Archive for October 11th, 2018

MPCNC: Acrylic Engraving First Light

Posted by Ed in Machine Shop on 2018-10-11

Just to see what happened, I chucked a drag knife in the collet pen holder:

MPCNC Collet Pen Holder - drag knife

MPCNC Collet Pen Holder – drag knife

The blade, being fixed in the collet and lashed to the adapter, doesn’t rotate: it’s not behaving as a true drag knife.

Twiddling the cut depth to about 0.2 mm produced a credible Guilloché pattern in some scrap acrylic:

MPCNC Collet Pen Holder - drag engraved acrylic - 0.2 mm depth

MPCNC Collet Pen Holder – drag engraved acrylic – 0.2 mm depth

The sidelight comes from an LED flashlight off to the side, with a bit of contrast tweaking to suppress the workbench clutter.

The MPCNC’s lack of rigidity produces visible jitters in the Guilloché pattern and backlash makes the characters somewhat wobbly, but it’s OK for a large and inexpensive CNC gantry machine.

A brace of diamond-point engraving bits are making their way around the planet even as I type. A symmetric 60° point may reduce the swarf thrown out by the drag knife, although it surely won’t improve the overall jitter and backlash.

 

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