Re: Control system for Harrison M250 CNC
Quote:
Originally Posted by
AdrianW
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.
Re: Control system for Harrison M250 CNC
Quote:
Originally Posted by
AdrianW
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
Re: Control system for Harrison M250 CNC
Quote:
Originally Posted by
m_c
I did have a look last night after I posted to see what they've been up to, and noticed that, but $240 for a XHC pendant you can get on Aliexpress for $99 does seem a bit steep.
Cheap and cheerful option for KMotionCNC is a gamepad. Quite a few people use wireless Xbox controllers.
Agreed, there is a markup however they have done all the integration bits to make it work reliably. Ive seen a gamepad being used for the Acorn system too, there was / is a Harrison 300 lathe on ebay with Acorn running with an xbox type controller.
Also, they are about to launch a 16 in / 16 out add on board, lack of inputs and outputs has not helped.
Re: Control system for Harrison M250 CNC
Quote:
Originally Posted by
Chaz
The potential problem with that, is it's a hollow shaft encoder, which aren't as easy to mount/drive.
Something like this would also work - https://www.ebay.co.uk/itm/1-pc-New-...oAAOSwImRYIVLB
But that's from China.
It really depends on what the existing setup is, whether it can be adapted, or if a complete new setup is needed. A photo of the existing setup would be good.
Quote:
Originally Posted by
Chaz
Agreed, there is a markup however they have done all the integration bits to make it work reliably. Ive seen a gamepad being used for the Acorn system too, there was / is a Harrison 300 lathe on ebay with Acorn running with an xbox type controller.
Also, they are about to launch a 16 in / 16 out add on board, lack of inputs and outputs has not helped.
A lathe using a gamepad controller fills me with dread for some reason!
Probably because I know how much a damage a crash on a lathe can do, where as at least on a router/mill, the biggest damage is likely to be a broken cutter.
I noticed the IO expansion as well. It's interesting they're having to rely on ethernet though. I would of thought using the i2c or UART ports on the BeagleBone would of been an easier option.
Re: Control system for Harrison M250 CNC
Quote:
Originally Posted by
m_c
The potential problem with that, is it's a hollow shaft encoder, which aren't as easy to mount/drive.
Something like this would also work -
https://www.ebay.co.uk/itm/1-pc-New-...oAAOSwImRYIVLB
But that's from China.
It really depends on what the existing setup is, whether it can be adapted, or if a complete new setup is needed. A photo of the existing setup would be good.
A lathe using a gamepad controller fills me with dread for some reason!
Probably because I know how much a damage a crash on a lathe can do, where as at least on a router/mill, the biggest damage is likely to be a broken cutter.
I noticed the IO expansion as well. It's interesting they're having to rely on ethernet though. I would of thought using the i2c or UART ports on the BeagleBone would of been an easier option.
Agreed, he often sells the shaft versions too. I bought a hollow one and struggled but had to be done.
Re: Control system for Harrison M250 CNC
I forgot to mention, British Encoder (www.encoder.co.uk) are a UK manufacturer/supplier, and are helpful. Not the cheapest option, but a direct drop in replacement for my Denford Cyclone was about £200.
Zapp Automation also supply some encoders, and Gary (who occasionally frequents here) is very helpful.
Other option is US Digital, where you can pick disc/reader head options to suit your application.
Re: Control system for Harrison M250 CNC
Quote:
Originally Posted by
Chaz
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.
1 Attachment(s)
Re: Control system for Harrison M250 CNC
Here's a photo of what's on there now - it's an HP HEDS-5310 - I'm pretty sure this range doesn't go over 512 counts/rev so it's well under the minimum. As you can see space it tight - I'll probably have to make a new bearing assembly to allow anything bigger to fit in. For clarity, the encoder is the smaller black housing up against the gearbox. The larger black cylinder next to the pulley is a bearing housing that's bolted to the mounting bracket.
Attachment 24867
Re: Control system for Harrison M250 CNC
If you check the RS part number for that encoder on RS, it is only a 500 ppr encoder.
I've just tried finding an official spec for suitable encoders, and although I've found it has to be a 5V differential output encoder, all they say is they recommend 2000ppr, not what the actual minimum or maximum possible is.
Chaz, what ppr is your encoder?
And do you know what limits they put on the appropriate setting in the software?
2000 is high for a spindle encoder on a controller aimed more at the hobby/light industrial end of the market. I've got an old mill that has a 200 line spindle encoder, and it would of been able to rigid tap using it's original controller, which is far more demanding on accuracy than single point threading on a lathe.
For a lathe, even a 50 line encoder would be more than adequate for most reasonable sized threads. I can guess why Centroid recommend such a high count, but that's just because I'm a bit of a geek.
If you're existing encoder is differential output with all the required outputs (A,B, Z, plus their compliments - should have at least an 8 core cable if it is), I'd be inclined to wire it in and try it. Worst case you have to change it, best case you get a functioning spindle encoder that does the job without having to change anything.
Re: Control system for Harrison M250 CNC
Actually, just found the datasheet for the HEDS encoder, and they were only available in single ended output.
Probably best to remove it, measure up the dimensions and see what you can find in a similar size, as space looks at a bit of premium. Plus I'd guess by the setup, and the datasheet, it's a hollow shaft encoder.
US Digital would probably be the option involving the least amount of modifying. Something like an E5 or E6 depending on shaft size - https://www.usdigital.com/products/e...emental/rotary
