CMT refit

Hi,

While this is mainly directed at Marc of CNC Service Northwest, I thought others might find it useful and maybe Keith might have thoughts.

OK so I finished my cnc7-10 project (less ethernet, which I thought I might get to but apparently not soon) but I have another issue I think Centroid products might help with.

Actually - its more the technicians I think will help, but I'm I also know the product would work too.

Anyhow to the meat of the issue: Our other shop has a 2000ish vintage dual head (non atc) cmt motion machine that has always been a bit flaky. It runs wincnc (upgraded at some point) and has yaskawa servo's (and drives? not 100%). The problem (we think) is positioning errors due to the layout of the electronics. On this machine the servo drives are in a ride along enclosure on the gantry which has the spindle (and secondary router) power passing through it also. The shielding of the encoder cables is also suspect as we've had issues with a bad fan connection on the HSD spindle causing position errors. That issue was sort of fixed (new fan setup) but others remain. Wincnc has no feedback loop that tells it if the encoder is not reading the right position - it just sends the step/direction and assumes all is fine but things are not fine. Oh and we seem to have some acceleration/deceleration issues maybe too which wincnc seems limited in its adjust-ability.

So the question is - what would be a ballpark to change it over to a centroid system? We have the drives/motors/ and computer (I think it is still ok but if not we can supply) and a cabinet that should be fine. I think we would need cables (to move the drives to the cabinet from the gantry enclosure) and a controller board. I saw the oak board and its not clear that it has a feedback loop, does it? Would the oak board work? And how easy or hard is it to make new cables to move the servo drives into the cabinet? Any guess on time (hours) and parts needed. We are in the same situation as the other machine, we may be selling this in the next year so we can't go overboard on it but on the other hand, it needs to work a bit better to get a good resale price and of course it would be nicer to work with until sold. I'd say our budget is about $5-6k us for this one - is that close?

My brother is currently playing with Kflop stuff (to get a feedback loop and with linuxcnc) but I think this needs more experience (and his time is precious these days).

Thoughts anyone?

CNT motions systems router, FYI.

CMT makes tooling I think.

Drives and motors are Teknics.

Graham,

I will have to get back to you in more detail once I have time to look at it a little more closely. It is likely that you could interface to the Teknic drives using either the Oak board or the MPU11 and GPIO4D.

In either case the Centroid control system would operate in a closed-loop mode, using encoder positions that are passed on through the servo drives. You will need to ensure that you have a 5V differential line driver encoder signal available from the drive (evidently some Teknic drives and motors use single-ended encoders, and others use differential line-driver encoders).

Also, if the Teknic drives use 5V I/O signals (e.g. for their enable input and for their ready/fault output) then you might need some additional components (e.g. diodes and/or pull-up resistors) to work with the Oak board, as it is generally designed to work with drives that use 24VDC I/O.

I would recommend configuring the system in analog-controlled velocity mode. With the Oak board, you would also have the option of configuring it in a pulse-train position mode, provided the drives can accept position commands in a pulse train mode (A and B quadrature channels, as opposed to step-and-direction).