Fehlmann Picomax 50 CNC conversion/refurb

[Agathon]

Here's the latest on the Fehlmann table. Sorry that it's a bit long - will try and be brief in future.



Making good progress on other stuff and will post more soon - watch this space!

[Clive S]

Coming along nicely I enjoyed the vid. Re the Nema34 they might run better with a higher voltage that 70v I think you can get 230v drives for them.

[Agathon]

Coming along nicely I enjoyed the vid. Re the Nema34 they might run better with a higher voltage that 70v I think you can get 230v drives for them.

Hi Clive, just come in from the workshop after more fun. More vids tomorrow...

Do you think it sounds like they're missing steps or is it a step-generation/processing issue? Difficult to answer without test I suppose. The quill has always made the same noise from time to time. I've was driving it with one of those crappy HY-DIV268 things and when running a repeating cycle of ten up an down movements it always returned to the same place with better than 0.01mm variation - which I was very impressed with.

I think after going to the effort of buying the highly recommended AM882 drivers, in the short term at least, I'd rather replace the motors - they only cost £27 for the pair including delivery so I can afford to replace them!

In the longer term I still favour going all-out for servos. Those Teknic Clearpath things look very impressive. If confidence in Sterling would just improve a little I'd be tempted to order.

[Agathon]

Motor operation and control issues:

[Clive S]

One problem using the PP is that until the pc is powered up the pins can be in any rambled state and they can also chatter as the pc is powering up causing all sorts of unexpected happenings. That is the beauty of a motion controller this behaviour does not happen with Lcnc and a Mesa card.

edit Having said that you might be able to use the charge pump in Mach3 so that the bobs are not enabled until the charge pump signal is seen.

[Agathon]

One problem using the PP is that until the pc is powered up the pins can be in any rambled state and they can also chatter as the pc is powering up causing all sorts of unexpected happenings. That is the beauty of a motion controller this behaviour does not happen with Lcnc and a Mesa card

Mmm.. yes, I understand that, but it's more of an issue with the BOB itself in that they've used the NC rather than the NO side of the relay - can't see the reasoning behind this or a way around it.

BTW I'd love to move over to LCNC, but my impression is that it's for people with an interest in programming and computing rather than just wanting to get on with using a machine. I've looked hard, but I can't find the equivalent of the Mach3 User's Guide. I find that I can't get to a position where I can understand what I need to do to use Mach3 - and I regard myself as being moderately savvy with PCs.

[m_c]

Without seeing the videos (my broadband is currently not working, so am limping along on mobile broadband), if you're using a parallel port, you really need to use a charge pump for safety, regardless of what software you're using. As Clive has already said, parallel port pins can act randomly during loading. If the BOB you are using has no charge pump, the easiest option is just not to power up the machine until the computer is fully loaded.

The Clear tecknic servos do seem good, however you have to remember as they need the step/dir signal directly, it adds in a lot of extra potential for interference and losing/missing steps. If I was to use them, I'd be looking at adding differential signal drivers to avoid potential noise issues.
Plus I think they're more closed loop stepper, than what's more commonly referred to as a servo. Good in the fact they're better for direct driving ballscrews, but does mean top speed is limited.

Performance wise, you're more likely to be better of with some good Nema23 motors, and adding a 2:1 drive ratio. Nema 34 really need high voltage drives to get the best performance from them.