PRODUCTION OF PARTS
Manufacturing parts with polymers from individual drawings
Plastmass Group provides a full range of production services for the machining of plastics, both own production (PLASTMASS™ materials) and raw materials (caprolon, polytetrafluoroethylene (teflon), polyacetal, etc.).We manufacture prototypes and in serial productions of parts based on drawings or samples of customers.
HOW WE CREATE UNIQUE PARTS
The use of automated machining centers ensures improved quality and precision machining parts, minimizing the spoilage. Thanks to modern machines the labour intensity and impact of human mistake factor reduce, saving time significantly for setup and changeovers of equipment.
Our specialists are able to produce parts on order made of polymeric materials for domestic and imported equipment:
Bushings and plain bearings for any equipment
Sliding guides (for chains and belts)
Slide plates (track shoes, bearings, guides) for the shafts and sliding mechanisms
Seals, gaskets, washers
Non-standard parts and fasteners
The cost of parts’ production is negotiable and depends on the material and quantity of the products. The term of manufacturing is from 1 to 20 days. The minimum quantity is not limited.
Watch the video on manufacturing of a finished part from a PLASTMASS™ material blank part.
TOLERANCES FOR MACHINED FINISHED PARTS
Plastics are subject to different physical laws respect the metals. Thermal expansion up to 10 times bigger, lower stiffness, moisture absorption, anisotropy, post- shrinkage and warping due to stress relaxation, lead to higher manufacturing tolerances. Generally, the IT-tolerance from 9 to 12 are used. The IT-tolerance ranges of 7 and 8 are available in special cases.
Due to the high thermal expansion coefficients, it makes sense to control the dimensions only when the room temperature is reached. Tolerances for the dimensions of polymer parts are higher than for metal parts.
It is recommended to heat some PLASTMASS™ polymers before processing and process them in a preheated state. To exclude the formation of cracks, any mechanical treatment should be performed at temperatures not lower than + 18 ÷ 25 °C
For processing products from PLASTMASS™ materials, machines with lower capacities are sufficient than for processing the same metal products.
Tools should be very sharp and smooth, with a large rake angle.
For small production, the use of tools from HSS is possible. To produce a large number of products, the use of HM tools is recommended. Serial production of parts with small tolerances requires the use of diamond coated tools.
Lathe turning should be made with a large chip cross section removal and high feed rate speed. the cutting should be done in 1 operation.
The best dissipation of heat is achieved over the chip. In addition a jet of compressed air, that also pulls the shavings away, can be used.
The band saw cut speed should be between 8 – 25 m/s.
Applicable tool: metal blades or carbide tines. To obtain a better cut, it is recommended to use, a saw blade with a pitch from 4 to 6 mm.
To dissipate the milling machining overheat, it is suggestible to choose the largest possible milling stressed cross section. This process is obtainable with a high feed rate, a large depth and a not to high cutting speed.
Very tight bore tolerances are obtainable by reaming with a reamer according to DIN 206, DIN 212, DIN 219. A minimum machining allowance of 0.1 mm has to be planned, because of the plastic elastic behavior.
Tap drill holes for screw threads up to M8 and bigger than M10, should have respectively a diameter dimension ca. 0,1 mm and ca. 0,2 mm, bigger than the metal´s one.
FILING & RASPING
Filing with rough-hewn wood rasps is well-tried, but filing with a file blades represents an advantage.
Generally, the PLASTMASS™ high performance polymers can be grinded and polished.
To grind a workpiece can be used commercial abrasive belts and grinding discs, possible with a coarse grain size.