Machining Composites
Much like other materials can be machined, so can composites. Everything from basic fiberglass fabrications to advanced composites materials can be machined to add details and features.
This can be accomplished using hand-held tools guided by fixtures and measurements. Hand tools such as air routers, drills, and saws. A disadvantage is that the operator can commit errors and must be protected from safety hazards. These hazards include airborne dust, bending strain, lifting strain, and physical cuts.
For high volume or high precision applications, there are CNC routers that can be employed. These are fast, efficient, and safe. They may be expensive though.
Several manufacturers make CNC routers, and Thermwood is one as shown below.
This video shows several different applications and parts that can be routed with this large machine.
1992 GM Ultralite Concept Car
I found a very interesting video demonstrating the 1992 GM Ultralite Concept Car. What a blast from the past!
This project, like all concept cars, was well before its time. They had some cutting-edge engineering that went into this vehicle to work towards several goals.
Reducing vehicle weight was important, so carbon fiber materials were utilized to decrease the weight of the body/chassis. Efficient drive-train options were also developed, including the use of two-cycle engines and battery power. Designing for great aerodynamics was also considered.
Many years have passed by, and some things were right on, some were not. Aerodynamics have been improved. Lighter weight materials have been used as composites have been working their way into vehicles, though it has been SMC/BMC reinforced with Fiberglass rather than Carbon Fiber.
Gull-wing doors have not been adopted for family cars, and I am not sure if I am disappointed or not.
Composite Guitar Cases
Not being a musician, I had not been familiar with instrument cases, specifically for guitars. Many of them are made of composite materials, both fiberglass and carbon fiber.
The advantages of composites align well with requirements for handling musical instruments. Composites are strong and lightweight, as well as impact resistant. Composites are also not affected by moisture.
I came across an interesting video by WallyUpdabungenstein who does a comparison of a Calton deluxe fiberglass guitar case as compared to a Hoffee carbon fiber guitar case.
He does a great job comparing the actual fit and handling of the guitar in the case. He does not discuss the construction materials of the cases, but does look at the important aspects of them. Any item that is intended for a primary purpose such as protecting musical instruments needs to do a good job at this primary purpose.
Making a Small Mold
There are many methods and materials that can be used for making a fiberglass composite mold.
I found a video from Eastbay Composites that demonstrates a method for making small molds in a very quick an inexpensive fashion.
As you see from watching this, the basic construction materials are tooling gelcoat and inexpensive bondo for the support structure.
This mold construction technique certainly has drawbacks, but also has several advantages. None of the materials required spray equipment, which is messy. Brushes are inexpensive and easily disposed. A disadvantage of this method is that surface finish might suffer from a lack of consistency on the coating thicknesses for the gelcoat and the release agents.
Using bondo as the support structure is quick and easy compared to glass and resin, but can cause problems as well. It is more likely to crack, and can warpage issues as it cures and may be hotter in some areas than others. Bondo may have some difficulty maintaining dimensional tolerance as it shrinks during cure. Industrial resins used to create molds have minimal shrinkage in their chemistry and are placed on slower to minimize heat from the chemical reaction.
For quick, inexpensive and easy parts, this method from Eastbay Composites may work well for you. What has not been discussed yet is that the mold model can be the most difficult part. Off the shelf items are easy, but custom ones may be difficult. Creating a shape or surface is time consuming and tenuous. After that is complete, you can make your mold and final production parts!
Cutting Epoxy/Fiberglass with Ring Saw
Cutting and machining of cured composites parts can be challenging. Cured composites can wear cutting blades out very quickly. They are also very dusty when cut without using some sort of cutting fluid.
Many of these problems can be eliminated with the proper equipment. I found a very interesting video of a fiberglass-reinforced epoxy resin block being cut using a water-cooled ring saw. This saw is called the Revolution XT and it uses some neat technology to get a relatively quick and clean cut without making dust. It looks like it would also allow some good freehand movement to cut curves and angles in composites parts.
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