Machining plastic

Plasticating single-screw extruders will typical range in size from 15 mm up to 250 mm in diameter. Larger diameter plasticating machines are very rare and were likely built years ago. Plasticating rates above about 4000 kg/h are more economically processed using twin-screw machines. 

Thermoplastic polyurethanes are normally processed in conventional plastic machines and when heated to above 120 to 150°C will soften and can be processed. By definition, this process can be repeated over and over. The TPU is supplied as a polymer chain extended to a suitable length with terminal groups that do not allow any further chain extension. 

Rohifs, T., Plastics Machining Understanding the Basics, MD8cDI, Apr. 2002. 

Koenig, K. M., Fixturing Routing Plastics with CNC Tooling, Plastics Machining Fabrication, Winter, 1997. 

Laboratoryware, plastics Ladders, plastics Lamp bases, plastics Lamp shades, plastics Lenses, plastics except ophthalmic or optical Lifejackets, plastics Liferafts, nonrigid plastics Lock washers, plastics Machine nuts, plastics Microwaveware, plastics Molding of plastics for the trade, except foam Monofilaments, plastics not suited for textile use Netting, plastics Nuts, plastics... 

The odor is unpleasant with a nutty, blue-cheese, plastic, machine oil and raw mushroom flavor (Chemisis, 1998). 

Injection molded, molded and extruded into articles. Readily plasticized, machined, and glued by solvents. 

Cutting of fiber-reinforced plastics Machining of CFRP and composite materials... 

The polymer has a lower melting temperature (220°) than poly(tetra-fluoroethylene) (327° C), and so can be processed at 250-300° C on the usual plastics machines. But these machines must be corrosion resistant because of the decomposition already possible at these temperatures. 

Drum extruder n. A plasticating machine having a rotating cylindrical element inside a concentric or eccentric housing. Pellets or powder are fed into the gap between drum and housing at the top. Shear action melts the solids and the melt exists through a slot about 270° around from the feed point. 

Figure 8.2 Classification of thermoplastics. Source Laura Pugliese, Defining Engineering Plastics, Plastics Machining and Fabrication, January-February, 1999, Courtesy DSMEngineering Plastic Products.)...

Machine screws and bolts. Parts molded of thermoplastic resin are sometimes assembled with machine screws or with bolts, nuts, and washers (Fig. 9.8), especially if it is a very strong plastic. Machine screws are generally used with threaded inserts, nuts, and clips. They are rarely used in pretapped holes. Molded-in inserts provide very high-strength assemblies and relatively low unit cost. However, molded-in inserts could increase cycle time while the inserts are manually placed in the mold. When the application involves infrequent disassembly, molded-in threads can be used successfidly. Coarse threads can be molded into most materials. Threads of 32 or finer pitch should be avoided, along with tapered threads, because of... 

Parts molded of thermoplastic resin are sometimes assembled with machine screws or with bolts, nuts, and washers, especially if it is a very strong plastic. Machine strews are generally used with threaded inserts, nuts, and cups. They rarely... 

Tools with an up to 30 pm diameter Tool material carbide, diamond, steel, and ceramic Machining of steel, brass, copper, bronze, aluminum, plastics Machines with up to 5 axes... 

When a filler is added directly at the hopper and passes into the barrel, there is wear from the dry filler rubbing against the screw and barrel lining until the plastic melts and encapsulates it. All fillers are much harder than plastics and most plastics machines are designed to use pime plastics only. 

Korane KJ (2000) Guidelines for Bonding Plastics. Machine Design... 

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