The following is a procedure for creating double sided etches that must align on each side of the material and applies to transparent surfaces such as Plexiglass.
- Move material box inside from edge and make sure its size is accurate. You'll want about 1/2" on all sides from the edge of the laser bed so the maximum size of material can only be 17" x 31". The final piece will be cut from this material and so should be larger than the final desired size.
- Place a blue vector etch registration marks as shown in each corner of the material box. Each registration mark must be aligned in the horizontal and vertical directions
- Place a vector cut box inside the material box, this will serve as your final material size, material outside the box will be discarded.
- Place your design inside the final cut box. In this sample our design is the letter R.
- Now that the design has been finalized select the design layer and name it "Side A", this layer should include the material box, the registration marks, the cut box, and your design components.
- Create a new layer called "Side B". Select the entire contents of Side A and duplicate it inside of the layer Side B by option dragging the selection box in the layers palette to the Side B layer.
- With the entire Side B layer selected go to the menu Object, choose Transform > Reflect and set the options to Vertical. With the arrow keys and the transform palette move the selection around until the registration marks exactly match up with the marks from layer Side A. Notice that the design, material box, and cut box do not align, only the registration points need to be aligned. Remove the cut instructions from the Side A layer. Cutting before flipping over the material to align with Side B would defeat the purpose of the alignment registration marks. (Note: in the picture below the extra cut box from Side A has not yet been removed)
- Now that we've created a double sided file in the template, running the job in the laser is relatively easy. Start by running Side A, placing the material as shown by the Side A material box in the file.
- Now flip the material over from left to right, not top to bottom, and place the material as close as possible to the placement specified by the material box in Side B.
- With the lid of the laser open, run only the registration marks from layer Side B. As the red diode travels the four corners readjust the position of the material until all four registration marks align with the path of the red diode. You may want to slow the speed of the red diode to get a better look as it passes over the registration marks from the backside.
- Once registration is complete, run the design from Side B. It should be exactly aligned the Side A design. Reserve running the cut box until all the design components have been printed.
Considerations: Obviously this process will only work on transparent materials, This shouldn't be an issue as I can't imagine a situation where you would need to align front to back on opaque material. When using acrylic etching on both sides requires removing the paper backing from both sides of the material. This can caused undesirable effects on the down side of the material. Cutting usually involves back-burn where hot fumes hit the surface of the material that is usually protected by the paper and results in discoloration of the surface. Cutting will also heat up the honeycomb bed of the laser that will melt portions of the underside surface of the acrylic.