Cost of injection mould is very high. If we are aware of the factors that affects injection mold and unit cost. It can help us in cost saving by modification in plastic part design.
In this post we will discuss factors that affect injection moulding tool and unit part cost.
Following Factors affect the cost of a injection molding tool.
Large parts require larger molds. That results in more material and higher machining cost. As a result overall cost of mold increases.
For example mixer grinder housing injection mold will cost less compared to air conditioner housing mold.
Complexity of Part Design
More complex the part is, more time will be required to create a mold. Complex part injection mold requires very precise and costly mold parts. For complex parts material flow rate, cooling time, injection time and other parameters also need to be optimized. That results in increase in tool design and manufacturing cost.
By simplifying part design, tool cost can be minimized. For example, following points can help in reducing mold cost.
- Reduce number of sliders and lifters.
- Avoid thin sections.
- Avoid mold cooling requirement.
- Use of EDM and wire cut during mold manufacturing increases mold cost. Design part features in such a way, use of wire cut and EDM can be minimized.
Molding Material (Plastic Resin Material)
Abrasive materials also damages the injection tool . Harder tool steel is used for abrasive and hard materials. Abrasive materials also shorten tool life.
For example P20 pre-hardened tool steel can can give 5000 shots tool life for ABS but for 20% glass filled tool life will be 2000 shots.
A good designed mold helps in reducing tool maintenance cost and injection cycle time.
To achieve tighter tolerances, very precise injection mold is required. Manufacturing precise tool increases tool cost. Tighter tolerances also increase rejection rate and process control also becomes a challenge.
To reduce mold cost generous tolerances shall be applied to parts. Do not over define part tolerances.
For high production volumes, more reliable injection tools are required. Tool has to run longer without maintenance and breakdown.
For example if production volumes are less than 5000 units, pre-hardened steel (P20) can fulfill the requirement. Whereas to produce millions of units, hardened steel (stavax tool steel) is used.
Number of Cavity
Multi-cavity injection molding tools are used to produce more than one part in one shot. This helps to achieve high production rate and reduce unit price .
Higher number of cavities require more tool steel material and machining cost will also be high. Therefore tool cost will increase. But increased cost can be amortized for high production volumes.
For uniform cooling and to cool thicker sections, special cooling arrangement such as heat exchangers are required. Uniform cooling throughout the cavity yields good quality part and fast cycle time.
To reduce mold cost part and tool design shall be done in such as way, requirement of heat exchanger can be avoided.
Mould Manufacturer location
Cost and quality of molding tool vary in different locations. In china you can get very low cost tool. Sometimes lower-cost tools gives bad quality parts. Check out defects in plastic parts here. Take a right decision depending on the requirement.
To sum up, It’s very difficult to predict the cost of injection molding tool without detailed design. But depending on requirements mold price can be reduced. Check basics of plastic part design here.
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