In today’s world of injection-molded products the decisions regarding mold design and structure are typically determined by the initial cost and delivery. This manner of mold acquisition can put the molded product in a situation of not being at its long-term advantage to the company producing the first generation of components, and not contributing in a proportional way to the bottom line profits of molds even with short runs.
When a new model of the same basic part is produced, plastic manufacturer often modify the existing tooling under the assumption that this will make production so profitable that competitors will not receive the new contract. In reality the company that has molds that are designed for long-term part production, at the best ROI compared to manufacturing runs, can have an advantage in bids, especially if those same procedures are reflective of the overall corporate vision.
Factors to Consider When Choosing an System
Here are some things to think about for both short-run and long-run injection molded plastic parts.
When evaluating the gating system to be used in a plastic mold, all of the elements of an economically-sound mold operation should be considered the initial mold cost, mold trial cost and setup time, cycle time as well as scrap, maintenance, secondary operations as well as auxiliary equipment and quality.
In the process of making a cold bushing, single-cavity mold with edge-gating of the piece, an additional dimension is needed to accommodate the runner as well as distance of the cavities from bushing sprue. A well-designed system will offer the runner with a low profile to transfer the resin to the offset needed for edge-gating, without a significant growth in mold size.
Reduced Mold Size Offsets Hot Runner Costs
The smaller mold size often offsets the hot runner’s initial cost and may allow the making use of a larger press that is compatible with the parts requirements. With a valve gate to the line of separation, less resin is required per shot, which saves energy and decreases scrap (sprues) or the percentage of regrind used.
The economies of using a hot runner in order to replace offsets from molds are so that it is recommended for all components above 50g, with an anticipated production time of 150,000 parts. The bigger the component and the more expensive the overall amount of components could have to do with the costly mold base required by the cold runner, but with very low rises in cost of a hot runner.
The advantages of using a sprue Bushing
Utilizing sprue sprue bushing to direct gate into a single-cavity mold has several advantages for the design and use of the mold over the cold runner kind. The size of the mold’s base is only dependent on the specifications of the component and will be used with the smallest press needed.
If you use a cold sprue bushing, a sprue is created that must be removed, leaving a mark. This is often removed using additional operations if the appearance or maximum height of the remaining sprue are considered to be part of the issue. To prevent this issue, a hot sprue bushing is utilized, which usually leaves an unacceptable mark, decreases the operating window, and increases the degree of internal stress (warpage).
A valve gate system won’t make a sprue but eliminate undesirable marks and maintain a good operating window and provide a part with the least possible strain. A majority of valve gate systems need a larger mold–both in the mold base footprint and height–since they require an insulated manifold that can move the valve gate’s operating system from mold centerline, and also install a manifold as well as the operating mechanism inside the mold. More efficient systems can do this without increasing the mold footprint base, and often without an increase in mold height since the gate sits on the mold’s centerline and does not use an operating mechanism that is external to the mold.
Cold Runner System Identifies Larger Mold Sizes
When designing injection molding PLA molds for multicavity layouts using cold-runner systems, the size of the mold often is increased to accommodate the runner, slides and mechanisms–and the cavity is more difficult to position for intricate parts. The operating window of the molding process becomes very restricted and warpage control is dependent on modification to the part or long processes.
Three-plate molds are frequently utilized to allow more cavitation levels along with better cavity layout and automatic mold operation. Utilizing a hot-runner system with direct thermal gating in place of traditional mold constructions can allow the use of the multicavity mold in an efficient manner. It has the lowest surface for the parting line per part, lower mold height, higher cycle speed, minimal scrap, and the most efficient automated function.
Utilizing a traditional valve gated hot runner will provide additional advantages in terms of cycle times, less strain on the parts and more durable components. But, the latest valve gated hot-runners which do not cause a rise in mold height and are more affordable can help alleviate the initial costs and mold height increases of valve gated hot runners that reduce economical effectiveness.
To ensure better timings for delivery of mold, the hot runner order may be for the entire “A” half, minus cavities. This can spread the burden to a larger facilities base, which can reduce the amount of time spent on mold construction.
Hot Runner System reduces costs time, effort and waste
When the summaries above are used to purchase molds, it is evident that a hot runner system will significantly cut down costs for initial construction, time, and operating expenses of testing, setting up cycles scrap, maintenance and secondary operations. With an effective valve gate system, no additional equipment is necessary. The hot runner provides the consistent quality demanded by most applications.
Mold designs using hot runner thermal gated systems as well as valve gates are typically designed to offer the highest quality performance in molding. They will produce very constant shot-to-shot consistency, quicker cycles, better automated mold operation, and higher quality of the part.
A well-designed hot runner valve gates can typically outperform other systems–both thermal and valve gate-related. This type of system requires less mold height, uses less power, and does not require other power or control systems. In the end, a hot runner system will provide overall advantages that should be considered in almost every injection mold acquisition.
Valve gate installations must be made to the specs issued by their manufacturer to gain the benefits required to ensure the competitiveness of injection-molded parts in today’s marketplace. The advantages of valve gates over the thermal gate systems are due to the very straightforward, sturdy construction of all components, which is derived from the basic concept with the least amount of parts to provide the best gate flow/control situation.
The main point is that molders who desire and require top-quality employees to maintain their molds must offer higher wages than average while ensuring a clear path to growth and an ownership stake in the process. So, how do employers keep their enthusiasm alive?
Creating the Job Description
Before any training can be conducted, the recruiter needs to develop a realistic job description. This is not just about having an knowledge of the typical maintenance and repair technician’s work however, it also needs to be aware of the diverse individuals, the company’s culture, and expectations of management. After conducting many mold inspections and audits on a variety of plastics manufacturers I am able to declare that the task of mold maintenance and repair isn’t completely understood by the people who write the descriptions.
The majority of mold repair specialists are employed with job descriptions that are vastly different from one another, even though the job is essentially identical from company to company. This is primarily due to the different perceptions of the skills required from different organizations and departments. This includes the ones directly affected by poor-performing molds or high maintenance costs, as well as those working in production, processing or on manufacturing side of business, as well as those which offer moldmaking and molding. For the latter group, repair techs are often trained in toolmaking, allowing them to make the most of the number of employees. There is a belief that toolmakers produce better repair technicians, but I don’t think this is always true when it comes to repair of mold.
According to our research, most bonified mold builders are not interested in mold repair. The majority of them are not equipped to clean and repair molds. They are able to construct tools and components with tools for metalworking. Repair technicians typically work at a bench , using hand tools and working their way through the eight stages of repair, relying on their knowledge of the function of mold. This includes preventive maintenance preparation and disassembly. They also troubleshoot corrective action, clean assembly, final inspection and staging. This is important to note because the initial stages of repair technician training do not include learning how to operate the metalworking machine or programming the path of a CNC cutter or establishing a complex setup at a grinder.
To ensure that they provide the best maintenance and repair training, they need to understand the job of mold maintenance, as it applies to the types of molds and products the company produces, and they should have actual mold performance and shop efficiency measures to evaluate the performance of repair technicians.
Being able to monitor and quantify particular parameters and then compare them to shop averages is extremely valuable, for example, number and type of molds that are repaired and issues fixed, molds with immediate issues after start-up, tooling and labor costs, etc. Here are a few mold repair job descriptions as well as measures to help you get started:
Mold Maintenance “C” (Apprentice level ) typically offers three pay increases.)
Has a good mechanical ability and hands-on hand tools expertise.
is able to assist in the safe removal of components, disassembly, and cleaning troubleshooting of molds and components in a methodical manner and is equipped with the fundamental equipment, physical abilities and determination to follow specificprocedures and methods during the work. It is expected to manage simple in-press cleanings and the lubrication of molds.
Understands the importance of accurate documents that are legible and follow prescribed methods/procedures during work.
Recognizes and enjoys the challenges of this trade, works well with others and displays the desire to study the function of mold and the motivation to grow.
Maintenance of Mold “B” (Intermediate stage and offers three pay increases.)
At this point the manager must use maintenance metrics as an accurate measure of their skills. For example, a reasonable price of total repair efficiency (CORE) and the results of overall repair proficiency (RORP) maintenance scores can be calculated by comparing shop averages.
Have the necessary mold function and maintenance knowledge and hand skills to safely efficiently and effectively disassemble clean, troubleshoot, and assemble 40 to 75 percent of an organization’s active molds, with an efficiency rating of 75.
It demonstrates safe and reliable mechanical reasoning, desires to improve troubleshooting skills minimize mold and part imperfections and improve root cause discoveries and is knowledgeable about the role of mold in cold runners.
Make use of precision tools to measure and calculate basic (static) stack-ups of tooling to determine preloads for components and clearances, or to confirm print dimensions.
is familiar with the hotrunner function and performs related maintenance and troubleshooting techniques. For instance, this person is familiar with the removal of probes, cleaning as well as reworking, as well as basic troubleshooting of probes as well as thermocouples, heaters cables, and manifolds.
Shows the ability to safely and efficiently through the eight steps of repair.
Provides concise, clear data into the documentation system and mold maintenance manuals. Contributes to and makes use of a mold knowledge base.
Proficiently uses and cares for hand tools, performs work in a systematic manner utilizes organization skills and contributes to the cleanliness of shops.
Basic skills in operating machine shop equipment like the surface grinder, lathe and drill press to carry out intermediate-level repairs like drilling, reaming , tapping and drilling holes, threading operations and dusting vents.
Maintenance of Mold “A” (Advanced Level ) provides three pay increases.)
An annual review of performance metrics is necessary to keep in mind how to judge maintenance and mold proficiency ratings. A high CORP and RORP rating could be using shop averages.
Has the knowledge, skills and tools to efficiently and effectively disassemble, clean, polish, troubleshoot/repair and assemble between 75 and 100 percent of a company’s active molds.
Performs sophisticated part repair (like welding or fitting, stoning or polishing) for issues such as scratches, scuffs and dents, rework of worn or damaged plates or tools; and fabrication of simple tools, fixtures, and jigs.
The company’s molds start and run productively without repeated pulls for defective or improperly installed tooling components or repeated mold/part imperfections.
Completely dimensional mold tooling stack-out (static and dynamic) to determine tooling component preloads, clearances and fits, using any/all available prints.
Determines “best” procedures to establish possible causes for mold or part defects. corrects and prevents certain actions by shop employees and has a thorough understanding of how molds function.
Clean and repair hot runner molds, including various issues.
Performs work in a consistent, professional manner with little or no supervision.
The mentor instructs the apprentices on proper mold-care techniques and methods.
Has a basic understanding of manufacturing requirements for molds such as proper venting, cooling, and polishing, as well as the setting up of nozzles, sprues, gates and runners.
Knows the critical mold function, plating applications and requirements for hardness of steel.
Continuously strives to enhance understanding through continuous studies, conferences, seminars or other exhibitions focusing on the development molds, constructing and maintaining them.
Metrics allow managers to make technicians accountable for the work that technicians perform. For example, instead of using a vague phrase such as “you need to work smarter or more efficiently,” it’s better to use data to create tangible, achievable shop standards for satisfactory, above average or outstanding work performance.