K’s MINI Enclosure

An Enclosure for Prusa MINI

K’s-MINI-Enclosure by Stefan Katerkamp / CC BY

V0.81 / 30.01.2020

This is a modular enclosure for the Prusa MINI. It is based on 20mm x 20mm Type-I (5mm slot) aluminum extrusions and quite a few DIY 3D printed parts such as quickrelase locks, feet, handles and brackets. Some additional parts like screws, Polycarbonate and PVC foam sheets make it complete.

Maximum temperature of the chamber should not exceed 40°C. Precautions have to be taken to prevent the air from getting hotter, building a temperature controller is the next step. Electronics and power supply are located outside of the chamber. There are DIN rail mounts on the bottom of the frame.

3D printable part files (STL) and their FreeCAD sources are available on Github.

Sources URL: http://github.com/katerkamp/K-MINI-Enclosure.git.

This is work in progress. I’ll keep updating this page and the git repository as I am getting along with this project. See project status section below.

Impressions

Access to buddy board stays outside of chamber:

There is sufficient real estate available for a Raspberry Pi (heat chamber control etc.) and a 5V power supply. Shoes on this pictures are still the old version, the new shoes are 1/3rd shorter:

Display:

Quickrelease locks for panels:

Advantages

Smallest size possible: 40cm x 45cm (54cm incl. handles) x 49cm (Width x Height x Depth).
Perfect access to print bed due to large front door opening on corner.
Easy access to printer by using quicklocks for panels.
Electronics stays outside of chamber, air temperature limited by stepper motors and 3DP parts of printer only.
DIN Rail mount for power supply and chamber air controller
Cost efficient, needs slightly less than 6m of cheap No-Name extrusion (Extrusions are manufactured in lengths of 6m).
Cost efficient blind joints used.
DIY tapping possible using M5 Tapping bit and cordless screwdriver, 3DP tapping guide tool included in repo.
Hex wrench access holes DIY friendly, need 3.5mm drill and drill rig.
M5x16 BHCS screws and panels available in DIY stores
3DP center plates for blind joints are sufficient

Current Status (30.01.2020)

Prototype assembled, all fits fine. MINI mounting brackets will be redesigned as foam rubber is needed to prevent noise. Vertical beams now have 380mm length.

For symmetry reasons a beam has been added on the rear side of the handles.

Drawings are not up to date yet. Check FreeCAD sources for accurate dimensions.

Aluminum Extrusions (20x20 Slot5) Frame: OK: The beam layout, sizes and positions are fine so far. See BOM below. Slightly less than 6 meters are needed.
Feet (3DP): OK: There is sufficient height available now to mount powersupply and other components on DIN Rails in the bottom area.
Powerbrick Shoes (3DP): OK: New version now has 10mm less depth compared to the ones on the prototype. Mounting holes for either APRA low profile or DRG-01 Aliexpress DIN Rail brackes have been added.
DIN Rail Holders (3DP): OK: They need M5x8mm BHCS screws. There are 2 holes for M2x15 or M2x20 screws on the back side. These are optional and used for reinforcment only.
Prusa MINI mounting brackets (3DP):: Brackets fit fine. However, there is no sufficient acoustic isolation. New brackets are coming soon. They’ll also be simpler to install. No changes to aluminum frame required.
Bottom enclosure panels: OK: PVC foam sheets with a thickness of 3mm are used.
Walls (3DP): OK: These walls keep the bottom panel in place.
Top Handles (3DP):: Need to be a bit wider to fit additional beam.
Quickrelease Parts (3DP): OK: FreeCAD source has a parameter for panel thickness. STLs for 2, 3 and 4mm are provided. Print with ABS or ASA. Slice mesh part with 50% infill, 7 layers and 5 perimeters.
Covers (Polycarbonate 2mm) and Front Doors (4mm):: Detailed shapes and sizes still have to be documented.

Enclosure Assembly

Frame

The frame is built using 20mm x 20mm Type-I (5mm slot) aluminum extrusions.

Extrusions (1 is missing on the pic):

Extrusions assembled (1 missing):

Blind Joints

Blind joints are cheap, simple and stable joints:

They just need a round head hex M5x20 screw and a centerplate. Here is a 3D printed one:

For improved stiffness, metal ones may be used:

The prototype has been built with 3D printed center plates. This saves about 7 €.

One side need a 3.7mm (3.5mm) hole for the hex wrench, the other extrusion needs to be tapped.

Tapping and Drilling Best Practices

Always first tap the beams, clean them and then finally drill hex access holes.

DIY tapping needs an electric drill with a hex tapping adapter for the tapping tool, bicyle oil and an air compressor. It is important to keep the tapping tool in line with the hole. A guide for the tapping tool is available in the tools directory for 3D print.

Apply oil and tap. Then clean the tool and the aluminum extrusion hole with pressured air. Once all taps are made, drill access holes. (If the holes get drilled first, the extrusion cannot be properly cleaned with pressured air anymore).

3D Printed Parts

Use ASA or ABS. Slice with at least 50% infill, 5 perimeters and 7 layers. Use 0.15mm layer height.

BOM

Extrusions

Extrusions need to be cut in length, for blind joint they need holes and threads according to the abbreviations below.

M5x20 inner thread on front side:

LTP	Left front side tap
RTP	Right front side tap
TPW	Tap on both front sides

3.5mm diameter wrench access hole for blind joints on edges:

LCH	Left side horizontal
LCV	Left side vertical
RCH	Right side horizontal
RCV	Right side vertical

3.5mm diameter wrench access hole with distance from side:

LSHxx	xx mm from left side horizontal
LSVxx	xx mm from left side vertical

Qty	L [mm]	Position	Machining
1	435	T-Y-Left	TPW-LSH165-RSH125
1	435	B-Y-Left	TPW-LSH85-RSH135
1	435	B-Y-Middle	TPW-LSH85-RSH135-LSH165
4	370	V-FL, V-BL, V-BR. V-FR	LCH-LCV-RCH-RCV
2	340	T-X-Middle, B-X-Back	TPW-RSH110
2	340	T-X-Handle, T-X-Back	TPW
1	260	B-Y-Right	TPW
1	260	T-Y-Right	TPW-RSH125
2	240	T-X-Front, B-X-Front	LTP-RCH
2	220	B-Carrier-F, B-Carrier-B	TPW
1	155	T-Y-Middle	TPW
1	100	B-X-Right	TPW

Polycarbonate Sheets

t.b.d.

What’s next

Other things to add/todo:

Fan and controller for enclosure
LED Stripes for lighting
Camera for Printbed
Camera for Spool
Bracket for Raspberry Pi and 5V power supply