value. Do you have a link for the guy selling encoders? The minimum recommended spec is 8000p/r (seems excessive?) and even the 2000p/r ones I've found are in the hundreds of quid.

What's currently fitted to drive the spindle?
Any VFD should be useable with. Only issue would be if the spindle has a DC motor, and a basic non-isolated KBIC style speed controller.

Encoder wise, you need to differentiate between counts/edges per revolution, and pulses/lines per revolution. The 8000 spec will mean counts per revolution, which translates to a 2000 ppr/lines per revolution.
What you're looking for is an "incremental rotary encoder" with a minimum of 2000 ppr/lines, however I'm not sure if the Acorn requires single ended, or differential output (a differential output encoder can be used to drive single ended inputs, but a single ended output encoder would need a differential driver to drive differential inputs). They can be had on eBay for under £40, although you may need to do a bit digging into specs to ensure they do meet the required minimum spec.

[Chaz]

Cheers - those VFDs look like great value. Do you have a link for the guy selling encoders? The minimum recommended spec is 8000p/r (seems excessive?) and even the 2000p/r ones I've found are in the hundreds of quid.

https://www.ebay.co.uk/itm/Hengstler...EAAOSwySlaJSLx

[AdrianW]

https://www.ebay.co.uk/itm/Hengstler...EAAOSwySlaJSLx

I was looking at that earlier - the listing isn't very helpful as it only quotes the P/N and not the code that gives the spec - zooming in on the photo it looks like it's a D/500 which from the datasheets I've seen give it a 500 counts per rev, which is well under the minimum spec. for the Acorn.

I checked the resolution a 2000 count encoder would give assuming a workpiece of 250mm diameter, and it's about 0.4mm, so having 2000 as a minimum spec. doesn't seem that unreasonable.