Make it even less tight.


I still seem to have the parameters wrong, it seems to be the same size as v7.  What the hell is this geriatric fool doing?


I had a lot of issues getting the damned tophat to stick to the plate.  I discovered there were platen issues.  Someone had gouges indentations in both plates.
The filament was not sticking, and looked like it would end up with an indentation in the side like v7.  I rotated the plate and changed filament and got a decent print.

The good

It actually fits well enough that I have been able to wear it for almost 24 hours continuously.  It is perhaps still a tad tight, but it isn’t worrying me unduly.

The bad

  • The finished object had a lot of minor scarf on it that need picking off because it irritated my wrist, especially at the opening round the circular end.  I scratched it off and it was much better.
  • White shows the dirt!


Rounding the end and putting fillets on the both endges of the opening would probably help.

I’ve been playing with e-paper displays a bit, and all of them seem to have some magic power electronics that are not described on the web-sites. However I came across this German company called Plastic Logic that seems to be quite forthcoming.

They have a flexible tiny e-paper display and they show the schematics for driving them.

Single voltage power supply (1.7 … 3.6 V), on-chip regulator control for generating driving voltages (external booster circuit required)

Two of there displays seem like they might fit into a cuff, assuming I can figure out how to create a transparent cover.  This might be the show stopper.

The two candidates are

The schematic has a network called “HV booster” that has some scary wiggly components on it.
I’m wondering if it means I have to make a board, and find some sort of connector?
It appears that this can be interfaced directly to a uC with not extra stuff because it has an embedded “Ultrachip” processor 
There’s a git library of code too. https://github.com/plasticlogic


This one has the entry gap canted 10° to take account of the wrist asymmetry.

In Progress


Complete misfire on this version.  Somehow I managed to shrink the wrist width parameter and made it way too small.   Pretty much impossible to get on, and uncomfortably tight.


Adjusted the parameters and re-printed.

The Good

  • It came out almost as intended this time
  • It flexes well
  • It fits snugly

    The Bad

    • It’s quite a lot harder to get on with the reduced gap
    • It’s still perhaps a bit too tight.
    • Top flexing
      If a display is to be mounted in the top surface then it has to be able to flex, or I have to find a design that doesn’t flex when you put it on.

    The Ugly

    • There was a minor printing issue.  The top-hat didn’t stick properly and it curled up.  This led to a small imperfection in the cuff itself.
    Here’s a brute force parametric model.  It took me two revisions to get it up to the point where it was worth printing.  It’ is indeed a crock of shit, but it highlights some of the more obvious problems.  There are parameters for every dimension so it should be easy to change the cavity size, width and wall thickness etc.
    The gray block in the second picture is a battery, and the green block is the DW1001.  I was looking at curved batteries, but I think it perhaps makes more sense to use two smaller LiPos mounted end-on at each end of the cavity.  Then I think the cavity can be a lot smaller.
    I’m thinking there will be a plug that somehow pushes into the open side of the cavity.  The plug could even have a couple of brass terminals for charging.
    I rendered it in a wood finish because it’s easier to see the shape. 
    I printed the cuff and a battery model using ABS to see how it fitted.

    The Good

    • The model printed!  
    • It flexes enough that I can force it over my wrist without it snapping
    • It is really snug.
    • The dummy-battery, DW1001, and tickler all fit inside OK with  to spare.  It doesn’t look that bad, considering it’s a first attempt.

    The Bad

    • The battery sagged, and it’s radius changed as it printed and I had to sand it down to fit which looks nasty. but it fits.

    • It’s translucent. Maybe nylon will be less so, or maybe I have to figure out how to make the translucency a feature.
    • It seems clear that “one size ‘fits’ all” isn’t going to work

    The Ugly

    • “Snug” is an understatement.

    This one is 8mm wider on each internal radius.

    The Good

    • It was a much better fit.  It’s still probably tight enough.  I slipped it on my wrist and have been wearing it almost continuously for since I got home, about an hour ago.
    • It’s actually easy to put on quickly.

      The Bad

      • The molding had rough edges from where I removed the top hat – always to be expected.  I filed it down.
      • The end of the cuff by the opening digs into my arm still.  When I removed it there were indentations on my wrist, which is probably going to be unavoidable to get a snug fit.  More worryingly, red marks were beginning to develop on my wrist.  

      The Ugly

      • It isn’t that it’s too tight, it’s more that it is a poor fit.  My mistake is assuming that the wrist is symmetrical.  Notice that it doesn’t wrap around and meet symmetrically on the middle of the underside of my wrist.