Kinds of plastic for a job

[GlennD]

Hi Folks

I have a small machine to design that the client wants to use molded plastic in a larger role. previously they used molded parts for what I call inconsequential items, rollers knobs and things that are easily replaced and are usually wear items. now they want to use molded parts in the main frame as structure or as adjoining parts in a framing capacity . Has plastics progressed far enough for that? if so what kinds are being used successfully for these things, I envisioned the unit still having a light steel structure and use the plastic to fill out the bulk of a part so the plastic doesn't have to deal with as much force by itself. or even laminating the molded parts with steel. The units have to have a nice fit and finish like a consumer product when done. Ultimately they admitted they are going for a more flowing and rounded look. their competitors use thermoformed covers on ugly structure to get their look but thats not what they want, they want this look built into what would normally be pretty angular sheet metal bodies. Damn it's getting too busy ..

[JAlberts]

Considering the lack of information as to the size, application, types of loadings, etc. it is hard to give any specific information; however, structural shapes such as I beams, angles, floor grating etc. for use in supporting structures, walkways and stairs for highly corrosive plant environments have been manufactured for several years by extrusion molding with a chopped fiberglass reinforced polymer. However, the finish of fiberglass molded components may not meet the level desired by your customer.

Also for a reference on a variety of molded polymer enclosures both large and small see the below website:

http://www.hoffmanonline.com/product...2&CatID=159992

[jboggs]

Also, have you looked into extruded aluminum for your structure? It has a nice look which can be varied significantly and can be bent to shape to some degree. You are probably already familiar with some of the many manufacturers of this type product. As far as plastic, when I think structural, I think of large toys like kiddie kitchens and playgrounds. Speaking of playgrounds, check out the play area at your local McDonald's. You'll see lots of large, somewhat structural plastic.

[GlennD]

Thanks for your replies.

Basically the machines consists of a formed channel frame about 3' x 2' and 6" deep on 4 legs like a table but with casters so the tops of the legs have to be strong. They want to use plastics to add more organic kinds of shapes to the unit and reduce costs. thinking they could get a lot of the little attaching parts popped out at the same time as the larger frame components. Glass reinforced sounds like it could work even with the rough finish because I might be able to offset some of the rough appearance with smooth painted metal especially if I use metal as well to reinforce joints and things. Can that material be injection molded? or cast?

Do you think Polypropylene like in your link could be used for large structural components like this? what about if it was backed up with metal. sort of laminated or layered in with the plastic parts?