Unit Values for Indexer

[shawn_]

I have a PRT, but I am using a stepper motor from a PR model shopbot to run a transformed lathe as an indexer.

For the X,Y my VU setting is 183.347 but *4 is not working for the indexer

VU for Indexer set to 733.388
MA,3.6 - Gives me approx 310deg rotation

VU for indexer set to 916.7328
MA,3.6 - Gives me approx 420 deg rotation

Does anyone know a number that should work?

Also... I use Visual Mill to program the 4th axis, but I am unsure how to define a clockwise or counter-clockwise rotation. The rotation axis for the indexer is along the X, so is clockwise considered the top of the stock turning away from you? or towards you?

[richards]

For the indexer, you use steps-per-degree. On my test bench, I have a Gecko driven motor, so 360 degrees / 2000 steps per revolution = 5.5555 steps per degree. Then I would multiply that number by the gear ratio used, i.e, a 10:1 gear ratio would require 55.5555 steps per degree.

Then, assuming that the Indexer is using the A-axis, you would give the command MA, 180 to spin the indexer 1/2-revolution.

[shawn_]

Mike, thanks... The math makes sense, but it does not give me a number that works. You said, MA,180 gives you 1/2 a revolution. My post processor for visual mill posts 1/2 a turn as a MA,1.8 (or MA,3.6 for a full revolution) Reading the ShopBot documentation, this seems to be standard, that a MA,3.6 should achieve a complete revolution.

Here is where I am now
-Stepper motor being used - Vexta PK296A1A-SG3.6
-Steps at .5deg per step (720 steps per revolution)
-Motor has a 3.6:1 gear ratio.
-If I assign 800 to the VU setting for the Accessory drive, I get pretty close to one full turn (visually)
-Indexer is being run as a direct drive

But, this is my math, based on your post.
360deg or 720 steps per revolution = 2 steps per deg. multiplied by the gear ratio of 3.6:1 meaning i need 7.2 steps per degree.

Now how do I translate all that into a VU setting for the accessory channel that is close to 800 so when I say MA,3.6 I get a full revolution?

I know there is some part of the equation I am missing here, But i just can not find it! Thanks so much for any help that can be offered

[rnels]

According to the figures you gave would this work:

The old math: 733.388/310 = x/360
310x = 360(733.388)
x = 360(733.388)/310
x = 851.6764