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Author Topic: Deeper into the 4th A Axis  (Read 6941 times)

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Offline budman68

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Deeper into the 4th A Axis
« on: December 30, 2008, 01:11:22 PM »
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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Offline docltf

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Re: Deeper into the 4th A Axis
« Reply #1 on: December 30, 2008, 03:29:46 PM »
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

Offline Hood

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Re: Deeper into the 4th A Axis
« Reply #2 on: December 30, 2008, 03:46:44 PM »
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 ;)
« Last Edit: December 30, 2008, 03:58:56 PM by Hood »

Offline budman68

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Re: Deeper into the 4th A Axis
« Reply #3 on: December 30, 2008, 03:52:44 PM »
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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Offline budman68

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Re: Deeper into the 4th A Axis
« Reply #4 on: December 30, 2008, 03:54:42 PM »
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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Offline Hood

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Re: Deeper into the 4th A Axis
« Reply #5 on: December 30, 2008, 03:57:28 PM »

As for clocks, we use those to tell time in the shop
[/quote]

We just look at the sun to tell the time, if we see it we know it must be August ;D
Hood

Offline budman68

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Re: Deeper into the 4th A Axis
« Reply #6 on: December 30, 2008, 04:12:36 PM »
 :D
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Just because I'm a Global Moderator, don't assume that I know anything !

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Re: Deeper into the 4th A Axis
« Reply #7 on: December 30, 2008, 04:26:41 PM »

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

Offline Hood

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Re: Deeper into the 4th A Axis
« Reply #8 on: December 30, 2008, 04:34:52 PM »
 

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

Offline budman68

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Re: Deeper into the 4th A Axis
« Reply #9 on: December 30, 2008, 04:44:11 PM »

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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Just because I'm a Global Moderator, don't assume that I know anything !

Dave->    ;)