Joe's 1000x600x200 steel and aluminium router started

[JAZZCNC]

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.

[devmonkey]

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



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:


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?

[Neale]

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



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:


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...

[JAZZCNC]

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.

[devmonkey]

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.

[Kitwn]

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'

[devmonkey]

Just in the process of rigging up some dust extraction which is going well, but I also need air assist for aluminium chip removal. I have a very loud compressor I don't want to use, can anyone point me towards something quiet that has the required flow rate and pressure (apparently some people use pond air pumps??) for blasting chips out of deep pockets?

I've also seen these small plastic fans you can slide onto the cutter but I can't imagine they can blow chips out of deep narrow pockets.

[Voicecoil]

I found a little side channel blower in fleaBay for about £60 - with a little nozzle it blew chips everywhere, so much so that I had to throttle it back a bit. If you're tempted to go the same route just be aware that those things come in different flavours of pressure and volume delivery, the one I found did quite a reasonable pressure, ~280mBar IIRC.
I find the noise of the air jet far louder than that of the blower itself.

[devmonkey]

I found a little side channel blower in fleaBay for about £60 - with a little nozzle it blew chips everywhere, so much so that I had to throttle it back a bit. If you're tempted to go the same route just be aware that those things come in different flavours of pressure and volume delivery, the one I found did quite a reasonable pressure, ~280mBar IIRC.
I find the noise of the air jet far louder than that of the blower itself.

Thanks for the tip I will keep a look out for one, what power rating is yours? Could probably machine up a really small one on a brushless RC motor and mount it on the Z. Another project...

[Voicecoil]

Thanks for the tip I will keep a look out for one, what power rating is yours? Could probably machine up a really small one on a brushless RC motor and mount it on the Z. Another project...

Mine's about 500W @ 50Hz mains, will do a bit more at 60Hz.