I made an enclosure (case) for the Seven-Segment over Serial Small device.
I designed the enclosure in Fusion 360, and printed it on my Cetus3D.
I made one key design decision: the PCB has a friction-fit in the enclosure. That is the plan: no screw, no glue, maybe a bit of click.
JLCPCB offered me to try their 3D-printing services, which is gladly accepted.
Goal is to design an enclosure matching LEGO Technic dimensions: a 7×3×3 (LEGO) studs.
I started by modeling the PCB with some key components (the 4 7-segment units, the IDC socket, and the ATmega328).
Here is the PCB, but now in its enclosure. The width and height are 3 by 7 LEGO "units" (studs). At the back some "wings" for mounting to Technic pieces.
This is the enclosure in isolation. At the back the hole for the IDC socket, on the inside the ridges where the PCB rests and a gutter (hardly visible) above the ridges to click the PCB in place.
The final figures show a sectional view on the short and long side. The short sectional view shows the gutter for the PCB more clearly.
Here is the STL file for the enclosure. It is a single stl file Print on my Cetus3D (0.15mm layer height, 13% infill, fine quality, with support and raft) was estimated at 1.9h and 15.0g of PLA.
The fit is tight. It was hard to get the PCB in, no risk of it dropping out, but also hard to get out.
Finally, with cable and hub.
JLCPCB offers various 3D printing technologies: SLA, MJF, SLM, and FDA.
-
SLA (resin)
SLA or Stereolithography is an additive manufacturing process that belongs to the vat photopolymerization family. The vat (tub, container) contains a photo sensitive (liquid) resin. A light source (e.g. laser) is used to cure (solidify) the resin (youtube). This method is popular because it produces high-accuracy parts with fine features and smooth surface.JLCPCB offers 3 resins: LEDO 6060, 9000R and 8000. They are all white. Also the lowest cost, my model is $1.
-
MJF (Nylon)
MJF or Multi Jet Fusion is an industrial 3D printing process that quickly produces nylon parts. It uses an inkjet array to apply (fusing and detailing) "ink" across a bed of nylon powder, which are then fused with heat. The process repeats layer after layer (youtube).JLCPCB offers 2 nylons: PA12-HP (black or gray) or PAC-HP (multicolor). The PA12-HP is still affordable ($3.64 for my model), but PAC-HP gets expensive ($23.64)
-
SLM (metal)
SLM or Selective Laser Melting (aka DMLM or direct metal laser melting), is a method for a metal additive manufacturing technology. It uses a bed of powder with a heat source to create metal parts (youtube)JLCPCB offers 1 material: 316L stainless steel. Higher price range: $23.56 for my model.
-
FDM (ABS)
FDM or Fused Deposition Modeling (or Fused Filament Fabrication) is the offical name for the well-known process used in hobby printers. It works by depositing melted filament material (plastic wire from a spool) over a build platform layer by layer until you have a completed part (youtube).JLCPCB offers 1 material: ABS in white and black. Moderate price point: $3.83.
| abbr | full name | material | price($) |
|---|---|---|---|
| SLA | Stereolithography | LEFO6060 | 1.00 |
| MJF | Multi Jet Fusion | PA12-HP Nylon | 3.64 |
| SLM | Selective Laser Melting | stainless steel | 23.56 |
| FDM | Fused Deposition Modeling | ABS | 3.83 |
JLCPCB offered me to try their 3D-printing services, so I tried the three low-cost versions: SLA, MJF nylon, and FDM. After submitting my model, JLCPCB does a (presumably) automated design rule check for manufacturability. And my designs came out negative :-(
The wall thickness like those red area are too thin which has a high risk of crack, loss and deformation.
SLA LEDO 6060 Resin:
Will this risk be acceptable for you? If not, could you please kindly increase it to be at least 0.8mm to proceed? 1.5mm will be better.
MJF PA12-HP Nylon:
Will this risk be acceptable for you? If not, could you please kindly increase it to be at least 1.0mm to proceed? 2.0mm will be better.
FDM ABS White:
Will this risk be acceptable for you? If not, could you please kindly increase it to be at least 1.2mm to proceed? 2.0mm will be better.
I answered that these are LEGO Technic dimensions, so I can not really change them. That I printed the object on my own Cetus3D, and that worked. My last argument was that this is a trial anyhow to see what JLCPCB can deliver.
So they agreed to proceed. But apparently, closer to the machine, there is a manual design rule check by a human auditor.
Our auditor advised we can't print the ABS part [...]. The part will be broken at those thin area less than 1.2mm.
So I canceled the FDM ABS print. Which is a bit funny, because my home printer is a hobby grade FDM printer, and the professional FDM printer apparently can't do what my hobby printer can.
But I am impressed by the quality assurance process. This is human work and thus costly. Would be good if there was a design rule checker just like for the PCBs.
I ordered May 15, production started May 18 due to the checks and my overrule and finished may 20, and arrived May 31. So a turn-around time of two weeks with slowest shipping option.
On the photos below see my home print (on the left, white), the SLA print (middle, less white) and the MJF print (right, gray). The home print is a prototype model; the connector hole is a bit too small, and I also removed the ring around that hole.
The prints are great. No failures due to the thin walls, and very important, they fit LEGO pins and beams well. Good (fine) printing of small features.
Also the electronics fit well (bit of a push, and hard to get out). See here my home printed enclosure and the MJF enclosure fitted with the electronics.
I really like the MJF texture. Downside is of course that you do need to like that color.
(end)