Gas station without pumps

2019 July 14

Shakespeare cookie cutter

Filed under: Uncategorized — gasstationwithoutpumps @ 14:49
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I have been trying to create a cookie cutter and stamp of Shakespeare’s head on my 3D printer.  I started by hand tracing one of the engravings of Shakespeare’s head using inkscape, to get a simplified line drawing:

The tracing looked good to me, but there may still be too much detail for a cookie cutter.

I decomposed the drawing into two parts: the outline and the internal lines (as shown by the colors).  I then used OpenSCAD to create three designs: a stamp for the embossing the lines, a cutter shell to cut the outside edge, and a knob for putting on the other end of a shaft for the stamp.  I had to install a new version of OpenSCAD, because the old one I had could not import splines.  The new one does, but gives no way to control the number of polygons created, so I often had 10-minute waits as it tried to generate the geometry.

My first attempt (to make a 5cm cookie) was a miserable failure, because the holes for the shaft closed up, being almost 1mm smaller in diameter than specified. Also the thin lines for the stamp ended up being too thin and too close together (particularly for the mouth), so the printer ended up blobbing them together.  The design might have worked with a higher-quality printer, but the almost any filament printer is going to have trouble with 0.5mm wide ridges that are 2mm tall.

My second attempt widened the lines and separated them a little, increased the cookie size to 6cm, and added some compensation for the spreading that was closing the holes.  Here are the parts:

From left to right, we have the stamp, the cutter, and the knob. The knob has been fitted with a 5cm ⅛” stainless-steel rod and a 4cm spring.

The parts looked much better this time, and the shaft fits comfortably in the holes in the knob and the stamp, though I will need to find a good glue for attaching the PLA and the 316L stainless steel.  I don’t think I want to use a 2-part epoxy (I have trouble mixing small quantities), but standard superglue may be too brittle—I’ll probably try it anyway, if I have any that has not solidified in the container.

Both the stainless-steel rod and the spring are leftovers from previous projects: Two-electrode vs. four-electrode impedance spectroscopy and Physics Lab 4: spring constants results.

I did one trick in Cura to save some printing time.  Rather than doing 100% infill for the whole stamp and knob, I used only 20% infill, but requested a thick top layer for the stamp and bottom layer for the knob—thick enough to be solid down to the end of the shaft.  I also requested thick side walls, so that the sides of the hole were solid. The reduced infill doesn’t save much on the stamp, where the hole for the shaft is rather shallow, but it made the knob substantially lighter and somewhat faster to print.

There were still some problems with stringing and blobbing around the eyes and mouth:

The eyes and the mouth still have serious problems with stringing and blobbing.

I tried trimming off the excess plastic in the details and found that the top few layers of the stamp delaminated too easily.  Things look a bit better after the cleanup, but the stamp no longer has uniform height ridges, with a variation from 1.5mm to 2.5mm high.

After cleanup, the stamp looks better, but the details still seem to be too small for cookies, and the printing is too messy.

I’m not sure what my next step is on the design is.

  • I could make a larger print (up to about 10cm), which might make an Instagrammable cookie, but would be a bit large for a really useful cookie cutter.  Even then I’ll probably have problems with stringing and blobbing on the fine details.
  • I could try to simplify the eyes and mouth further, to reduce the need for fine details.  I’m not much of an artist, so I don’t know how successful I can be at that, but I think it will be essential for a usable stamp.

I’m feeling now that I should have been less ambitious for my first cookie-stamp design (maybe even doing a simple cutter, rather than cutter and stamp).

1 Comment »

  1. […] first post on the Shakespeare cookie cutter was a about versions 1 and 2 of the cutter and stamp—both of which were basically unsuccessful.  […]

    Pingback by Shakespeare cookie cutter v3 | Gas station without pumps — 2019 July 15 @ 20:28 | Reply

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