By Zachi Fizik, ZF Consulting
Throughout this series, I have focused on plastic parts used in your medical device and the associated mold production process. I began with the fundamentals needed to define and design a plastic part, then suggested a methodology of transferring this design into production, and then I guided you, step by step, through the procedure of starting a mold production. Two-Color Injection Mold
At this point of the process, we’ve released our designs to our vendor and molds build has started. The time we have now could vary from 3–4 weeks to 20 weeks or more, depending on the mold and part. During this time, there are two things we should do:
I’ll explain how I see the difference between T0 and T1.
The first stage before injection of the plastic that will form into parts is to see that the mold works. This is what I call T0. This is the first time the mold maker mounts the mold on the injection machine and sees that the moving elements move well, that the plastic melt flows well, that the cooling performs, and more. Just like every car manufacturer will have a “dry run” of the car before it is driven out of the assembly hanger, the mold maker should ensure this machine performs its basic functions before handing samples for examining.
If the mold performs well in T0, then this test can be called T1 because we have samples. However, T1 samples might not (or, in some predefined cases, should not) be within the final dimensions; the surface finish is not final; and we may have visual marks, flashes, and mismatches. That being said, the samples are a milestone with two main aspects: one is that the mold maker delivered a mold — a tool, a machine — that can produce the parts we had up until now only as a CAD file, 2D drawings, and models. The other is that the developer gets the queue to initiate the final stage of the product development, what we call the “T1 to T-final” (the well-known Tf) phase, which is the “money time” of our project.
To clarify, this stage is not a mold process validation (installation qualification, operational qualification, performance qualification). This is the stage in which we aim to achieve a verified, stable part that will qualify our definitions. Once we get that, we may initiate mold performance validation.
T1 samples are pre-matured for our keen quality control teams and the ones to handle them are the engineers and designers. Since injected plastic part quality and mechanical behavior depends on the material preparation and the injection parameters, I recommend that you answer the following questions prior to making any decision regarding the T1 samples:
Even though we are in the digital era, sometimes good old-fashioned clips and pictures of the workstation and injection machine, a mold injection cycle, part handling from the moment the mold opened and until it gets into packing, etc., are more illustrative than all the reports.
Also, remember that an injected plastic part could be an open book to professionals. Flow marks, weight, surface finish, gate appearance, deformations and flashes can all tell the story of the injected part. Include your vendor’s and your plastics expert’s reviews and recommendations in your gathered data. Some of these remarks may not influence part performance but could improve mold and part performance and reduce risk to mass production.
T1 samples usually look great when they are taken out of the delivery parcel, or if you view them near the injection machine, but the trouble starts emerging only after we dive into the details. We need to be sure that the samples are what we intended them to be. Here are some example scenarios:
The extent of testing and analysis done on the T1 samples depends on sample quality, project complexity, and timetable. In either case, you should issue a report to the mold maker with instructions. I tend to classify these remarks as follows:
Once you send your T1 remarks to the mold maker, we will be able to set up T2. We hope that this will be the last test, but it might not be because the part has still not reached its final dimensions and performance. Even if we have T2 samples, we can approve, they will not have the final surface finish, which will only be added after dimensions and performance are confirmed. Beware of that and plan accordingly. Texturing or polishing followed by injection trial can take as long as a week. Only after these samples are approved can we declare we have reached the destination of Tf.
To sum up, a proper basic Tf and mold certification should include the following:
Especially in cases where we have more than a few molds and parts, each with its own demands, this phase of mold production has a high potential of causing serious and expansive delays to the project. If you designed and planned well, if you choose your vendor well, and if your data and expectations were clear, you will save time. However, there are also factors that are beyond your control. This phase is where you need a combination of experience and agility. Assign a trusted point person on your team to this phase, and do not hesitate on using several “navigation systems” consultants.
This article concludes a series of articles that encompass the path of an injected plastic part for your medical device from design to manufacturing. The path is based on the following principles:
There is no one way of doing things, but this one methodology will increase your chances to reach success.
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 zachi.fizik@zf-consulting.com and connect with him on LinkedIn.
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