Tentative de gravure en FabLab

by David

The project is to engrave an image for a relief printing.

The starting point is a image created for an USB key made for an album by musician &apos. 

This image was created by letterpress printing brass rules "air lines" , scanning them and edit the scan to give the shape I wanted.

The result is an image that fits on a business card (the USB card) of 5,5 x 8cm.

 

For the project, I would like to print a poster of this image. It will letterpress printed. 

Therefore, the image has to fit on the press. A size of maximum 50 x 70cm, can't exceed 3cm height and need to resists to pressure.

I need to "remove" material around the image I want to print (as it is relief printing, not etching print).

 

The first step was to create a vectorized image, in order to enlarge it to the pster size. 

Then, I needed to choose which material and which tool to engrave it.

 

MDF is a good choice. It's flat, hard and cheap. But no MDF in the lasercutter. As the image is quite detailed, I needed a 1 mm drill to achieve the engraving with the right amount of details.

After creating the toolpath on STLCam, the estimated work time was around 15h +.

 

I decided to move to the laser cutter, it would maybe be faster.

For the lasercutter, no MDF.  I went for plexiglass. 

The first try was with a 2mm thickness sheet. Max. power: 30 - Min. power: 30 - workspeed: 600mm/s. The heat was too high and quite fast, the plexiglass wasn't flat anymore.

Second try with a 5 mm casted pleixglass. Max. power: 30 - Min. power: 30 - workspeed: 600mm/s. First pass was good but not deep enough. It needed a second one that I couldn't do. Unfortunately, it was impossible to place the plexgilass exactly at the same place, so this try out was cancelled.

Work time / layer = roughly 2h45.

 

Third try: 4 mm casted plexiglass. First layer engraving: Max. power: 30 - Min. power: 30 - workspeed: 600mm/s. Second layer engraving: Max power 45 - Min. power 45 - workspeed: 900mm/s. 

Engraving is deep enough, but unfortunately,  the heat was too intense and the plexiglass looked like a banana. I could manage to cut out the shape of the image from the big plexi sheet. After some attempts to flatten the plexiglass, I could mount it on a wood pannel and place it to the press. The edges of the plaxiglass aren't flat enough, because of the heat, and print on the poster. Also, with the intensuve heat (?), the surface of the thin lines look burnt and dont print well.

 

Next try with 2 layers of engraving at Max. power: 30 - Min. power: 30 - workspeed: 600mm/s.

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Date: June 2021 - September 2021

Last updated: 4 weeks ago

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