Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: budman68 on December 30, 2008, 01:11:22 PM
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Hi all,
Ok, I have a few questions concerning the setup with the 4th axis. For the moment, I will be using this in a horizontal position to either cut gears and splines using the Wizards in Mach 3, or using the "Wrapper" program that is a slick little program that was made up by a user on the Vectric forum. This can be found here if you're interested:
http://www.vectric.com/forum/viewtopic.php?t=2920
A few questions:
1- Looking through many forums, I have seen of users setting up their 4th axis steps different ways such as "Angular" or "Linear". Which do I choose for the programs I want to run? I would be thinking angular but not positive. Is this something that the user would change for certain jobs using the 4th axis?
2- My stepper is indeed a 200 step/ 1.8 degr. per step and it is set up for microstepping so that's 2000 steps/ 0.18 degr. per step, correct?
Which also means it's 144,000 steps per 360 rotation, correct?
Does this mean that by dividing 144,000 by 360 , I then put "400" into the steps per box for the A axis?
3- Any ideas on a slick way to check the actual backlash on a rotary table. By just putting an indicator on it, the "play" in the table is .0012" . Not too shabby but if you have any other ideas, please let me know -
Thanks as always-
Dave
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if you don't have gear reduction the 400 looks good for steps per degree.check box angular.checking backlash,get you a 12" or 14" flatbar to extend the center of your A axis out.use your dial indicator
on the end of the flat so you can rock the aixs back an forth from 0.0 to .200 or whatever suits you.
bill
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I have no experience of 4th axis but would have thought if you have your steps per set correctly then just putting a clock on some convenient part of the axis and then rotating by step mode in mach one way, note the clock reading and zero the DRO then step back until the clock moves and read off the DRO in Mach.
Hood
Edit, BTW a clock is what we call a dial indicator here, just in case you USA guys dont call it that ;)
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Thanks, Bill, and yes, no gear reduction at all. You can see it here:
http://www.machsupport.com/forum/index.php/topic,9964.0.html
As for the backlash measurement. When I have the flatbar clamped to the table and the indicator at the far end of the bar, what am I looking for to determine the backplash.
Is the PDF I'm including in this post the formula I'll need to use?
Dave
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I have no experience of 4th axis but would have thought if you have your steps per set correctly then just putting a clock on some convenient part of the axis and then rotating by step mode in mach one way, not the clock reading and zero the DRO then step back until the clock moves and read off the DRO in Mach.
Hood
Edit, BTW a clock is what we call a dial indicator here, just in case you USA guys dont call it that ;)
Yes, Hood, now that I can be sure of the steps, that should work, I would think.
As for clocks, we use those to tell time in the shop, not to measure the things that take time in the shop..... :D
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As for clocks, we use those to tell time in the shop
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We just look at the sun to tell the time, if we see it we know it must be August ;D
Hood
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:D
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I just had a look at you steps/deg calculation and I think there may be an error.
Wiith 1.8deg stepper it is 200 steps per 360 deg. With micro stepping it should be 2000 steps per 360 deg or 5.55555steps/deg
C
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I just had a look at you steps/deg calculation and I think there may be an error.
Wiith 1.8deg stepper it is 200 steps per 360 deg. With micro stepping it should be 2000 steps per 360 deg or 5.55555steps/deg
C
I think there will be reduction in the worm gear in the axis but maybe not?
Hood
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I just had a look at you steps/deg calculation and I think there may be an error.
Wiith 1.8deg stepper it is 200 steps per 360 deg. With micro stepping it should be 2000 steps per 360 deg or 5.55555steps/deg
C
Thanks for looking, but with the 72:1 ratio, doesn't that come into play with the angular measurement?
Thanks,
Dave
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Dave
if you got the sherline p/n 3700,it has a gear of 72-1 then the steps you did are right ,400 per degree. set A axis angular. clamp the flat stock to the axis not the table. look at your PDF. use mach3 to
control the axis back and forth.
bill
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If it helps, I gave up trying to calculate the steps per degree for my 4th axis. Nothing about the A axis was intuitive to me like the linear axis were, and anything I actually calulated was way off.
Ultimately, I just used the degree wheel and interated down till I got one degree of movement for one degree commanded.
So I would suggest you just command 45 degees and see what the result is and go biger or small on the count until you get close. At that point the number of steps per degree you are using will be some identifiable muliple of what you have step and gearing wise and you should be able at that point to get the exact number you want.
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steps pr rev on motor X microstepps X gear ratio /360 = Step per degree
200X10 = 2000
2000X72=144000
144000/360 =400 steps per deg
or 1 step = .0025 deg
(;-) TP
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;D
Dave
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simpson36
why did you give up? there are plenty of people here that will be glad to help. just post your A axis specs. type of motor,how you drive it,all the gear reduction stuff and should it be
angular or linear.
bill
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docltf;
Being a total novice at this, I really had no idea that Mach was asking for.
As for the forum, I must say that this forum, unlike many, is very helpful and focused on the topics and not on flaming and personalities. A refreshing change from some.
Once I just went with observation instead of calculation, it only took a couple minutes to figure out what Mach wanted. It would have taken much longer to collect and post all of the specs and wait for an answer.
My 4th axis is actually just a stepper powered spin index, so it already had a degree wheel on it. I posted pics in the 'show and tell' section.