Hello Guest it is February 24, 2020, 09:51:09 AM

Author Topic: Motor tuning question..  (Read 2553 times)

0 Members and 1 Guest are viewing this topic.

truckeic

• 40
Motor tuning question..
« on: March 22, 2017, 01:50:02 PM »
OK I am a newbie.. and I just got my motors turning yesterday..
I have set the mill to SAE.. not metric..
I have figured up my number by  200 x 8 x 5.08
I am using 1/8 stepping and I have 5mm pitch screw. .
I was told that co.es out to 5.08 inches
So I figured out my steps per inch to be 8128.
I have DROa on my mill actual mechanical one not just looking at MACH3..
I told the mill to mobe G0 x1 y1
The mechandicap dros showed .100

That is off by a bunch..
Any ideas on my screwup..

Thanks

truckeic

• 40
Re: Motor tuning question..
« Reply #1 on: March 22, 2017, 08:41:49 PM »
Well to be sure I checked tonight..
I haver 1.8 step motor.. which I am told is a 200
My driver is 8 microstepping
And I have the Chinese balls crew c7 1605... which I am told is 5mm.

I have been told that convering the 5mm to tpi is 5.08

So doING the cal. I get 8128 steps..

I put that in then tell Mach  3 to move 1... G0 x1

I am looking on this with dial indicator and my mechanical dro..
.189 is actually what it moves...
What gives..
I tried to use the auto cal... and it got closer moved ..6 something but I may have done that wrong ..

This does not seem like it should be this hard...

joeaverage

• 5,901
Re: Motor tuning question..
« Reply #2 on: March 23, 2017, 02:20:56 AM »
Hi,
your calculation is correct, the explanation is a bit wonky....

Your ball screw 1605 is indeed 5mm pitch, ie it moves 5mm per revolution.

1 inch= 25.40mm therefore the screw has to rotate 25.4/5 =5.08 revolutions to move 1 inch. It takes 200 fullsteps or 1600 1/8
microsteps  for the motor to turn one revolution. So your microsteps per inch is 1600 times 5.08 =8128. Set your steps per unit
in Mach3 to 8128 and leave it that way. If you pulse the motor 8128 times the axis should move 1 inch, if it doesn't then the driver
and or motor is missing steps. Fix it.

Make sure your native units are inches, Config/Select Native Units....set to inches and leave it that way. If you need to run a job in
mm's use G20/G21, DON'T mess around with native units.

When your motors move do they move smoothly? What sort of sound do they make, if its in anyway rough it may indicate that the motor
is missing steps. If I understand your description of the fault you first called G0 X1 and it actually moved 0.1 inch. Later you called another
G0 X1 and it moved 0.189 inch. Is this correct? If so that means its not a screwup so much as the motor not be able to pace the instructions
given to it.

In the first instance set the motor tuning slow and the acceleration even slower. Dave often recommends the acceleration be about 10% of
the speed. Try setting the speed to 20 ipm to start with.

Stepper motors exhibit GREAT torque at low speeds, in fact they blow most servos into the weeds at slow speeds, but they can't 'pull the
skin off a rice pudding' at speed. As a start don't expect your steppers to go faster than 500rpm. With 5mm pitch screws that means about
2500mm/min or 98 in/min.

Try settings around these values and let us know how you get on.

Craig
My wife left with my best friend...
and I miss him!

truckeic

• 40
Re: Motor tuning question..
« Reply #3 on: March 23, 2017, 02:06:17 PM »
Hi,
your calculation is correct, the explanation is a bit wonky....

Your ball screw 1605 is indeed 5mm pitch, ie it moves 5mm per revolution.

1 inch= 25.40mm therefore the screw has to rotate 25.4/5 =5.08 revolutions to move 1 inch. It takes 200 fullsteps or 1600 1/8
microsteps  for the motor to turn one revolution. So your microsteps per inch is 1600 times 5.08 =8128. Set your steps per unit
in Mach3 to 8128 and leave it that way. If you pulse the motor 8128 times the axis should move 1 inch, if it doesn't then the driver
and or motor is missing steps. Fix it.

Make sure your native units are inches, Config/Select Native Units....set to inches and leave it that way. If you need to run a job in
mm's use G20/G21, DON'T mess around with native units.

When your motors move do they move smoothly? What sort of sound do they make, if its in anyway rough it may indicate that the motor
is missing steps. If I understand your description of the fault you first called G0 X1 and it actually moved 0.1 inch. Later you called another
G0 X1 and it moved 0.189 inch. Is this correct? If so that means its not a screwup so much as the motor not be able to pace the instructions
given to it.

In the first instance set the motor tuning slow and the acceleration even slower. Dave often recommends the acceleration be about 10% of
the speed. Try setting the speed to 20 ipm to start with.

Stepper motors exhibit GREAT torque at low speeds, in fact they blow most servos into the weeds at slow speeds, but they can't 'pull the
skin off a rice pudding' at speed. As a start don't expect your steppers to go faster than 500rpm. With 5mm pitch screws that means about
2500mm/min or 98 in/min.

Try settings around these values and let us know how you get on.

Craig

OK so I will set my acceleration and velocity at what starting points. The motors don't souND bad... I think I am at 200 acceleration . The 2 numhers to the right of these.. I forgot what they are called but they are both set to 5.. I don't think I changed them but what should they be at..

Should I try to do auto calibration?

It just seems like I am way off.. if the were 20 thou off I would not be so concerned... but I am off almost .800...

joeaverage

• 5,901
Re: Motor tuning question..
« Reply #4 on: March 24, 2017, 01:57:58 AM »
Hi,
sounds like your accel is to high, start it low, very low and see if that fixes the problem. Then you can experiment to find
the useful maximum for your machine.

You can use the auto-cal function, I don't because I built my machine and I KNOW the parameters and can calculate the
steps per EXACTLY. The auto-cal function is for people who don't know their machine and can't be bothered to find out
and/or get confused over basic arithmetic. You decide which camp your in.

Work your axis backwards and forwards using MDI, going a useful distance each time. Set x=0 then go to x=4in and the back to x=0.
G0 X0
G0 X4
G0 X0
It should go back to the exact starting point. If it doesn't no setting or autocalibration is going to do you any good.

The numbers on the motor tuning screen are:
Step per unit, as discussed above should be 8128
Velocity in/min, recommended less than 98in/min, say 30in/min for a conservative starting point.
Acceleration in/sec/sec, recommended less than 9.8 in/sec/sec, say 3in/sec/sec for a conservative starting point.
G's, this is a display only and tells you the 'G force' corresponding to your acceleration setting above. For hobby machines
0.01 to 0.1 are common, high speed production machines can go upwards of 10.
The next two parameters are the pulse length presented to the motor drive by Mach3. My drivers are good quality Japanese ones
and the specs say 1.25us is enuf. If you have crappy ones 5-10 us might be better. If the pulse is to short the driver might miss it
altogether. Note that when you make alterations on the tuning page you have to 'save before exit' or the changes will not be implemented.

The trick to getting this stuff to work is not to change everything at once, change one item and establish what effect it has. If you can
understand each effect then you are well placed to find the right balance of parameters/settings.

Craig
My wife left with my best friend...
and I miss him!

truckeic

• 40
Re: Motor tuning question..
« Reply #5 on: March 24, 2017, 07:25:16 PM »
Hi,
sounds like your accel is to high, start it low, very low and see if that fixes the problem. Then you can experiment to find
the useful maximum for your machine.

You can use the auto-cal function, I don't because I built my machine and I KNOW the parameters and can calculate the
steps per EXACTLY. The auto-cal function is for people who don't know their machine and can't be bothered to find out
and/or get confused over basic arithmetic. You decide which camp your in.

Work your axis backwards and forwards using MDI, going a useful distance each time. Set x=0 then go to x=4in and the back to x=0.
G0 X0
G0 X4
G0 X0
It should go back to the exact starting point. If it doesn't no setting or autocalibration is going to do you any good.

The numbers on the motor tuning screen are:
Step per unit, as discussed above should be 8128
Velocity in/min, recommended less than 98in/min, say 30in/min for a conservative starting point.
Acceleration in/sec/sec, recommended less than 9.8 in/sec/sec, say 3in/sec/sec for a conservative starting point.
G's, this is a display only and tells you the 'G force' corresponding to your acceleration setting above. For hobby machines
0.01 to 0.1 are common, high speed production machines can go upwards of 10.
The next two parameters are the pulse length presented to the motor drive by Mach3. My drivers are good quality Japanese ones
and the specs say 1.25us is enuf. If you have crappy ones 5-10 us might be better. If the pulse is to short the driver might miss it
altogether. Note that when you make alterations on the tuning page you have to 'save before exit' or the changes will not be implemented.

The trick to getting this stuff to work is not to change everything at once, change one item and establish what effect it has. If you can
understand each effect then you are well placed to find the right balance of parameters/settings.

Craig

Ok I am frustrated..LOL
So here is what i am using
KL-5956 driver and a C10 BOB

I have double checked my microstepping which is set to 8
I am using a 1.8 degree motor which is 200..
C7 1605 ballscrews

That said ..
I put in 8128 and when I run auto cal..
MACH3 says it ran 1.0 but my DRO and Dial Caliper agree It  moved  .188
I have velocity @ 10 Acceleration @ 7
Mach 3 says my steps per inch need to be 43234. which is way to high.

I have tried to run the velocity and acceleration up to very high numbers and my motors don't seem to change...

Yea I know it chinese stuff but I know others are running this stuff..

any ideas???
I really don't see anything set wrong.. but I am sure it is...

joeaverage

• 5,901
Re: Motor tuning question..
« Reply #6 on: March 24, 2017, 10:11:46 PM »
Hi,
provided there is not some mechanical fault or slippage then your driver is set incorrectly.

Try setting for zero microsteps, ie 200 pulses per revolution and set your steps per unit to 200 times 5.08=1016 and try it out.

Craig
My wife left with my best friend...
and I miss him!

joeaverage

• 5,901
Re: Motor tuning question..
« Reply #7 on: March 24, 2017, 10:29:53 PM »
Hi,
I found a manual for Keling 5056 driver online. Is this in fact the driver you have?

I noted that the switch arrangement for 8 microsteps is 'off off on on' whereas the switches for 40 microsteps is 'on on off off'.
Is it possible you've got the switch arrangement backwards?

Craig
My wife left with my best friend...
and I miss him!

joeaverage

• 5,901
Re: Motor tuning question..
« Reply #8 on: March 24, 2017, 10:39:58 PM »
Hi,
have been doing some more reading and Keling drives have a solid reputation, if I made an on the cuff or biased
remark please accept my apologies. I am not fond of people who criticise on the basis of preconceptions but I am
capable of doing exactly that!

Craig
My wife left with my best friend...
and I miss him!

truckeic

• 40
Re: Motor tuning question..
« Reply #9 on: March 25, 2017, 12:08:18 AM »
Hi,
have been doing some more reading and Keling drives have a solid reputation, if I made an on the cuff or biased
remark please accept my apologies. I am not fond of people who criticise on the basis of preconceptions but I am
capable of doing exactly that!

Craig

No you have not made any remarks. ..