Parametric Design

What is the strategy?

This strategy manual will be detailing the process of how to make parametric adapters. 

Parametric adapters are adapters that are automatically generated based on (easily) measurable dimensions. This strategy can be used to connect either:

• self-made 3D printed parts (the wheel adapter)
• or parts from other brands/versions to your (broken) electronic device (hose adapter).

In what cases is this method applicable?

This strategy is most applicable for parts that have a similar shape and connection method between different brands and versions. The examples in this strategy are for the front wheel and hose connection of a vacuum cleaner.

The example of the wheel holder will be used to explain all the steps.

The hose adapter example will be located and explained at the last step.

If these parts have similar shapes and connection methods across brands and versions, then the part can be based on the same measurements for all these different brands and versions. The user of such a file would only have to measure these dimensions, generate the file and print it to be able to use it. Allowing anyone to be able to generate their own adapters, regardless of experience.

DISCLAIMER:

This project requires you to take apart your product and to tinker with it. This will cause any warranty on the product to be void. Please approach this safely and if you're not sure, ask an expert.

ALWAYS unplug the product when taking it apart and reassembling it. If the product is hot, let it cool down first.

We and any other linked resources do not hold any responsibility for anything that you do while following this guide.

Please read the master page for supply details!

It is advised to use a CAD program that is able to link variables together in a way that is easy to keep track of.

All parts in this manual are generated using openSCAD.

Also having access to multiple brands/versions of the device you are trying to repair could help during the rest of the process.

For designing a parametric design it is most important to fully understand the connection between the parts. So the first thing you should do is analyse the connection and make sure you understand the principle behind it.

Most connections make use of some kind of elastic deformation, like snap-fits. For more commonly used connection methods click here.

Once you understand how the connection works, make a 2D drawing of it. This will help you discover whether or not you completely understand how the connection works and show the variables that are important within this connection.

Using the 2D drawing created previously, you will be able to determine where the base dimensions are. We refer to base dimensions to being the measurements that are variable, so users of the file can change them to fit their product.

Most parts will only require 3-5 of these base dimensions. The base dimensions for the wheel adapter are shown in the figure above:

• The green dimensions are ones needed to make the part fit into/onto the vacuum cleaner.
• The red dimensions are the ones used to make the connection work.

Having access to different brands/versions of the product you are trying to fix may be helpful in this stage, since they should use the same or similar dimensions.

Once you have determined the base dimensions, give them recognisable names to help prevent confusion later on. (In the pictures above this the dimensions have not been named to keep the pictures clearer.)

And lastly measure these dimensions.

For the example shown here, it was more useful to divide it into two different parts: the main part and the adapter.

This was done to allow for easier adaptation to different brands/versions because reprinting only the adapter takes far less time than reprinting the entire part.

The main part is the component that replaces the original function. In this case the main part is used to make sure the vacuum cleaner can roll smoothly.

Then the adapter is used to make the main part fit into/onto every different brand/version.

So when designing the main part it is important to make sure the adapters can be fit tightly into the main part.

The following links show some useful connections you could use:

How to connect two parts.

How to design snap-fit joints for 3D printing.

3D printed joinery.

How to 3D Print Joints.

For more information on the snap-fits used, check out the snap-fit guide.

When designing the adapter you have to make sure that it fits into the main part, this of course also depends on the design.

It is very useful to divide the adapters into different parts. In this case the adapters were divided into:

• connection adapter to vacuum
• connection adapter to main part

The adapter was separated into two different parts to allow for easier testing. This way the connection to the vacuum could be tested separately from the connection to the main part, allowing for quicker testing and quicker iterations.

When all the parts work separately, it is time to combine them into the final part and print it.

There might still be a few problems when you test it.

If you have problems with it just not fitting by the slightest, you could take a look at the tolerancing chapter on the master page, or you might need to adjust the dimensions to explore the tolerance of the part.

If there are problems with the connection just not working the way you want it to, it might be useful to re-examine the connection on the original part and/or try making a few more partial prototypes.

If the main part doesn't function the way it should, return to the previous step and make more partial prints to test it.

And lastly if the final part works, then you’ll be able to finish parameterizing the entire file.

A few things to look out for:

• Are there any values that don’t change based on the input parameters? Should they?
• Are there other products you can test this part on? Does it work on them?
• What happens if the measurement is not perfectly accurate? Can you change it in such a way that it will still work?
• When using snap-fits, are they strong/weak enough on every occasion? Should they change based on the input parameters?

The final OpenSCAD file and the instructions can be found in the supporting files.

This process was also followed in order to design a hose adapter file. This file allows you to connect any brand/version of hose on any brand/version of vacuum cleaner.

This part was basically two adapters on top of each other, and therefore did not need to be divided into two individual parametric parts as all of the model would change no matter on what brand/version it is used for.

In this case the part also needed quite a bit of strength to make sure it wouldn't break. So it was not divided into two parts like the previous example, as this would most likely reduce the strength significantly.

The snap-fits were not included in the base dimensions. This was due to the fact that the measured snap-fits all had very similar sizes. Therefore, it was possible to use the same values for all of the snap-fits. This was a useful discovery as the users don't have to go and measure their snap-fits which may be difficult without specialised tools.

So as mentioned this part consists of two adapters:

• The adapter the hose has to fit into
• The adapter that has to fit into the vacuum cleaner

These adapters have the same shape, but not the same diameter. So to combine these two adapters into one part, extra material was added in between. This extra material was added with a 45 degree angle to make sure it would not require support.

Lastly, snap-fits were used in this part. 3D printing snap-fits requires quite a bit of tweaking, especially when you try to make them scale based on the input parameters.

For more information on these fit check out the snap-fit guide.

The final OpenSCAD file and the instructions can be found in the supporting files.