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Author Topic: Wrapper and toolpath view  (Read 12745 times)

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Offline Sage

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Re: Wrapper and toolpath view
« Reply #20 on: March 09, 2009, 09:10:01 AM »
Thanks for all your help on this people. I think I'm finally getting the picture.

I hadn't noticed that setting the diameter in the settings page, in addition to making the toolpath display proper, does affect the feed rate for the A axis. Perhaps I didn't have all the settings applied at the same time in the various places.

I have only looked at the tool path display but the speed of  X and A now appear about the same. I'll have to see what it actually does on the machine.

So - I presume what Mach is doing when applying the diameter factor, is managing the feed of A by inches per minute based on calculating the circumference of the part in inches rather than applying the feedate number as the usual degrees per minute. Is that what's going on?? Seems so.

This looks more manageable by a single feed rate in the code.

I'll have to try it out on the machine later and see what the movements look like.

Sorry for being so dense on this issue. It was difficult to see how all the pieces fit together.  :P

Very cool !!  8)

Sage


« Last Edit: March 09, 2009, 09:15:59 AM by Sage »

Offline budman68

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Re: Wrapper and toolpath view
« Reply #21 on: March 30, 2009, 08:58:05 PM »
Sage,

Just wanted to know if you ever got this figured out?

I'm starting to actually cut with my setup (72:1 sherline rotary table) and I get the same results as you were getting, super slow rotations and super fast x movement on straight segments.

Thanks,
Dave
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Offline Greolt

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Re: Wrapper and toolpath view
« Reply #22 on: March 30, 2009, 09:42:41 PM »
G'day Dave

Did you pick up on the "Use Diameter for Feedrate" setting on the toolpaths dialogue box?

This will try to adjust the rotary axis feedrate to account for the diameter of the job.

The other issue is that often the gearing of the rotary axis simply will not allow for the axis to rotate fast enough to give 60 ipm cut speed on a 2" diameter job.

As the rotary axis speed bumps up against the max steps per min for that axis, Mach will slow down the other axis to achieve a coordinated move.

My rotary axis will only achieve about 4 rpm which translates into about 25 ipm at 2" diameter.

So no matter what feedrate I command in gcode, feedrate will sometimes be limited by that factor. Depending on the move segment.

Greg

Offline Glenn

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Re: Wrapper and toolpath view
« Reply #23 on: March 30, 2009, 09:57:30 PM »
Hi Guys,
  I'm trying to find a less expensive way to make a rotary table,
would a 425ozstepper turn something like this, or would this worm gear have
lots of resistance? They seem to be fairly cheap compared to some of the rotary
setups I've seen associated with cnc.
  Thanks, Glenn :)
Don't assume anything.....it'll make a Manager out of U and Me!

Offline Greolt

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Re: Wrapper and toolpath view
« Reply #24 on: March 30, 2009, 10:41:10 PM »

.....would a 425ozstepper turn something like this, or would this worm gear have
lots of resistance?


That probably depends how fast you want to turn it.  Steppers lose torque with rpm.

I made a rotary axis using a similar gearbox.  See this link,

http://www.machsupport.com/forum/index.php/topic,6158.0.html

It works pretty well for a router.  Probably not backlash free enough for a mill.

However I do believe it compares reasonably well with some of the rotary tables hobby users employ.

Greg

Offline RICH

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Re: Wrapper and toolpath view
« Reply #25 on: March 31, 2009, 05:52:55 AM »
Glenn,
An easy way to check torque requirerments is just turn the axis wiith a torque wrench and
see what the readings are.
Look around, you can find them used in in-oz.
RICH

Offline Glenn

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Re: Wrapper and toolpath view
« Reply #26 on: March 31, 2009, 09:01:19 AM »
Greg,
  Thanks for link and helpful information, I see that your red box is what I am looking to use
and I have found one in ebay at a reasonable price.  :D
  Now that you have been using yours with great success, if you could do it all over
again, would you choose a different ratio, or are you satisfied that the ratio you chose is
best suited to your application? (which is the same requirements I will be seeking!)
  I ask this because there are several different ratios to choose from, and 10:1 looks good
but will a stepper turn it? ???


RICH,   

Thanks for the tip-   
  I am going to have to get a torque wrench! This would be very helpful. :D

  Glenn
 
Don't assume anything.....it'll make a Manager out of U and Me!

Offline Greolt

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Re: Wrapper and toolpath view
« Reply #27 on: March 31, 2009, 09:19:56 AM »

 I see that your red box is what I am looking to use and I have found one in ebay at a reasonable price.  :D
 

It would not want to have any wear in it.  There is no way to adjust for that.

Quote

if you could do it all over again, would you choose a different ratio, or are you satisfied that the ratio you chose is best suited to your application?


I think mine is 40 to 1.  I got got it for almost nothing.  That is why I used it.  Mildly surprised it works as well as it does.

Not sure about the ideal ratio. It is fairly stiff.  Made for much higher loads than it is getting.  Large bearings and seals and thick oil, all contribute.  400 oz stepper is only just enough.

Greg

Offline Glenn

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Re: Wrapper and toolpath view
« Reply #28 on: March 31, 2009, 09:40:10 AM »
Greg,
  Now I'm not so sure about this ...I wondered about the large loads this
box was designed for; I can see (now that you bring it to light), how the large gears and bearings and thick oil would rob my little
stepper of most power- just to turn the gears. So I may not rush into a $50. purchase yet, until I can somehow actually test it's
torque with a wrench(Thanks RICH), the difficult part  is, a person can't test things from mail order or ebay.
  I will generally only be using 4th axis on items 1.5 " or smaller, I would like to put design or customers name
on lower barrel part.
Glenn
Don't assume anything.....it'll make a Manager out of U and Me!

Offline budman68

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Re: Wrapper and toolpath view
« Reply #29 on: March 31, 2009, 11:36:03 AM »
G'day Dave

Did you pick up on the "Use Diameter for Feedrate" setting on the toolpaths dialogue box?

This will try to adjust the rotary axis feedrate to account for the diameter of the job.

The other issue is that often the gearing of the rotary axis simply will not allow for the axis to rotate fast enough to give 60 ipm cut speed on a 2" diameter job.

As the rotary axis speed bumps up against the max steps per min for that axis, Mach will slow down the other axis to achieve a coordinated move.

My rotary axis will only achieve about 4 rpm which translates into about 25 ipm at 2" diameter.

So no matter what feedrate I command in gcode, feedrate will sometimes be limited by that factor. Depending on the move segment.

Greg


Hi Greg,

Thanks as always for chiming in.

I believe I have that checked but I will look to be sure when I get out to the shop.

I'll report back soon -  :)

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

Dave->    ;)