The bars on the original MPCNC drag knife / plotter pen adapter had a 100 g/mm spring constant:
MPCNC – Plotter pen force test
Making the bars slightly thicker improved their print-ability:
MPCNC knife adapter mods – OpenSCAD model
The reddish tint marks the new bars, with their location carefully tweaked to be coincident with the stock STL.
Shoving the pen into the scale with 0.1 mm steps produces another unnervingly linear plot:
Modified MPCNC pen adapter – Spring Constant data
Real plotter pens want about 20 g of force, so this isn’t the holder you’re looking for.
A bunch of plots at Z=-1.0 mm turned out well with the ballpoint pen insert, though:
MPCNC Modifed pen adapter – first plots
The globs apparently come from plotting too fast for conditions; reducing the speed to 1500 mm/min works better.
#1 by Frans on 2018-10-11 - 15:00
Tell me more about this scale with all the nice physical buttons. Does it annoyingly turn itself off or does it stay on? :-)
#2 by Ed on 2018-10-11 - 19:18
Got it from Harbor Freight long ago, had to figure out the counting function on my own, and it’s worked ever since.
It shuts down after a minute, which is surprisingly long.
I’d probably get something similar from Amazon, if only because Harbor Freight is the Home of Single-Use Tools. In your part of the world, you’re on your own! [grin]