Indexer Unit values

[elcar903]

Hi I am trying to figure out the calculations need to get correct Unit values.

My indexer motor is a vexta pk299-02AA 1.8 degree/step
I am running a 1:1 ratio no gear box.

here is a picture of my VU settings,
I have only changed the A Unit Value.
24522


I came to the 5.555 setting by playing with the options and looking at some other posts
and it appears to be moving correctly but I need to know what the formula is to calculate the indexer A Unit Values

Thanks for the help
Adam

[steve_g]

Adam…
The “formula” for me was to creep up on the right value, mark a spot, command 10 or even 100 rotations and see if it stops at the right spot. Your error will be multiplied by the number of rotations.
SG

[Brady Watson]

You really don't want to run a direct drive motor without reduction. You will be EXTREMELY disappointed with the resolution & performance. The larger the part, the worse it will be. Not to mention this, but the part positioning is completely reliant upon the motor torque & with cutting forces applied, it won't be much without the torque multiplication of gear/belt reduction.

Stock PRT-Ss had a 7.2:1 PK 296 SG & Alphas were 10:1. I run my setups around 18 to 20:1 depending on the machine because speed is irrelevant & resolution + torque is king for indexing.

-B

[elcar903]

Thanks Steve & Brady,

So would say 4:1 work? because I already have some high precision gates timing belts and sprockets
that are used on cnc's that would fit the motor and they are 4:1 ratio.

Also is there a formula that I can use to verify my settings to confirm that my math is correct?

[steve_g]

3:1 was adequate for these bracelets… 1:1 wasn’t!
it’s going to boil down to how much you expect to remove per pass.
SG

[Brady Watson]

4:1 is OK. The Desktop uses a total reduction (both electronic and mechanical) of 6:1.

I might have a PK 18:1 motor around NIB, but you'll have to give me over the weekend to locate it - If interested. It is compatible with any PRT or Standard tool.

-B

[elcar903]

Brady if you think that motor would do better I would be interested in at least knowing if you still have it,
the one I have is one I picked up at a cnc auction I went too.

[myxpykalix]

STEVE G !! I sent you a PM...:p:rolleyes::cool:

[Gary Campbell]

Adam...
Here are the numbers: (1/10th step is 10* full) Step resolution is the smallest amount indexer can move at given diameter

http://www.talkshopbot.com/forum/attachment.php?attachmentid=24524&stc=1

[elcar903]

Thanks for the chart Gary.

[myxpykalix]

OMG Gary....I thought we lost you forever...glad to see you pop in once in a while!