Alternative to PC based Cnc controllers

[EmgeeParticipant @emgee]

Posted by Phill Spowart on 20/10/2020 10:35:24:

If it is of any use to anyone, I've rebuilt a boxford TCL with PlanetCNC stuff. It's not bad for the price. The cost of all the electronics, including two steppers and two power supplies, was £655. You still need to plug it into a PC through the USB port to set up, but I think you can get it running off a flash drive of some kind. Support is excellent. Only drawbacks so far are that it doesn't support constant surface speed or feed per rev for turning, which is a shame. I'm also struggling to get the spindle speed feedback loop to work.

That cost seems way OTT for a control system that doesn't support CSS or FPR, also if the spindle position is not known it probably won't do threading.

Emgee

[blowlampParticipant @blowlamp]

Posted by Phill Spowart on 20/10/2020 10:35:24:

If it is of any use to anyone, I've rebuilt a boxford TCL with PlanetCNC stuff. It's not bad for the price. The cost of all the electronics, including two steppers and two power supplies, was £655. You still need to plug it into a PC through the USB port to set up, but I think you can get it running off a flash drive of some kind. Support is excellent. Only drawbacks so far are that it doesn't support constant surface speed or feed per rev for turning, which is a shame. I'm also struggling to get the spindle speed feedback loop to work.

 

 

I'm fairly confident that feed per rev works (I use feed per min) and I am certain the spindle feedback loop works as I have a rock solid tachometer reading as well as being able to screwcut with G76 and G33.

My PlanetCNC controller isn't set up to vary spindle speed so I don't know if G96 is operational, althought the Gcode manual indicates that it is. Other (currently) non-functioning gcodes have TODO after their description.

Are you setup with an up to date version of PlanetCNC TNG2 software/firmware?

 

 

 

Martin.

Edited By blowlamp on 20/10/2020 11:17:42

Edited By blowlamp on 20/10/2020 11:25:16

[Joseph Noci 1Participant @josephnoci1]

Posted by Phill Spowart on 20/10/2020 10:35:24:

If it is of any use to anyone, I've rebuilt a boxford TCL with PlanetCNC stuff. It's not bad for the price. The cost of all the electronics, including two steppers and two power supplies, was £655. You still need to plug it into a PC through the USB port to set up, but I think you can get it running off a flash drive of some kind. Support is excellent. Only drawbacks so far are that it doesn't support constant surface speed or feed per rev for turning, which is a shame. I'm also struggling to get the spindle speed feedback loop to work.

Hi Phill,

I am a little confused by what you say – What board are you using – the MK3 4 axis or 9 axis?

Either way, ( For Emgee) both support threading fully in the lathe – uses a quadrature encoder with index (AB and I)  on the spindle. Takes proper care of spindle RPM variation from index to index pulse as well.

Phill, I have researched the Planet CNC boards and Centroid Acorn boards very deeply – many emails with the supplier with many questions! I use MACH3 with the good old Par port, and have run out of PC's with said port..

Also, MACH 3 works, but is antiquated – I am moving to PlanetCNC ( for the advanced hobby user, way ahead of the Acorn offering) – awaiting boards. Hence my confusion with your statements – The PlanetCNC boards ALL require a connected PC running the interface software – neither the 4 or 9 axis boards support standalone operation – there is no display connection, no graphics output, no key/button/ etc control inputs that could work standalone….The PlanetCNC TNG software runs on the PC and is the only way this works, so not sure where you got the idea of possible standalone operation with a flash drive? The connection tween PC and controller is either USB ( not recommended in a noisy shop) or ethernet ( works well..)

WRT your spindle speed problem – this is often due to incorrect settings in the table where the quadrature encoder is defined – number of pulses/rev, etc, and, very important, any noise on the encoder signals ( due to extraneous electrical noise, poor grounding, etc). And of course, the encoder must spin at the same speed as the spindle, if not, you have to set the PPR and number of index pulses/rev to correspond to the spindle/encoder ratio…

Joe

Edited By Joseph Noci 1 on 20/10/2020 11:33:43

[blowlampParticipant @blowlamp]

There is this, but I don't know if it works with TNG2. This SD adapter card was used to allow the CNC machine to run gcode with minimal computer equipment, I think.

Martin.

[Phill SpowartParticipant @phillspowart84010]

Morning Joseph,

According to their blog, you can (or maybe could) set up a machine to run off an SD card. It does say that in this state, you can run sans computer:

https://planet-cnc.com/using-sd-card-adapter-planet-cnc-controllers/

Although personally, I wouldn't.

My spindle problem still needs a good coat of looking at, I only mention it as it is about the only unsolved problem I have atm. I've been through all the parameters with no joy. I've not tried threading with it yet, in fact the project has spent 6 months gathering dust as I rebuilt part of my shed over summer.

Why do you think PlanetCNC might be better than Acorn? I'm actually considering going the other way if I ever do a conversion on my mill. PlanetCNC does not support CSS, feed per rev (for turning, of course) or encoder feedback, whereas I think Acorn does? Or am I mistaken?

[Phill SpowartParticipant @phillspowart84010]

Forgot to say-I'm running a Mk3/4 board. Other than the CSS/FPR issue, I'm really pleased with it.

[blowlampParticipant @blowlamp]

Posted by Phill Spowart on 20/10/2020 11:57:23:

Forgot to say-I'm running a Mk3/4 board. Other than the CSS/FPR issue, I'm really pleased with it.

You'll certainly have an issue if you haven't got the spindle synchronisation working properly.

[sam sokolikParticipant @samsokolik60334]

Constant surface speed and feed per rev example with linuxcnc.. (about half way through the video – I ramble)

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