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Questions to Ask Your Molder During Mold Design

Know what questions to ask about your new mold during the mold design phase.

What you know and don&#;t know about your mold design can impact the timing, costs, quality, risks, and life of the mold. The mold design phase defines most of the quality of a mold. You need to ask detailed questions about your new mold during mold design, so you can make changes early on.

If your supplier makes meaningful decisions such as shortcuts to save time and money at the expense of accuracy, you should know. Asking these specific questions helps you learn about both your final output and your supplier. The answers help you select the right provider who will extend your mold&#;s performance and longevity to get the most value from your investment.

Q1: CAN I REVIEW THE MOLD DESIGN?

As the owner of the mold, you have every right to review and approve the mold design prior to mold construction. If they decline your request, this raises red flags. Either your supplier does not use a mold design, or they are unwilling to share their design with you. Either way, this supplier introduces extra risks into your project, and you have to ask yourself why. Your goal is to reduce project risks, not introduce more, and this supplier may not be the right fit for you.

We have had clients transfer molds to us that they own. They were surprised to discover that the mold had no cooling lines or ejection because they had never seen the mold before. Maybe you cannot physically review the inner workings of your mold in person. But you can review the mold design which can reveal these types of issues before building the mold.

You want to make sure not to assume that a high-grade mold is automatically a well-designed mold. A Class 101 mold might be made with hardened steel, but that provides little insight into the rest of the mold design. In other words, a Class 101 mold can still have a poor mold design or lack the ability to run automatically. You can read more about mold classifications here.

Even if you do not want to delve into every minute detail, at a minimum you can review parting line assignments, knockout locations, and gate locations to assess the impact on the final part. You can also review inserted areas and venting locations which will also have an impact on the final part.

Q2: WHAT SIZE MOLD WILL YOU BUILD?

We have had many molds transferred to us for molding or repairs where the customer wanted a robust, efficient production mold and ended up with a mold which was much larger than necessary. These molds suffered from inappropriate mold designs. Larger molds consume more raw material and produce unnecessary waste.

In general, you are looking for signs that you are getting the right mold. This means the mold design does not include unnecessary waste. You want a lean mold. You determine waste based upon the purpose of your mold. For example, a rushed mold design could result in a mold that requires a 200-ton press versus a 60-ton press.

That might work if you place priority on speed to first parts as your priority. If the mold will produce a low number of parts quickly, the rapid mold design might work best for you. Rapid molds use quick designs by cutting out steps not needed in pursuit of getting a number of samples as quickly as possible.  Building a robust mold with optimized cycle times proves unnecessary with a primary purpose to validate the part design. As Donald Knuth said, &#;Premature optimization is the root of all evil.&#;

As the need for higher quantities of parts increases, a more efficient mold design grows more desirable. If the mold will produce many parts without wasted processing time during injection molding, a smaller, more compact mold works. This means the mold will fit into a smaller press, consume less energy, decrease cycle time, and yield a lower piece price. The smaller press will generally use a lower clamping force and create less wear on the mold. This helps extend the life of the mold.

Aluminum seldom makes sense if a mold is fabricated in China (which we cover later). Steel is the most common injection mold material, but choosing the right injection mold steel material is similar to selecting the foundation for a building: it dictates the mold&#;s durability, performance, and ultimately, the quality of your parts. As engineers, we understand the critical nature of this decision.

With competitive price and timely delivery, Qisheng sincerely hope to be your supplier and partner.

Let&#;s delve into the three most common types of hard steel and pre-hardened steel utilized in injection molding:

Hard Steels:

1. / / H13: This trio offers a workhorse option. After hardening, they achieve a Rockwell C hardness of 49-53 HRC, making them suitable for ordinary hardening molds. Their versatility allows for applications across various projects.

ESR: This steel takes the performance of the previous group a notch higher. It boasts the same hardness range (49-53 HRC) after hardening but excels in applications demanding both durability and a highly polished finish.

S136 / S136SUP / : Don&#;t be fooled by the &#;steel steel&#; reference &#; these are actually high-performance stainless steels. Their strength lies in corrosion resistance, making them ideal for molds processing materials like POM and PVC, which can be corrosive to standard steels. Additionally, they hold their own when it comes to achieving a polished finish.

Lifespan: Mold tooling made from hard steels like 1.#, #, and # will usually last for around 300k-500K shots, but can reach 1 Million if the mold structure is simple.

Pre-Hardened Steels:

S50C / S55C: These steels offer a cost-effective option for mold bases, providing adequate strength and machinability. However, their lower hardness limits their suitability for high-wear applications.

718 / 718H: Renowned for their toughness and ability to achieve a good surface finish with standard polishing techniques, 718 and 718H are popular choices for mold cavities and inserts. Their well-rounded properties make them a versatile option for various applications.

738 / 738H: Offering superior rigidity compared to 718 grades, 738 and 738H excel in core and insert applications. While their polishing capabilities are considered &#;ordinary,&#; their rigidity often outweighs this limitation for specific applications.

A Note on P20: It&#;s important to clarify the perception of P20 steel in China. While technically encompassing a series that might include materials like 718 or 738, the term &#;P20&#; in China often refers to a lower-grade steel with potentially less desirable properties compared to the 718/738 series.

NAK80 / XPM: The champion of pre-hardened steels, NAK80 boasts a hardness of 37-43 HRC. This, coupled with its excellent polishing capabilities, makes it the go-to choice for molds requiring high-precision parts from materials like PC, PA+GF, and PC+GF.

Remember, this is just a starting point. Selecting the optimal steel grade requires careful consideration of factors like part complexity, plastic-type, production volume, and budget. Consulting with experienced mold makers and material suppliers is crucial to ensure you make the best choice for your specific project.

Lifespan: For pre-hardened materials the mold life is usually 100K-300K shots.
In particular:

• 278#; 718#; p20#: 100k-200K;
• NAK80; XPM: 200-300K

Watch these videos on how to test steel&#;s properties which may help you to select the types you require.

If you want to learn more, please visit our website Precision Mold Manufacturing And Molding Solutions.