Mistery Box - Useless Machine 3D print model

So this is the chance to show everybody that the 3D printer that you bought is not a useless toy. It is in fact a fantastic machine that can produce useless toys...

This is a simple Useless Machine / Mistery box to be made with a 3D printer and a few basic parts very cheap and very easy to obtain (links provided to all of them). Just a couple of switches and a motor. No arduinos, no programming, no nothing. Wiring plan included in the files.

PRINTING The model has been carefully designed to make it an easy print . Tolerances have been worked out to produce an easy to assemble functioning USELESS MACHINE on all printers. Nonetheless, STEP files are included in case you want to squeeze more the gaps for your extremely accurate resin printer (more on tolerances and plays later) or perhaps you want to redesign the cover with your own embossment, or maybe change the motor mount to assemble the device with a different motor.

Printing of all the parts of this device is pretty strightforward.

The provided STL files already position the part in the recomended printing position.

Only one of the parts (Top,stl) needs aditional support. I reccomend using only a support enforcer for the back part of the part, and print the hinge holes with no support. All holes are shaped in a way they will print all right withoul support and perform perfectly as rotating hubs

Only one of the parts (Finger.stl) needed a raft to be printed.

I have printed the model in PETG and in PLA with equal results.

Mechanically, the most solicited parts are the lever ones (MecLever.stl, LeverFixed.stl, LeverFloat,stl). I reccomend printing them with extra perimeters and a nice infill.

TOLERANCE ADJUSTMENT

The design play between rotating shafts and hubs range from 3 to 5 tenths of a millimeter. If, after performing the assembly you think that the device has too much play, and things could be tighter (or too little play and things could be softer), you only need to tweak the design of three parts (MecHinge x3.stp, MecRightCam.stp and MecLeftRoll.stp). Just enlarge (or make smaller) the diameters of the hinges a couple of tenths of a milimetrer and try again. The three parts prints in a few minutes, so repeating the prints is no big hassle.

TWO COLOUR PRINTING

The cover can be printed with a normal 3D printer and also with a dual extruder printer if you want to get the fancy two colour effect. The ones in the pictures has been printed in a PRUSA MK3 with a multimaterial unit. If you are using a single colour 3D printer just ignore the file CoverColourSecond.stl. In a dual colour printer just import both CoverColour files (CoverColourMain.stl and CoverColourSecond.stl) to the slicer at the same time. The part only has four filament changes, so there's not much room for errors.

GCODE FILES

The settings I used to make these gcodes (and print the parts) are: -Layer height 0.3 mm (Except part finger.stl, that was 0.15 mm)

• 3 perimeters
• Infill 15% (Except parts LeverFixed.stl and LeverFloat.stl that were 60% infill and 4 perimeters)

All the gcode files provided are to print the MisteryBox in PETG in a PRUSA MK3. If you are using a multimaterial unit, all the parts are set for extruder#1, except the finger (part Finger.gcode) and the second colour for the cover of the box, that are both set for extruder#2

DESIGN IMPROVEMENTS All small changes. I included 4 new holes for screws to close the box. They are not necessary. You are not meant to use them unless when you print the part Bottom.stl you get a warped base. In that case, you can use these holes to close the box and avoid repeating this 7 hour print

Batt space has been slightly enlarged and a hole has been added to the top (in case you forget the batteries inside and they bloat, now you can easily get them out). Also, a drill hole has been added so now the battery connector can be locked in place (not that it had room to move before, but it looks tidier this way). The wiring routing out of the batt conpartment has been changed too

I have included a couple of alternative embossments for the cover, though of course, you can use the step file to create your own.

PARTS LIST

Soon to follow, I will include a link where you can buy all the following parts as a kit

1- Motor - aprox 0.90€ - https://es.aliexpress.com/item/4000783754249.html?spm=a2g0s.9042311.0.0.406963c0EkDjVq

2 - Switch - 0.35€ - https://es.aliexpress.com/item/33013168141.html?spm=a2g0s.9042311.0.0.406963c0EkDjVq

3 - Limit switch - 0.24€ - https://www.amazon.es/gp/product/B00J2N3D78/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1

4 - 4AA Battery holder - 0.48€ - https://es.aliexpress.com/item/32984502842.html?spm=a2g0s.9042311.0.0.406963c0EkDjVq

5 - wire AWG #24,#28 - 80 cm aprox

6 - bolt M3x8 - 5 units

7 - bolt M2x7 - 2 units

8 - lag screw 3x16 mm - 4 units (+4 more)