Engrave Personalized Stamps

If you have access to one of those awesome fab-labs which are growing up in cities all over the world, you would like to make something unique with a 3d printer, a CNC router, or a laser cutter.
I begun experimenting with a special rubber which can be engraved by laser to make personalized stamps.

For this project you need a laser cutter, of course, and a sheet of special rubber. I found this green A4 format rubber sheet at a printing house supplier, it's about 12€ each.
The laser machine you see in the picture is the bigger one of the WeMake fab-lab here in Milan, and I used it to cut the wood support for the stamp. I used the smaller laser cutter to engrave the rubber, you don't need much power, although with a more powerful machine you will take probably less time.

As subject for this tutorial I chose a famous game character. Since the image has colours and tones, I converted it in b&w and worked on levels to improve visibility and contrast between different areas. Try to have full white where image is lighter and keep black only for outlines. You can use Photoshop or any other software for photo retouching.

Then enlarge or reduce your image to about 1200 pixel. This will let you apply effects with a certain standard.

Also remember to flip the image around the vertical axes, since the stamp will be mirrored. I forgot to do that with my Supermario.

Since image is a drawing we want to extract outlines and overlap them on the gray tones.

Duplicate the layer, take the top one, apply the "stamp" effect, play with settings to obtain the better b&w outlines image, then refine it with the pencil tool.

This powerful effect lets you render grey tones in a black and white dots motif.
You have to decide now how much detailed will be the shades of gray, the smaller the dots are, the more precise tints will be, but thin rubber spikes will be hard to maintain.
Use a value from 12 to 18 as max radius and 45° for other settings. Apply the effect to the background layer.

Select the outlines layer and with the "magic hand" tool select all external white area. Go to background layer and with same mask fill the image with white color. This will remove any outside undesired dot.

Now you can choose which details of your image shall be totally white, like eyes and teeth. Go on the background layer and paint them with white.

I think that image appearance could be improved adding a thin space between outlines and halftone filling.

To do that you have to select the empty areas and reduce the selection of about 4-5 pixels. Then invert the selection, make a new layer, fill it with white and place it between outlines layer and background layer.

Now your image is ready to be imported in a drawing software to be converted to vector graphic. Flatten all layers and save the image in png or a good quality jpg file.

Since image is already optimized you can probably use any software with the capability to convert raster to vector images. I used Illustrator, which also let you to refine some details of the final result, like thickness of the black shapes, and to remove dots which are too tiny.
Illustrator has also the same Pixelated effect, and so you can do everything with this software.

Open a new document and drag your raster image on it, then go on window -> image trace and open image trace settings window. Choose b&w, open advanced settings, and play with them until you're satisfied. I only changed noise to about 20. Try also "ignore white" setting.

Then click on "expand" button, which will explode all into shapes. Select all and ungroup everything.

This step is needed since Illustrator creates some hidden duplicates which will be a problem in the laser software.

Click on a black area, then select -> same -> fill color, and object -> hide -> selection. This will apparently hide everything, but select -> all and you will see there are white areas which you wont need. So cancel them, and object -> show all.

You need two outlines, one to make external engraving area border, the other one to cut your stamp around the border. Double click the drawing and select the external spline. Esc or click outside the image and paste a duplicate of that spline, then go to object -> path -> offset path, choose the width you wish (I used 1mm) and apply the effect two times. Change the colour of the middle path to a different one and also cancel the inner path, to avoid duplicates.

Since laser software doesn't want filled patterns, change the visibility of all shapes to empty areas with stroke border.

Then save the file as .dxf with R14/LT98 version, 1mm scale, and "maximum editability" checked.

In the software lasercut5.3, file -> import the .dxf, then edit -> center to table. Use tools -> unite lines, and tools -> check data.
There could be some self-intersect lines, just ignore them if you don't have patience to fix the dxf.

Look at lines colors and assign as first the engrave and then the cut process.

Choosing right values for laser speed and gap is the difficult part. Power is usually at 100% to optimize the job.
I made some tests with the 60 watt laser. To engrave that rubber foil you need a quite slow speed, and a very low gap. But if you exceed lowering these parameters you will lose details. I decided that a value of 100 speed and 0.06 gap is quite right, deep engrave and good detail although slow process.

You can also try to use gap 0.10, to be faster. Look at the pictures to see the different appearance of slopes on types borders for different values of grade width. First line of bigger test rectangle is made with simple engrave (no grade).

Now click "download", delete all previous jobs on the machine, and upload current one. Wait half minute, since this file is quite big.

Choose in the software menu as starting point the left-down point (or another one as you wish) and place your rubber sheet on the machine plane.

With "Z" function you will raise and lower the laser to set up the focusing distance, exit from this function clicking Z again.

Then click "esc" a few times to go back to home menu, and move the laser so that it's on the starting point you chose before. With "test" button you can see the perimeter of the job and check that you have placed rubber right.

When you are ready close the cover, start chiller and air compressor, and click "start".

At the end of the process you can click "datum" to send the laser to home, and take out your stamp.

A similar process is to cut the support from a 5 or 6mm thick wood board.

I used the bigger laser machine of WeMake workshop, more powerful than the other one.

In software change colour of the external line, assign to that colour "cut" parameters as in the picture (100 power, 25 speed) and check output only for that layer. Place board, upload (or "download" if you follow software label) the file to the machine, and start the cutting. That is really fast compared to the engrave process.

Now you only have to clean stamp surface with water and a brush, glue the rubber to the wood support, and choose a good handle for that.

Your rubber stamp is ready to be tested. If you are satisfied with the result it's time to begin making stamps for your friends ;-)

Remember that you can also import a bitmap in the lasercut5.3 software, and with tools -> half bitmap you can obtain the same effect to print gray tones. Obviously this function although is very easy and fast, doesn't let you a large flexibility.