Double sided project

[cooperkb@tpg.com.au]

Have been doing some double sided projects with drilling dowel holes into the waste board to hold the reverse side in place when flipped but was wondering if the probe setting could be changed to the opposite corner and reset it that way-
eg I set my XY and Z on the lower left hand corner which then becomes the lower right hand corner when flipped so could I change the setting to work off that corner when flipped over so saving on drilling the dowel holes
Anyone tried it or reasons why it wouldn't work?
Be interested to know
Thanks Kerry

[mrmfwilson]

I’m not sure that I understand the question exactly. The index pins are used to align the two sides as closely as possible. If you don’t use the index pins you may not get a close alignment between the two sides. If you’re material is perfectly square, you could use other methods of alignment. Like a corner jig. I can’t think of a reason that it would make any difference where the origin of the toolpath is to the alignment between the sides. I personally prefer to use the center of the material.

[cooperkb@tpg.com.au]

Thanks for your reply and usually use the pin method but did have a problem with it changing for some reason the other day and was just thinking if the software is so accurate that if I flipped it along a straight edge along the X axis and changed the XY probe to the other corner that it should be the same point to begin but on the other side ie on the first side the X would start from zero and increase and on the reverse side the X would start from zero but reduce ie become negative
Have to try it myself and see what happens

[adze_cnc]

It’s not so much that the software is accurate it’s can you flip the material over so that it is aligned with the x and y axes as the first side was? Or if it isn’t can your machine’s control software adjust for that skew so that effectively it does match the other side in axial accuracy?

[rscrawford]

How are you finding your X0Y0Z0? If you have an accurate way of finding those, then you definitely do not need indexing dowel pins. The method you described is very efficient, especially if you use an edge finder (probe or other edge finder) to set an accurate X0Y0 once you flip the piece. More accurate than dowels.

[mrmfwilson]

How are you finding your X0Y0Z0? If you have an accurate way of finding those, then you definitely do not need indexing dowel pins. The method you described is very efficient, especially if you use an edge finder (probe or other edge finder) to set an accurate X0Y0 once you flip the piece. More accurate than dowels.

How do you know that the material isn't skewed using an edge probe? Do you probe more than one spot on each edge?
I'm interested in using an edge probe. What probe do you use?

[dealguy11]

In my opinion a mechanical method of alignment is better than any gauge or edge finder. Easier to set up and more likely to give good results if you pay attention to a couple of things.

I do double-sided work by flipping the material against pins or a corner fence. For large work I have indexing pins on my machine that are pretty accurate when the work is bumped up against them properly (the work bumps up against the pins - the pins don't go through the work like dowels). For smaller work I bump a sacrificial board against the pins, screw it down to keep it in place and then cut a corner to provide an accurate fence for flipping. If I cut it as needed, then I'm sure it's accurate for this particular job. Make sure to put a either a dog-bone or t-bone fillet in the corner to allow the work to sit snug on the fence.

The key to making flipping against a fence work is to have material with parallel sides. You can pre-cut the material so it is a perfect rectangle or square. Or, if you are absolutely sure that you have 2 perpendicular edges, you can make a squaring cut on a parallel edge and flip to that edge, making sure the perpendicular edge remains indexed. You do need to remember to set the material size to the size of the material **after** the squaring cut has been made.

Don't depend on sheets from the factory being square...more often than not they aren't.

[RickW3DS]

Indexing pins.

[rscrawford]

How are you finding your X0Y0Z0? If you have an accurate way of finding those, then you definitely do not need indexing dowel pins. The method you described is very efficient, especially if you use an edge finder (probe or other edge finder) to set an accurate X0Y0 once you flip the piece. More accurate than dowels.

How do you know that the material isn't skewed using an edge probe? Do you probe more than one spot on each edge?
I'm interested in using an edge probe. What probe do you use?

This only works if you mill your workpiece so the edges are square, and you have a reference to butt up against so one edge is always perfectly aligned with your axis.

I use a Mitutoyo 050102 mechanical edge finder. This lets me get to 0.001".

[StrataBoy]

In my opinion a mechanical method of alignment is better than any gauge or edge finder. Easier to set up and more likely to give good results if you pay attention to a couple of things.

I do double-sided work by flipping the material against pins or a corner fence. For large work I have indexing pins on my machine that are pretty accurate when the work is bumped up against them properly (the work bumps up against the pins - the pins don't go through the work like dowels). For smaller work I bump a sacrificial board against the pins, screw it down to keep it in place and then cut a corner to provide an accurate fence for flipping. If I cut it as needed, then I'm sure it's accurate for this particular job. Make sure to put a either a dog-bone or t-bone fillet in the corner to allow the work to sit snug on the fence.

The key to making flipping against a fence work is to have material with parallel sides. You can pre-cut the material so it is a perfect rectangle or square. Or, if you are absolutely sure that you have 2 perpendicular edges, you can make a squaring cut on a parallel edge and flip to that edge, making sure the perpendicular edge remains indexed. You do need to remember to set the material size to the size of the material **after** the squaring cut has been made.

Don't depend on sheets from the factory being square...more often than not they aren't.

I do something very similar to this. I have bench dog holes in my spoilboard that I use. Two along the bottom edge and one on the left side where I probe for zero. If I'm doing something like a clock that is 18" in diameter, I will design my project by specifying the board is 19" x 19", but then cut the board so it is a little wider. I then trim the bottom right corner with an end mill to make it exactly 19" to match the design. Once I carve the front of the clock, I can then flip the board left to right and bump against the corner that I trimmed. Since all of my geometry was centered on the 19" board design everything will match up. The key here is that your bottom edge must be as straight as you can get it and the bottom left corner should be square in the region where you place your touch probe. I use this method because measuring the width of the board with a tape measure isn't accurate enough to be spot on when you flip it. By using the CNC to mill the right end it can't get any better.