3D print a new HP28S case

3D model to print HP28S case
3D model HP28S all parts

3D print a new HP28S case

I am working on creating a 3D image file in order to 3D print a new HP28S case. So the question is: How to 3D to that?
My keyboard on the calculator had one row which would not work any longer, so in order to try to “fix” it, I had to open the HP case. Well there are no screws and it does not have a snap mechanism, so you have to break the case. So once the 3D file is created, you can 3D print your new HP28S calculator case. The keys will be used from the original calculator as well as the inner parts


  1. 3D Model
  2. 3D-Printer
  3. Cost
  4. Mailing list

3D Model

Aug 26th 2017:
Since you have to “destroy” the case to open the clamshell calculator I am going to have a 3D model designed which I can then 3D print a new HP 28S case.
I decided a few days ago to purchase some “broken” HP28S calculators on eBay. I got lucky and I was able to purchase 2 of them. They should arrive in a few days so I can open them and send send the empty shell to a person for hire which will create a blender 3D model which will incorporate screws to open and close the case for maintenance/repairs.

Aug 30 2017:
They arrived and I finished drilling the left side of the calculator. See pictures in prev. post.

The metal parts (for example the battery door) should be saved so the plastic part can be reprinted and the metal added so at the end you have a new battery door. All parts of the calculator should fit into the new case.

Sep 4 2017:
The 3D modeler and printer expert is hired and the drilled open case was sent of to England for digitization.

Sep 14 2017:
The case arrived in England and the freelancer started the job.

Oct 25 2017:
first picture of the 3D rendering

3D model HP28S
casing 3D model HP28S

Nov 26 2017:
the next picture of the HP-28S

3D model HP28S
3D model HP28S

Dec 05 2017:
All the parts now. Perfecting the putting together option, screws or snap in or …

3D model HP28S all parts
3D model HP28S all parts

Oct 2018:
still trying to work out the details. There is not much space between the keys on the keyboard to make sure that the calculator is working after assembly.
When done, we will have Step/STP file which are good for additional design work and STL files for printing.

May 2020:
Finally some progress. Instead of working on the whole case I decided to work just on the HP-28S battery compartment door. See my new post.

3D Printer

Once the prototypes print and are stable enough I will release the 3D file for download and you can print the case yourself or have it printed.
There are several different kind of printers, the goal is to reproduce the case cost effective.

Oct 2018:
there are 3 known online printing companies, which use SLA technology. There is also the FDM technology but it is quite expensive.


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