By Zachi Fizik, ZF Consulting
I have been engaged in injection molds production since the early 1990s. Even though so much has changed (mostly improved), two things haven’t changed: tighter budgets and requests for shorter delivery mold production projects. Trying to compensate on delays in part development by pushing mold development time is, in my experience, the equivalent of trying to shorten a natural nine months of pregnancy. No matter how much empathy, commitment, funds, and experience are brought in, it “takes what it takes” to develop a mold ready for mass production.
In this two-part article series, I will discuss the mold production process. In this article, Part I, I will detail the phases and the milestones that are relevant and necessary for all mold production projects. In Part 2, I will describe how we should prepare for the first mold trial, called T0, and I will share recommendations for the process that will get us to the final trial: mold approval for mass production.
So: What are the four steps to a successful mold production process? You must gather your data for the mold maker, establish a statement of work with your mold maker, approve the design for manufacturing report, and approve the mold concept check.
Step 1: Gather Your Data For The Mold Maker
When you choose a vendor to build your molds and inject your parts, keep in mind the data that you issue and transfer to your vendor is the basis of interaction from the quotation phase until the final approval to start mass production. How you present your data to the vendor will influence the way they approach your project. The following data are not only the “face of the project” but also the cornerstones of success:
- The level of detail in your 3D data and drawings
- The accuracy in the material definition
- The clarity of quality control requirements
- The accuracy of production forecasts
- The identification of your deliverables
In my experience, a supplier that pays no attention to the quality of the data given by a client should be reconsidered regardless of how well the working relationship fits in your budget. Why is that so? Medical parts in particular usually undergo tests and verifications starting with the first test samples. It should be a common interest of all parties that these samples will be injected using the correct material, that there is sufficient amount of material to produce a predefined number of samples, that the mold is calibration ready, that sensitive areas in the part are predefined and supervised, that the mold maker knows what to measure and how for the first article inspection (FAI), that the parts are arriving in the required cleanliness level, and more.
We sometimes rush to start a project when our design is not yet finalized. It is within the “play rules” to ask for quotations before the parts design is frozen, as long as there is an understanding of what impact part design has on mold concept and hence also on cost and delivery. Once we submit the 3D CAD files to the vendor, they are used to design the mold using mold design software. That’s why we should take into account that sometimes changing the location of a rib or boss — even by a few tenths of a millimeter — or adding a radius on a part edge means revising and even restarting mold design.
Note that molds could be specified in different ways. Mold standards, steel definitions, gating systems, accessories, and clean room-ready specifications will define cost, delivery, life span, and warranty of a mold. These should be cleared and agreed upon at early stages of the Request for Quotation (RFQ) or the Statement of Work (SOW) and should be the basis of the mold order. The RFQ defines the what and the SOW defines the how of the project.
For example, if your project is composed of several parts, there is a stage in which the parts are assigned to molds. Once given the relevant data, and based on the expected quantities, material type, accuracy, etc., the mold maker can define the molds arrangement — which parts and how many cavities will be in each mold. My recommendation is to predefine that to the mold maker. For medical parts, we should consider mold validations, quantities needed for validations and verifications (V&V) or other regulatory testing and some parts are more critical than the others.
Step 2: Establish A Statement Of Work With Your Mold Maker
Mold development is an evolving event, so it’s important to establish predefined milestones.
When we provide the files to the vendor to start mold manufacturing, we define our end contract for injected parts supply, but we are about to go through essential stages on our way there. I like using the term “mold development” because it emphasizes the uniqueness of the mold-making process and remind me that molds are machines, custom-designed and built to produce a specific product, and as such cannot be considered as an off-the-shelf mean of production.
A custom tool for a specific part with specific characteristics has, by definition, many combinations as to how it will be specified, designed, built, and tested. This results in a procedure with predefined interactions between you and the mold maker, which should be strictly kept by both sides. As the mold development reaches predefined milestones, those milestones are also used to define operational and commercial phases of the contract. Let your vendor know when you wish to check and approve, or if you just want to stay informed.
At this stage, you now have an agreement that defines what parts are to be produced, by which molds, for what cost, and on what delivery schedule. But more importantly, it sets mutual expectations as to how we would mold development to take place. For example, if you need a certain quantity of samples for environmental, biocompatibility, or V&V tests, this is the time to set this up. If your material grades are special-order, this is the time to coordinate material orders. If you have special demands that influence the injection process and workspace, special packaging, secondary operations, or testing near the machine, this is the time to ensure your vendor knows what you expect.
Step 3: Approve The Design For Manufacturing Report
This stage of the project kickoff is a crucial one and should not be avoided even if time is scarce. In most cases, once the mold maker receives the final data, they will create a design for manufacturing (DFM) report for each mold and each part, and each one will need your approval. This report is the basis for the mold concept design and is usually composed of the following:
- The aforementioned data you’ve given them regarding the parts
- Details regarding the mold specifications
- A visual sketch of how the mold witness lines (parting lines, inserts, and slides footprints, etc.) will look like on the parts
- The gate type location and the expected vestige after removal (in some cases, this will involve mold flow analysis to define gate location and size)
- An ejection map and ejector projections regarding location and size
- Identification of locations and projections of sub-inserts and slides
- Details about engravings and writings on the part
- Wall thickness and draft analysis and, in case of design errors, requests and recommendations of part design modification
- Undercuts or any issues related to mold design and part moldability and a request to have the part modified.
In management terms, you should allow for a few rounds of communication and revision between you and the mold maker until all issues are resolved and agreed upon. Also, consider that you as the designer will need to modify part design to meet the mold and the injection requirements and that means time. Because of that, it is difficult to predetermine the duration of this stage, but it is essential to ensure that DFM is approved before moving forward.
After the DFM is approved, the mold maker will start mold design. Mold designers use standard mold bases and standard components, and they follow the concept approved in the DFM. They use specialized software for mold design and usually are very skilled. Nevertheless, during detailed design, they might encounter complications and might ask for some part design modifications. That would necessitate an update to the part’s file and drawing(s).
Step 4: Approve The Mold Concept
The level of the mold concept check depends on your company’s culture and ability of understanding this type of engineering. It can be divided into three levels:
- Checking the part forming: Parting lines, gating, and ejection, steel safe, sub inserts, etc.
- Checking the mold functions: Steel, components, ejection systems, cooling, gating system, moving elements, slides, etc.
- Checking the mold’s compatibility with the machine, safety requirements, serviceability, etc.
Once you approve the mold concept check, the mold maker will order mold bases and steel, will complete detailed mold design, and will prepare a detailed work plan to be the basis of the progress reports you will receive. Especially when working with Chinese mold makers, this is the time when the delivery time that was offered in the quotation will start the countdown to T0, the first mold trial.
To conclude, these four steps will build confidence between you and the vendor, whether it is the mold maker or the injection company that sources the mold for you. By appreciating the importance of the information you deliver to “downstream” vendors, including providing clear and accurate deliverables and setting expectations for the level of your involvement in mold development, you are setting up your project for success. You increase the chance of getting your first samples in the manner that will enable you to transform your medical part from development into mass production mold.
About The Author
Zachi Fizik specializes in all aspects of plastics engineering with particular expertise in injection molding tooling and supply chain strategy. He has more than three decades of experience supporting both startups and well-known brands in the medical, military, telecom, and consumer industries throughout the entire plastics lifecycle, from the early design phase through the engineering phases and into mass production. He holds a BSc. in mechanical engineering from the Technion Israel Institute of Technology. Recently, he served as consultant to several promising innovative Israeli medical startups whose novel devices reached regulatory approvals. You can reach him at firstname.lastname@example.org and connect with him on LinkedIn.