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Stepper motors seem a LITTLE slow
« on: October 11, 2011, 12:33:15 PM »
Hi all

This may be something or nothing.

I have just converted a 7x14 mini lathe to two axis CNC. Everything works fine but when I increase the jog above 5% the drives start to loose steps and grind to a halt.
If i'm set to 5% and below everything is fine.

My config is as follows:

3.06Ghz processor.
TB6560 driver card. DIP switches set to 75%, FAST, Half step.
57BYGH603 stepper motors. 1.0amp 1.8 step angle 14.5 kg.cm running at 24vdc.

Using this information I have set the Mach3 steps per unit to 4000 which gives me the correct travel as per the DRO.
I have the step/dir timing set to 1us.

I have the acceleration set at 0.6 seconds and the velocity at 200in/min.

The kernel speed is 60,000hz.

Any help would be appreciated. It might just be that my motors are not man enough to go any faster which is fine as I can work with it as it is.

Cheers
Phil

Re: Stepper motors seem a LITTLE slow
« Reply #1 on: October 11, 2011, 12:40:08 PM »
Correction:

Driver card set to:
Current (amps) 75%
Decay mode FAST
Microstep setting 1/2

Offline Hood

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Re: Stepper motors seem a LITTLE slow
« Reply #2 on: October 11, 2011, 02:30:41 PM »
First thing to say is you should not have the kernel any higher than you need. Next is likely you would be better set to 1/8 stepping. You then need to set the steps per unit correctly and then set Velocity and Accel on Motor tuning page, the latter two need trial and error to set as there is no hard and fast numbers that will work on all machines as there are so many variables.
Hood
Re: Stepper motors seem a LITTLE slow
« Reply #3 on: October 11, 2011, 03:11:18 PM »
Hi there

So, I set the board to 1/8th microstep.

The Mach3 steps per unit works out at 32000!! to get the correct travel. However, no increase in speed despite playing with vel/acc graph.

Are the motors supposed to get hot when running?

Cheers
Phil

PS I lived in Aberdeen for 10 years. The granite city.

Offline Hood

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Re: Stepper motors seem a LITTLE slow
« Reply #4 on: October 12, 2011, 02:29:15 AM »
Phil can you attach your xml please.

Aberdeens quite a nice place, its about 70-80 miles up the coast from me.
Hood

Offline RICH

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Re: Stepper motors seem a LITTLE slow
« Reply #5 on: October 12, 2011, 06:53:34 AM »
Are the motors supposed to get hot when running?

They can get hot if the drive current setting is to high and when they get hot they can start to act wierd.
Any motor which is doing work will increase in temperature. No increase in temp and they are not doing much work.
You don't want to exceed their rated temperature.
If they get hot ( can't touch and leave your hand on them ) you are over 140 deg F and you'll get a burn.
If they get hot quickly upon engagng them and not running your current setting is to high.

FWIW,
RICH

RICH
Re: Stepper motors seem a LITTLE slow
« Reply #6 on: October 12, 2011, 11:08:39 AM »
XML attached.

The motors are not so hot that I cant touch them.

Cheers
Phil

Offline BR549

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Re: Stepper motors seem a LITTLE slow
« Reply #7 on: October 12, 2011, 11:16:42 AM »
With an accel rate set to .6 /sec/sec it would take forever to get up to speed with a max vel of 200in/min. with short moves involved you have to accell up to speed then slow down to a stop in the givin move. You may NEVER get any speed with some code.

Just a thought,

Offline Hood

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Re: Stepper motors seem a LITTLE slow
« Reply #8 on: October 12, 2011, 02:14:47 PM »
Ok first glance at XML looks fine except from as Terry says accel is slow and also so are your Velocities.
Can you just clarify what you are meaning by this " Everything works fine but when I increase the jog above 5%"
What is the 5% you are talking about?
Hood
Re: Stepper motors seem a LITTLE slow
« Reply #9 on: October 12, 2011, 11:10:10 PM »
When I had the velocity set to 200in/min I couldn't go above 5% in the slow jog % box in the manual screen. Since I have lowered the velocity to 10in/min and the accel is set to 0.5 in/sec/sec now I can go to 100% but these numbers are academic as the overall velocity is no higher than before. I hope this makes sense cause i'm confused as hell...lol.

When I say everything works fine, this is what I mean. My lathe is only 14" across the bed so 10 in/minute is slow but workable. I would have thought that for a rough cut I could have got 20-30 in/min but i'm no expert in machining. I'm an electronics man, not a turner. It's just something I fancied learning.
I should also add that i'm working with delrin 150 so I should be able to go quite a bit faster than working with alloys.

Also, my steppers are only 1 amp rated, I suspect they are underrated.

Cheers
Phil