Tooling for Injection Molds

Overview:

Parts Design (client may provide completed 3D files)

The tooling process begins with a completed and checked part design. Titoma can optionally optimize your design for Design for Asian Manufacturing (TM) before tooling in order to lower your costs and ensure that your design will work well with Asian processes.

Parts Prototyping (if necessary)

If you would like to validate your parts design with a machined piece that you can see and feel, Titoma 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 Tooling Information Worksheet.

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 international courier. Once sent, these usually take around 2-5 days to arrive.

Tool Modifications and Texturing

At this stage Titoma 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 for) are made free of charge by Titoma.

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.

Technical Topics:

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 prior to 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.

Injection

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 in order to maintain the good characteristics of the melt completely during 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 mold 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. Below is a graphic image of the pressure and fill patterns of a typical plastic molded part.

(Part is filled in 0.23 seconds)

Legend:

Example of Tooling Process: Three Plate Tooling

Three plate tooling means that when the mold opens, three plates are separated. Between two of the plates the plastic runner is ejected, and in the second space, the plastic molded part is ejected. Three plate tools allow parts to be gated in the interior region of its body, which means that parts are a significant step away from the turbulent region of injected plastic flow. Melt temperature and pressure profiles are more uniform which results in better molded part dimensional stability. These three plate tools must be made with very high precision, and the gear cavity should be replaceable since part shrinkage can never be completely known before the tool is used to mold the gear.

Precision Characteristics

Runner and part configurations must be optimized for proper molding. Gate locations and sizes are also critical. Mold temperature control is extremely important. Every piece of steel in the vicinity of molten plastic should be held at a constant determined temperature. Usually the mold base should be insulated from the mold machine at its mounting points to prevent uneven cooling from the large steel machine platens. Designing part ejection is also quite important. Can pin ejectors be used without deforming the part?

Designing part ejection is also quite important. Can pin ejectors be used without deforming the part?

Administrative Topics:

Payments

Our normal payment schedule is 40% initial deposit, 30% on First Shot, and 30% on approval.

Timing

For tooling, it usually takes 5 to 6 weeks from receipt of deposit funds for molds to be made, assuming that 3D files are correct. If you have a special urgent request, we can reduce the lead time to 3 weeks (additional fees apply). “T1” samples are the first stage test shot samples produced based on your 3D files. Depending on the original 3D design and complexity of the plastic parts, it takes usually one to two weeks, sometimes longer, to complete the test shot stage. Lead-time for production depends on parts complexity and tool and material requirements, as well as the quantities requested by the client. If you have a dead-line to meet, please let us know. We will discuss it with our factories to see whether it is possible to meet your date. Usually we estimate 2 weeks for orders of 10,000 units. Please contact us for details on exactly how long your project will take, as times (and project scopes) vary greatly.

Freight Forwarding

Shipment times depend on which shipment method is used (i.e. DHL, UPS, FedEx, TNT, air cargo or sea shipment).

Our prices are quoted FOB China or FOB Taiwan.

If you have appointed a freight forwarder, we can use your account and existing agreements for a nominal fee.

If do not have a specific forwarder, we can provide names of forwarders we have worked with in the past.

Based on our experience, depending on the final destination, it samples usually take about 2-5 days via international courier, 2-5 days by air and 20-45 days by sea.

When deliveries are sent FOB China, international courier service is not usually recommended as procedures can be complicated. EMS is an alternative for small quantity if the delivery is urgent, however.

Additionally, standard times for custom declarations vary from country to country. Please check with your local freight forwarders service.