Problem with mirror images

[Dale gribble]

Hi, I making the letter Z from three pieces of M.D.F. 18mm thick. if you see the cad image, I created the middle Z first then added dowel holes, then copied the one to the right. I then mirror imaged the one to the left. When cutting on my router I drilled through the middle Z and then only half way on the two outer Z's. These holes are for lining up when gluing. I then cut the Z out with tabs to hold the part.

The middle and the copied Z to the right are the same shaped, but my mirrored image Z to the left is a different shape in places, see photo's of misalignment. I'm racking my brain to find out whats going on. It's seem something to do with the mirror image. I've also cut an A using the same process which had the same problem. I'm using the camware to calculate the cutter compensation which is mastercam x3. Machine operating system is Mach 3. Any insight to this problem would be gratefully recieved.

kind Regards

Dale gribble

[christinandavid]

If you have used a straight-forward mirror image then you will be moving the cutter clockwise around one part and counter clockwise around the other. The cutter could be deflecting off centreline, digging in one part and pushing off another. This effect could be more pronounced on tighter radii with higher surface speeds.

DP

[Dale gribble]

Hi, DP

I've programmed both images to cut clockwise / climb mill, and yes you are right they are two different images and will have different cutting forces in various places. It's not clear as to the scale of the parts from the pics but these are 200mm 8" high, and the misalignment is 1mm / .04". a lot of deflection. I roughed out all three images out first plus .1mm / .004" then finished with two .05mm /.002" passes. feed-rate is 4000mm/m 157"/m @ a depth of cut 1.5mm / .06". I'll do some trials just cutting the mirror image and make sure the finishing cuts are cutting all the way round the part, I my need to leave more on and do more finishing passes. the router cutter is a long series, this could be a wee bit shorter. After saying all of the above the finish on the part is crisp and shows no sign of digging in or push off.

Thanks

Dale

[christinandavid]

I think you've eliminated that possibility then...

Suggest you mirror a simpler symmetrical shape with datum on centreline and check that the software is pumping out the same figures for mirror image/non-mirror image.

DP

[Dale gribble]

Hi,

Good idea, I'll try that.

Regards

Dale

[Dale gribble]

Hi, sorted the problem.

I checked out the cam ware by mirroring a square and g code was fine. it then occurred to check the squareness of gantry, it was out. the error was adjustment of one of my home switched on one of my dual lead screws. I made a fine adjuster with an m6 bolt in stead of just knocking the switch left or right. Also none of my three squares I had at home to check it were, well, square. I got my hands on a calibrated square and the machine now runs fine. I've only had the machine up and running for 2/3 months and all my part so far have been one offs and until you make multiples of the same parts then that shows up any errors with your machine set up. also mirroring image will double any out of squareness. thanks for your help DP

Regards

Dale