I have another thread going that has been viewed quite a number of times but with only a couple of responses, I'm thinking my subject is perhaps missleading. I labled it as a mirroring issue. I think perhaps a double sided cut issue may be more realistic.
In simple terms I need to be able to cut a pattern, say a square on a piece of material 4 x 4 and 1 inch thick in the lower left corner of the material. My bit will only cut 1/2 inch so I have to cut one side 1/2 inch and then flip the material and cut the other side in exactly the same spot so the piece can be removed from the material.
The one response on my other thread showed how I can reverse the toolpath by changing the axis on which the material is flipped from 1 to -1. This absolutely changes the code but my question is how do I do this without having to re zero the machine, if I move the zero point there is a really good chance the cut is going to be off.
I thought I could maybe zero out in the exact center of the material so it would be in the same spot when flipped by zeroing out to the exact center of the material would be a chore in itself.
I know many of you must have done this in the past as I'm sure I'm not the first one with a "Small Bit Problem"
Any suggestions recommending how such a process should work would be greatly appreciated.
Thanks
Randy

HI RANDY, When you do two sided machining you have to develope a system of references that allow you to machine accuratly both sides as one unit. Not always easy.
Normally I would set up a fixture to hold the piece for the first side and then flip it and be able to re reference it or design the Gcode to compensate for the flip.

Not knowing what you are working with it is hard to figure that part out. If there are holes involved that go all the way through they make good reference points as they are present on both sides. IF no holes then a known edge or corner to touch off on or probe for position.

The centerpoint at 0,0 is also a good strategy if it works for that situation.

So how you do it is kinda dependant on what you have to work with.

Do you have a picture?

IF you can do it at the drawing level it makes it easy sometimes as when you flip the piece as your would in the fixture you flip it at the reference point so it will stay in relation to itself. Then when converted in CAM and both sides or the code are developed they will have the same origin point 0,0 so the part will comne out perfect.

Many ways to do it,(;-) TP

I've attached the picture, all these patterns are layed out on a 4 x 8 sheet of MDF, 3/4 inch thick. The material is blocked in place by two L shaped blocks that are 22 inches long on each leg. The machine is zeroed out into the  bottom left hand corner and after the first side cut the material is flipped horizontally so that the lower left corner is now in the lower right corner.
There are no holes on the first cut that go all the way through but I could possible make some alignment marks on the first cut around the outside edge. or possibly somewhere else.
I would guess that the best spot would be down the Y axis as this is the axis its flipped on and then once flipped make sure those alignment holes still line up with the original spot.
After you have a look at the picture let me know what your thoughts are.
Thanks
Randy

i cut receivers for firearms (4sided milling) 3 flips. first i ensure that the piece is square , true and flat (both sides, i maching the Left side face up first, i have a set of soft jaws to aid in lining up with the assistance of thru holes, also using a runout guage in the spindle to ensure the piece is flat, on first side i 0 from the back right corner, when i flip i 0 from the forward right corner (same corner, and invert my Y) in your situation it would probably be a whole lot easier to dowel pin 2 of your scrap areas on your jig/table