Joe's 1000x600x200 steel and aluminium router started

Bed is now fully fixed. I reckon it is within 0.02mm total error, not that I really trust this digital DTI.

The rear cross member and the outer edges of the other cross members that did not have the milled shim were done as follows. I laid some narrow strips of closed cell self-adhesive glazing rubber either side of each bolt hole. Then I re-placed the bed and tightened the central set of bolts down hard onto their milled shims. I then indicated the entire bed adjusting the outer bolts to zero, the glazing rubber provided a bit of resistance to bias the bed plate high so the bolts had something to tension against. Finally I got under the machine and injected some construction resin into the gap, this set hard in a few minutes as it is so hot today, it is basically bondo in a cartridge.

The bed plate had a very thin film of WD40 on it to act as a release so hopefully it will be possible to get it off again should I ever need to., not sure the resin sticks well to the shiny aluminium plate anyway.

Attachment 28469 Attachment 28470 Attachment 28471

This is the very last time that bed will look so nice!

EM806 question.

All the documents state that the alarm output is 'active high' by default and that 'active high' means

"Active High
means high output impedance for drive error and Active Low
means low output impedance for driver error. "

When I connect to the drive over RS232 it indeed states it that the alarm is active high. However it is behaving opposite to the manuals, rather it is high impedance normally and low impedance in error, I verified this by stalling a motor. I have now configured it to active low which allowed me to daisy chain all the alarms together - they are conducting to ground until a drive goes into error or the fault wiring is broken.

So my question is why is the behaviour opposite to the manuals and should I be concerned that things like the step edge setting may also be reversed? Is the manual just wrong and 'active high' means their logic output is high in error driving the base current on the NPN which then conducts, i.e. has low impedance?

I've had this many times with the AM882 and the EM806 and it's a random thing, it's like they must put something in backward...Lol

Regards the Step edge then I'm not so sure because while I've had many drives be on the wrong side of the edge I never actually checked which was at fault, the controller, or the drive. I just do a quick back n forth check with g-code and if it drops steps then flip it over. I do this on every machine regardless if the drive and controller say they match or not.!

Quote:

---

Originally Posted by JAZZCNC

I've had this many times with the AM882 and the EM806 and it's a random thing, it's like they must put something in backward...Lol

Regards the Step edge then I'm not so sure because while I've had many drives be on the wrong side of the edge I never actually checked which was at fault, the controller, or the drive. I just do a quick back n forth check with g-code and if it drops steps then flip it over. I do this on every machine regardless if the drive and controller say they match or not.!

---

Thanks for clarifying Jazz. All 4 drives I have here behave the same way, opposite to the manual. Possibly there are multiple versions of the firmware floating around.

Will do the test for step edge, does it lose a step everytime the axis reverses, i.e. I should be able to test it as creep on a DTI at either end of the stroke?

Quote:

---

Originally Posted by devmonkey

Thanks for clarifying Jazz. All 4 drives I have here behave the same way, opposite to the manual. Possibly there are multiple versions of the firmware floating around.

Will do the test for step edge, does it lose a step everytime the axis reverses, i.e. I should be able to test it as creep on a DTI at either end of the stroke?

---

Yes it drops a step every direction change. I just zero the axis put DTI on it and do 200-300 small G0 moves, 5mm or so, with the last move back to zero.

I squared the gantry today. I used the method of equalising diagonals. First I had to make a measuring stick:

Attachment 28479 Attachment 28480

Then I had the machine drill 4 holes in a rectangle and inserted dowel pins, zero'd the DTI on one diagonal then measure the error on the other. The arduino board I made for axis squaring only had 8 bits of step offset. This machine uses 1610 screws and 16x microstepping so 8 bits represents 255*10/(200*16) = 0.8mm of software correction to the limit switch. Therefore I had to get it close first by moving the proximity sensor targets first, I got the diagonal error down to 0.32mm.

Fine tuning squareness was then done by changing the offset in the arduino code. After lots of messing around trying to calculate the gantry error angle then the actual number of steps to offset one switch I gave up. I just drilled holes with offset at zero, then with offset at 255, then interpolated the two errors to get the 'correct' offset (note this is not the correct way to do this but it works well enough over these very short distances). Plugged this into the software and low and behold:
Attachment 28481

0.01mm error over ~1000mm diagonals. Square enough for now, it is repeatable. Can't do better than that without a much better DTI and some measurement of backlash.

Annoying sources of error whilst doing this were 1) a dowel pin that got scratched up pulling it out with pliers, 2) not having the DDCS home twice, this made it a little more consistent, don't know why.

I also noticed that the EM806 stall detection is not working for a stalled start, it works fine if you stall a spinning motor. Is this something I can tune or is it just a limitation of sensorless stall detection?

Quote:

---

Originally Posted by devmonkey

I squared the gantry today. I used the method of equalising diagonals. First I had to make a measuring stick:

Attachment 28479 Attachment 28480

Then I had the machine drill 4 holes in a rectangle and inserted dowel pins, zero'd the DTI on one diagonal then measure the error on the other. The arduino board I made for axis squaring only had 8 bits of step offset. This machine uses 1610 screws and 16x microstepping so 8 bits represents 255*10/(200*16) = 0.8mm of software correction to the limit switch. Therefore I had to get it close first by moving the proximity sensor targets first, I got the diagonal error down to 0.32mm.

Fine tuning squareness was then done by changing the offset in the arduino code. After lots of messing around trying to calculate the gantry error angle then the actual number of steps to offset one switch I gave up. I just drilled holes with offset at zero, then with offset at 255, then interpolated the two errors to get the 'correct' offset (note this is not the correct way to do this but it works well enough over these very short distances). Plugged this into the software and low and behold:
Attachment 28481

0.01mm error over ~1000mm diagonals. Square enough for now, it is repeatable. Can't do better than that without a much better DTI and some measurement of backlash.

Annoying sources of error whilst doing this were 1) a dowel pin that got scratched up pulling it out with pliers, 2) not having the DDCS home twice, this made it a little more consistent, don't know why.

I also noticed that the EM806 stall detection is not working for a stalled start, it works fine if you stall a spinning motor. Is this something I can tune or is it just a limitation of sensorless stall detection?

---

I think that stall detection only works if the motor speed is greater than 300 rpm - so won't detect a stationary, stalled, motor. Unfortunately...

Quote:

---

Originally Posted by Neale

I think that stall detection only works if the motor speed is greater than 300 rpm - so won't detect a stationary, stalled, motor. Unfortunately...

---

Yep Stall detect only works above 300Rpm and yes it's limited in its accuracy and reliability.

Quote:

---

Originally Posted by JAZZCNC

Yep Stall detect only works above 300Rpm and yes it's limited in its accuracy and reliability.

---

Fair enough, it was a rather artificial scenario caused by me not plugging in the signals to one of the motors on the dual axis whilst still powering it (so the driver had it locked), the other motor stalled obviously.

Quote:

---

Originally Posted by devmonkey

0.01mm error over ~1000mm diagonals. Square enough for now, it is repeatable.

---

Nice job Joe. I think most of your readers would consider that 'square enough for now' :thumsup: