Alesis repair
Summary
This is a repair for the screw holes of a vintage drum machine - the Alesis HR-16. In this page there are photos and description of the repair, as well as STL files for implementing it.
The damage
The screw holes/pegs that are used to screw down the board with the drum pads have sustained serious damage.
Since the instrument is about 40 years old and is made of plastic, it is expected that these regions on the chassis could be damaged because they absorb the shock of the player hitting the drum pads. The damage could also be an effect of a sloppy repair attempt.
Seeking solution
There is some material on the internet about repairing exactly this damage on the Alesis HR-16 but it mainly consists of using two component clay to stuff up the screw hole regions and then drilling new holes after it sets. In this repair and since clay was not available, an alternative approach was used. A small part was 3D designed to be glued in place of the old screw hole/pegs.
The initial part was designed to be easily 3D printed on its side. This is important because the weak 3D print layer direction must not be positioned perpendicular to the tensile loads that are expected.
The part is also made extra long in order to offer a bigger bottom area for strongly gluing it to the casing.
This solution has the benefit of not requiring drilling since the hole can be designed to be 3D printed. The STL file for this part is available for download here.
Implementing the solution
In the beginning one screw hole replacement was 3D printed with ABS filament for every damaged peg on the casing.
A detailed drawing was made marking down the exact positions of the pegs that would be hard to locate after removing them.
Afterwards, the damaged pegs were removed with the help of a rotary tool and then the area was sanded down flat. Using the existing drawing and visual markings were made on the casing to help position the parts properly. Super glue was used to glue them in place.
All the screw holes were positioned properly and the board was able to be screwed back on the casing.
