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Author Topic: Set Up START MOTOR SPEED in Mach3  (Read 4965 times)

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Set Up START MOTOR SPEED in Mach3
« on: September 07, 2008, 02:14:06 AM »
Hi, I made a four axis machine which can move at 10000mm/Min, it is specialized for rapid prototiping. The problem is vibrations that appears in rapid moves (When starting and stoping, you can hear a "tuc!!"). I would know if is any way to set up de start frequency in Mach3 (If it exist, where can I do it?). In some programs you can chose it (10hz to 100hz)

Regards
Tiwnacote

Offline Hood

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Re: Set Up START MOTOR SPEED in Mach3
« Reply #1 on: September 07, 2008, 01:47:31 PM »
Dont think there is a setting but then again I am not really sure what you are meaning ;D
 Hood
Re: Set Up START MOTOR SPEED in Mach3
« Reply #2 on: September 09, 2008, 12:09:03 PM »
There is a start frequency when stepper motors start to move, usually is betwen 20Hz to 100Hz (Pulses are send not from 0Hz, the Program start to send them from 20 to 100Hz depending on the setting). The problem is that if it is set very high teorically, you will have a big acceleration and that means vibrations on the system.
I hope to be clear...
Regards
Tiwanacote

Offline Hood

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Re: Set Up START MOTOR SPEED in Mach3
« Reply #3 on: September 09, 2008, 02:16:23 PM »
Sorry still not quite sure what you are meaning but maybe you just need to lower the acceleration on the motor tuning page to achieve what you are after?
Hood
Re: Set Up START MOTOR SPEED in Mach3
« Reply #4 on: September 09, 2008, 03:02:48 PM »
What Hood means is to increase the ramp in acceleration. in motor tuning
See attachment. This should get rid of jerk.

Ed V
Ed VanEss

Offline RICH

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Re: Set Up START MOTOR SPEED in Mach3
« Reply #5 on: September 09, 2008, 06:05:58 PM »
Hi Tiwancote,
10,000mm/min is equivilant of approx 400 in/min and that is a rather fast movement.

If you pop the clutch pedal and stomp on the gas pedal of a high preformance car she'll plant you right into your car seat along with your neck being thrown back .Then when you slam on the brakes, and if she could stop instantly , you would probably go thru the windshield. Hard on the car parts even when built for it. I think Newton said the Force=Mass x Acceleration.

So if your steppers have enough torque to move a table from standstill to 400 in/min rather instantly, all that torque
goes goes quickly into the drive train. So you just "punched" the drive train with a hard force. It certainly can make the ball of the screw create a "tuc". So one way to keep from creating a larger force on the drive train is to ramp up over a  longer period of time. So we ramp up ie; slowly let the car clutch out and press on the gas pedal, we walk- then jog- then run.
Like ED V showed you.

Now vibration is another story and can be mechanical and electrical in nature. To have vibration it must be induced by something at a some natural resonant frequency. Another reason you ramp is to quickly go thru the resonant frequency of somthing so it dosen't start to vibrate. So not sure on your vibration comment, but, if your ramp up and down within the
capabilites of you system you shouldn't need to deal with one.
RICH



 

Offline RICH

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Re: Set Up START MOTOR SPEED in Mach3
« Reply #6 on: September 09, 2008, 07:38:49 PM »
Tiwancote,
Attached is a screen shot from a program which supposedly allows you to create an acceleration curve ( ramp ). Looking at the curved red ramp, supposedly you can create a ramp with different steps per second values at "nodes" and end up with a combination of linear ramps or a custom curved ramp. Mach dosn't let you do this.  I don't know how MACH is programed and just ass u me it's of the total linear type shown in blue ( It works so I don't care). Now Quantum, I think, is implementing a different kind of ramp curve for MACH  but out of ignorance I will just leave it at that. I think this is what you meant by settinig the initial HZ value, but only you can be the judge.
 :) RICH
Re: Set Up START MOTOR SPEED in Mach3
« Reply #7 on: September 15, 2008, 02:11:05 PM »
Thank you for that explanation, Rich!!!!!  I supouse that Mach3 dont´t allow you settinig the initial HZ value.
I analyzed the vibrations and they are low frequency, they come from little movment changes an especific frequency (Resonance). I will make a little program to process the G code to prevent this movments!!

Thankyou!
Tiwanacote