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I cam across an issue today where a composite fiberglass part had been modeled with no draft (angled faces). Production stopped because they couldn’t make it by the print and get it off the mold. A hostage situation ensued, the problem was corrected and production cheered the results. All was well, except for the unapologetic engineer that was immediately flogged.
This brings up some modeling methods to consider when creating composite parts that follow a certain manufacturing process. The following is a quick and really simple approach to how to get the best results.
Understand the manufacturing process
If you haven’t spent some time with the friendly composites group, take a trip down to breath in some nice resin and fiberglass dust. These guys can help you understand in one mind-blowing hour what they do and how they do it. Stay away from the guy with the beard.
Basically, most shops will use some sort of lay-up tool (mold) to form the fiberglass to. They may also make parts in two halves (tubes) or multiple pieces (things with flanges). If they need to slide it off the lay-up tool, it usually needs about 2-5 degrees of draft.
Model for single part manufacturing
Here’s the process for a simple 1 piece lay-up in a few easy steps:
- Sketch the Lay-up Tool Shape
- Extrude with Draft
- Add Fillets
- Shell Outward
- Add flanges, holes, etc.
Here’s an example part (SolidWorks 2007) – Simple Single Part (238 kb)
Model for multi part manufacturing
Here’s the process for a simple multiple piece lay-up in a few easy steps:
- Sketch the Lay-up Tool Shape
- Extrude with Draft
- Add Fillets
- Shell Outward
- Split in half
- Add flanges, holes, etc.
Here’s an example part (SolidWorks 2007) – Simple Multi Part (238 kb)
This approach is very quick and allows you to adjust easily for manufacturing. When it comes down to how you decide to model any part, the shop is almost always going to be helpful place to start.
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Everyone doing any kind of design should spend time with their manufacturing folks when they can. Ohh…. the things you learn and the good will you can gain by listening to your manufacturing folks and helping them, where you can, to make their job easier.
Cheers,
Anna
Yeah, but then they know your face when they go to hunt you down
It really is a good idea. All our new guys spend some time in the shop learning.
Take the time to actually work (with) them. WATCH the process unfold.
I spent a few months in a machine shop learning what can and cannot be done.
From there on, almost every vendor I try to visit and ask them to explain what works best for them and what does not.
What do they expect to see on a print.
What solid files can they work with.
How do they expect to see the model - in relation to tolerances from the prints.
LK