Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: AlanETM on November 20, 2006, 04:30:10 PM
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I have just added a rotary axis to my set up the A axis. I am now trying to find out how to calibrate it and verify the DRO reading to the table position.
I know the table reduction ratio (worm/wheel) and I can set my micro stepping motor as usual , but how do I know what units the DRO is reading? degrees? Radians? or something totally different?
Advice on the correct setup procedure would be appreciated.
Alan
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I would think it would be however you set up your steps equals. The DRO is only counting pulses sent. I don't know this for sure but I would like to as I'm planning on a 4th axis eventually. ;D
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Not so sure as the motor tuning page sets steps per .... and that refers to the native units used inches or millimeters. Nowhere can I find any reference to setting steps per revolution.
So my question remains what is the DRO indicating on a rotary axis and how is it set?
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I would think you would set it to what ever you are going to be programing. If I was using mm, I would do the math for that. Degrees, I would do the math for that. ______ steps=1 degree. You just wont put in the word degree. All the DROs are doing are showing pulses sent. What do you want to set it up in? How many steps of the motor will give you this?
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OK, if the steps per box is interpreted as degrees then I just calculate the number of steps required to turn the table one degree and enter that in the steps per box.
Thanks.
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:)
Keep us posted.
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Hi, AlanETM
On my Sherline rotary table it's 144072 step's pre one full turn, divided by 360 = 400.2 per deg.
Velocity 2500 Acceleration 500 the blended speeds, blended and feed's read funny though actual rate seems fine, don't forget to set the A axis dia. in settings page.
Hope this Helps, Chip
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Did Mach 3 take the 400.2 steps/ degree or does it only take an interger number?
Not sure yet what the A axis diameter actually does. Is this the stock material diameter or the finished work diameter?
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Not sure yet what the A axis diameter actually does. Is this the stock material diameter or the finished work diameter?
Where is this at? In Mach or a cam package?
If i neede 400.2 i would try it and see. ;D
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My understanding that this is the stock diameter. Also you can use 400.*************************** , it doesn't have to be an integer.
Chad
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Hi, All
The diameter set's the feed rate, a 1 in. dia and 10 in dia. will have different feed rate's so the actual surface cut speed will be the same.
Just an example of my setup, 1 full turn of your table (the number of step's it takes) divided by 360 = 1 degrees step's required.
As far the .2 if it doesn't divided out evenly then, I think Mach keeps track of the number else, you would have cumulative error in 1 full turn.
Your's may be even number's
Thanks, Chip
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Hello,
I just set a 4th axis up on my Taig. I bought a 6 inch rotary from Grizzly, a 207 oz stepper from Circuit Specialists and I am using the original Taig controller.
My settings for A axis:
Steps - 80
Vel. - 50
Accel - 400
Pulse - 13
Dir pulse - 1
1 degree = .125
So I just multiply the degree desired by .125 and it goes there.
eg. 360 x .125 = 45 (360 degrees)
eg. 10 x .125 = 1.25 (10 degrees)
eg 22.5 x .125 = 2.8125 (22 1/2 degrees)
Hope this helps,
Robert
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You are making life hard for yourself,
If your rotary table is 50 to 1 ratio and your motor is 200 steps per rev multiply 50*200 and this is your steps per rev
set velocity and accel to what ever it will index at safely
That way if you want it to move 90 degrees you enter G00 G90 A90.
Graham.
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Hi, Graham
I think that work's fine for Linear, but unless there have been changes in the last couple of rev. of Mach3R2.0 to get A axis Rotational
speed up you need the 1 deg value in step's in A unit's Motor Tuning. Full turn step's divided by 360 = value.
May be fine with A axis that have closer step's ratio's (A10,000, X,Y,Z,2000) not for (A144,000, X,Y,Z,2000) Step's, very very slow.
I don't really understand why its not compensated for in the software so actual step's per 1 full rotation of a axis could be used in setup.
Way, way beyond Me.
Thank's, Chip
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I see your point, 25,000 steps per port pin per second is probably the reason.
I built my rotary indexer at 10:1, thats probably why mine is fine.
Graham.
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Just a question. Does it matter? It is going to take the same amount of step pulses per rev. right? Is it going to matter if you set it up for 1 minute, 1 degree, or one reveloution? A couple of thoughts on things that might help would be to do a belt drive (1-3 or 4) and get away from micro stepping?
HAPPY THANKSGIVING! ;D
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Hi, Chaoticone
That's true a non micro stepping A axis would help allot on My R-Table, it would decrease the resolution but balance out the large difference
in A verses X,Y,Z, step's required, would be 6.67 to .66 Step's Per. Minute, more or less.
If I've done the Math properly, Still need's to be per 1 deg. for any speed though.
Just some trade offs.
Thank's Chip
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Yes, but wouldn't it also help the speed? If 25kHz is the problem. I have a rotary table I would like to hang a motor on. ;D It is 90-1
With microstep and 1-1 gearing 200 X 10 X 90 =180,000 steps per. rev. 4.0 seconds per rev. I'm running at 45KHz ;D
W/O microstep and 1-1 gearing 200 X 90 = 18,000 steps per rev. 0.4sec per rev. with a res. of .02 degrees. I think this is about 1.25 minutes. I'm just asking because I don't know. What kind of res. is acceptable? ???
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Accuracy is all relative to the diameter you are working at, if you are working at 1" dia 1.25 minutes of arc is nothing, if you are at 20" dia it may be a problem.
Graham.
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Hi, Chaoticone
The 25kHz isn't rely the problem it's the way Mach treat's linear versus Rotational setup.
If I get some time later, I'll post 2 different way's to look at it, then it will be clear
Hi, Graham, This is very true.
Thank's, Chip
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Very good info!
Didn't mean to intrude usually I just listen.
Thanks,
Robert
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I agree Graham. I just didn't know what would be acceptable on my mill. I know, what kinda tolerance do you want to hold. I don't know yet. I do know that the max diam. would be 12" or less.
Thanks Chip,
Looking for you to school me.
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You will find its not the step accuracy thats the problem, it will be the backlash, the worms in the less expensive tables are not made to the kind of tolerance the electronics can control.
Even if you adjusted the unit you would have tight and light spots in places.
Lash on large dias is a big problem, locking the table unless its made for it is even harder.
Graham.
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I have built and installed a 4th axis on my machine. I have seen several posts regarding this but have not discovered a solution to my problem.
My "A" axis is set to 22.222 steps per, 10002 as the velocity and 1700 as the acceleration.
The problem is that when you are doing a move that uses one of the linear axis, say the "Y", and the "A", the feed rate may be 35 ipm or similar. It takes forever for the rotary axis to move to the desired position based on that feedrate. How do you deal with this big difference?
Can someone help me out?