Costs to consider in Plastic Injection Moulding
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Costs to consider in Plastic Injection Moulding
Plastic injection moulding is a highly popular manufacturing process used to produce plastic parts and products in high volumes. It involves injecting molten plastic material into a mould and allowing it to cool and solidify into the desired shape. While injection moulding is a cost-effective way to mass produce plastic components, there are several costs that must be factored into the overall process.
Understanding these costs are crucial for companies looking to leverage injection moulding to manufacture products and parts.
Mould design expenses
The design of a mould is a crucial part of the injection moulding process, and also a cost component. Creating an optimised plastic part design suitable for plastic injection moulding requires upfront engineering time for activities like 3D modelling, mould flow analysis, structural simulations, prototyping, design reviews, and obtaining manufacturing feedback.
Minimising costs requires experienced engineers and designers who can develop economical designs tailored to the plastic injection moulding process. Simple or poorly designed parts can result in higher scrap rates, processing issues, and even mould reworks down the road. Investing in proper part design optimisation upfront saves significant costs over the long run.
Prototype and validation costs
Before commencing full production, prototypes are usually produced to validate the mould tooling and injection moulding process. Multiple rounds of prototyping may be required to refine the tooling and process parameters to meet all product specifications. Machining prototype tooling and producing each set of validation parts generates costs that should be planned for. Minimising change orders after tooling kickoff helps reduce overall prototyping costs.
Building the mould
Before production can begin, upfront mould costs have to be incurred to develop the tooling required to produce the plastic parts. The production of the mould involves CAD modelling, CNC programming, machining electrodes, constructing the mould base/components and fabricating the final tool. Man-hours for qualified mould designers and engineers make up a significant portion of the mould design cost.
For very simple moulds, design costs may be just $1,000 – $5,000. However, for large multi-cavity moulds producing intricate parts, design costs can be $80,000 or higher. The complexity of the required mould and the design team’s expertise determine the final design development expenses.
Raw plastic material costs
The plastic resin or pellets used in plastic injection moulding represent an ongoing production cost. There are many different types of plastic materials used in plastic injection moulding, including polyethylene, polypropylene, acrylic, nylon, polystyrene, etc. The cost per pound of plastic resin can range anywhere from $0.50 to $5.00 or more depending on the material type.
When calculating overall material costs, scrap loss should also be factored in, which can be 5-15% of the total material usage. Optimise the moulding process to minimise scrap losses due to defects or processing inefficiencies. Recycling scrap material back into the process helps offset some of this material loss. Material costs at high volumes become very sensitive to part design – slight design changes can impact the amount of material consumed.
Labour costs
There are labour costs associated with operating and maintaining the plastic injection moulding equipment. Skilled machine operators and technicians will be required, especially for large production runs or complex moulding processes. The labour costs can vary widely based on the geographic location, complexity of the moulding operation, and skill level required.
Many manufacturers minimise direct labour costs by highly automating the plastic injection moulding process. However, there may still be some direct labour required for activities like finished part inspection, packaging, and material handling. Streamlining workflows and processes can help optimise labour usage.
Energy consumption
Plastic injection moulding machines require significant energy inputs in the form of electricity and/or natural gas. The plastic must be melted at high temperatures, and the hydraulic systems of the moulding press have high energy needs. Larger machines can consume over 50 kW of power when running.
Energy is also consumed by any auxiliary equipment like resin dryers, machine cooling pumps, conveyors, etc. Ongoing energy consumption costs should be budgeted for when estimating the overall operating costs. Use energy-efficient injection moulding machines and optimise the moulding process to minimise cycle times and avoid excessive power consumption.
Mould maintenance costs
The plastic injection moulds must be properly maintained or they will degrade over time, leading to defects, reduced part quality, and lower production yields. Mould maintenance involves activities like periodic cleaning and polishing, repairing or replacing damaged components, and general mould upkeep. Neglecting mould maintenance can severely impact costs in the long run.
For high production moulds, the maintenance costs can tally up to thousands of dollars annually. However, well-cared for moulds can last for many years and produce hundreds of thousands or even millions of parts over their lifespan. Plan for regular preventative maintenance downtime and budget for periodic mould refurbishing costs.
Quality control expenses
To ensure consistent, high-quality parts are produced, plastic injection moulding requires rigorous quality control procedures. This includes inspecting samples from each production batch, periodic machine performance checks, control testing on critical part dimensions, monitoring process parameters, and maintaining complete traceability.
The costs of all consumable materials, testing equipment, and labour time required for quality control should be accounted for in the project budget. It’s also critical to catch any defects early on to prevent larger costs of scrap material or customer returns down the road. Automated inspection systems can help minimise labour costs and improve quality oversight.
Inventory carrying costs
For high volume production, plastic injection moulding operators may produce and stockpile significant quantities of finished parts in inventory. While this levels production output, large in-process or finished goods inventories create carrying costs. The costs include warehouse space rental, inventory tracking systems, taxes on unsold goods, insurance, and the opportunity cost of capital tied up in unsold stock. Reducing inventory levels through just-in-time principles can help minimise these expenses.
Shipping and logistics costs
Shipping raw materials to the production facility and outbound distribution of finished parts make up a portion of the total supply chain costs. With plastic resin often representing up to 40% of the total part cost, inbound shipping of these bulk materials in railcars or tanker trucks can be expensive.
Outbound shipping costs will depend on the size and weight of finished parts along with order volumes and destinations. Look to consolidate shipments when possible and determine the most economical shipping methods.
Project management costs
Smoothly managing a plastic injection moulding project requires expertise and oversight. From contract negotiations, design reviews, prototype approvals, production ramp-up and beyond, there are personnel costs associated with properly running the project. Dedicated programme managers may be required, especially when dealing with large Tier 1 suppliers or overseas vendors. Careful organisation and communication are critical to contain overall project management costs.
Payment terms
Upfront payment is often required for injection moulding tooling, especially when working with overseas vendors. This results in cash being tied up until the tools are received and approved. For approved vendors, deferred payment terms can potentially be negotiated, which provides extra flexibility and improves cash flow. Account for the impacts of different payment term options when budgeting the project.
Insurance coverage
Risks like delayed or damaged shipments, natural disasters, quality defects, or production interruptions can all impact plastic injection moulding projects. Reviewing insurance plans to ensure proper coverage of inventories, production capabilities, shipments and liabilities provides protection that can be invaluable if issues arise. Factor appropriate levels of insurance into cost estimates, especially for high value or long term programs.
In conclusion
Having an understanding of the costs that affect the production of plastic injection moulding products is important when selecting a reliable partner to manufacture your product.
Discussing both the upfront and ongoing costs allows businesses to budget appropriately and make injection moulding projects as lean and profitable as possible. With an optimised understanding of the costs, plastic injection moulding can be leveraged to economically manufacture quality plastic components at production scales ranging from prototypes to millions of parts per year.
If you are looking for a trusted partner to work with, reach out to the team at SDI Plastics on 0738078666 for a confidential discussion.
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