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Author Topic: speeding up my 4th axis rotary table?  (Read 4505 times)

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speeding up my 4th axis rotary table?
« on: October 08, 2008, 09:33:03 PM »
I need a little help getting my rotary table , Axis A , up to speed .

I when I am using it to cut flutes in bbls etc it pretty easy to enter speeds of f200 and it takes a little over 1.5 minutes to make a full 360 degree revolution .

When I generate my etext engraving files  I need the x axis to move at aprox 6 IPM but when cutting in the A or a combination of X and A I would like to move at speeds of 200 or a little better.

any thoughts

Offline RICH

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Re: speeding up my 4th axis rotary table?
« Reply #1 on: October 08, 2008, 10:31:56 PM »
I just assume that rotary table is driven by a stepper.
As a steppers speed increases the torque decreases. You need a certain amount of torque to turn the rotary table.
For example, suppose your stepper can run at 500 rpm and has adequate torque at that speed to turn the table without loosing steps, for discussion, if there is a 50:1 gear ratio then your table can turn 10 rpm max ( you can convert to inches per unit if you wish). You can change the reduction ratio and increase rotary speed or you can get a stepper that will run faster with adequate torque for some desired rpm or a combination of both. But as you know both have practical limits.

I may be wrong, but believe MACH reverts to the lesser speed of the two or more axis's on circular paths.
Re: speeding up my 4th axis rotary table?
« Reply #2 on: October 09, 2008, 02:02:57 AM »
I am running a huge servo motor on an 8" rotary table, its cabaple pf spinning the table at quite a high rate of speed. I have the max IPM on the x and y axis set somewhere around 150 IPM on a bridge port and the rotary at 2000 degrees per minute(rotary is capable of over 40K DPM).

I think my problem may be the software I am using to generate the gcode, its set for 6IPM which is correct for the engraving tool I am using to engrave 4140 steel tubing, but when its moving the rotary axis its also only moving it at 6 degrees per minute which is painfully slow

Offline Greolt

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Re: speeding up my 4th axis rotary table?
« Reply #3 on: October 09, 2008, 02:41:56 AM »
I might be barking up the wrong tree here

but don't you need to set the axis diameter on the settings page

so Mach knows how much to adjust the rotary axis travel speed?


Offline jimpinder

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Re: speeding up my 4th axis rotary table?
« Reply #4 on: October 09, 2008, 01:43:26 PM »
Lets just get the right angle on this ( couldn't resist that)

From what you are saying you have your step per degree set correctly and your velocity set at 2000 degrees per minute - so, if you do a G0 on your A axis - does the thing turn at 5.5 revs per minute - or 11 seconds per rev (approx)

If it does then Mach is working correctly and the problem obviously lies in your program.

When using two axis (or more) at once, Mach moves the slowest axis at its fastest speed, all other axis are slowed to start and stop at the same time. I don't know whether this could affect it.

I see you have said that your program is limiting the axis to 6 - the program says inches per  minutes - and the machine is using the 6 and converting it to degrees per minute. You might be better to alter the A axis to linear motion, and alter your steps per to the correct number to move the cylinder round one inch ( and this will clearly depend on the diameter of the cylinder). If it is something you do a lot of, then it is worth caculating it.

If it is a one off job, then keep on rotary but use your speed in inches multiplied by 33.3/D ( to convert to speed by degrees) to get the correct speed. Check the maths, I think it is right, I am a bit off song tonight.

Not me driving the engine - I'm better looking.

Offline Bodini

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Re: speeding up my 4th axis rotary table?
« Reply #5 on: October 09, 2008, 06:27:49 PM »
Try this: mach>[pull down] config>toolpath>tick use diameter for feedrate

and then like the other poster said: set your 'rotational diameter ' on the settings page.