HP-28S Battery Compartment Door
The redesign of the whole HP-28S scientific calculator case is quite difficult and very time consuming. In most cases the only thing broken is the HP-28S battery compartment door, so I decided my first step was to get that re-designed.
Print testing phase of battery door
The 3D-print of the HP-28S battery compartment door is being tested right now (05/2020) from a few volunteers. I have reached out to a few 3D designers asking what printing method would be best in making this part. See below for PLA printing picture (not). The answer is Selective Laser Sintering or SLS printing using polyamid (PA). The characteristics are robust and the pegs can be melted down to keep the metal plate or battery contact, in place.
Having no experience with 3D printing, I’ve now learned that the following printing methods have certain advantages and disadvantages.
- Fused Deposition Modeling or FDM printing
- Stereolithography or SLA printing
- Filament PLA printing (see below)
With FDM printing it is not possible to have the part mechanically resilient. The problem with printing via Stereolithography is with melting the material afterwards. Please find some printing companies here.
Small Assembly of Battery Compartment Door needed
You should keep your original metal plate from the battery door. After printing the part, you just re-insert the metal plate and melt down the 3 pegs, and voila you have a new battery door.
- 3D Viewable PDF (Adobe Reader needed)
- After testing the STL file print, I will make it available for download
PLA printing results
Feedback from one Tester: PLA filament does not print very well. Adjusted were temperature and speed of print after 3 tries, below pictures show the best it can do. That is the limitation of an entry level 3D printer.
Best to use laser type 3D printer, hence SLS printing.
SLS printing results
Today June 12th 2020, the first parts arrived and I must say the quality is quite good. I compared the original with the new printed version and I have to make a few adjustments. But now I sourced a printing company close by and progress should be much quicker now.
Yesterday July 9th 2020, I finally had some time of from work to pick up the 2nd set of printed parts. Very nice quality and the color is just right. The metal plate fits right into the grooves and the 3 pegs are ready to be melted down. Take a look for yourself. I added 2 drops of glue just to be save below the metal plate.
Here the file to download in order to 3D print it. I hope you enjoy the hard work that went into it.
Ordering and pricing
I was asked if I had printed a few battery compartment doors and if some could be ordered. So I did some checking on pricing and I ordered 40 of them, which makes sense for that size machine as a minimum order.
So if you do NOT want to print them yourself or do not have a SLS printer, you can contact me for payment information.
Cost €5 a piece + shipping & packaging. (I would recommend to order 2, so you have a spare)
Packaging: €1 (padded envelope)
Shipping: €2 (for 2 parts) within Europe and all other countries
Payment fee: €0 using IBAN, €1 using PayPal
As of Oct 2020, I have them available.
Once received, do not forget that you need to melt down the 3 pegs to secure the metal plate (you can also use a drop of glue). I used a small soldering iron.