We often use the vegetable slicer accessory of our Bosch MUM 6120 kitchen appliance. Unfortunately one of the twist locks that holds the cover of the slicer securely in place broke. This basically makes the whole vegetable slicer unusable, as you don't want to hold the cover with one hand while pushing vegetables with your other hand on to a rotating blade. As this Model is from the 1980s there are no replacement parts around any more. But I did not simply want to throw it away and buy a new one, only becase such a small part broke. So I redesigned the part myself in Fusion360.

The part I designed is identical to the original in its function but a bit chunkier for better printability and durability (I needed to fit a screw inside while the original part is just an injection molded plastic part).

Original twist lock

Closed	Open	Broken part (lower part)

Animation how the twist lock works. When opened you can clean the inside of the vegetable slicer and change the blades.

Repaired twist lock

Closed	Open

Exploded view

Bill of materials

Per twist lock you need

• BoschMumVegetableSlicerTwistLockTop (printed part)
• BoschMumVegetableSlicerTwistLockBottom (printed part)
• M3x40 screw
• M3 hex nut

Print parts with 4 walls and 75% infill for best strength.

As you maybe want to put the part in the dishwasher print with PETG and use stainless steel screws and nuts.

Installation

• Insert the M3x40 screw in the BoschMumVegetableSlicerTwistLockTop
• Put in the upper part from the top
• Insert the M3 hex nut in the BoschMumVegetableSlicerTwistLockBottom
• Put in the lower part from the bottom
• Tighten the screw

Changes to the original part and thoughts during the design phase

Just trying to reprint the original part with an FDM printer would not work. There are a few reasons why:

• The original part is held in place by a metal sheet that is pressed on and bites into the plastic. An FDM print would just split at the layer line, where the metal sheet would attach.
• The metal part with the exact dimensions needed for this application is more difficult to source.
• The original twist lock is desigend for injection molding and the geometry is far from ideal to print with an FMD printer.

I decided to use a standard M3 screw and M3 hex nut to attach the replacement as they are easily accessible. This meant that twist lock needed to be separated into two parts. In the upper part the screw is inserted and in the bottom part the hex nut is inserted. When tightened both press against each other and hold the twist lock in place. Due to the design of the repacement part and the print orientation the campling force impacts the parts perpendicular to the layer lines giving the part good strength.

To make space for the screw the middle of the part the twist lock needed to get a rounder, more chunkier shape.

For the layerlines to be perpendicular to the clamping force the part needs to be printed upright. I did not want to use support for the latch and wanted to make the contact area of the first layer as big as possible for a reliable print, so the part is printed upside down. This makes the top of the part not as round as the original, but does not influence functionality or user experience.

The hole for the screw has a special geometry that will force the printer to use bridges instead of trying to print a round shape in mid air.

Original Exploded View	Replacement Exploded View