The carbon fiber process

We received a lot of mails asking us about carbon fiber. So, let’s talk carbon fiber. What’s the process, how do we do it and why is it so difficult and time consuming to produce?

The first step: the master pattern

First, a master pattern needs to be CNC milled out of a solid block of epoxy. The master pattern needs to be as dimensionally accurate as possible. This process is ideally done with finer and finer end mills in multiple steps in order to get a smooth surface. This is how the M1K master pattern looks once it has been CNC milled:

This master pattern is not entirely finished yet as you can still see some marks from the end mill on the surface. Several tool changes and a little post processing help to further smooth out the surface. We then apply more than a dozen layers of mold sealer in order to get a smooth and glossy surface. Nothing is as painful as a carbon fiber mold that won’t come off your master pattern, so we apply several layers of release agent to help prevent the carbon fiber prepregs from bonding to the master pattern. Now onto making our female carbon fiber mold. This is how it looks like:

It looks a bit like patchwork, but after it has been in an oven for over thirty hours the carbon fiber patches solidify and we end up with an extremely robust female carbon fiber mold that looks like this:

This female carbon fiber mold is what we use to make the top shell of the M1K. For this we use a special kind of carbon fiber called carbon fiber prepreg.

Carbon fiber prepregs: fire and ice

Carbon fiber is a composite material consisting of two parts. The actual carbon fibers, and the matrix (usually an epoxy resin). For the M1K we use a special form of carbon fiber that comes pre impregnated with epoxy resin; in short: carbon fiber prepreg. Carbon fiber prepregs have the exact amount of epoxy resin needed for the job already impregnated. That is a huge benefit.

The actual carbon fibers for a carbon fiber prepreg are literally created with fire. Polyacrylonitrile fibers are burnt in a furnace with a temperature of 1,800 degrees Celsius (3,272 degrees Fahrenheit). Once the epoxy resin is added to the carbon fibers it is wound up on large rolls: the carbon fiber prepregs.

In order to prevent the carbon fiber prepreg from slowly reacting and thus hardening, the prepreg ideally should be stored at minus 18 degrees Celsius (0 degrees Fahrenheit).

I still remember how we ordered our first roll of carbon fiber prepreg. The roll was a bit bigger than we had anticipated and space in our normal household freezer was quickly running out. In the end we barely managed to cram the carbon fiber prepreg roll right next to a big chunk of deer. We have a bigger freezer nowadays.

Preparation stage

The real work begins now. If you defrost carbon fiber prepregs too quickly, in too warm temperatures or in an environment that is too humid, your carbon fiber part is ruined before production even started. After defreezing the carbon fiber prepregs for at least an hour we now have to cut out the pieces that together will form the carbon fiber top shell of the M1K. To make sure that the pieces we cut out fit perfectly into the mold we use templates:

Laminating

We now have to drape the carbon fiber prepregs into the mold. This process is called laminating. Laminating takes a lot of experience to get right. Once the brown paper is removed from the prepreg you have to work fast and accurate. Fiber orientation is important and the prepregs have to be tightly consolidated in the right place. You also have to avoid bridging of the material as this will ruin your carbon fiber part. Perfect consolidation especially in the corners is a must. The prepreg is very tacky, so once the prepreg is put into place, there is no more room to wiggle or readjust it. This is how laminating process looks like:

Bagging

Once we draped all the carbon fiber prepreg pieces into the mold, a thin release film is applied on the back of the prepregs. Then we put the mold into a nylon bag with breather cloth to allow air to travel through the bag. Then, we set up a connection for the vacuum hose and tightly seal the bag with a special sealant tape developed for this purpose (commonly referred to as tacky tape). This is how these steps look like:

And this is how vigorously you have to work the tacky tape to ensure a tight seal:

After the bag is sealed we hook it up to a vacuum pump. And then we have to check whether we indeed succeeded in sealing the bag: this stage is tricky as one small leakage in your seal means loss of pressure, ruining your carbon fiber part. You really have to work the tacky tape with your fingers to get it properly sealed. Cannot find a leak? Redo the bag until perfectly sealed, there is no room for error.

Finally, the sealed bag is put into an oven while still being connected to a vacuum pump. In a precisely controlled process, the carbon fiber prepregs get cured with a specific curing cycle.This curing cycle consists of a slow temperature ramp up to 130 degrees Celsius (266 degrees Fahrenheit). Ramping up the temperature too quickly can ruin the carbon fiber part. Applying not enough pressure, and your carbon fiber part is ruined. Insufficient usage of release agent and not only your part is ruined, but your mold as well. Experience helps.

Post processing

Once cured and demolded, the M1K needs to be CNC milled in a multistep process. To keep the carbon fiber in place we use fixtures which also need to be precisely manufactured. The cured carbon fiber material has outstanding mechanical properties. As a result, cutting through it requires special tools. We use tungsten carbide and diamond-coated end mills for the job. But even then your end mills tend to break and go blunt sooner than you would like. The following is a close-up of an M1K carbon fiber top shell being CNC milled:

Making carbon fiber parts is craftsmanship

This article has given you a glimpse of what it takes to make carbon fiber parts. Traditional gaming mouse companies make their plastic mouse shells with a production method called injection molding. These injection molding machines spit out plastic mouse shells every few seconds. It is easy to produce tens of thousands of mice when using injection moulding.

Each M1K carbon fiber top shell in contrast takes us hours to produce. Working with carbon fiber is craftsmanship. This is the reason why we cannot offer the M1K in the same numbers that traditional gaming mouse companies offer their plastic mice. For our Kickstarter launch in September this year we thus have decided to only offer a very limited number of the M1K: 333. The price after Kickstarter will be 249 Euros. For Kickstarter only you can get the M1K starting at 149 Euros.