Tag Archives: brain teaser

Evaluation of Preform 0.8.1

As I was explaining in my previous post, the form1 printer software is still a work in progress. Some bugs have been squashed with the 0.8.1, but some remains and I’d like to go though the some of the current challenges that a fellow formers might encounter. The first ones are the most critical in my opinions…

Object skin is not always sticking to the filling

[I’ve submitted this bug #1123 to the community board]

I’ve chosen the impossible heart brain teaser available in Thingiverse to see how very simple and smooth pieces would print… First it was not a brilliant idea to print it without supports. I had to use a clamp to pry apart the pieces from the platform and in the process damaged a bit the puzzle surface.


But the real issue was, as some of the Reuleaux spheres in my previous post, the perimeters on some of the pieces didn’t stuck and I ended-up with a ugly result. What you see behind are the back and forth inside filling profiles. My hunch is, depending on the pealing direction, the perimeters might not be completely merged with the filling leaving a weak spot in the structure…


If I was Formlabs, I would try to extend the filling paths so that it overlap at least the last perimeter to make sure everything is correctly glued together.


[.form file]

25 microns prints non sticking to the platform…

This point a a bit a hit or miss. I’ve followed the advice in the community forum that using the “grey 25 microns” material profile was increasing the chance of sticking and so far I had 2 out of 3 prints working. The sticking might be affected by the location of the print on the plate and the orientation of the base platform. If you have a long platform, turn it so that the peeling starts on a small side.

To solve this it would be great to have more control on the laser, like being able to set the speed of the scan, the number of repetitions, the number of perimeters. That would open quite a few possibilities and for the most advanced users it could be a great way to experiment.

Overlapping supports are creating pockets of uncured resin

[I’ve submitted this bug #448 to the community board, and it’s marked as closed]

That one is strange but apparently it’s already fixed for the next revision. The problem arise when the software decides to place 2 supports so close that they are overlapping. In this case the internal filling back and forth of the laser is missing at the intersection. That will create a hole of uncured resin and I it’s safe to assume the support strength is gone…
[.form file to test]


Peripheral loops are overlapping on very thin walls

[I’ve submitted this bug #1124 to the community board]

Preform is drawing 3 loops around perimeters. These loops are continuous and when the geometry has a very thin wall, these perimeters will get inverted and even create filling outside of the geometry… (Yes I know it’s not clear, just look a the picture to understand the issue…)
[.form file to test]


That’s all for today 🙂 If you have any comment or extra bug to report on this release please comment I’ll investigate them!

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First prints & lessons learned

After many tests print I finally got to print some real stuff these last day. The first object was something completely useless but full of gears and very cool (so by my standard indispensable).

One of the mistake I made, was to print the raft and the pin out of PLA. I could not get them to stick to the bed without but couldn’t separate the result so my yellow internal pieces have a black layer 🙂 GearCube_Assembly

The end result is a nice transformer like cube…GearCube_EndResult

My second print was one of my puzzle: double dovetail with a twist.

The pieces are large and I got warping as my bed is not heated… Nevertheless, the comb infill is nice to see…DoveTail_warping

The dovetails ended pretty flat, and just a little bit of sanding was necessary to allow a nice sliding between the parts. DoveTail_separated

And here is the final assembly 🙂 I need to design more puzzle!DoveTail_assembled

And here is the puzzle in action!

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Brain Teaser: Double Keys Box

Today’s puzzle is an other trick opening box. From the puzzle classification list by Slocum this is the family where the goal is to take apart the assembly. In this box you have a hidden mechanism that let you open it if certain steps are followed.

The box is rather plain for outside, but the interesting part is the internals. With 6 sliding pieces this is by far the most complex assembly I’ve built to date. As you can see, the master sketch part starts to be a bit crowded! In on of my next post I will probably describe the process of creating complex assembly and shapes with Inventor.master_doublekey

The assembly instruction gives a better overview of the different pieces.Instructions

The Main body (box) is were all the other pieces are sliding into. On both side a panel and a key have a round slot to catch one of the 1/2″ marbles. The pieces are symmetric so that the same geometry can be reused. Once everything is pushed inside, the door slide from the top.

To keep the door shut the pins have a spring bar that I saw in another Thingiverse object by Ttsalo.

As I do not have a printer yet, I use the schematics and cut views to make sure everything will work.


The Interesting part is to have a look at the lock pin cut:


In this cut one of the ball is placed in the slot. The pin is in locked position (note: the spring is not bent, so it’s going through the back wall). The door cannot slide up, the only way is to pull in the pin using the side panels. But unless both keys are activated at the same time, the door should not move…

As always I’ve uploaded the STL on Thingiverse here.

Happy brain teasing!

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Brain Teaser: the Padawan Dovetail Box

And here is this week puzzle: the Padawan Dovetail Box. Once more you have to wonder how is it even possible to have dovetails on only 2 sides and the “L” shape prevent to use the same trip as previous puzzle… The goal is to open the puzzle to access the compartment inside the assembly but this time gravity force will not help you… Time to work on your Jedi powers young padawan!


The Puzzle is build around 2 main pieces and two 1/2″ diameter (12.7mm) steel ball bearings. I’ve settled for 1/2″ because it’s the standard size for small marbles called peewees. In this case we need steel balls for the puzzle.


First piece of the Padawan Dovetail puzzle (and steel ball bearings)


Second piece of the Padawan Dovetail puzzle (and steel ball bearings)

A transparent side view of the puzzle reveals that the holes are tapered so whatever the direction you hold the puzzle, at least one ball is in the way to prevent sliding of the puzzle…


I will let you figure out how to solve it, but I’ve included clues in my post that should help you. I can’t wait for my printer to come and try it.

To assemble the puzzle, push the steel balls in each holes and hold them between 2 fingers. Slide the pieces starting with the arrow side, then try to open it again!

As always I’ve uploaded the STL on Thingiverse here.

Happy brain teasing!

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Brain teaser: the double doveTail puzzle with a twist

[April 27 update: I finally printed this puzzle, see this post for the pictures and video!]

[March 20th update, the puzzle is now at Rev 2, the rev1 was too small and the marble could ‘escape’ the assembly, so I’ve re-generated it with more space. The puzzle is now a bit large with standard 15.5mm, so I’ve also built a 10mm version available on Thingiverse]

I really like brain teasers and while I enjoy trying to open/disassemble the one I have, I never got the chance to really build one. Maybe it’s because it requires some good wood working tools. Anyway, the 3D printer is the perfect way to build new puzzles and a lot are already available on Thingiverse (see some examples in my collection).

So here I start a new series of posts dedicated to brain teasers. I will start with a classic: the double dovetail puzzle. This puzzle is not really complex to disassemble, but the fun is to figure out how it was built. The two dovetails are crossing the assembly from part to part in a seemingly impossible manner…

Now I got an idea to modify the puzzle to add a new twist and add some difficulty to separate both pieces. When doing the right actions there is a maximum of 4 steps to open the puzzle, but there are traps and dead-ends that will play tricks with anyone who’s tempting to solve it. It’s not an insanely difficult puzzle probably 3/5 but should be challenging enough.

The puzzle has 2 main pieces and 2 marbles (15.5mm diameter). The goal is to separate the assembly. The marbles a here to prevent the sliding of both pieces.


Double Dovetail puzzle assembly


First piece


Second piece

Anyway the STL for the parts are here.
Happy Brain Teaser!

For those who are ready to burn the thing and jump though a window I’m providing a full diagram of the different internal states here for the solution.

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