- Parts Design (client may provide completed 3D files)
The tooling process begins with a completed and checked part design. CNMOULDING can optionally optimize your design before tooling to lower your costs and ensure that your design will work well.
- Parts Prototyping (if necessary)
If you would like to validate your parts design with a machined piece that you can see and feel, Cnmoulding can use Computer Numerical Control (CNC) techniques to prototype your parts.
- Tool Design
At this stage the tool is designed, using the information from your completed tools and molds design
- Tool Check and Mold Flow Analysis
The tool design is validated for correctness.
- Tool Fabrication (including use of Computerized Numerical Control (CNC) and Electrical Discharge Machining (EDM) technologies)
The tool is precisely fabricated according to the validated design.
- First Shots To Client
Once the injection molds are made, the first test shot samples will be sent out soon after via an international courier. Once sent, these usually take around 2-5 days to arrive.
- Tool Modifications and Texturing
At this stage, Cnmoulding completes the tool and makes any required changes to bring the tool into the approved spec. Changes made to bring the tool to spec (specifically excluding design changes, which are always charged) are made free of charge.
At this stage, texturing also takes place, which is normally the last stage before mass production.
- Mass Production Run or Export
At this stage, parts are produced and delivered to the customer, or the tool is released for export use.
Molding begins with tooling. No matter how good the design, if the tooling is not up to the task, the quality of the parts will suffer.
The Molding Machine
Achieving consistent dimensions and quality requires up-to-date molding machines, operating to specifications, with precise position and pressure control capabilities. The basic construction of a molding machine is fairly straightforward.
Material is fed in through a hopper into a screw and barrel where it is heated to a molten condition. The melt is then injected under high pressure into the mold while the mold is held closed with the high force of a toggle or hydraulic ram. The goal is to melt resin in a very uniform and repeatable fashion, inject it into the mold under very precise and repeatable pressure conditions, and hold the steel temperatures in the entire flow system very stable. After the molten plastic is solidified, the mold is opened and the gear is ejected. It then continues to cool in the open air.
There are many handling and pre-processing requirements for injection molding materials. Engineering polymers quite often must be dried to a specific dew point before use. When parts are made, runners are formed that some shops regrind and put back in the melt. This quite often raises more quality concerns than the slight savings in material expense may justify, and CPIM uses only virgin material.
The method of injecting the plastic into the mold is very important. In most cases, the plastic should be injected under high pressure very quickly to maintain the good characteristics of the melt completely during the injection. As the mold cavity fills, the injection pressure should be held at the same high value and the speed of injection slowed to maintain that pressure. At the moment when the part is filled, and the molding machine switches over from injection to a pack & hold condition, the plastic melt is held at the same high pressure. This pressure is held for as long as it takes to freeze the gates and achieve the highest weight possible for the molded part.