Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: gtonini on January 05, 2013, 11:37:06 AM
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Hi
I' ve built my 4th axis rotary indexer not sure what I did wrong when I go into mdi and type in g0 a45 the indexer rotates full circles
not the 45 degrees. Ive specified. I saw somewhere on here to specifiy my a axis as rotational in general config but i cant find that setting any ideas please.
Thanks
Gary
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Multiply the steps per unit by 8 for the A and see if that helps.
Hood
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Just a question why would you multiply by 8 ? If I have my stepper driver set to 1/16 wouldnt it be 16 ? Just asking ?
Thanks
Gary
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You said it moves 360 degrees when you command a move of 45degrees. That means it is travelling 8 x too far so your steps per unit are 8 x too small.
Hood
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That changed it some my biggest problem is that I dont have any documentation for the motor I'm not sure if it is 200 steps per revolution or not is there any way to figure this out ? Thanks for your help !
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Tell me a little about your setup, is the motor direct coupled to the rotary or is there gearing ? If geared what amount?
Hood
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I'm using a drive belt with 2 pulleys it is a 40 to 1 ratio .
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Ok so in a rotary axis with 200 step per rev stepper and 1/8 stepping it would equal 177.7777777 steps per unit, for a 0.9 degree stepper( 400 per rev) it would be 355.555555
Meant to say the rotational axis setting is on General Config page.
Hood
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How should that setting should be set at ? I tried the numbers you mentioned . If I tell the machine go a45 I not sure how many revolutions the chuck rotates . I think the motor has some sort of weird steps per revolution number. I have my stepper driver set at 1/16 steps . Is there any way I can use the calibration tool in Mach 3 to set this up?
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If you have 1/16 setting then you would need either 355.5555 or 711.1111111 steps per unit.
Also make sure it is set as a rotational axis on Genral config page.
Hood
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I look at the rotation choices on the general config page there three options which do i want or am i looking in the wrong area ?rot 360rollover, angle short rotation on go ,rotational soft limits
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Make sure this is set to angular, see pic.
Also you will likely want the 360 rollover but depends on how you will work.
Hood
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That is checked so I'm not sure what is going on has to be something wacky with the motor I tried 35.55 in steps it almost seemed that
this was closer that the other numbers I tried. God bless you for all your help and patience !
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If you attach your xml I will take a look and see if there is an issue with it.
Are you sure your belt drive is 40:1 reduction as that seems quite a lot for a single belt reduction, would mean your driven pulley would have to have 40 times more teeth than the driver pulley.
Hood
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Sorry my mistake you said two belts ::)
Even still thats quite a reduction.
Hood
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No it's only one belt
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So that would mean if your driver pulley had 10 teeth your driven had 400? Seems a lot.
Hood
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No the main pulley has 40 and the small pulley has 10 and the belt is 40 teeth
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Ah ok so 4:1 reduction that means the 35.55555 is the correct number :)
Hood
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I'm going to work more with this tomorrow . I truly appreciate you help so tomorrow I will use the 35.555 when I used this number it seemed that the rotation was rather slow.
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I was using a velocity of 500 and a acceleration of 5
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That means 500 units per min, one unit is 1 degree so that means it will take nearly 3/4 of a minute per rev.
Have a read of Greolts post here as it has some good info on rotary axis speed
http://www.machsupport.com/forum/index.php/topic,23361.0.html
Hood
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Thank you for all your help I'm sure I'll be back for more help
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No probs, there are plenty of people here with a wide range of knowledge so your questions are almost certain to get a reply :)
Hood