Design for Manufacturing (DFM) – The Case Chapter

HestiaPi has done great so far but we need to push even further if we want this project to be financially self-sustainable.

From our latest crowd funding campaign we realised that 3D printing will be a bottleneck if we want this for mass production.
As our volumes are below 10k units, injection molding is very expensive. So we looked around for alternative solutions taking these into consideration:

  • It should look good
  • People should be able to make it themselves too without exotic materials
  • Stronger than 3D prints
  • Smoother surfaces without the need for post-processing
  • Relative cheap

Fiddling with all the above parameters we came up with a possible solution!
Use sheets of fiber resin (FR4) cut to shape by laser. And if all that sounds too complicated we have one more secret.
FR4 is the material used by PCB manufacturers all over the world that can produce these really cheap.
Some manufacturers offer a range of colours too!

The flat faces of the case have solder points on the inside that will be the “glue” for assembling. The front and backplate are 2mm thick and the 6 x wall sides are 1.5 (nominal 1.6mm). Wall sides and front are “glued” together and form the cover while the backplate with the electronics PCB are fixed to the wall.

One exotic part we use (and we still try to find alternative) is a solderable standoff nut (SMTSO) for fixing the main electronics PCB to the backplate with protruding at the back.

Little design details:

Wall and front pieces have lines to help proper alignment.

The backplate incorporates surface mount pin header connectors to accommodate the sensor without the need of that ribbon cable we used so far going all over the place.

The front cover has a wiring guide to help installation.

One thing we haven’t implemented yet is the way the cover will secure in place once closed. We are thinking of male and female pin headers (all surface mount so that they don’t appear on the outside) which can easily be found.

To be continue (and shared)…