routing accuracy from both sides?

[anothernewbie]

We are interested in a PRSalpha CNC Machine. Lets say you are routing some patterns into a half inch acrylic sheet. How accurate and easy is it to be able to flip the sheet over and have the routing line up perfectly with the other side?

[chiloquinruss]

Two sided routing accuracy is a direct product of your hold down accuracy. If your hold down is off by 2 or 3 thousands your route will be off. Most of what I do is in wood and so that is not that big of an issue, in your case that may make a big issue. I have used pins, adjustable stop blocks, etc,. The cutting pressure also has a direct bearing on how will your hold down methid will work routing two sided. Russ

[Gary Campbell]

Erwin...
There are a number of way to accomplish this. The best one would have to be determined by your material and cutting strategies.

Short answer, yes. Many of us do this on a regular basis.

[gc3]

http://www.talkshopbot.com/forum/sho...FLIP+MACHINING

[dana_swift]

Erwin- three things to consider, the first is very simple. If there is a rigid part of scrap you can use route a hole through it while you machine the first side. When you go to the second side, use the hole for alignment. The simplest and fairly accurate method is to use a dowel rod to align the hole with a hole in the spoilboard.

The second and most accurate method is: Shopbot provides a routine for centering on a hole that is more accurate than any other XY alignment method I have found. The trick is to make the hole the outside diameter of a copper sweat fitting. The "center in hole" routine needs to make electrical contact with something to know when it has hit the edges of the hole. Aligator clips make the connection to the sweat fitting and the bit.

The third method is to zero on a corner of the stock using a super-zero. You have to build or buy that yourself, there are several articles on the forum about them. I had a machinist make me one and it is excellent, almost as accurate at the center on hole method.

Hope that helps-

D