Semco cnc mill problem

[scottmk1]

That makes sense, I did wonder how it could detect pulses from the disc, I'll have a look again tomorrow and see if I can see the lines.

 

[Hood]

Is it a shafted encoder or did you have to cut the motor shaft?

 

[scottmk1]

The encoder has a hollow shaft that slips over the motor shaft, with two grub screws that are tightened onto two flats on the motor shaft. The first grub screw came out, but it was very very tight, the grub screws take a 50 thou Allen key, and are impossible to get to with the short end of the key. On the second one, the ball end sheared off inside
the grub screw, and it was in there solid.

Standard length drill bits were too short to reach it, so I tried with the only long series bit I had that would fit between the motor body and the base of the encoder, which is about 3mm,unfortunately the Allen key material was too hard and I couldn't drill it.

I found this carbide reamer, at least I think it's a reamer, and used it at 90 degrees to the offending grub screw to eat in to the material either side of it, with the hope it would weaken the collar enough to allow me to prise the bugger off the shaft. Fortunately it worked.

There's probably a better way of doing it, but that's what came into my head at the time.

 

[scottmk1]

If it's of interest to anyone, this encoder only seems to have 5 lines on the disc and the run between the inner and outer tracks on the disc.

 

[Seadog]

There's a lesson the be learned about ball-ended Allen keys. They aren't meant for cracking tight screws using the ball.

 

[scottmk1]

There's a lesson the be learned about ball-ended Allen keys. They aren't meant for cracking tight screws using the ball.

I know, but the other end isn't long enough and I didn't have any other 50 thou keys.

 

[scottmk1]

Just got home today, so got the new encoder fitted to the Z axis motor.

 

[scottmk1]

Originally all of connections between the motor wires and the harness were made with chocolate block types, quite bulky and made it a pain in the hoop to get the end cover on. I've redone them with these insulated crimps, and it fits nicely in the end cover now. Are they OK to use in this application? Or also had to drill the end cover adjacent to the cable exit from the encoder to run the cable through.

 

[Hood]

Shouldn't be a problem.

 

[scottmk1]

Glad to hear that. Hopefully get the motor installed today and run the new encoder cable to the controller

 

[scottmk1]

Ok so back to this once again.

I’ve fitted a new 2500ppr encoder to the Z axis motor and wired it up, and I keep getting the following alarms, and upon resetting them the Z axis gives a sudden movement and I get the alarms again.

430: The position deviation value in Z axis stop state exceeds the setting value.

433: The position deviation value of Z axis exceeds +/- 32767, or the speed command value of DA converter is beyond the range +8191/-8192. This alarm occurs usually because of setting error.

So, I’ve got the setting for all 3 ballscrews set for 5mm pitch, which I’ve verified that they are. The Z axis is belt driven and the pulleys give a 2:1 ratio with the motor pulley being 22T and the ballscrew pulley 44T.

So I think I need to change a setting to reflect this ratio. In the manual there is a setting called command multiplying ratio, would this be it?

 

[Hood]

Was the original encoder the same count as the one you put n?
Have you changed the gearing by using different pulleys?
Is it doing this when trying to home?

 

[scottmk1]

I think the original was 1000ppr from memory.
The pulleys haven’t been changed.
It’s doing this as soon as it’s powered up, the X and Y don’t do anything and the Z gives a small movement and it’s straight into alarm.

 

[Hood]

You will definitely have to alter the encoder settings then. In my control that is done with two parameters but yours is likely different. It may be that parameter you listed above but whether you can enter a different value in rather than the ones listed I don't know. It seems to suggest if you use 1 then it is a random value so it may then allow you to enter the "random" value.

 

[scottmk1]

Hmm ok, just checking the gearing for the other axis and it’s 2:1, with the smaller pulleys being on the motor.
So once I’ve done that I’ll see what I can do with the settings but if they all have a 5mm pitch screw, a 2:1 reduction on the drive and 2500ppr encoders then the parameters should be the same Shirley?

 

[m_c]

The sudden movement would have me questioning the A/B signals are sequenced correctly.

If the phases are switched, it'll lead to a runaway situation, where the control sees a positional deviation so tries moving the motor to correct it, but unknown to the controller, the encoder is counting the wrong way, so the deviation keeps increasing and the controller keeps moving the motor faster to correct, until the maximum positional error is reached at which point the controller faults out, and displays an error.

The gearing is a separate issue, but you may find the higher count encoder limits how fast the controller can run the axis.

 

[scottmk1]

Ok I’ll check my wiring, any suggestions for how best to connect these tiny wires?

 

[scottmk1]

Ok so I swapped the A and A’ wires and no alarms now, just got to try and get the parameters figured out as the actual movement of each axis is a lot less than what readouts say

 

[m_c]

At a minimum, you'll need to change the axis gearing, and maximum speed.

But as mentioned, maximum speed may be limited, and you may also have to make tuning adjustments.

 

[scottmk1]

At a minimum, you'll need to change the axis gearing, and maximum speed.

But as mentioned, maximum speed may be limited, and you may also have to make tuning adjustments.

Ok thanks, deciphering this manual is proving to be a challenge