PDA

View Full Version : Droping Steps, closed loop ? HELP !!!



bobin
11-05-2009, 12:49 PM
Hi lee well, heres a one to give some thought to or for every-one that may want to participate...
Built a mediem sized metal milling machine with 10 amp routout boards and nema34 160 oz-inch steppermotors running mack3,
Overall gearing reduction is 6 to 1(toothed belt and lead screw)...works great moves great...but it drops steps!!!
Is there any-way encoders could be fitted to the motors and (controlers and software) to create a closed loop control like the professional systems....bobin

Gary
11-05-2009, 01:51 PM
Not with your current hardware.
Would be better to go for a servo system if you want to add closed loop control.
If you are losing steps then you are most likely under powered or trying to push the speed faster than the system can handle.
I donít know this driver that well, but i suspect that the voltage is quite low and that is most likely the problem.
The cheapest option would be to buy a better driver and run at a higher voltage.
Then it may not loose steps?

Gary



Hi lee well, heres a one to give some thought to for every-one that may want to participate...
Built a mediem sized metal milling machine with 10 amp routout boards and nema34 160 oz-inch steppermotors running mack3,
Overall gearing reduction is 6 to 1(tooted belt and lead screw)...works great moves great...but it drops steps!!!
Is there any-way encoders could be fitted to the motors and (controlers and software) to create a closed loop control like the professional systems....bobin

bobin
20-05-2009, 12:42 PM
hi kip thanks for infor on emc2 (linux prog ) this looks like a rock solid platform to run cnc machines from , but couldn't even seem to down load it,so how it works is way beyond me...

bobin
20-05-2009, 12:52 PM
eh no whats iso.thought it could be run from disk...without installing linux operating system..tried down loading took ages and got nothing on the disk?

BillTodd
20-05-2009, 01:01 PM
eh no whats iso.thought it could be run from disk...without installing linux operating system..

An 'iso' is a image file - your cd burning software can use it to create a CD.

The 'live' CD will run on any PC without installing over or damaging your windows installation (it will be slower than an installed version obviously)

To download the iso click here (http://www.linuxcnc.org/hardy/ubuntu-8.04-desktop-emc2-aj13-i386.iso)

Save the file on your harddisk somewhere (e.g. desktop) then open your CD burning software (e.g. Nero) select Recorder/Burn Image...

Set your PC to boot from the CDROM drive (you may need to adjust BIOS settings) and run the CD.

John S
20-05-2009, 02:11 PM
That's the problem with EMC, it's written by techies, for techies

One thing I noticed in the first post Nema 34's rated at 160 oz in ??

How old are those motors ? if they are the old round style and not the more modern square type this could be your problem.

Another thing is has anyone checked the Routout 10 amp drives on a scope for clean signals ? the smaller drives are terrible but I have never tried the larger drives, I can't see any point in going to 10 amps but having a voltage ceiling of 37 volts and this is advertised as Absolute maximum so say 30 volts for safety.

I was dubious reading the spec sheet where it says can run up to a Bridgeport at 2500 mm / min ???????

.

bobin
20-05-2009, 04:10 PM
hi they are in fact an old superior electric (slo-syn)round style motor ,have been running them at at voltage of 25...will lift it to 32v......but dont want to push the rout-out boards too far,blown one set up,,,(replaced mosfets..and working again)
I tried running mill at 25mm per min in aluminum and in a 18mm pocket it drops about 25 thou off the size all round(very little slog on lead screws and compensated for on mack 3) as you say may have to go for bigger motors(brother and i built a big bridgeport using plug and play {low cost rerofit} servo system,not a cheap solution,but it is spot
on with no droped steps ....but cost an arm and a leg for hobby machine...thanks for the reply bobin

bobin
20-05-2009, 04:56 PM
yes calibrated with dial micrometer to be sure..not too sure what else i can do with this set up....dont think i am going to get the acuracy i was expecting ...will try bigger motors and drop the gearing to see what happens...had the gearing high to give a good step resolution not particualy bothered about speed acuracy is more important so have dropped the speed right down in the past.....thanks going for bigger motors...bobin