Long term Z axis problem
Posted by
John Stevenson
on 2006-09-07 15:36:02 UTC
The machine is a NC5 Beaver mill, about the same size as a series II Bridgy.
It's on type 42 steppers direct driving 5tpi screws and it was made this way, it's not a conversion.
For any years it ran on an old bi level driver with little or no trouble except for old and dated components.
When the last driver borad went pear shaped I changed over to modern drives and settled on Gecko 210's running at 10 microstep.
X and Y have alway run OK but the Z axis has always lost postion 'slightly'. on a normal small part at the finish I could be a thou or two short of zero.
It's never bothered me as nothing I do is that critical in Z.
On some parts where I have to drill literally 1,000's of small holes I could be 15 to 20 thou short, again not a problem as these are thru holes and there is enough clearance both sides.
The machine runs AHHA software which is very good as it's customisable in many ways.
Different settings were tried to try to cure this, pulse width's, leading edge, trailing edge etc. Marriss was consulted but he put it down to a bad motor even though I had tried three different ones.
Last weekend I had the misfortune to crash the machine, my fault I chose the right tool but wrong offset and stuffed the 20mm cutter into the vise jaw.
Not a bad crash as things go, 30 thou cleaned the jaw up on the grinder and the tool was resharpenable without taking loads off but it took the Z Gecko out.
Fuse was Ok but all the mosfets are burnt.
OK, my fault, hands up and learn from the experiance.
Replaced it with a brand new Gecko 210 and away we went.
Ran the rest of Sunday and all day Monday, switched off Monday night and rezeroed the Z as usual, 10 thou out.
Switched on Tuesday morning, hit start and no Z moves, checked the drive, no light on but fuse OK and it had 62 volts to the drive ?????????
Why ?? running OK on the night, did nothing and no drive in the AM and fuses intact. Internally the drive shows no damage.
No spare drives left, new or secondhand but I did have a couple of 80 volt 7.8A Chinese drives handy.
Wired one of these in, same motor, same fuse and everything and did a dummy run of the program to try it out.
Worked OK but when it had finished the Z was back to zero.
Since then the machine has done 8 hours of continious drilling and hit zero at every finish.
Nothing has been changed as regards setting, ramp, acceleration etc other than the steps being altered as these Chinese drives are 8 microsteps instead of 10.
The Gecko's had the jumper set to the 42 motor setting but the Chinese ones don't have a setting.
Just have to wait and see what the long term results are.
John S.
It's on type 42 steppers direct driving 5tpi screws and it was made this way, it's not a conversion.
For any years it ran on an old bi level driver with little or no trouble except for old and dated components.
When the last driver borad went pear shaped I changed over to modern drives and settled on Gecko 210's running at 10 microstep.
X and Y have alway run OK but the Z axis has always lost postion 'slightly'. on a normal small part at the finish I could be a thou or two short of zero.
It's never bothered me as nothing I do is that critical in Z.
On some parts where I have to drill literally 1,000's of small holes I could be 15 to 20 thou short, again not a problem as these are thru holes and there is enough clearance both sides.
The machine runs AHHA software which is very good as it's customisable in many ways.
Different settings were tried to try to cure this, pulse width's, leading edge, trailing edge etc. Marriss was consulted but he put it down to a bad motor even though I had tried three different ones.
Last weekend I had the misfortune to crash the machine, my fault I chose the right tool but wrong offset and stuffed the 20mm cutter into the vise jaw.
Not a bad crash as things go, 30 thou cleaned the jaw up on the grinder and the tool was resharpenable without taking loads off but it took the Z Gecko out.
Fuse was Ok but all the mosfets are burnt.
OK, my fault, hands up and learn from the experiance.
Replaced it with a brand new Gecko 210 and away we went.
Ran the rest of Sunday and all day Monday, switched off Monday night and rezeroed the Z as usual, 10 thou out.
Switched on Tuesday morning, hit start and no Z moves, checked the drive, no light on but fuse OK and it had 62 volts to the drive ?????????
Why ?? running OK on the night, did nothing and no drive in the AM and fuses intact. Internally the drive shows no damage.
No spare drives left, new or secondhand but I did have a couple of 80 volt 7.8A Chinese drives handy.
Wired one of these in, same motor, same fuse and everything and did a dummy run of the program to try it out.
Worked OK but when it had finished the Z was back to zero.
Since then the machine has done 8 hours of continious drilling and hit zero at every finish.
Nothing has been changed as regards setting, ramp, acceleration etc other than the steps being altered as these Chinese drives are 8 microsteps instead of 10.
The Gecko's had the jumper set to the 42 motor setting but the Chinese ones don't have a setting.
Just have to wait and see what the long term results are.
John S.