Setting Up a Composites Shop > Page 1, 2
Layup
With the tools cleaned and released, and as much material kitted as possible, you're ready to start the actual layup process.
- Layup room: Most layups, whether prepreg, wet, or even molded, are performed in a clean room. The room must be large enough to accomodate the part, and it must have sufficient access to move the tooling in and out.
- Local storage: You will need tables or shelves in the layup room for temporary storage of kits, tools, and consumables.
- Climate control: Do you need temperature and humidity controls? Are you required to monitor and keep a record of conditions?
- Cleanliness control: Likewise, do cleanliness specs require any special measures such as positive air pressure, tacky mats, hair nets, gloves, etc.?
- Lighting: This is often overlooked, but of course you need good lighting. Light fixtures should be sealed and recessed so they don't gather dust.
- Material handling: Do you need any power equipment for handling materials or moving tooling? Depending on the size of your operation, you may need a forklift or an overhead crane.
- Equipment: For anything other than hand layups, your facility may need to accomodate large equipment such as filament winders, fiber placement machines, presses, chopper guns, RTM dispensers and molds, etc. Even for hand layups, you may have equipment such as laser alignment systems.
Cure
How will you be curing your parts?
- Vacuum: Do you want a central pump for the entire shop, or portable pumps for individual products? Don't forget the hoses, valves, ports, and gages.
- Oven: Consider the size of your parts and how many you will be curing at one time. What kind of carts will you be using, if any? Do you need forklift access into the ovens? Other options include maximum temperature, control system, monitoring and recording system, and vacuum access. If most of your parts are large, you may want to consider a second, smaller oven for test coupons.
- Autoclave: Most of the considerations are the same as for ovens, but autoclaves in general are bulkier and more difficult to maintain. You may also have a gas purge system.
- Press: Options to consider are platten size, maximum pressure, heat, and vacuum.
There are, of course, other methods for curing, such as integral heating and e-beam curing. In general, your curing equipment takes up the most space and, unlike tooling, cannot be moved out of the way. It is important to plan your facility around this equipment from the start. If you decide to move it later, it's not just a matter of shifting physical equipment: there are also power and gas lines to think about, as well as allowable floor loads.
Post-Layup Processing
Although composite structures are usually designed to minimize the finishing work required after cure, such work cannot always be eliminated:
- Drilling and cutting: Can you get by with hand tools, or are machine tools (possibly CNC) required? This work is usually dirty, so care must be taken not to contaminate the clean layup room. Also, graphite dust can create an electrical hazard, and all composite dust is a personnel hazard.
- Painting: If parts must be painted, you will need a paint booth. Paints are a contaminant, so they must also be isolated from the layup room.
- Bonding: Bonding operations are usually done in a clean environment, such as the layup room. Parts must be prepped (perhaps sanded and cleaned), and alignment fixtures may be required.
Inspection
Completed parts usually go through an inspection process. Specific inspections depend on customer and internal requirements but might include:
- Visual inspection for obvious flaws such as resin-rich or resin-starved areas, cracks, pinholes, etc.
- Tap test, to identify potential delaminations.
- Ultrasonic or other NDE techniques (thermography, shearography, X-ray, etc.), for a more thorough look at potential internal problem areas.
- Dimensional inspection, to verify the part meets the specifications as set out in the engineering drawings.
Delivery
When the parts are complete, don't forget that you have to get them to your customer. The facilities you might need for this last step are very similar to the requirement for receiving:
- Storage area for temporary holding until the parts can be shipped. This should include protective caging, to prevent accidental damage.
- Crating materials, tools, and work areas. Parts usually need to be padded within the crates; two-part pourable urethane foam is a common solution.
Setting Up a Composites Shop > Page 1, 2