Bjorns Fabacademy jurnal

documentation

For my moulding and casting project I decided to attempt to make a component for my old broken record player. The first image below is the old seal that through ages of being played had worn down over the past years. This is the only component that spins the record and for years I have been trying to find something like this with no successes, so now I’m making one.

images

The seal from my record player
My CAD model made in Rhino
The main reason I used Rhino as a software for this is because its easy to split surfaces
I used the Roland MDX 40A to mill out the wax. The wax block I fastened with double sided tape. Research suggested that one should use double sided tape and a glue gun to glue the sides of the wax to the bed but this was not necessary.

I used the Roland software that the machine comes with which was the VPannel for operating the machine and MODELA 4 for making the paths for the milling process.

The MODELA PLAYER 4 makes 3 different paths to machine. First Surfacing the wax which makes the wax level ,Second a rough path is milled which slowly removes the main material from the positive. Then the last or third process Finishing mills out the final more detailed profiles of the profile.

I used a 3mm square bit to mill out the profiles. For more rounded edges a round bit would be recommended. Below you can see the end result of the milling process.

It is advised to keep the wax that is left over from the milling process for melting down for a new wax block.

Because of were the Milling was done and were I zeroed the machine, the walls of my mould were milled away so I built a Perspex box to seal and cast the mould. It is advised to design walls to create pockets for the OOMOO Resin.

I used OOMOO 25 to make my mould, it is advised to read the spec sheet before opening the container and begin the mixing process. The OOMOO was mixed 1:1 so one part of A to one Part of B. I did read all the other info on the SMOOTH-ON website and it was recommended that first pour part B into the cup before A to ensure easily but thorough mixing.

OOMOO is poured. It is advised that the OOMOO is poured evenly and slowly on one area to ensure an even bubble less casting process.

Once it is cured after 75 minutes, I left it in there for 2 hours just to make sure.
Just to double check if my design was done correctly
After the trimming was done.

I used Q20 as a release agent, it works pretty well.

The first cast I used PMC-121/30 Wet to cast my positive. It is mixed to 1:1 Ratio and takes 16 Hours to cure, I left it overnight +- 20 Hours.

The wait.

Finally it set and I de moulded it, works pretty well and my Record player is finally fixed.

Time for trying Smooth-Cast 305, a hard white plastic. Curing time is 30 minutes and mix ratio is also 1:! but READ THE SPEC SHEET

Positive done, I was quite surprised of how well it casted with the detail.

what not to do.....

So I wanted to try and cast OOMOO into a OOMOO mould so that I could get a positive of OOMOO as it has a much better strength and durability for what I am trying to achieve

This does not work.... at all... the OOMOO mould became part of the part I was trying to cast. I did use Vaseline (and allot of it) as a release agent.

Downloads

.