Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: skanner on September 15, 2010, 06:30:30 AM
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hi all,
I'm new to cnc so still very wet behind the ears so please forgive me if I'm not making any sense i will try to explain as best i can.
i bought a cnc router with the intention to use the motors and board on my mill i put the z axis on the fine feed as i didn't think the motor would be strong enough to lift the whole head (i think the motors are about 400oz)but there was to much play in the spindle unless it was locked off every time,so i made a rough coupling and with the motor held by hand tried it on the column and to my surprise it moved the head up no problem at all.
then while trying to make a bracket i had bother with cambam and mach i couldn't get a circle cut, then my pc went down when i got it back up and running i had lost all the settings for the board and the whole thing was dead in the water.
so i bought a new board (TB6560AHQ) and every thing was ok i got cambam to work with mach and made the bracket for the z axis but now the motor will not lift the head it just makes a clicking sound its as if i have lost some power from the motors, i did notice with the old board when the power was on and the motors lock up it was hard to turn the mill handles but with the new board it seems easier to turn them, i have tried adjusting the motor velocity and acceleration so its just going slow but this never made any difference.
any help would be great thank you.
john
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Have you got the motore wired up the same? Other things to check is you have the correct current setting for the motor as current gives you torque but dont set to high as it will cause too much heat.
Hood
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Hi John,
Sounds like you are not supplying enough current to the stepper. Most boards have some form of current adjust, check the max current specified for your motor and adjust the board current accordingly. Although the motor voltage can be exceeded by many times the motor's rated current should never be exceeded so it is a careful adjustment.
Hope this helps,
Tweakie.
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Did I miss something? - what was wrong with your old board?
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hi thanks for the replays I'm not to sure about the specified motor current for my motors they dint have anything on them but i will take a look at the board to see if there is some adjustment and take it slowly. this is the ebay number for the new board i got 250682276810 if you can see any adjustment please let me know
as for the old board there is nothing wrong with it after my pc went down i had to reinstall mach3 and i never had the board settings so it worked on screen but the motors never went around knowing nothing about cnc i thought it would be best to go for a new board with the settings .the old board and motors were bought about four year ago.
john
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Your current settings are dip switches 1 & 2 as follows :-
setting 1 2
100% on on
75% on off
50% off off
You would be wise to look up your motors maximum current rating as specified by the manufacturer.
Tweakie.
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hi,
thanks for getting back my settings are 1 on 2 off so if I'm right I'm running at 75% so if i set them both to on i should be at 100%
told you i was new to all of this, the motors have no names or markings on them so i will just have to take the chance they will be OK, there a good size motor and like i say they were alto harder to turn with the old board so must have been getting more juice.
thank you again for your help
john
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Good luck, hope it works OK.
As Hood said too high a current will cause too much heat in the motors so keep checking they are not running too hot to comfortably hold your hand on.
Tweakie.
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ok mate thanks again I'm off to give it a try
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skanner,
Simple intial test would be to be to select the lowest current setting and see how warn / hot it gets to the feel in say 5 - 10 minutes.
Work your way up. If the current setting is to high the motor will get hot rather quickly and then drop down by one setting.
With that setting see if you can move the Z, if not, then you may be able to change the wiring. Go through the currrent testing again if you wire the stepper differently. Go to the Geco site as they have explainations on stepper wiring and how it affects speed and torque.
With the current setting right, now you can test for velocity and acceleration settings. Too high a current and the stepper may not run correctly
ie; like having it set right on the max.
RICH
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hi rich
thanks for the reply the board was set at 75% so i only had one more step up,after setting it to 100% the z worked ok although the motor sounds like its missing a step every now and then but the measurement is ok also the motors are making a little nose when standing still, i worked the z up and down for 15mins and the motor was only warm so i guess this is ok i left it for one hour and the motors got a little hotter but i could keep hold of then with my hand no bother.
i will take a look at the geco site as you suggested. thanks again for the help.
john
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Hi all, I know I am a little late on this, but hopefully someone will see this. I too am having issues tuning the motors. I am running the ebay chinese tb6560 board, 24 volt power supply, I tried 2 different sets of motors and get the same results. I have everything working correctly, I just can't get any speed. As soon as I try and increase velocity, the motrs seem to stall. I can get anything faster that 20 ipm. I tried setting different current setting, for 25% to 100% and it really doesn't make a difference. I am running 1/2 step, fast decay ( I think, not too sure what this does), my acceration is set to 4,
any ideas on how I can get more speed without the motors stalling out. I have the motors wired for torgue, ( I thinnk that is parralell?)
any help would be appriciated.
Don
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I think your problem is likely the low voltage. Voltage dictates the speed you will get, so if you dont have enough voltage you are not going to get much speed.
Hood
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The problem I have is I can get more speed, but loss the power(torque) of the motors, So I set to 60 ipm, and tings might move a little, then you can here the motor grinding almost, but the DRO keeps moving. If I increase voltage, with this also help the torque. I guess I can live with 20 ipm, but I find if I mill plastic, it heats up too much and melts. I tried 2 different sets of steppers and get the same results.
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Torque will decrease as the speed increases. Not all steppers are the same and only a torque to speed curve will show you the tested difference. If you increase the voltage you will get more speed but you would be changing the motor curve. Most curves are based on 24 or 36 volts, so if you apply say 60volts the curve changes.
I just recently changed out my steppers on the mill with the new steppers having 2.5x the torque of the old ones but at the same max voltage. The increase in reliable speed was about 10% so don't assume anything. You can play with the acceleration some and see what happens as your starting and stopping slower and once the axis is moving you usualy don't need as much torque.
Must add, that depending on how they are wired you can change the operating characteristics of the motor. Have a look at some of the info on the Gecko site for more detailed information.
FWIW,
RICH