Plastic sheet production and machining are different operations. Sheet stock is formed first; cutting, drilling and CNC machining then create parts from that stock. A process suited to a bottle or molded housing is not necessarily suitable for a flat sheet. For our sheet and machined-part orders, we review the material, drawing and requested processing scope before quotation.
1. Choose and Prepare the Resin
Thermoplastics include PE, PP, PVC, PS, ABS and PC. Resin may be supplied as pellets or powder, depending on the material and forming method. The specific grade must suit the process and intended service conditions.
- Additives, fillers and pigments affect the formulation. Specify the required grade and properties rather than treating all grades of one polymer as interchangeable.
- Drying is material- and grade-dependent. Standard PP does not normally need pre-drying, but some filled grades may. Follow the resin supplier's storage, moisture-control and processing instructions; do not apply one drying schedule to every plastic.
2. Distinguish Melting from Sheet Reheating
In extrusion and injection molding, the screw heats, mixes and conveys the thermoplastic melt. Thermoforming reheats an existing sheet instead. Machining removes material from solid stock without remelting it.
3. Compare the Forming Methods
Part geometry, resin grade, production quantity and tooling requirements help determine the process:
- Injection molding: molten thermoplastic fills a mold cavity to form a discrete part, such as a housing.
- Extrusion: melt passes continuously through a die. Sheet extrusion uses a wide die, followed by cooling and cutting to length or winding, as appropriate.
- Blow molding: air expands a heated plastic tube, or parison, inside a mold to form a hollow part, such as a bottle.
- Calendering: material passes through a series of rolls to make sheet or film; PVC film is a common example.
- Thermoforming: a heated sheet is shaped over or into a tool. Vacuum forming is one type of thermoforming, not a synonym for the whole process family.
- Rotational molding: resin is heated in a rotating mold to form hollow products.
4. Cool, Release or Cut the Product
Cooling and release depend on the process. Molded parts are released from a mold when ready; extruded sheet is cooled and then cut or wound. These are different operations, so demolding is not a stage of every plastic manufacturing process.
5. Machine and Finish to the Drawing
Further work may include cutting, drilling, deburring or CNC machining. Welding, printing, assembly and heat treatment are separate requirements to confirm for the material and part design. A drawing should identify critical dimensions, hole positions, edge details and tolerances; do not assume a sheet-stock specification also defines the finished part.
6. Agree the Inspection and Packing Requirements
Agree dimensional and surface checks before production. Mechanical testing, material documentation and inspection records need their own specified scope; they should not be assumed to accompany every order. Packing should protect the supplied sheets or parts during handling and transport.
Specify the Sheet or Finished Part
- Supply form: state whether you need full sheets, cut-to-size blanks or finished machined parts, with thickness, dimensions and quantity.
- Inspection: identify critical dimensions, tolerances, surface requirements and any required tests or documents.
- Packing: confirm protection, pallet or crate dimensions, marking and destination requirements before dispatch.
Get a Factory Quote
Send the material grade, thickness, sheet dimensions or part drawing, quantity and delivery destination. We use these details to review the proposed material and processing scope, then confirm the quotation and order conditions.
