Where it stands
- The grip works. The adjustable grip tightened more easily than the ones before it and held the pen through the hardest pull we could give it by hand. That was the earlier, larger version of the grip, and the pull was not measured.
- The fit comes next. The latest body, cap and insert are drawn and pass their checks on screen, but have not been printed and tried in the carriage. Each pen still has to reach the height tool, the grip has to hold and let go, and then it has to draw.
So there is no finished file to recommend yet. The files for the latest trial are on the project site, for anyone who wants to test along.
How it works
- The body stands in the plotter's tool carriage, as Graphtec's own holder does: a flange rests on the carriage, and a collar below it gives the clamp something to hold.
- The pen drops down through the body. Its barrel sits in the insert, whose bore is 10.05 mm across.
- Screwing the cap down pushes the insert into a tapered seat in the body. The taper closes the insert's slotted fingers round the barrel, so the pen cannot slide.
- The writing point is set with the plotter's height tool before it draws.
How it got here
It started as one solid holder, snug round the pen, that printed well. Each version after that asked a smaller question, often with a short sample that prints in minutes instead of a whole holder: does it pass through the carriage, does the clamp reach it, does each pen go in.
The clamp was the first surprise. A narrower body passed through the carriage, but the clamp did not grip it. A collar fixed that, and a measurement showed it could reach only 3.2 mm below the flange before meeting the carriage's metal throat.
Pens differ too. Two barrels measured 9.75 and 9.85 mm across, so a solid bore sized for one is loose or tight on the other. That is what the grip that adjusts is for: a screw cap and a slotted insert.
The first cap and insert went together, but the pen slipped. Ridges on the cap helped fingers turn it, and a later insert, with a smaller bore and freer fingers, was the first to hold.
Measuring Graphtec's own PHP31 holder then showed that the body's upper part had to be narrower, too narrow for that thread, so the latest body, cap and insert are a smaller set. A small nose on the body stopped the pens short of the height tool, so the latest body takes it off and opens the way down with a smooth cone.
Follow the details
Every step is written up on the project site: each version and what it taught, a 3D view to turn, cut through and pull apart, the print files for each version, and the plan for the next test.
The whole project on graphtec.mhilo.com (opens in a new tab)
In development, as of 13 September 2026