Originally Posted by
bergerud
For double sided carves, the rails are smooth so the board can slide in and out. (No sand paper or the rails flipped over so sand paper is down.) The rails are adjusted so that the board is slightly below the carrier sides. Shims are put under the board to raise it the 1/8" for the measurement stage. After the measurement, the shims are removed and the board dropped back down as the head is cranked down. The side clamps produce the friction to hold the board from moving during the measuring and the carving. The board can be removed at will without lifting the head by simply releasing the clamps and sliding the board out. (With the stop blocks removed from the design, the board comes out the front.)
The advantage of all of this is that, since the board is measured only once, the x line up of a double sided carve will be exact. When the board is flipped over, it is slid back in to exactly the same x position. (Up against a stop bolt in a side hole.)
The y line up is another matter and is the subject of my ongoing experiments. The mpc has to be split into two separate projects and so on. It is complicated and one wrong button press can mean having to start all over again. If I had found a simple way to do it, it would have been incorporated into the UCB.