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Probing & alignments of a part on VMC

scollins

Aluminum
Joined
Mar 26, 2005
Location
Sheffield, Yorkshire UK
I am hoping the machining centre experts can offer some advice.
I am inspecting parts that comprise a laser profiled piece of 15mm thick steel with 2 x 45mm pilot bore holes at 415mm centres. The profile is approximately ‘banana’ shaped. Two bosses 90mm diameter and 25mm thick, bored out at 45mm are then aligned and welded over each hole in the laser cut part.
The final machining operation is to open up the 45mm through bores to 50.00/50.06 first by milling both holes to approx 49.5 then single point boring both holes to size.
The current method on a Haas machine is to approximately locate the part parallel to the X axis, on packers, clamp and then probe each 45mm bore of the laser cut part in turn. I believe these are then assigned as G54 & G55 datums. The machine then machines the 2 bores using these datums. I have been told that the benefit of this method is that the part doesn’t have to be particularly accurately located however it does mean that any error in the hole centres of the laser cut part are repeated on the Haas rather than corrected to precisely 415mm.
The hole positions relative to the ‘banana’ profile are not critical but the hole centres are important.

Is there a way of probing as described above and then compiling a programme using one of the 45mm holes, say the LH side hole, as the X0, Y0 datum, then using the probing results for the 45mm RHS hole to obtain the part ‘alignment’, (effectively calculating the position of a line that intersects the 2 x 45mm holes), and then machining the RHS hole at co-ordinates of X415.00, Y0.0 or their equivalent to obtain the 415mm centres.
This may be run of the mill stuff to some but any advice would be appreciated.
Regards Stephen
 
See if your HAAS supports G68 Coordinate rotation. This will rotate your axis coordinate system by an angle.
Use the probe to calculate the angle (basic trig from the probed points relative to the X axis) then rotate the coordinate system by the calculated amount.
 
Tonytn36, thanks for your response. If the Haas does support G68 can the calculation of the angle from the probing positions be done automatically within the programme? ie. load part to approximate position, cycle start, probe both holes, (angle between holes calculated within programme), start and complete the machining.
 
If the Haas was bought with the Haas probing package then it should have the coordinate rotation available. PM with your email addy and I'll send you a Probe manual pdf I got from a renishaw rep that goes into all the canned programs that come on the Haas preloaded including measuring features and updating the coordinate origin and rotation to them.
 
Once you get the manual from JP, go to page 136 and check out macro O9834. This is a feature to feature measurement and will store lots of info in variables.

What you will want to do is probe the LH hole with O9814 (bore measurement). This will store the hole size and location in a set of variables. By using an S1. in the O9814 line, you will set G54 X and Y at the center of that bore. Then run O9834 with no inputs, which stores the aforementioned variables in another place. Then go over and probe the RH bore with O9814 again. Then run O9834 a second time, but using inputs X, Y and A. Now your X and Y distance from bore to bore, and the angle from the LH to the RH bore is stored in variables 185, 186 and 189.

Now you use G68 to rotate.

G17 G68 A0. B0. R#189;

Now you have rotated the XY plane around the LH bore, by the angle found by O9834.
 
Thanks for all the advice. I will talk to our programmer. I had a quick look at a list of G codes in the Haas manual and I don't think G68 was listed but I will look into this further. The machine is equipped with a Renishaw part and tool probing system.
 
You can always do a test program to see if it works....

Prerequisites of program.....then

G17
G0 G90 G54 X0 Y0
G68 R45.
G91 G1 X2.
G69 G90
M30

It should move 2" at 45° to the normal X axis.
 








 
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