I initially planned to create/design proper cable bushing for all the cable openings but never designed the actual cable bushings. I've implemented the threads in the sheet metal parts but didn't design the actual bushings. 

Status quo

The opening for the 230V-Input, 12V-Output and 230V-Heatbed is the first one which I want to improve.

Design process

For this opening there should be five cable bushings in total:

- 3-cables for L , N and PE of the 230V (I'll change the color as soon as I get the right cables) @3.5mm

- 2-cables for + and - of the 12V for the Duet-Board @3.5mm

- 2- cables (insulated) for the 230V-Heatbed @3mm

I'll continue with a two piece design of which the first part is shown above. It consinst of a robust Mainpart (picture above) and a elastomeric inner-part (in process of designing)

The three TPU bushing inserted and ready to be tested. The bushings are nearly split in half so you can easily insert the cables and then push them inside the housing/cable bushing frame to secure. 

At the end there is a small lip which should interlock with the cable bushing frame to ''lock'' when fully inserted. We'll see...