After finally purchasing a desktop letterpress or platen printing press, I wanted to try etching printing dies from acrylic instead of sending artwork out to make metal or polymer dies or investing in type. After experimenting for a few weeks, I came up with a process for etching a die and mounting it for printing in a letterpress.
Laser etching was done at the San Jose TechShop.
Material needed for this project are:
½ to 3/16 in. acrylic plastic sheet. (High temperature material is better because it will not burn.)
½ to ¾ in. thick hardwood block for mounting die. Use ½ with ¼ inch acrylic and ¾ with 3/16 acrylic.
Access to a laser cutter
Graphics Software (Corel Draw, Adobe Illustrator, or Inkscape)
Rubber cement or carpet tape
Weights or other objects (books, etc) to be used for mounting die to wood block
Step 1: Creating the Image Files for Etching
Prepare the image and/or text using a graphic software of your choice and place a .001 inch line box around the image. This will be used to cut the etch area from the acrylic sheet. There is no need to reverse the image or color. The stamp setting of laser cutter driver for the Epilog laser will take care of this, along with providing other options.
I create the image with three layers. The first layer is the image to be printed. The second is a mask, which is used for etching the bulk area of the material surrounding the image surface creating a raised area for etching the printing surface from. The result will be a stepped die with looks like the printed area has been tooled out of the bulk material. The third layer is a hairline outline of the plate that will be used for cutting out the die from the piece of acrylic and provide a reference for the other two layers.
Figure 1 shows font test that will be etch and proofed to determine which fonts print the best. The lines of text are in layer 1. The image and text blocks should be centered left to right.
Figure 2 shows the mask layer. For the mask shapes, either remove line around the filled shape or make the outline wider that .001 inch. If the line is .001 inch wide, the shape will be cut out. The mask shapes should also be centered left to right.
Add a third layer with a box around the images and mask with a line width of .001 inch and no fill. This box needs to also be centered left to right. This box will be used to cut the die from the piece of acrylic and used to align both layers. Note down the size of the box. This will be used to set the piece size when etching the die.
Create two different PDF files with with resolution of 600 dpi. Use layers 1 and 3 for the first and layers 2 and 3 for the second. The system attached to the laser cutter does not have the same fonts as the computer used to make the layout. Using PDF files eliminates the need for the system attached to the laser cutter to have the same fonts installed. Figure 3 shows the settings I used for creating the PDF files.
Open each of the PDF files to verify each is the same size.
Step 2: Etching and Cutting Out the Die
Open the mask PDF file first on the system attached to the laser cutter and select print. In the Page Sizing and Handling section, select Actual size, Figure 4.
Click on the properties button. Set the Piece size to be a little larger than the dimensions of the box that surrounds the design, Figure 5.
Select Combined job type in order to set both the Raster and Vector settings. Change the Resolution setting to 600 DPI.
Change the Raster settings to
Engraving Direction Top-Down
Image Dithering Floyd Steinberg
(Floyd Steinberg is the only dithering setting that supports 600 DPI.)
Change Vector settings to
Freq 5000 Hz
(The speed is determined by the thickness of the acrylic. ¼ inch thing acrylic needs 8% speed. Thinner material can be cut with a faster speed.)
Click Advanced on the top of the properties window, Figure 6, and choose...
Raster type – Stamp
Shoulder – use default or 10%
Go back to the General settings and select Raster job type, click OK, and etch the mask PDF image, Image 1.
Open the other PDF and click print. Open the printer properties and verify the settings match Figure 5 and 6. Click OK and etch the image that will be printed and cut the die from the piece of acrylic, Image 2.
Step 3: Mounting Die
n order for the die to be printed in a letterpress press, the die needs to be mounted on a block so the total height is about .918 in. The usual mounting block is made from hardwood, like maple or birch.
Using acrylic that is 3/16 in thick and attaching it to a ¾ inch thick block will result in a die that is about .938 tall. If you can find a block this is about .7305 inches thick, the mounted die will be type high. This can be done using the laser cutter to etch a ¾ inch down to about .7305. For the pattern, use the outline layer, layer 3, created when doing the graphic. Change the settings in the print driver for raster to:
Vector settings to:
Frequency 500 Hz
and advanced settings choose Raster type basic.
Experiment with the raster settings to remove the required amount of wood. Print with vector turn on to make lines on the block for use as cutting guide.
For ¼ in thick acrylic, attaching it to ½ inch thick block will require increasing the mounting thickness from .75 in. to .918 in. This can be done by gluing press board and paper to the back of the block. Another option is to reduce the thickness of a ¾ thick block to .668 in. using the laser cutter. Several passes raster will have to be done to accomplish this. Be careful not to start a fire when doing this.
Glue the acrylic die to the wood block using Contact or rubber cement. After gluing the back of the die to the block, place the mounting print side down onto a hard service, place weight on the block and let stand until the glue has cured. (Heavy book(s) can be used for a weight.) If the die is cupping, try attaching the acrylic to the block using nails or small flat head screws.
Once the glue has cured, clean off the acrylic with some solvent and the die is ready to use for printing.
Step 4: References
Information about letterpress can be found at http://en.wikipedia.org/wiki/Letterpress
I purchase pieces of acrylic from the scrap bin at Tap Plastics, http://www.tapplastics.com/
Information about Stamp Engraving from Epilog Laser, http://www.epiloglaser.com/sc_stamps.htm.