GOAL: FIND A METHOD THAT IS ABLE TO REPLACE OUR CURRENT MDF METHOD

Session recordings at the bottom of the page

Next check-in: Saturday, March 20th

General Molds Knowledge

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A mold is used to create our parts with carbon fiber. Because we use prepreg carbon fiber, we need the molds to be able to resist vacuum pressure and temperatures of 90+ degrees Celsius for 8-12 hours. 

To do its job, the mold needs to meet two physical requirements. Geometry and surface finish. 

1. Geometry is just ensuring that the shape of the mold is the shape of the desired final part. This may seem trivial but, if done incorrectly, renders countless hours of work useless. 

   1. This can happen when the mold distorts under pressure/heat, or just with CAD mistakes

2. Given that the carbon fiber will be molded by the mold, under vacuum pressure, the final part will have every feature that the mold has. This means that if there are any surface imperfections on the mold, it will transfer to the part. 

   1. Let’s use a bump in the mold as an example. This bump will cause surface imperfections in that part. 

Open

The geometry factor is mostly taken care of in the virtual CAD world. However, surface finish is usually controlled during manufacturing - which is what we want to deal with right now.

Context

Current manufacturing is tedious and error prone. We use MDF and follow the process outlined below

This has several pitfalls

1. Hours of work: this process is incredibly time-consuming. Since MDF does not machine to high surface quality, we must put in manual labor and time to achieve that same surface quality that we want. 

2. Weight: MDF is stupidly heavy. For our largest molds, we need a forklift to move them around. This is a big logistical pain. 

3. Cost: MDF can be a pretty big hit on our wallets

Potential solutions

I spoke with a retired composites lead from ETS that gave us two new ideas. I want to look into them more in-depth. 

Foam plug

This option basically entails creating the desired part out of foam, then doing a fiberglass layup on top to create the mold. The issue with this method is that foam is either expensive or hard to work with. Your task is to try to find a way to negate one of these cons. 

The quality of the foam plug, which in turn dictates the quality of the mold + part, depends almost entirely on either

1. Machinability. Tooling foam can be machined to very small tolerances and high surface finish qualities. This means very minimal surface prep work afterward.

   1. The only pitfall here is that tooling foams - that is, foams that are machinable - are usually really expensive. 

   2. The pros of tooling foam can also be replicated using tooling paste. It is basically this plaster that has a high degree of machinability. What this basically requires is for you to machine a shitty block of foam, slap on a bunch of tooling paste, and then machine the tooling paste to the shape that you want. However, this method is also expensive. 

2. Man hours put into the mold. With enough time and people thrown at the mold, eventually, we can get the surface quality to match higher quality foams.

   1. The pitfall here is that we are limited by both bay capacity and SDC hours.

However, this is not gospel. These walls can be broken down.

1. The cost downside of machinable mediums - either tooling paste or foam - can be negated with sponsorships. They can also be avoided using clever manufacturing techniques that use cheaper versions of the high-end products

2. Man hours can be reduced by combining and streamlining processes; or by finding a new process altogether.

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