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  #1  
Old Thu 18 October 2012, 13:45
viz
Just call me: viz
 
Kaunas
Lithuania
Nema 34 set at 6000 velocity stops rotating

Hello,

Have some problems again, need your help.

I calculated "Steps per" and entered it to mach3.
Motors: Nema 34 1600oz, Curent: 3.5A.
Drivers: Wantai DQ860MA, Input voltage 24-80VDC, Output current 2.8A~7.8A
On drivers i set "2000 puls/rev", PEAK 4.5A and RMS 3.5A.

Problem is that if i set on mach3 velocity to more than 4500 one of the motors starts rotating and at full speed it stops, but the voice seems like it's working.

If i set that axis velocity to 4000 the motor works perfect. Other motors at 6000 velocity working without any problems.

I have uploaded video to youtube: http://youtu.be/YgC682F7pmA (in this video X and X Slave set at 6000 velocity and as you see it is working, and one motor Y axis velocity set to 6000 also, but it is not working at full speed)

Maybe you know what is the problem ?
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  #2  
Old Thu 18 October 2012, 14:07
smreish
Just call me: Sean - #5, 28, 58 and others
 
Orlando, Florida
United States of America
? - Possible that the driver attached to the slower motor is not tuned (amplifier card) not set the same as the other, thus limiting it's top speed.

? - are all motors wired the same....1/2 coil or full coil?

? - bad motor with bad windings

Does the slower motor perform correctly when driven on a KNOWN good channel? If so, then I would look into a setting in Mach 3
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  #3  
Old Thu 18 October 2012, 21:11
KenC
Just call me: Ken
 
Klang
Malaysia
The video looked like your motor is loosing steps... I suspect you set your acceleration too high on Mach3. try reduce it significantly to see if this is the cause.

While we are at it, Did you ever test the motors? I know of 2 tests,
1) The slow test, measure the motor coil inductance & resistance with a multi-meter. The inductance & resistance of each coil should be very close to each other.
2)The quick test, motor shaft should turn freely when all the wires are seperated from each other. The shaft should jam up when all the wires are touching each other.
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  #4  
Old Thu 18 October 2012, 23:07
viz
Just call me: viz
 
Kaunas
Lithuania
Yes if i reduce velocity to 4000, the problems gone. But why only one motor have this problem ?

I have checked all setting in wiring and selecting PINS on drivers, all setting are the same.

I can turn by hand the shafts of motors. Also i have checked the inductance & resistance.
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  #5  
Old Thu 18 October 2012, 23:11
KenC
Just call me: Ken
 
Klang
Malaysia
Not the velocity, Check the ACCELERATION setting in Mach3.
when you turn the motor shaft, are the coil wires connected to the motor drivers? If they are connected, the test is useless.
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  #6  
Old Thu 18 October 2012, 23:14
viz
Just call me: viz
 
Kaunas
Lithuania
Quote:
Originally Posted by KenC View Post
Not the velocity, Check the ACCELERATION setting in Mach3.
when you turn the motor shaft, are the coil wires connected to the motor drivers? If they are connected, the test is useless.
I tried before then the coil wires were disconnected from the drivers.

I tried accleration setting in mach3, set to 30 then to 50, then to 100, the same problem.
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  #7  
Old Thu 18 October 2012, 23:35
KenC
Just call me: Ken
 
Klang
Malaysia
reduce acceleration setting, increasing will only make things worse.

Also, you only did half of the quick test... Please read the whole thing.
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  #8  
Old Thu 18 October 2012, 23:38
viz
Just call me: viz
 
Kaunas
Lithuania
Ok i will try to reduce acceleration.

Also here is my STEPS PER calculation 106.103 <- i entered this number into mach3.

Maybe my motors can run faster than 4000mm/min ?
Attached Images
File Type: jpg Steps per.jpg (127.3 KB, 224 views)
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  #9  
Old Thu 18 October 2012, 23:41
Surfcnc
Just call me: Ross #74
 
Queensland
Australia
Hi Viz

Yep lost steps.
You are making the acceleration faster not slower as the number increases.
Try something really low like 5 - that's around .5 sec to spin up to full speed.
Dropping the microstepping to below 10 will also give more torque and encourage the motors to spin up more reliably.

Also you currently have no shielding on the stepper wires, do not expect a perfect result.

Regards
Ross
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  #10  
Old Thu 18 October 2012, 23:47
viz
Just call me: viz
 
Kaunas
Lithuania
Quote:
Originally Posted by Surfcnc View Post
Hi Viz

Yep lost steps.
You are making the acceleration faster not slower as the number increases.
Try something really low like 5 - that's around .5 sec to spin up to full speed.
Dropping the microstepping to below 10 will also give more torque and encourage the motors to spin up more reliably.

Also you currently have no shielding on the stepper wires, do not expect a perfect result.

Regards
Ross
Thank you, i will try later at home. I think the main reason will be too big microstep
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  #11  
Old Fri 19 October 2012, 01:11
Surfcnc
Just call me: Ross #74
 
Queensland
Australia
Unlikely to be the 10x microstepping, really just mentioned that for later when the motors might have some load on them. 10x is quite standard.

Ross
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  #12  
Old Fri 19 October 2012, 02:11
viz
Just call me: viz
 
Kaunas
Lithuania
What settings i have to use for my 3.5A motors ?

PEAK 3.5A and RMS 2.4A
or
PEAK 4.5A and RMS 3.5A

Don't understand what is different between peak and rms and witch one is close to motor 3.5A
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  #13  
Old Fri 19 October 2012, 03:12
KenC
Just call me: Ken
 
Klang
Malaysia
honestly, nobody can answer your overly general question...
Just keep on trial & error.
If the motor don't melt down & still running, you will be fine...

Peak is PEAK as the name implies, RMS is root-means-square, if you are still interest, Wikipedia gives a very comprehensive explanation. definately better than what I can explain...
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  #14  
Old Fri 19 October 2012, 03:52
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Peak = sometimes
RMS = all the time

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  #15  
Old Fri 19 October 2012, 10:29
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
1600 oz*in motors are at least two times larger than most of us use. Typically, the larger the motor, the longer it needs to get to speed. A large motor usually has more inductance than a small motor. Inductance can be thought of as resistance to change. It takes longer for a motor with high inductance to change from one speed to a higher speed (more ramp time).

Because you already have the motors and the drivers, you will need to experiment to see how SLOWLY you have to ramp those motors (acceleration setting) to make the motors 100% reliable. If a motor is accelerated too quickly, it loses steps. If it loses steps, the length of the movement is too short and the cut will be faulty.

As a side note: Having large motors is not an advantage. Choosing the properly sized motor for the job is better. If you're using a 3:1 to 7.2:1 gearbox/beltdrive, a 300 oz*in motor is excellent. If you're driving things without a gearbox or beltdrive, a 600 oz*in or slightly larger will work just fine.
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  #16  
Old Fri 19 October 2012, 10:50
viz
Just call me: viz
 
Kaunas
Lithuania
Yes now i am trying with acceleration settings, but if i set in mach3 velocity to 6000, the lowest acceleration number i can set is 25, and at this settings one motor sometimes spins, sometimes not.

So i think i will add that motor to Z axis, because there is speed about 1500 and at that speed motors runs without problems, don't know how will be then it spin for longer time.
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  #17  
Old Fri 19 October 2012, 11:11
viz
Just call me: viz
 
Kaunas
Lithuania
Tested about 10 minutes with velocity set to 10000 and acceleration to 41 (the lowest i can choose) on X A Y axis and only one time i loose steps, it is bad. So i set now to 6000 and acceleration to 25, seems to work without loosing steps. That one bad motor plug into Z axis but the velocity i can set only to 500 and acceleration to 20. Now it is working... but don't know how long.

Is these speeds is good enough for starting with OSB cutting ? Because have never tried to do it before

The table size is 3.5mx2.5m

And here for interesting i attached my cnc picture
Attached Images
File Type: jpg cnc.jpg (115.0 KB, 205 views)
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  #18  
Old Fri 19 October 2012, 21:34
KenC
Just call me: Ken
 
Klang
Malaysia
why 6000?
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  #19  
Old Sat 20 October 2012, 11:28
viz
Just call me: viz
 
Kaunas
Lithuania
It too big velocity or too small ?
I was testing, can my steppers work on 10000 but got loosing steps, after trying to decrease i got that velocity set to 6000 was working 3 motors but fourth didn't. Maybe this speed is too big, because i didn't tried on cnc machine. What is your velocity ?
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  #20  
Old Sat 20 October 2012, 19:21
Surfcnc
Just call me: Ross #74
 
Queensland
Australia
Viz I see that is not a Mechmate CNC machine, this forum is usually only for people who are building a Mechmate.
Cnczone is the place for non Mechmate machines, you will find them very helpful.

Lastly you can manually enter speed and acceleration figures in the motor tuning in Mach3. Press save to set the figures.
It must be an issue with language but to date you have have left out far too much information in some of your questions.
To get a good answer on the CNCzone you will need take the time to ask a good question.

Ross
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  #21  
Old Sun 21 October 2012, 02:49
viz
Just call me: viz
 
Kaunas
Lithuania
Ok understand thank you for your support in this forum it was really helpful !
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