A Brief Discussion on Mould Cost Control and Various Factors Affecting Mould Costs

General
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First, a fundamental question: what constitutes the cost of a mould? During a lecture I gave, some attendees quickly responded: “The cost of a mould is the material cost + processing cost + taxes.” Of course, there are also labor costs, but we can consider labor to be part of the processing cost. Additionally, there’s the design fee. From a narrow perspective, this answer is correct. But I would ask, if this is the case, aside from cutting corners or evading taxes, how else can we control or reduce costs?

1. Reasonable Product Design I believe many of you here might not agree with my point of view. How could the rationality of product design be the biggest factor affecting mould costs? At first glance, this seems like shifting the responsibility to the automobile manufacturer. However, think carefully: if the product design is unreasonable, what impact does that have on the mould company? It’s disastrous. I’ve been in the mould industry for over 40 years and have encountered many situations like this. Sometimes, to achieve an undercut in the product design, there is a lack of proper communication between the product engineer and the mould designer, leading to a significant increase in mould costs.

I was fortunate enough to be involved in the design of interior parts for a small car tailored for people with disabilities for a car company in Shanghai. One of the parts, called the central partition, was originally very large, with the mould production cost estimated at around 4 million RMB. The accompanying injection moulding machine would need to exceed 4,000 tons. I later suggested splitting the part into two pieces. The total cost for producing two moulds didn’t exceed 2 million RMB, and the injection moulding machines used were 1,500 tons. In the end, everyone was satisfied. There are many such examples. Therefore, a product designer must strive to learn more about moulds to ensure their designs facilitate the mould engineering process, rather than unnecessarily increasing mould complexity and costs. Ensuring good communication with the mould department, while meeting the overall vehicle assembly requirements, is the most effective and direct way to reduce mould costs.

There is also a philosophical issue involving productivity and production relations. Some product engineers believe that mould costs are solely the responsibility of the mould company and have nothing to do with them. However, imagine if production relations were reorganized, and the injection moulding and mould companies became one entity—what would happen? In fact, this is a growing trend. Nowadays, the most successful companies integrate both mould manufacturing and injection moulding. Companies that only rely on mould making are struggling to survive. Therefore, unreasonable product design will directly increase mould costs.

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2. Product Design Changes

Mould companies often encounter situations where, just as a mould is designed and the mould base is ordered, the client issues a design change notice. If it’s a minor change that doesn’t affect the overall mould structure, it’s usually not a big issue. However, in more serious cases, changes to the product shape may require additional mechanisms on the mould, or even necessitate reordering the entire mould base. This significantly increases costs. Therefore, it’s essential to minimize design changes.

Nowadays, there are many rapid prototyping methods available. By creating a 3D-printed prototype and conducting a full vehicle assembly test before starting mould production, product designs can be corrected in time, reducing the cost increases caused by design changes. I recall when I participated in the development of the Beijing Jeep Cherokee 213. The sample parts, injected in Shenzhen, had to be transported to Beijing for trial assembly. We made dozens of trips back and forth by plane, and it’s hard to say whether that cost was material or processing-related.

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3. Completeness of Mould Design

This factor can be analyzed in two aspects:

a. Rationality and Machinability of Mould Design

In most mould companies, design teams are usually a mix of experienced designers and young engineers fresh out of school. We can’t expect a new engineer to be capable of independently designing a high-level mould right away. Even experienced mould engineers can’t produce flawless designs on their own without overlooking some details. The most important and effective method to ensure quality is through collective design reviews.

I remember purchasing a German mould book in the 1970s, something like 80 Advanced Mould Structures. The most impactful lesson I learned from it was the importance of collective review throughout the mould design process. This has had a lasting impact on my career in the mould industry. Nowadays, I believe most people agree on this point. Various simulation tools are now available, such as mould flow analysis, dynamic mould structure analysis, and 3D comparison of the tested product against the design. These tools can help significantly reduce cost increases caused by unreasonable mould designs.

b. Design Waste

If a customer only needs a mould to produce 500 sample parts for market testing, but we design the mould for a lifespan of 300,000 cycles, this results in unnecessary cost, which is a form of design waste.

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4. Minimizing the Number of Mould Trials

Many mould companies calculate processing fees based on the number of days from when a mould order is received until the mould is approved and delivered. If a mould requires multiple trial runs before it can be accepted, not only will the company face penalties according to the contract, but the longer the mould stays in the factory, the higher the processing cost. Additionally, trial runs themselves are expensive, so excessive or uncontrolled trial runs represent a major blind spot in mould cost management.

Let’s analyze the reasons behind excessive trial runs:

a. Inadequate Design Review

The first reason is that mould design did not undergo thorough collective review, leading to unreasonable design structures. This causes the mould to require several rounds of modifications after trial runs, pushing costs beyond the budget. If the issues can be resolved after a few revisions, the company is considered lucky. However, many cases do not go as planned, and in extreme situations, the mould may need to be scrapped and remade, which results in uncontrollable costs.

b. Insufficient Machining Accuracy

In some cases, the mould design is solid, but poor machining quality increases the number of trial runs. This directly drives up mould costs. There’s no dispute on this issue, which is why many mould companies have increased their investment in measurement equipment to ensure machining accuracy.

c. Suboptimal Moulding Process or Machine Selection

Another common issue, especially among smaller mould companies, is failing to choose the optimal moulding process or injection moulding machine. The mould itself may be well-made, but poor results during the injection process unnecessarily increase the number of trial runs, further raising costs.

d. Incomplete Understanding of Plastic Properties

Lastly, insufficient knowledge of the physical properties of the plastic, including inaccurate shrinkage rates, can lead to mould trials being repeated. This situation occurs frequently. Therefore, before designing a mould, a comprehensive understanding of the plastic’s characteristics is essential to effectively reduce the number of trials.

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5. Mould Material and Standard Part Procurement

It’s crucial to choose reliable and reputable suppliers. If mould companies opt for cheaper and hastily sourced materials or standard parts, and these cause issues with the mould, it can lead to significant losses. Unfortunately, such situations are quite common. While it’s possible to hold suppliers accountable, the biggest losses still fall on the mould company and the mould user.

Selecting high-quality materials and trusted suppliers is a key factor in ensuring mould reliability, durability, and performance. Cost-saving shortcuts in material procurement may seem advantageous in the short term but often result in far greater expenses due to mould failure, production delays, and potential redesigns. Hence, establishing strong relationships with reputable suppliers helps safeguard the long-term success of mould projects and effectively controls costs.

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6. Product Qualification

Let’s say we invest 100,000 RMB to produce a mould for a car storage box, using PA+30% GF plastic, with an injection cycle of 30 seconds and a mould lifespan of 300,000 cycles. The mould is completed, and the sample meets the required dimensions and physical properties. However, during injection moulding, part removal proves difficult, causing the cycle time to double to 60 seconds. Furthermore, after producing 100,000 units, the mould becomes unusable. To meet the full production demand, three new moulds are required.

In this case, even though the initial investment was 100,000 RMB, I would consider the cost of this mould to be three or even six times the original estimate, given the additional moulds required and the extended production time. The situation highlights how mould design and performance directly impact not just the initial cost but also the overall cost effectiveness. Therefore, ensuring the mould is fully optimized for production efficiency and longevity is essential for keeping costs within the original budget.

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In summary, to effectively control mould costs, it is essential to focus on the following key areas:

  1. Reasonable Product Design – Ensure the product design is optimized to avoid unnecessary complexity that increases mould production costs.
  2. Minimizing Design Changes – Limit design changes as much as possible to prevent costly modifications after mould production has begun.
  3. Comprehensive Mould Design and Processing Workflow – Ensure the mould design and manufacturing process are thorough and well-structured to avoid excessive trial runs and redesigns.
  4. Effective Communication between Product and Mould Engineers – Maintain good communication between product engineers and mould engineers to ensure that designs are feasible for mould production and that mould costs are kept under control.

By focusing on these aspects, companies can significantly reduce mould costs and improve overall project efficiency.