Common materials for machined plastics components
- Acrylic – is one of the least expensive plastic materials that can be used for aesthetic purposes due to its clarity. Acrylic has the properties of being able to transmit 92% of light and looks as clear as window glass. Acrylic is also fairly hard and scratch resistant but it can suffer from brittle failure and limited chemical resistance to strong solvents. Stress cracking of acrylic can be avoided through proper Plastic Machining.
- Polycarbonate or Lexan – has strong impact resistance during Plastic Machining. This resistance is different from stress cracking resistance since like other amorphous plastic materials, polycarbonate does not tolerate steady state stress well. Polycarbonate has better chemical resistance than acrylic although it has lower scratch resistance. Since it is slightly softer, it has the toughness that will not suffer from brittle failure.
- Polysulfone – is plastic that is used for hot liquid applications because it has higher continuous service temperature than polycarbonate and acrylic. This makes polysulfone more expensive however, it has better performance
Important tips in Plastic Machining
When machining plastic, it is important to take into account various factors like the right kind of blade, blade speed, friction, bite-angle, tooth-counts, fume production and pressure. The general rule when working with plastic is to use as little force as possible particularly when working with brittle plastics like acrylic. When cutting plastic, it is essential to feed slowly, avoid friction and side forces and choose the right blade. Once melting starts, you should either slow down or completely stop. If you will allow melting to continue, it will eventually ruin the power tool. Melting also leads to hazardous fumes that can compromise the health of the operator.
Drilling is a process in Plastic Machining where slow to medium speed is used with only a slight downward pressure. The drilling bits should be specifically made for plastic with that shallow bite angle that prevents the drill bit from digging into the plastic material. Once the bit gets stuck, it can bit off a piece of the plastic sheet material. The processes of milling and lathing in Plastic Machining need to follow speed and feed rate guidelines. When making use of a laser cutter, it is important to take into account the effect of laser radius since it can cost secondary material loss outside of the beam area. Fume production is also a concern that has to be considered during laser cutting of plastic material other than acrylic.