I’ve been doing a lot of cutting and engraving of acrylic for a large project I’m working on. I”m engraving text with a V bit, so it’s critical that the acrylic be completely flat. Even a tiny 0.01” difference across the surface of the workpiece can make the text noticeably different - faint on one end and bold on the other.
Today, I finally got fed up with the tedious process I used before and I decided to make a fixture to ensure a dead flat surface and also to help in making the workpiece orthogonal and to make zeroing the machine less tedious. Here is the result:
First, I cut a hole pattern to match the hole pattern of the threaded inserts in my waste board. Then I fastened it securely to the waste board leaving the bolt heads recessed well below the surface. I cut out the outline and faced off the surface to flatten the fixture with respect to the spindle. I also engraved concentric rectangles to act as guides when I fasten my workpiece. From the zero position in the lower left hand corner, the rectangles form guidelines every 1/2” both vertically and horizontally. This matches the offsets I usually use in Carbide Create, so I can eliminate measuring. Now I can just eyeball the placement of the workpiece and always get it well within the tolerances I need for this project.
I borrowed a neat trick that I remember @WillAdams mentioning a month or two ago. He said he designed all of his fixtures to use one of the default rapid position points as the X&Y zero position. I did that with this fixture, setting the zero point at the middle rapid position point closest to the operator. This really works well, essentially eliminating XY zeroing completely. This may be a common practice among the folks in this forum, but it was a revelation to me.
Here are a few more photos showing how I used the fixture to make a control panel for a spaceship cockpit I’m making for my kids. I use Nitto tape to secure the acrylic panel to the fixture. I have a total of 14 control panels to make for the spaceship cockpit, so I think this fixture will save me a huge amount of time and produce better results.