Hello Guest it is December 13, 2019, 03:55:23 PM

Author Topic: M3 - pick up on a part for remachining  (Read 1876 times)

0 Members and 1 Guest are viewing this topic.

M3 - pick up on a part for remachining
« on: June 21, 2016, 02:25:16 PM »
Hello

Is there a way to touch off and repickup on coordinates to remachine a part?

Let's say I have a square piece of stock, and my intended finished part (a flange) has a  number of holes in it, I have cut some of them, didn't finish the part,

I've since decided to rotate one set of mating bolt holes, re run the post processor (sheetcam), and now want to finish off my flange, how would I go about picking up the coordinates of the first set of holes, and rotating my machine coordinates to match those same bolt hole coordinates in the gcode.

Would I probe out the hole centres already machined then use trigonometry to work out the angle of my part, then probe out a hole and use that as my 0,0 coordinate, then rotate the machine coordinates accordingly?

Is there a routine or some other method.

Thanks for your time and any advice (besides start off with a new piece of stock...)
Rob

Albert Einstein ― “If you can't explain it to a six year old, you don't understand it yourself.”

Offline Hood

*
  •  25,856 25,856
  • Carnoustie, Scotland
    • View Profile
Re: M3 - pick up on a part for remachining
« Reply #1 on: June 21, 2016, 02:52:52 PM »
Not sure if I am understanding what you mean but from what I think you mean then I would make a simple fixture with some holes machined in it so I could use some dowels to place the flange on, clamp then remove the dowels.
Hood
Re: M3 - pick up on a part for remachining
« Reply #2 on: June 21, 2016, 03:31:04 PM »
Thanks Hood for replying,

I'll try to explain again (it may have been me trying on a phone).

Attached are two screenshots, basically the first one shows my original flange.

The second, my revised flange shows the original flange as an underlay,

The flange is to join a gearbox to a transfer case (4x4).

Hence I've decided to clock the transfer case.

I've cut a couple of the boltholes for the the flange (they are less important as they align via a spigot), and are for the gearbox.

Hence what I'm trying to do is to have a method to accurately pick up on these holes already cut and align their co-ordinates with the second attempt, and also allow for rotating the part co-ordinates slightly ( unfortunately the part export to DXF and my editing of the two objects to get their clocking means that when I created the new flange DXF, they unfortunately don't align as far as cad world co-ordinates and part rotation (I could rotate the 2nd flange in cad to align the first, but I was wondering if there was a method of picking up from on a previous part).

Rob

Albert Einstein ― “If you can't explain it to a six year old, you don't understand it yourself.”
Re: M3 - pick up on a part for remachining
« Reply #3 on: June 21, 2016, 04:33:00 PM »
Since you have a Cam program I'd fix the problem there. Pickup center of one hole by sweeping with dial indicator. Zero X and Y axis.  Move to a second hole and again pick up center. In Cam move the center of the first bolt hole to 0,0. Rotate part to move second bolt hole to X and Y you got from finding center of second hole. Repost the program and you can continue on from there.
« Last Edit: June 21, 2016, 04:37:09 PM by garyhlucas »
Re: M3 - pick up on a part for remachining
« Reply #4 on: June 21, 2016, 04:55:01 PM »
Hmmm, it's not really a "fix" that's required... it's a suggestion as to how would you realign a part you may have partially cut once, to finish it off later.

The precision of the holes that have been cut is not actually that critical, I was more curious about a suggested method (ie what would you do?)

Here is another more complex and precision scenario

I had a guy EDM cut an internal spline into an input gear of a transfer box, once completed it was test fitted and a bit too tight a fit.  He suggested that he would open the spline out and recut it again a little oversize.... problem was he was not sure how he would "pick up" the spline to recut it

~ 1 1/4" outside diameter, 31 teeth involute spline profile.  After some weeks of sitting on it, I asked if he wanted another blank to recut as it may be easier than attempting to "pick up" the existing spline and open it out a bit... he took me up on the new blank and recut.
Rob

Albert Einstein ― “If you can't explain it to a six year old, you don't understand it yourself.”

Offline Hood

*
  •  25,856 25,856
  • Carnoustie, Scotland
    • View Profile
Re: M3 - pick up on a part for remachining
« Reply #5 on: June 21, 2016, 05:37:45 PM »
Would do similar to above. Make a quick fixture by drawing in CAM (would probably be already be done) Draw three circles around the spline so they were tangent to each side of a spline, post code for the holes and bore into the fixture, fit dowels, place spline on, clamp and remove dowels. If a clear hole was required I would have a removable centre piece to the fixture and once spline placed I would remove the dowels then the centre core of the fixture.

For a lot of things that I may have to realign I try to have something that I can align to again. For example on the VDI Turret I made I had the centre hole as the zero XY reference and then machined a slot on the face so that if I needed to re-machine at a later stage I could chuck it up lightly, find the centre then rotate the part about the centre whilst using the Haimer to get the slot true to the axis.

Hood
Re: M3 - pick up on a part for remachining
« Reply #6 on: June 21, 2016, 06:01:19 PM »
Thanks Hood as always

Rob
(You were in the 52 for Scotland, are you in / out (just curious), I'm in)
Rob

Albert Einstein ― “If you can't explain it to a six year old, you don't understand it yourself.”
Re: M3 - pick up on a part for remachining
« Reply #7 on: June 21, 2016, 06:17:14 PM »
Robert,
I know you weren't looking for a fix, however when you have a Cad model that you can manipulate it is nearly always easier to do the manipulations there as opposed to doing it on the actual part.

I once repaired a cast iron wheel hub for an old fork truck that had 3 out of  5 lugs broken off and one was missing. They were all tapped holes too.  I clamped it down on the CNC, picked up the center hole and one of the still good bolt holes.  I transfered those numbers into my cad program.  This gave me the bolt hole circle and location of all five bolt holes. Then I rotated the drawing of the hub to the coordinates I actually measured and did the CNC program from that.  I brazed all the pieces back on and spiral milled the tap size hole for each bolt. Came out great. No one believed it could be repaired.

Offline Hood

*
  •  25,856 25,856
  • Carnoustie, Scotland
    • View Profile
Re: M3 - pick up on a part for remachining
« Reply #8 on: June 21, 2016, 06:18:29 PM »
I was one of the 45% .

I have voted remain, the time for Scotland to decide whether it is in the EU or not  is when Scotland controls Scotland :)
Hood
Re: M3 - pick up on a part for remachining
« Reply #9 on: June 21, 2016, 08:37:23 PM »
Thanks Gary, I've reread your original post, again, and yup that makes sense now, (don't know why it didn't last time... think I shut off at cam, fix problem there....)

I'll give it a go,

Hood, oops, sorry got the wrong Scotland group, I was surprised how close that was (thought it would be out for sure), I hope this is more definitive or you end up neatly half not happy, but expect it'll be close (I've never guessed a vote right ever, so I don't think it'll happen this time), heyho, at least I've don't my bit with a tick in a box)
Rob

Albert Einstein ― “If you can't explain it to a six year old, you don't understand it yourself.”