Z axis error woes

**Swarfing** · 08-02-2012

Hank how did you get on today with the investigations?

**HankMcSpank** · 08-02-2012

Never got a chance to do a thing today

I have doubts about my stepper board being pucka (a mechatronics easy cnc 3 axis)...I'm of the opinion that this board is causing some missing steps - also two of the 3 Allegro A3977 ICs on it are in part duff (they don''t allow microstepping - therefore only full stepping ...so my resolution is not what I'd want), so therefore the lowish resolution & potential for steps going missing (the A3977 socket have poor contact with the IC pins), I feel is likely to be - in part significant. I have a rather out of proportion spindle (it's a beast for the size of the machine), so my stepper board needs to be up to driving it.....this I feel is likely to be my main problem area...steps going awol on the Z axis.

So I want to change my stepper board first - I have a TB6560 board lying around...but it's an ordeal to wire it into my setup as I have a CNC-USB board that I need to connect up to the TB6560 ....the CNC-USB has 10 way ribbon outputs...so got to do a bit of soldering. (I'm aware of the number of folks having missing steps issues with TB6560 variants too....but such a board is normally fed from a paralell port, whereas my CNC-USB board will be driving it....with a very short cable (which I'm hoping will avoid the need to buffer the signal - which is the normal workaround for when TB6560s miss steps.)

**JAZZCNC** · 08-02-2012

This would have probably been good Info to tell us at the start don't ya think Hank. :rofl:. . . . . Every things against you there mate.!!. . . Scrap them and start again.

**HankMcSpank** · 08-02-2012

Originally Posted by JAZZCNC

This would have probably been good Info to tell us at the start don't ya think Hank. :rofl:.

Which bit?!! (there's nothing confirmed about the driver board - just an inkling only that it might be the problem ....it's certainly caused me no end of problems & googling reveals that A3977s should never be socketed blah blah). The significant part for me was that one remaining A3977 on my board is still fully working & therefoe allows microstepping, so yesterday I dropped that particular chip into my stepper board's Z axis position ....my probed errors became less (about 0.1mm vs 0.350mm over the same 10mm Y0->Y10 probing run ...now if it was mechanical or bed levelling, I reckon the error would be the same no matter what the resolution of the steppers.

I wasn't keeping this a secret - my 'post 11' on this thread yesterday alluded to this!

the thing is I'm likely to be coughing up for a better machine (which will come with very good stepper drivers), so just need to limp on investigating as best I can ...probably until the chap I'm buying off has more machines in stock (22nd feb)

oh...btw - All your jokes are falling ahem 'flat' :heehee: