Z axis error woes

**Swarfing** · 08-02-2012

It will cost nothing to check the bearing holders placed on a rail supported across two supports of a known height surely. The exercise here is to eliminate what it is not so that what ever is left must be the issue?

**JAZZCNC** · 08-02-2012

Ok first Jonathan is correct.! We are talking about the planes the rails are on rather than being parallel to each other.

Think about it more and you'll see that after surfacing the bed theres no way the bed plane can differ from the rails plane.!!

Would we agree If the rails are level and correct and on equal planes along there entire length then the bed will be surfaced level and the distance from spindle to bed will be the same any where on the table.? . . . Well the same apply's if the rails are not on equal planes after surfacing.! The cutter as machined the bed into the same plane as the rails so therefore the distance from spindle to bed must be the same. . . . .Cant be anything but.!!

That said I'm not saying it's ok and everythings ok having it like this, it's bad because you can't machine anything truely flat and parallel but in this case it's correct or I'm(WE) are right that the distance will be the same.

**Swarfing** · 08-02-2012

Jazz all I'm saying is from experience with badly made bearing holders and supports that even leveling the bed would not fix the issue for me until i leveled them out. I re-leveled the bed and all was right then. As i said before it will cost nothing to test this out to see? If i am wrong i am wrong at least it will be something to tick off the list.

**JAZZCNC** · 08-02-2012

Originally Posted by 2e0poz

Jazz all I'm saying is from experience with badly made bearing holders and supports that even leveling the bed would not fix the issue for me until i leveled them out. I re-leveled the bed and all was right then. As i said before it will cost nothing to test this out to see? If i am wrong i am wrong at least it will be something to tick off the list.

Yep mate I know what your saying and believe me I know all about crappy round rail bearings I've had to re-machine quite a few, along with there rail mounting surfaces.!

To be honest I'm pritty sure it won't be that at all and more likely a tuning issue.?

**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.