Developing & Validating A Molding Cell For Medical Products
Today's injection mold manufacturers are much more than 'just mold makers.' As medical OEMs become more and more dependent upon their supply chain to go the extra mile in engineering and developing new products and the molds that produce these devices and disposables, mold manufacturers must increase their capabilities and services to meet these expectations.
It was only a couple of decades ago that mold makers would to take a part print, design and build the mold, provide a quick tryout - usually at a local molding company - to prove the dimensional specifications of the mold's cavities to make conforming parts, then ship the mold to the customer all within a 12 to 16-week timeframe. Today, while mold manufacturers have been able to reduce the mold design and build time thanks to cutting edge software and advanced, high-speed machine tool technology, mold manufacturers are now receiving requests for services from their Medical OEM customers that go far beyond just building the mold. Those services often begin with dimensional shrinkage analysis, cooling and warp analysis, and studies on the melt flow balance, just to mention a few. And in some cases medical OEMs require the mold manufacturer to build the entire molding manufacturing cell, which means that designing and building the mold, in some cases, is the easy part.
So what does it take in terms of time, resources and expertise to develop and validate a mold or a molding manufacturing cell?
Evaluation of the Part and Customer Requirements:
First, the engineering process begins with evaluating the 3D solid model of the part. The customer requirements for that part are also evaluated: How many parts will the mold be expected to produce per hour, or per year or over the life of the program? What is the material? What is the cycle expectation or goal for the parts? The answers to these questions and others help guide the mold manufacturer in understanding the customer's needs with respect to the type of mold and auxiliary equipment that may be needed for the manufacturing cell.
Next, an extensive review of the part design details is performed by the engineering team, generally in collaboration with the customer's engineering team. This is to identify any design challenges that might interfere with the molding process or slow the cycle time, or increase costs-to-manufacture, at a critical juncture of the project: up front at the earliest stage of the development cycle. Part design and the material requirements both have a big impact on the mold design and ultimately on the requirements of the mold and of molding cell. Catching these challenging issues early in the project's timeline mean fewer changes, or surprises downstream after the mold build has started or has been completed, which could add both time and cost to the mold build. However, OEMs need to keep in mind that not all challenges can be anticipated, which means that some flexibility must be permitted throughout the process.
In parallel with this, the automation supplier needs to be brought into the picture so that as the mold is designed, the automation tooling and systems can be designed in tandem. Additionally, if a new molding machine is being brought in for the project, collaboration with the molding machine supplier will also be required.
Design for Manufacturability (DFM):
Critical to the entire process and to achieving the goals of the customer during the evaluation phase is determining design for manufacturability (DFM). DFM is a proactive approach that has become key to developing products in today's collaborative manufacturing environment. Taking into account DFM, a mold and molding process can be developed that provides optimum cycle times, quality parts with exacting dimensional specifications and that achieve the cost goals of the customer.
Part of this process may involve doing a material flow analysis to determine the optimum gate location and identify any hot or cold spots that might be inherent in the part that can be addressed by the mold design and cooling conditions that need to be considered in the mold.
The Benefits of Bridge Tooling (Prototype Molds):
Many companies go from 3D solid model design to a production mold choosing to bypass the intermediary step of building a 'bridge' or prototype mold. A bridge mold - also called a pre-production mold - can serve several functions and has a number of benefits.
A bridge tool can provide customers with a one or two-cavity mold in which to test out the part design under real-time molding conditions with the actual raw material for the part. While a bridge or pre-production mold might add a few weeks to the total lead time at the front end of the project. However, it might also save the OEM several weeks at the back end.
A bridge tool can show you where might have missed a design issue in the part that prevents optimum cycle time or a manufacturability issue. Using the bridge tool, the mold maker can identify any challenges that might have gone un-noticed in the 3D solid model. Those challenges and issues can then be noted and changes made to the 3D solid model so that when the multi-cavity production mold is designed, these can be corrected.
Additionally, developmental tooling can give customers the ideal template for the production tooling and shorten the time it takes to get the production in service. It also allows the customer to use the parts from the bridge tool for automation debugging and to supply production requirements until the production mold has been completed and put into service.
Developing a Molding/Manufacturing Cell:
Once the mold is complete, and is usually in a steel safe condition, the mold is ready to be qualified and the process validated. Mold qualification, validation of the parts and the molding process often takes several weeks depending on the level of validation required. Even simple mold tryouts require hanging the mold, connecting the water lines, other electrical equipment for hot runner systems, etc., to a press that is already connected and ready to run.
There are three levels of validation that can be provided:
"Free and Easy" sampling, which is one in which the mold is hung in the molding press, started up and allowed to run in a "free and easy" manner for a specified number of shots so the customer can determine that the mold is making parts to spec.
Factory Acceptance Testing (FAT) is done in collaboration with the customer who attends the mold tryout to observe and participate in the molding process to ensure that it is comparable to how the mold will run at the customer's facility or the customer's molder's facility. If the mold passes the FAT, the customer accepts the mold and the mold is then readied for shipment.
Validation is an extensive series of tests in which both the mold is qualified dimensionally for the parts from each cavity, and the molding process is established and validated. In most cases the customer will ship in a molding press if the mold is to run in a new press, and both mold and press will be shipped to the customer's molding facility or the customer's chosen molder's plant. This is an extensive process that requires preparing the press for set-up, connecting the electricity, air and water lines. Next the press is started, the hoses and connections checked. The press manufacturer comes in to set up the press, calibrate it and certify it, perform the press leveling verification, and certify the gauges. Typically, the customer's engineering team will be on-hand for the validation process, working collaboratively with the mold manufacturer. For medical components - even medical disposable products - the mold and the press are validated as a unit and remain together throughout the life of the product. Some steps in this process include:
Cooling analysis, which involves flow studies on the different zones to ensure consistent cooling across all zones.
Viscosity curve to evaluate the resin's sweet spot at optimum molding conditions.
Balance study to ensure that there is no over-packing or under-packing cavities - basically a scientific molding test.
Scatter Design of Experiment (DOE) to zero in on acceptable DOE.
Run the mold under the optimum processing conditions uninterrupted for a customer-specified length of time. If the mold is interrupted for any reason, the process is repeated.
Shots from the run are collected, bagged separately according to cavitation, sequentially throughout the run, and documented.
Molding/Manufacturing Cell Validation involves all of the Validation set-up processes and the steps outlined above, but with the addition of any robotics, conveyors, vision systems label magazines (for in-mold labeling cells), and other automation equipment required.
Automation installers must be scheduled to be on-site to get all of the components of the automation working in sync with the molding operation. This is a full set-up because while the cell will be broken down into its various parts and moved after the validation process, it must be fully set up as if it were a permanent molding cell.
Customers come in and work with the engineering team and the molding processing technicians, the automation installers and set-up people, and a mold technician to validate the entire system.
All secondary operations must be addressed both in-line and off-line.
The mold maintenance manuals, mold diagrams, automation diagrams and complete cell diagrams must be put together for the customer, and shipped with the system.
Lastly, the molding press and mold must be prepared for shipment. The molding cell must be completely dismantled and readied for shipment.
These various levels of qualification and validation can take from one day to do a simple "Free and Easy" mold sampling to one week for a FAT. When it comes to a complete mold/molding process validation, it varies depending on the customer's requirements. For the validation of a complete molding manufacturing cell including automation, it can take from a month to six weeks or more, again depending on the customer's requirements and the degree of complexity of the molding cell.
Costs for these various levels of qualification and validation can vary widely, but are typically quoted up front with the mold quotation. However, medical device OEMs should keep in mind that because of the regulatory climate under which device makers and their suppliers work, there are instances in which the cost of the mold/molding cell validation can be equal to or in excess of the cost of the mold.
Validating molds in molding manufacturing cells is far more complex and costly than just doing the simple mold tryout to confirm part dimensions that mold manufacturers were required to do a decade or more ago. It takes planning and resources - both financial and human - to be a mold manufacturer in today's fast-paced environment.
Yet, there are several benefits to working with a mold manufacturer that can provide these services. An off-site dedicated mold qualification and molding cell validation facility means that these necessary activities can be done without interruption to the OEM's or the molder's production schedule. It also means that the mold/molding cell can be moved into the OEM's or the molder's facility with a "Plug-and-Play" startup.
OEMs want to get their products to market faster, reduce their costs to manufacture and improve quality, efficiency and productivity. All of that can be achieved through developing a mold/molding manufacturing cell. Allowing the mold manufacture to develop the cell from pre-production mold to finished process validation in a designated setting specifically for manufacturing cell development saves the OEM customer time and allows their production floor to focus on current production without the interruptions that come with validating a new mold/molding process in a complete manufacturing cell.
About Tech Mold: Tech Mold recently celebrated 40 years in business at its Tempe, Arizona, location. In addition to its main mold design and manufacturing facility, the company operates Tech Mold R&D, a mold engineering division which specializes in prototype molds and pre-production molds, and where collaborative mold development takes place prior to the production mold build.
Tech Mold East is a separate, 10,000-square-foot facility configured specifically for mold qualification and molding/manufacturing cell validations. With the addition of two new presses installed in the summer of 2013, Tech Mold East now has a total of seven presses in house with tonnage ranging from 40 to 440 tons to accommodate a wide range of customer molds for full mold testing and process validation. Tech Mold East also offers a secure facility for intellectual property protection and private offices for customers' engineering staff.
For more information visit www.techmold.com
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