Thermoplastic ducting parts

[idiroft]

Hi guys,

I have a project to redesign ducting parts and stop making them in aluminum (it’s a big pain). The thermal requirements are moderately high (service temperature 250°F) and the structural requirements are quite low (ultimate pressure 25psi). Under these conditions I think thermoplastic materials are the most appropriate but I don’t have any experience in terms of manufacturing processes.

What would be the best way to create a tube or hollow part that:

• Might have a flange attached to it somewhere
• Might be a Y part (a tube that splits into two different ones at one end)

I was thinking about creating the mold of each half of the part, then vacuum thermoform each half and finally bond the two together. The problem is how to bond the flange. Does anyone have suggestions for this problem?

Thanks!

[findhan]

Well lets ask the original question here, is your reason for suggesting thermoplastics based on service temperature only? 250F isnt a hugely high temperature so could certainly use a thermoset - an epoxy or if you want something else perhaps a speciality resin for higher temps: think exhaust systems for example. If its not structural then even better. What volumes are you talking as thermoplastics are better suited to higher volumes but manufacturing capital is normally considerably higher

Ducting can be made by a number of ways such as internal vac bagging, inflatable bladder moulding or a soluble core. Avoid the flange method if possible normally as it wont typically produce as good a result strength wise.

[riff42]

Thermoplastics are a pain to work with. yes, they can handle upwards of 600f service, depending on the part and pressure (which btw: is dependent on the layup not just the resin)

If you have th ability to thermoform, you can try that. if you can have a flange on your part, that will help bonding, else you will have to stepside the halves and then bond them with lapjoints.

Else, there is no real way to make a duct part, that does not involve ATP robots, and later autoclaving.

Don’t forget about extrusion systems. You can find a variety of thermoplastic resins with glass and carbon fill. That will strengthen and lighten the part as needed.

[idiroft]

Well lets ask the original question here, is your reason for suggesting thermoplastics based on service temperature only? 250F isnt a hugely high temperature so could certainly use a thermoset - an epoxy or if you want something else perhaps a speciality resin for higher temps: think exhaust systems for example. If its not structural then even better. What volumes are you talking as thermoplastics are better suited to higher volumes but manufacturing capital is normally considerably higher

Ducting can be made by a number of ways such as internal vac bagging, inflatable bladder moulding or a soluble core. Avoid the flange method if possible normally as it wont typically produce as good a result strength wise.

Hi,

thanks for your reply.

The ducting system already has some parts made out of polycarbonate through vacuum thermoforming of two separate halves that are afterwards bonded. What I’d like to know is if the main body of the ducting part can be done using thermoplastic materials, who do you insert a flange somewhere in a middle section? And what do you mean when you say flange method?

[riff42]

Red is adhesive, or just bolts.
Again, all depends on what your need is, how much pressure, any air/fluid flow concerns, etc.

Polycarb is a thermoplastic. But if you are looking for fiber reinforced, do you need continuous (fabric), or is short fiber (1mm-3cm) ok? You can use short fiber with extrusion, and MAAAAYBE if you can get it in sheet form, thermoform it later. You can do all this in thermoplastic fabric as well, but you need the processing ability.