Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: jazavac2302 on March 16, 2014, 03:16:26 AM
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First of all I'm new here and this is my first post. greetings to everyone. :)
I'm been reading a lot here about everything, but still have some questions.
My setup:
PC:
Dualcore 2600
2GB ram
500gb HD
graphic card ATI 256mb
Windows 7 32bit
MACH3 setup
Version 2,68 (With newer version I have problems wirth rapids when gcode is loaded)
V 2.68 works perfectly, but in version 2,68 the driver test in mach 3 folder is set to 25 khz and I cant change it to see how it performs under higher pulse rates.
When I change the khz in mach3 under pins and port to 100 khz and then goes to diagnostic tab under pulse freqency it stys at 94000 + - 50 khz.
I'm a metric user so under config tab a have:
select native units: mm
ports and pins: have set to 100 khz
(the other parameters are ok everything works like it should)
Motor tuning:
steps per: 200 velocity: 1500 acceleration: 100
same is for y,z and a axis
On the x axis I have two motors so I slaved A axis.
This is the setup:
I have nema 34 1600 oz 1,8 200 per rotation
My ball bearing actuator has 5mm per rotation
Driver: DM 860A set on 1000 (I tried every micro stepping mode but with more micro step per rotation I get lower speeds and more pulses are needed for faster rotation)
every driver has its own power supply on 60v 7,8 amp
And here is my problem.
I want to go faster but when I set the velocity to 3000 or 4000 the motor turns ok (I tried to stop it but they are to strong) but when 2 or more axis are engaged at same time i get missing steps.
Can someone calculate theoretical speed that I can get from my setup?
Is it possible that with 4 axis one is slave at 3000 my pulse rate is to slow even in 100 khz mode?
Or do I have to buy smooth stepper to go faster?
Thanks a lot.
Regards
mike
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kernel speed required = (steps per unit * velocity in units per minute) / 60. Choose the lowest kernel above this figure. Choosing anything higher is a) pointless and b) likely to cause problems.
Depending on what type of machine you have, you may well be another victim of the bigger is better mistake. Large stepper motors are NOT good for speed. They're better at shifting large loads slowly. Smaller motors may well be the way to go if you want speed.
Microstepping "typically" should be set to 10.
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Thank you for your fast replay :)
So I have:
(200*1500)/60 = 5000khz
and if I want to go 3000 velocity
(200*3000)/60 = 10000khz
So 25000 khz is more than enough for my spped.
Why do my motors lose steps when running at 3000 velocity?
And not to mention they are not connected to anything yet.
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Why do my motors lose steps when running at 3000 velocity?
And not to mention they are not connected to anything yet.
Steppers have all their torque at low RPMs, increase the RPM and torque falls of a cliff, also as Ian has mentioned, bigger is not always better, just depends on the machine and the way things are geared as to which mototr would work the best. I am a servo man, torque is more or less constant no matter the RPM and huge overhead of peak torque for short periods :) But steppers have their place, they work well as long as you work within their capabilities.
Hood
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Just read your OP again and although you dont mention the machine type/setup/weight etc it kind of sounds like it may be a router. It seems like you may be running direct coupled and if so 3m/min would be about 600rpm which is likely top end for a big stepper, might be worth your while gearing 1:2 if possible, you may still have plenty of torque with the big motors and you will get twice the Velocity for a given motors RPM.
Hood
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when I set the velocity to 3000 or 4000 the motor turns ok (I tried to stop it but they are to strong) but when 2 or more axis are engaged at same time i get missing steps.
This is curious. When you say "engaged" do you mean enabled or moving?
And not to mention they are not connected to anything yet.
Do you mean they're not bolted to anything i.e. sitting on a bench? If so then this can be misleading. Resonance is more likely to occur on an unmounted motor. Which also takes me back to your lack of microstepping. This is also likely to cause resonance problems.
Out of interest - do you have a link to the data sheets for your motors and drivers?
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Sorry
Yes it is a router and yes it is direct coupled
I have also smaller nema 23 400 oz and they behave the same.
Im currently running at 1600 velocity and when I increase to 3000 then it starts to miss steps.
Weight ?
It is a small router. 1000mm x 500mm. z axis 50mm
I know that the steppers looses torque with increasing speed but the motors are not connected to anything, they are running freely at the moment.
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when I set the velocity to 3000 or 4000 the motor turns ok (I tried to stop it but they are to strong) but when 2 or more axis are engaged at same time i get missing steps.
This is curious. When you say "engaged" do you mean enabled or moving?
And not to mention they are not connected to anything yet.
Do you mean they're not bolted to anything i.e. sitting on a bench? If so then this can be misleading. Resonance is more likely to occur on an unmounted motor. Which also takes me back to your lack of microstepping. This is also likely to cause resonance problems.
Out of interest - do you have a link to the data sheets for your motors and drivers?
Yes, when I mean engaged I mean moving two or more axis at the same time.
Yes. the motors are not bolted. It may be a problem. I didn't think about it.
I am currently running it on 60v.
Attahced I am sending you the datasheet for the driver.
Here is the link for the motor datasheet:
http://sine.ni.com/ds/app/doc/p/id/ds-311/lang/hr
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Another thing to try is this.
Go into the PC Bios, and disable C1E or EIST if you have them. This allows Mach3 to run much better on some multi core PC's.
However, most 1600oz steppers are very slow. Ebay is flooded with them, and I see this all the time. People buy them, thinking bigger is better. In actual use, a 450oz Nema 34 will often run a router at 5x faster than a 1600oz motor.
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There's no 1600 oz/in motor on that page. Anyway - IMHO you're making a rod for your back trying to use those motors on a small router - personally I'd switch to your 23s. You can't just say they behave the same - they're completely different motors and will need driving differently. Do you have a part number or spec sheet for them?
FWIW I use 3Nm 23s on my router which is just a little bigger than yours and I can get 15m/min rapids and 0.5G accel.
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Might also verify that your step pulse active states are set properly.
Increasing the pulse width slightly might also be worth a try.
Russ
:)
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I have these nema 23 motors
http://www.ebay.de/itm/From-German-WH-3pcs-Nema23-dual-shaft-stepper-motor-425oz-in-CNC-Free-Shipping-/201017269054?pt=Motoren_Getriebe&hash=item2ecd901b3e
I will try to find those settings in bios. Maybe it helps.
I can mount nema 23 but a thought that bigger is better so I didnt try the smaller nema 23 425oz.
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Some things are indeed better when bigger - but this doesn't necessarily include stepper motors. Unfortunately your 23s aren't ideal either - they're quite high inductance and would require approx. 100Vdc to get their *max* torque/speed potential.
All this said - don't make the mistake of chasing speed for the sake of it. As long as you can achieve the cutting speeds you need, rapids can be somewhat less important. The thing often not considered is what acceleration can you get - now that IS important.
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Another thing to try is this.
Go into the PC Bios, and disable C1E or EIST if you have them. This allows Mach3 to run much better on some multi core PC's.
However, most 1600oz steppers are very slow. Ebay is flooded with them, and I see this all the time. People buy them, thinking bigger is better. In actual use, a 450oz Nema 34 will often run a router at 5x faster than a 1600oz motor.
I disabled C1E and I think that did the trick.
Now I'm running 4000 per min with no problems.
This is more than double of what I was getting earlier.
It can go probably up to 5000 per min but for my steppers this is more than enough.
Thanks a lot to everyone.
This is one of the best communities and people here certainly know what they talking about.
Thanks a lot again
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Might also verify that your step pulse active states are set properly.
Increasing the pulse width slightly might also be worth a try.
Russ
:)
My drivers are set to
DIR low active (here is active low cause I have to change direction)
STEP low active (when I set high active the drivers dont work)
Where can I increase the pulse width ?
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All this said - don't make the mistake of chasing speed for the sake of it. As long as you can achieve the cutting speeds you need, rapids can be somewhat less important. The thing often not considered is what acceleration can you get - now that IS important.
This is wisely said.
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look on the motor tuning dialog for increasing the step pulse width. Unfortunately your driver data sheet doesn't specify what minimum pulse width is required (Chinese... what can you say?). Also your Chinese chappy is fond of using slow (as in cheap) optos but if it's not missing steps you're probably ok. The dir pulse value is the extension to the default min time the dir signal must be changed before the next step pulse. This should only need changing if you find you're losing the first step after a direction change.
I'm still a tad mystified by your early comment that you got stalling when you tried to move more than one motor at a time. Is this still happening?
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When I have disabled the C1E in bios now everything work very smooth and fast.
I have set my rapids to 3000 now (before the max was 1600).
I can go to 6000 without loosing steps but I have to reduce my acceleration.
So I set it to 3000 with very fast acceleration.
For the job that took 1h and 8 min to complete, now it is done in 48 min.
The cutting speed is the same.
And you were right about the motors running not coupled to anything,
I have mounted them on the CNC and they work perfectly.
Thanks again for all your help and advice.