Door Stop Buffer Renault Twizy (Part-Number: 908782937R)

Backstory

A friend of mine owns a Renault Twizy. The Renault Twizy is a small electric car with scissor doors. These scissor doors make contact with a door stop buffer (Renault Part-Number: 908782937R), which softens the movement when opening the door and defines the door's end position. Unfortunately, this door stop buffer frequently breaks after a few years of use. The problem with this is that it can lead to significant damage to the door. When the door stop buffer is damaged, there's also the possibility that it can be pulled out of its mounting and no longer define the door's end position. In such cases, the door continues to open until it reaches its highest point and then falls to the ground on the other side. It's clear that this door stop buffer needs to be replaced to use the Renault Twizy properly. All owners need to replace this door stop buffer eventually. Easy, right? Unfortunately, no. This door stop buffer has been unavailable for over a year. And because the Renault Twizy has not been in production since September 2023, it's unlikely that these buffers will be available again. Therefore, 3D printing comes to the rescue.

That's why I copied the original door stop buffer. Since the plastic used for producing the door stop buffer has different mechanical properties than the original, I used various modifications of the filling material to replicate those mechanical properties. The video below shows the functionality of the stop buffer.

Preparation and Print Instructions

To replicate the mechanical properties of the original part, the infill modifiers are used in Prusa Slicer. You can either use the .3mf-file directly or you can prepare the model on your own. The model uses modifiers at three different locations, which are visible in the image.

Depending on the exact material you are going to use, you may have to modify some of the parameters. In general, this model and the settings are quite similar to the original part based on stiffness and endposition of the door. Therefore I highly recommend using the .3mf file if you want to print it. I used Amazon Basic TPU to do the job.

If you stil want to prepare the project files on your own, here is what you have to do:

1. Import the TwizyDoorStopBuffer.stl
2. Right click on the model, pick add modifier and select Load… . Use the Prusa Help Page if you don't know how.
3. Use one of the three modifier stl-files. For example: PivotInfillModifier.stl. Make sure the modifier is on the build plate in Prusa Slicer. This can be done in bottom rigth corner if the modifier part is selected. Use the Drop to Bed Button next to the input of the x-y-z positions inputs.
4. Right click on the imported modifier and select Infill.
5. Set the parameters acording to the settings below in the table.
6. Repeat steps 2 to 5 with the other two modifier stl-files. In this example this would be ContactSurfaceCarFrameInfillModifier.stl and ContactSurfaceCarFrameInfillModifier.stl.
7. Select the print settings. I used the standard 0.20 mm Speed Profile. I changed the number of perimeters to 6. Infill to 15% and type to concentric. I also activated support.
8. In the filament settings I selected AmazonBasics TPU. This worked out great.
9. This step is optional: Restrict support at the inner part of the contact surface to car frame. This makes the removal of the support easier.
10. Now you can slice your model and you are ready to go. Happy printing.

Comparison to the original part

The dimensions are almost exactly the same as from the original broken part. The original part has additional extruded bases at both sides close to the pivot point. The height of those extrueded bases is less than half a millimeter and not necesarry for technical reasons. Therefore the 3D printed model don't implement those extruded bases.

In the pictures below the 3D printed part is above or on the left side. In the first picture you can sport the crack in the original part (contact surface to the door). The part is glued in place at the moment.

Questions

How to change the part within the car?

There are some instructions online but I am not an expert on this. This video explains it for example.

How long will it last?

This is the most recent design dated from September 2023. However. An earlier version with worse mechanical behaviour already lasted more than half a year inside, without damage to the part itself.

Credits

Cover Image: Matti Blume, Renault Twizy, Paris Motor Show 2018, Paris (1Y7A1672), Modified by faw3b. Added approximate location of the door stop buffer to the picture, CC BY-SA 4.0