Setting up 4th axis for the 1st time...

[jmcglynn]

I'm adding an RT-210B rotary table to my VF2.

I have a real noob question, what is the best way to:

1. check the alignment to the x-axis (I imagine putting a 12" length of precision round stock in it and traversing it end-to-end)

2. How do I set the coordinate system zero to the axis of rotation? I'm imagining probing (I have the WIPS) the side and top of the round bar and offsetting but this seems bogus and too fussy.

How do you do it?

Joe

[Donkey Hotey]

Can't you sweep off of the faceplate in the Y direction and do the same thing?

As for the center of the axis, you know the center height of the rotary (6"). Probe the table surface, then add 6" to your G54 Z height. That height is supposed to be within 0.001".

Y-axis direction would be a little more complicated. If you have probing and a symmetrical fixture, you could probe the front and back as a really fat web. The control will split the distance and set it on the centerline.

Setup done.

[Delw]

Just use an indicator ( good one in tenths) on the bar and you will find y 0

1st remember you will have to have the bar in straight and perpendicular, spin the a axis with the indicator up in the front then in the back, once those are set, the find y center with the indicator.

Like donkey said the height is set at +-.001 so you should be good on the 6" ( for some reason I thought it was 7" height)

if you use a precision bar make sure its ground as a machined one off a lathe wont be as good as you think. if you set the bar at a 12" length that should be good for most jobs that run 12" or less from the face of your a axis.

one thing to remember if your running a long part in the a axis youd better be dead on at the end of the bar or your parts wont be dead on and you will be fighting with your inspectors/ operators if you have to run 3 sides of a part on the farthest position from the a axis box.

if your off .001 on indication of x on the face plate 8"
at the end of a 10" bar will be off litte over .002
on 20" your off by over .004
then when you rotate times it by 2.5 90º each direction
I think that was the rule of thumb I was givin years ago its been a while, I always used 1,2,4,3 easier to remember.

remember that indicating the full width of the face plate 8" if you only indicate 1/2 of that your worse on the ends of 10 and 20 inches then if you indicated the full 8",

Another words indicate the face plate full width (as much as you can) and get it dead nuts, less to worry about if you have strict call outs on angles and finished dimensions not to mention true position.

one of the math junkies could give you the exact amount

Delw

[Delw]

Y-axis direction would be a little more complicated. If you have probing and a symmetrical fixture, you could probe the front and back as a really fat web. The control will split the distance and set it on the centerline.

Setup done.

will the control compensate for the a axis if it was off from one end to another? I know nothing about haas and probs so I am just asking if that is possible.
another words if you have a 15" part and your off 1º is there a way to probe it and make the machine compensate for that 1º off center line? if so that is cool.

I am still waiting for mine to show up so I can play.

[Geof]

One way to check the Y coordinate once you have set it using a bar and dial is to bore a through hole, index the table 180 and check the hole position.

Compensation for not having the A axis true to the X axis could probably be done using coordinate rotation if you have the option.

If you are only clamping the rotary down using the two slots front and back go easy on how you push things, it is easy to move the whole unit especially taking a decent cut several inches in front of the faceplate. All my permanently installed rotaries are either bolted from the underside onto baseplates. They exchangeable ones are held onto baseplates using four toe clamps and the alignment adjusted and held by four setscrews against the corners of the base. See the pretty picture.

[gpcoe]

I've had fairly good luck with indicating either the flat ground portion directly above the rotary platter (along y-axis) or across the platter itself. However, keep in mind that the platters will have a concave shape (up to .001" bow) across the face and the important area is close to the edges. Most of my parts are short so this may not be accurate enough for long pieces. A good fixture face alignment should both indicate true in Y and Z as well as indicate zero through rotary motion. I've noticed as much as .001" deviation from when the brake is released and then applied again so make sure the brake is re-applied when checking this. I'll usually write a quick MDI program with M00's at different angles. Most of our rotaries are bolted directly to the table with little issue except for a few machines with ball lock modular fixturing. Those rotaries have dedicated sub-plates. Good luck with it.

Greg