Scaling of axis

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9 years 7 months ago #88938 by Nondepietjes
Replied by Nondepietjes on topic Scaling of axis
For my encoder scale of the z axis. i have turn the servo motor by hand and measer the real distance and compared it to the DRO. so the encoder scale of 500 should be right. If thats the right way to do? The linear encoder doas use indeed a conversion box and will needs some testing. But first i want to get my z-axis right. My only problem is that when i ask to move 10 mm or 5 mm or another distance. My machine is going verry slow and not 2000 mm/min. When i set my output scale lower then the machine goas faster but if i change my P-regulator up, my servo begin to make lot of noise an the machine goes slow again.
So i don't know what the OUTPUT_SCALE does.

So all together
- i can't get the machine to the right speed
- and the regulation of the machine goes difficult

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9 years 7 months ago #88941 by PCW
Replied by PCW on topic Scaling of axis
In general you should not change the default output scale or output limits (normally 10, -10,+10)

The only things that normally need to be adjusted for velocity mode servos are:

1. Encoder scale

2. P term

3. FF1 term

4. Maybe FF2

5. You may have to reverse the sign of output scale if the feedback is wrong (you get a runaway)

Have you gone through JTs tuning tutorial?

gnipsel.com/linuxcnc/tuning/servo.html

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9 years 7 months ago #88964 by Nondepietjes
Replied by Nondepietjes on topic Scaling of axis
so there is no need to tune the I or D term?
And i have seen the tutorial but not properly done it.
surtenly many thanks for the help, i will let it know how it went or if i have other problemes

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9 years 7 months ago #89092 by Nondepietjes
Replied by Nondepietjes on topic Scaling of axis
Hi,

I have adjusted a few things, but my servo still make some noise ( i think vibration)
anybody that now what the cause?

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9 years 7 months ago #89121 by bevins
Replied by bevins on topic Scaling of axis
Vibration or oscillation?

Try dropping P until you get no Oscillation.

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9 years 7 months ago #89130 by Nondepietjes
Replied by Nondepietjes on topic Scaling of axis
Hi,

First of all thanks for the help,i found the solution to my speed probleme. The servo's can go 2000 rpm. so i have calculated my velocity, so 2000rpm = to 7.33 m/sec.
Now my other problem is that when i jog into the limitswitch on one side ia hit the hard limt and can't jog away from it by pressing the overwrite button. The other side where the homing is there i can jog away.
there is one limitswitch for eatch axis. Can anybody help me find the problem?

Thanks again ;)

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9 years 7 months ago #89179 by rodw
Replied by rodw on topic Scaling of axis
You should never hit a limit switch if the machine is properly set up. It is just there for safety.
Reduce the length of the axis in the ini file so you don't hit it. It might only take a mm or so to stop it. happening.

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9 years 7 months ago #89213 by cncnoob1979
Replied by cncnoob1979 on topic Scaling of axis
When you have your scale correct in axis you can just measure using the DRO to set your actual travel limits. With your actual travel measured you will set your "soft" limits.

As rodw stated the actual limit switches are used for the "crap" (*^&*@#@) moments :) They are there to save your hardware.

Find out what your actual travel limits are and set them in your ini file.
Code:
[AXIS_0] TYPE = LINEAR HOME = 0.0 FERROR = 150 MIN_FERROR = 150 MAX_VELOCITY = 32.33333333 MAX_ACCELERATION = 20 P = 10 I = 0 D = 0 FF0 = 0.0 FF1 = 0 FF2 = 0.0 BIAS = 0.0 DEADBAND = 0.0 MAX_OUTPUT = 8 ENCODER_SCALE = 5000 OUTPUT_SCALE = 10 OUTPUT_MIN_LIMIT = -10 OUTPUT_MAX_LIMIT = 10 MIN_LIMIT = -500 MAX_LIMIT = 500 HOME_OFFSET = 0.000000 HOME_SEARCH_VEL = -1.000000 HOME_LATCH_VEL = -0.500000 HOME_FINAL_VEL = 0.000000 HOME_USE_INDEX = NO HOME_SEQUENCE = 0 HOME_IGNORE_LIMIT = NO

MIN_LIMIT = -500
MAX_LIMIT = 500

This is where you set the soft limits of the machine.

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