If moldmaking and mold repair are indeed two separate entities the question becomes “What are the specific skill sets required for a mold repair technician?” Unfortunately the answer may be largely influenced by the specific repair environment. That is to say, if the in-house toolroom is fully equipped, the level of repairs may be quite a bit more complex than those performed in a bare-bones, band-aid shop.
If the molder has a specialty (i.e. automotive, medical, consumer products, etc.), the repair expectations may be entirely different and so too the attendant skills needed to accomplish them.
Repair Defined
One last major issue to wrestle with is the definition of repair. A repair can be anything from replacing a broken water line to troubleshooting an electrical problem to re-qualifying a damaged cavity.
All caveats considered, let’s agree to be specifically general (oxymoron intended): specific in regards to the distinction between building and repairing; and, general in regards to the variety of environments likely to require repair technicians.
hen speaking of skills almost by default, hard skills are the first to come to mind. These hard skills are those that overlap with mold building. In at least some measure, machining skills are required of a repair technician—at a very minimum, a fairly high degree of facility with the basic machine tools: lathe, mill and grinder. Even in environments with minimal repair expectations, replacing ejector pins, remaking damaged core pins and removing galled tooling are functions that require the use of manual machine tools. In the world of molds, the word welding is almost synonymous with repair. A technician with excellent welding skills is a rare find.
Other skills would include familiarity with measuring tools and practices, the understanding of mechanical functions—specifically the functions of mold actions, a basic comprehension of how molds operate and the need for draft and shrink. Math (trig) skills are high on the list and print reading/sketching skills are also very helpful.
A repair tech needs to be able to do the routine remove-and-replace repairs that entail swapping out worn or damaged components, yet some of the more valuable skills are on the soft end of the scale.
Ability to do root cause analysis—to provide best practices information for improvements in future builds.
Trouble-shooting skills—the systematic elimination of possible causes from simple and easy to complex and difficult.
Diagnostic skills—the ability to read the evidence on the mold surfaces; to judge the shutoffs, gas trails, resin build-up, PL hobs, gate strings etc.
Knowledge base—how plastic flows, conditions that cause flash, gating requirements, venting requirements, temperatures and pressures involved in the molding process and how these affect and are affected by mold design and condition .
These are the types of skills that are developed over time by individuals that are motivated by passion more than a paycheck. People whose normal practice is to analyze situations, compare results, build on experience and brainstorm innovative solutions. In the end, it’s solutions that matter, the requisite skills come full circle where the soft informs the hard and together they produce a repair that gets the mold back in the press doing what it was designed to do.
Mold repair skills, as in any trade or craft, require a certain amount of OJT (on-the-job training) to achieve proficiency. Some people need to work on a mold a dozen times or more to remember specific nuances about it, while another can pick it up after only two or three repetitions.
The speed at which employees can be trained is affected by the type of environment in which they work. “Reactive” maintenance cultures breed temporary, seat-of-the-pants repairs. Employees pick up bad habits and introduce unprofessional methods to new employees.
In “systematic” maintenance cultures, problems are addressed using root-cause analysis, and specific corrective actions are documented and followed. In such cultures, training is structured and much more effective.
Typical mold repairs involve a wide spectrum of tasks that can differ in complexity based on 10 mold characteristics:
Type of mold: Double-stack, rotary, two-shot, and in-mold labeling/decorating applications are examples of complex mold types that demand specific skills and plastics-processing knowledge.
Number of interrelated tooling stacks: Some molds have dimensional tolerances that are “stacked” or added together from a “0” corner to arrive at a specific position required for exact alignment. This also relates to tooling stacked vertically (A side to B side) to arrive at a specific preload necessary for clean parting-line shutoffs.
Tooling tolerances: The closer the tolerance (0.001 in. or less) for the tooling to mold a part within specification, the greater the degree of difficulty in all stages of repair. Fitting, handling, measuring, and even cleaning must be more precise to avoid causing flash or galling.
Number of pieces of tooling and plates: The more pieces of tooling and plates in a mold, the more time-consuming and complex the maintenance becomes and the more bench space required.
Size of mold: Molds weighing 6000 lb or less are normally manageable by one man on a bench. The larger the mold, the more hands and equipment are required to manipulate tooling and plates.
Type of material: Glass-filled resins and other abrasive materials can wreck havoc on gate inserts, valve pins, vents, and other close-fitting tooling components. Resins such as nylon and ABS require tight-fitting tooling while silicone molds need practically a press fit to keep from flashing.
Type of product: Where flash is hand-trimmed at the press, molds do not require the same degree of attention as a medical or pharmaceutical product with exacting dimensional and visual specifications.
Hot-runner molds: These are notorious for being difficult to work on due to thermal-expansion issues and required close fits of manifold tooling and stacks.
Age of mold: Multi-cavity molds designed and built 20 years ago or longer are usually piecemeal—that is, each piece of tooling is custom fit to a specific spot or tooling arrangement, making replacement or repair extremely difficult. Molds built in this era also relied mostly on nickel or chrome plating for corrosion resistance. The plating peeled like snakeskin if not cleaned often.
Mold design: Some companies attempt to cut mold expense up front by having molds designed and built with inferior steels and without interlocks, guided bushings, proper cooling, and venting—or simply by giving the job to the lowest bidder outside the U.S. They then count on the mold to run 24/7 with no issues and rely on maintenance to get the mold to a production-ready state.
Any of the above 10 characteristics can increase repair complexity, requiring extensive mold experience and excellent mechanical intuition, plastics knowledge, and physical coordination just to get through a repair. Performing these tasks safely and efficiently requires a better-than-average connection from the head to the hands.
Machining skills required?
Many companies assume (incorrectly) that only journeyman toolmakers qualify as skilled repair technicians. Such firms ask for extensive machining experience in assessing potential mold-repair technicians. I would agree that knowledge of toolmaking may be helpful in specific situations, but on a day-to-day basis, mold and part troubleshooting skills and craftsmanship are much more important.
Repairing plastic injection molds is a critical aspect of mold refurbishment. To ensure this process is carried out effectively, it’s imperative to embrace a structured sequence. This approach guarantees that each step is meticulously executed, minimizing errors and optimizing overall efficiency.
Keep a Structured Sequence
While the term “structured sequence” may not sound particularly thrilling, it’s the backbone of successful mold repair. Think of it as a meticulously planned roadmap that guides technicians through the intricacies of the repair process. Here’s why it holds immense value:
Reduces Mental Mistakes: Consistently following a structured sequence significantly diminishes the likelihood of costly errors during mold repair. When technicians adhere to a predefined order of operations, it becomes second nature, shielding them from potential blunders.
Improves Troubleshooting: A structured approach cultivates superior troubleshooting skills. Technicians can precisely identify issues and efficiently address them, thanks to the systematic method they employ.
Reduces Repair Time: Organizing the repair process enables optimal utilization of equipment and eliminates bottlenecks. This translates to swifter repairs, reducing downtime, and enhancing productivity.
Streamlines Training: For newly onboarded technicians, learning a structured repair process is considerably more straightforward. They can swiftly grasp the sequence of actions, facilitating efficient training and knowledge transfer.
The Military Approach
Did you know? The U.S. Navy employs a similar structured approach when it comes to maintaining jet engines. Before any engine disassembly takes place, a meticulous injection mold maintenance plan is crafted and discussed.
This meticulous planning ensures that work progresses seamlessly, even when multiple technicians collaborate, sharing equipment, tools, and workspace.
In essence, embracing a structured sequence is the cornerstone of effective mold repair. It minimizes errors, accelerates troubleshooting, and ultimately enhances the efficiency of the entire process.
Keeping injection molding dies in good shape is essential for making sure they work well and last long in manufacturing. There are several important factors to consider when fixing and updating these molds:
Material Selection: The choice of materials for dies and molds is paramount. It directly influences the performance, durability, and cost-effectiveness of these tools.
Catastrophic Failures: Addressing issues related to catastrophic failures is critical. These failures can result from design flaws, unforeseen events during operation, improper storage, or mishandling during transportation. Utilizing computer-based design and analysis tools can help prevent design-related failures.
Manufacturing Failures: Ensuring material conformity and paying attention to post-machining processes are essential in preventing manufacturing-related failures. Inadequate heat treatment and improper grinding processes can lead to significant problems.
Operational Failures: Operational failures are a primary concern and are often related to the specific applications of the dies, such as hot working, cold working, or plastic part manufacturing. Finite element modeling and analysis can assist in estimating wear and deformation in operational conditions.
Wear Phenomenon: Wear is a common issue in dies and molds. It occurs due to various factors, including complex geometries, material properties, heat treatment, surface quality, working conditions (pressure and temperature), and more.
Heat Checks: Heat checks are particularly prominent in hot working dies. They are caused by cyclic heating and cooling, leading to temperature gradients and thermal stresses. These checks manifest as small cracks with shallow depths on the die or mold surface.
Mechanical Fatigue: Mechanical fatigue often starts from surface defects such as inclusions, porosities, or oxide layers. These defects can initiate cracks and, when subjected to operational stresses, result in the eventual fracture of the die or mold.
Mold repair skills are very important for the mold industry，Even essential processes,In general, there are eight stages involved in mold fixing. Let’s take a closer look at each stage to grasp its significance:
PM Preparation
Proper preparation begins with providing technicians with a historical summary of past issues and corrective actions. This invaluable insight allows them to identify longstanding or unresolved problems that may require attention during mold fixing.
Mold Disassembly
Random disassembly should be strictly avoided. Instead, establish time-based disassembly levels based on factors like cycles, hours, days, or the number of parts produced. This approach optimizes bench time, reducing unnecessary handling of mold components.
Troubleshooting
Accurate and efficient troubleshooting hinges on a technician’s ability to correlate current and past defects with processing and production conditions. Issues should be methodically isolated, analyzed, and addressed one at a time.
Corrective Action
The effectiveness of corrective actions depends on various factors, including the shop’s culture, technician expertise, tool availability, and team skill level. Effectively addressing problems and finding viable solutions are intertwined processes.
Cleaning
Mold cleaning should be based on specific criteria such as cycles, hours, or production quantities, along with mold-specific factors like resin type, residue, vent location and capacity, and tooling considerations. The chosen cleaning level and method should align with these parameters.
Assembly
Precise assembly of mold and tooling components is a pivotal step. Rushing through this stage or neglecting attention to detail can lead to poor workmanship and costly errors. Effective communication, especially in multi-technician scenarios, is of utmost importance.
Final Check
Conducting a final check is an indispensable step before a mold is approved for production. This meticulous inspection helps identify and rectify any issues that might have been inadvertently overlooked, such as water leaks or heater problems. A thorough final check minimizes the chances of the mold encountering hiccups during production.
Staging
Following the completion of the repair process, the mold must be assigned a new status and placed strategically in one of three areas: storage, within the press, or as a backup mold in a molding-cell operation. Keeping tabs on the mold’s location is essential for maintaining operational efficiency.