Scientific molding is a process whereby the fill, pack and hold stages are treated separately to minimize fluctuations while improving overall product consistency. Separating the stages is also known as decoupled injection molding. Molders who utilize scientific injection molding equipment, software, and practices can, according to scientific molding educator John Bozzelli, “reduce cycle times, increase machine efficiency, and ultimately make more money.”
In the traditional method of injection molding, the mold is filled with a single shot under a constant pressure to pack the cavity. In scientific molding, the cavity is filled to around 90-97-percent at a certain velocity. In the next phase, the machine switches from speed control to pressure control, where the cavity is filled or “packed out” to complete the process. 
The scientific method allows for greater shot-to-shot consistency and improved control over the specifications of the part. Conversely, large variations in part dimensions are often the case cycle-to-cycle with the traditional method of injection molding.
A scientific injection molding approach is most essential in the production of complex parts and components where even the smallest variation in molding variables can have a remarkable impact on the process or finished product. That said, the goal of scientific injection molding incorporates two key strategies:
Another aspect of the traditional molding process has to do with machine-based control. It was believed there were 20 or more machine-based settings that could affect various problems with the molded product (dimensions, voids, warp, and other quality issues). The research sought to find parallels between problems with the parts with the settings of the machine.
Over the course of many years, when it was found machine settings had little or no correlation to part quality, research shifted from the traditional, machine-control method to a science-based approach. The “plastics point of view” became the revolutionary angle of modern research based on the laws of science instead of the settings of injection machines. Donald C. Paulson pioneered this scientific approach, having developed a plastics research laboratory at General Motors Institute in the mid-to-late 1960s.
It’s not hard to imagine a world without scientific molding principles: product variations caused by wide fluctuations in temperature, pressure and viscosity, increased cycle times, decreased machine efficiency, higher costs, more rejects, and lower quality parts for customers.
As stated in our post on the advantages of scientific molding, “Scientific molding practices are essential to achieving outcomes that deliver faster cycles, higher volume, and a more efficient injection molding process.” In addition, “quality control issues can be avoided by having automated containment control and traceability for specific applications.”
The technology behind scientific molding affords manufacturers the ability to operate more efficiently while creating the opportunity for a global competitive advantage. It also provides OEMs and customers higher-quality parts and fewer rejects at lower costs.“Scientific molding practices are essential to achieving outcomes that deliver faster cycles, higher volume, and a more efficient injection molding process.”
The principles and technologies involved with scientific molding solve the problem of how to get injection molding machines to make good parts each and every time.
The advantages of scientific molding would simply not be realized without the technological advances in the injection molding industry. Scientific molding, as governed by the laws of physics, is dependent upon technology-based innovations in engineering, equipment, and software. From machine setup to quality control and everything in between, technology plays a vital role in the injection molding process's overall success.
RJG Inc. is a training, consulting, and technology company specializing in the injection molding industry. A recognized pioneer and worldwide leader in scientific molding, RJG offers courses in decoupled molding, high-performance molding, and Master Molder 1 & II certification training, to name a few.
In addition to their training and consulting work, RJG produces the eDart process control system technology for injection molding manufacturers. This system helps molders monitor critical information while reducing scrap, stabilizing the process, and creating repeatable, high-quality outputs.
Rosti targets very high press utilization rates. High utilization requires flexibility from an agile fleet of presses and a solid foundation in scientific molding. The RJG eDart system brings additional control and flexibility to map and control highly-tuned processes with in-mold pressure sensors.
In 2009, Rosti introduced the RJG eDart system to two of our presses. As Rosti continued to convert presses with eDart systems and molds with pressure sensors, we quickly reached a critical mass where a plant-wide conversion became inevitable. Closed-loop process control was now ingrained into our operating culture. In 2010, we embarked on a two-year plan to incorporate the process control technology on all presses. The eDart system with in-mold pressure sensors has helped Rosti reach a critical mass of technology to enhance our decoupled molding operation.
As we discussed here, “Implementing the RJG eDart system has led to transformational change in managing part consistency across different material lots with reduced scrap and processing time.” eDart helps produce remarkably consistent products every time by monitoring and controlling in-mold plastic pressure variations.
Finally, some of the advantages of scientific molding with the RJG eDart system include:
The role of technology with mold flow simulation software and process control systems help enable automation for the scientific molding operation. We’ll discuss automation support in more detail next.
We’ve talked about the science of molding in terms of the laws of physics, steps in the process and the role technology plays in the areas of design, engineering, and process control. But scientific molding doesn’t end there. Not by a long shot. It also involves and benefits from automation and a highly-skilled workforce.
In this section, we’ll discuss the impact of automation on scientific molding and in the next, the importance of specialty-trained engineers and technicians.
The invention and deployment of automated tools and robotics have positively impacted virtually every industry. And the injection molding industry is no different. Make no mistake, the degree to which a plastic injection molder can automate its operations, the greater it will be able to grow its business and gain a globally competitive advantage.
The ultimate mark of a scientific molding operation is a fully-automatic production facility, like the one Rosti pioneered beginning in 2011 at its Bunsen Drive facility. A fully-automatic facility is at times, also called a “lights out” facility. The manufacturing process at Rosti's Bunsen Drive facility is so unique that the company was awarded U.S. Patent No. 8,827,674 B1 for the process: A specialized injection molding factory system and associated facility comprising machines on the first floor with the resin supply placed on a mezzanine level.
Four years ago, we published how a lights-out manufacturing facility has transformed injection molding. In it we described the lights-out process as follows:
“Lights-out manufacturing describes the process in which factories and production facilities are equipped with innovative and automated machinery to conduct tasks that would normally need a human [to be] present. Essentially, the production facility can run “lights-out” – or without substantial assistance from human labor, lights, heat, and other costly factors for a business. Lights-out manufacturing processes also allow companies to keep facilities running 24 hours a day, 7 days a week without the need of multiple workforce shifts.”
In this article, we also noted that “Not only has it allowed businesses to improve in the areas of cost and turn-around time, it has also allowed plastic part producers to lower the likelihood of defects and increase the overall quality of products created.” We noted a number of ways in which a lights-out facility has transformed injection molding, namely:
Yes, scientific molding includes the technologies of mold fill simulation software, RJG eDart process control, state-of-the-art material handling systems, part conveyance systems, robotics, and a fully-automated, lights-out facility.
Lights-out manufacturing describes the process in which factories and production facilities are equipped with innovative and automated machinery to conduct tasks that would normally need a human [to be] present.
Even so, these ever-evolving technologies and lights-out methodology do not allow a business to run completely hands-free. In fact, without knowledgeable and highly-trained personnel, all of this simply wouldn’t be possible.
Rosti’s mix of experienced veterans and highly motivated young professionals are vital to its automation-focused and growth-oriented global business model. Up next, we’ll delve into the important role specialty-trained engineers and technicians play in scientific molding.
One doesn’t need to know the laws of physics or the inner workings of software and machine technology to appreciate how scientific molding has drastically improved today’s injection molding process. You do, however, need specially trained engineers and technicians to properly operate science-based injection molding systems.
Specialized Training in Injection Molding at Rosti
Rosti hires and develops engineers and technicians following a three-prong approach:
Design for manufacturing is a top consideration for reducing costs in scientific molding. The first company to commercialize design for manufacture and assembly (DFMA), Boothroyd Dewhurst, Inc., found that 80% of the cost of a new product is directly related to design.
According to John Gilligan, President of Boothroyd Dewhurst, Inc., “The use of DFMA to help choose the right structures, materials, processes, and labor has become critical given that companies get few second chances in today’s global markets.”
Therefore, the best time for a tool-maker / injection molder to get involved in the design process is early in the development cycle. Doing so will help to best understand customer objectives and avoid unexpected surprises.
In Rosti’s comprehensive guide to design for manufacturing in plastic injection molding, we’ve laid out a four-part approach to design optimization. They are as follows:
Design for Manufacturing (DFM) describes the process of designing or engineering a product to reduce its manufacturing costs, allowing potential problems to be fixed in the design phase, which is the least expensive place to address them.
Throughout the plastic part design process, it is imperative to keep focus on the functional requirements of the part. Experienced design engineers should make recommendations about modifications that will help ensure the part meets its functional requirements including what elements the part will be exposed to, chemical or corrosive materials the part will need to withstand, functional cosmetic attributes, and more.
Design for assembly (DFA) is a process by which products are designed with ease of assembly in mind with the ultimate goal of reducing assembly time and costs. The reduction of the number of parts in an assembly is usually where the major cost benefits of DFA occurs.
Design for sustainability focuses on designing parts with print measurement intent in mind - sustaining tolerances with proper measurement on an ongoing basis.
According to Kip Doyle, author of an article on the Top 10 Reasons Why Molders Fail at Scientific Molding, many molders can’t get past a “machine-focused” approach and mold from the plastic’s “point of view.” He cites that many articles have been written on the four primary plastic variables (plastic temperature, plastic flow, plastic pressure, and plastic cooling rate and time), and a scientific molder must understand this approach and the process optimized from the perspective of the plastic.
Aligning with your injection molding partner to choose the best resin early in the design for manufacturability process, is crucial to a part’s production success. A good place to start is to have a general understanding of the two main types of resins – amorphous and semi-crystalline.
Polymers are made up of structures that are defined in terms of crystallinity – or how the molecules of the polymer are packed together.
Crystalline structures are, in most cases, very ordered, which gives the material strength and rigidity. Amorphous polymers are the opposite. Sometimes the distinction between the two is not clear cut. With most polymers, there is a mix of both crystalline and amorphous structures. How the polymer is processed determines the exact proportion of each.
In our post on Preparing for Injection Molding Resin Selection, we break down the differences in polymers further.
When considering the intended end use for your injection molded part, understanding these key characteristics is essential to selecting the best resin.
A part’s overall appearance and geometry have a significant impact on the molding capability and the type of resin that should be used. Part design, including size, shape, and wall thickness, can make a part prone to defects, while features like snaps, undercuts, bosses, ribs, and more can complicate the molding process.
It’s critical that injection molders use the latest technology to run simulations to optimize mold design specifications and resin choice before a project is finalized for production - this is where SolidWorks Premium plastics flow simulation provides predictive insight in the early stages.
Material selection also plays a critical role in the strength and flexibility of your molded part. Addressing specific needs early in the design process can help you avoid costly changes later. Balancing characteristics like stiffness, durability, toughness, and others are key in achieving optimal part functionality.
When material performance cannot be achieved with available resins, custom blends of materials can be created to boost the properties of multiple resins. Reinforcing materials with additives can build strength into parts and add stiffness that may reduce warping and shrink. Additives like glass or carbon fibers can be used to enhance part performance and improve flow, ejection, and dispersion.
We mentioned the important role of design in the injection molding process, and this is of particular concern when high-temperature materials are used to heighten a part’s strength, stability, and other features that are imperative to its unique application. Conventional molding techniques are not always effective with high-temperature and exotic resins.
Some characteristics of high heat and exotic resins are unique and may perform differently from one application to another. To realize both the design and material’s fullest benefits, experienced design engineers and injection molders have a number of factors to consider. In this post, outlined are a few basic and advanced tips that should be taken into account when designing parts for injection molding with the use of high-heat or exotic resins.
Learn more about Rosti’s Design Tips for Injection Molding with High Heat or Exotic Resins
Plastic residence time is the time that plastic or resin is subjected to heat during fabrication.
Taking the time to calculate the specific plastic residence time for the relevant manufacturing process will improve your material performance and the overall final product.
Understanding the residence time of material in the first stage of the screw can help you understand the optimal time and temperature for your manufacturing needs.
What Does Plastic Residence Time Affect?
If plastic residence time is too long, it can affect part quality in several different ways:
However, it can also impact machine performance, resulting in inconsistency in the melt quality and shot weight, as well as the melt temperature.
No matter how many shared formulas or calculations, plastic residence time should be calculated by each individual manufacturer in order to determine the ratio that works for their particular product.
Using scientific molding practices, Rosti uses recorded data to assess quality control and make any needed tweaks to tooling, thus improving overall part quality and avoiding the negative effects of poorly calculated plastic residence time.
Learn more about the importance of calculating plastic residence time here.
Plastic variables require understanding the nature of the material to be molded and its preferred molding conditions. When a material’s key characteristics, behavior, and response to processing is understood, scientific molders can optimize the molding process to produce the most consistent part possible.
The creation of tools for prototype and production components represents one of the most time-consuming and costly phases in the development of new products. To reduce the manufacturing lead-times and cost, prototyping and manufacturing processes have been rapidly developed through the evolution of scientific molding practices.
Scientific molding involves using data to develop a process that produces repeatable results with little to no variation. Through resin expertise and testing, dimensional and mechanical characteristics of a molded part can be optimized. Often achieved through the use of mold fill simulation and process control systems, predictive insight, process validation and complete process documentation are vital to producing demanding parts.
Design engineers should lean on past learnings and expertise in optimizing part design for unique applications. Scientific molding elements associated with part design may incorporate using the latest software and technology, including computer-aided engineering, mold flow, and prototype development that will validate the part’s end-use.
Design considerations may include:
Injection molders should understand how to avoid designing a part, building the tooling, and beginning the molding process only to find out that the design does not work in production. Prototype tooling is an excellent method to validate and optimize critical mold and scientific molding variables.
Scientific molding practices can also be used to optimize tool design or to optimize poorly designed tools. It is essential for injection molds to be evaluated for their performance in the production of consistent, defect-free parts. Engineers should examine every aspect of a mold’s mechanical functionality using the appropriate material settings.
Testing can then be applied to check for any imbalances among cavities. When this analysis is complete, a gate seal study can be performed to gather data on where the gates seal fully at what points in the mold cavities. Recording findings and making recommendations for adjustments in the process or tooling are essential to correcting potential defects.
Recorded data can be used to assess quality control and make any necessary tweaks to tooling - improving overall part quality. Once all quality parameters have been met, the implementation of scientific injection molding practices help to greatly streamline the production process. These actions can be so effective that less involvement is needed by both machines and operators. In fact, cutting-edge injection molders have begun instituting revolutionary lights-out manufacturing practices. This is where factories and production facilities are equipped with innovative and automated machinery to conduct tasks that would normally need the presence of a human.
As it continues to evolve, scientific molding has helped optimize injection molding production processes in a way that now allows manufacturers to lean on technology that creates an even greater global competitive advantage.
The advancements in scientific molding practices have impacted the plastics industry at a high level. Not only has it allowed businesses to improve in the areas of cost and turn-around time, but it has also allowed plastic part producers to lower the likelihood of defects and increase the overall quality of products created. Other examples include:
When designing and producing complex injection molded parts, there is a lot of advantage to having a partner that is implementing state-of-the-art processes but also easily accessible from a geographic standpoint. Many companies are realizing the benefits to having their manufacturing partners close. The ability to react quickly and make important changes on a tight timeline is an important factor that comes up often in selecting a manufacturer. When production facilities adopt advanced manufacturing processes, including lights out functions, it communicates to their partners that they are working and producing parts as efficiently as possible.
When manufacturing processes are set up and monitored in a smart and data-driven way, companies see their production capacities increase and orders completed at a much faster rate. While not appropriate for every job, automated molding is best for jobs that run at medium and high volumes, about 2,000 hours per year or more.
Additionally, the capacity, speed, and labor efficiencies created by scientific molding practices can be passed on to the customer – ultimately lowering overall product costs. When managed appropriately, the process improves OEM production flexibility as well.
When we talk about automation, lights out manufacturing, and other scientific molding offerings by an injection molder, much of the emphasis is placed on the positive attributes associated with reducing human labor. While the process can create a more streamlined approach to production and may enable fewer people to be involved, not all projects can be run by technology. State of the art technology and processes require a highly trained and dedicated workforce that can make smart decisions and maintain equipment.
When product manufacturers rely on innovation and speed to market to be competitive in their industry, offshoring various aspects of production can expose designs to patent infringement, counterfeiting and more. Working with a reputable and knowledgeable partner that keeps everything from design, development, and production under one roof, will ensure that the manufacturer protects and retains all intellectual property, as well as learnings that are acquired throughout the process.
You can save money by partnering with a molder who uses scientific molding processes to intelligently design molds and validate parts. When molds are smartly designed, less material is used, and defects are reduced - both contributing directly to reduced costs.
Additionally, working with an injection molder who can identify opportunities for improvement during a design for manufacturing analysis will result in significant savings. Identifying problems in the early stages such as radius, draft angle, wall thickness, gate location, and other moldable features will eliminate financial and cosmetic issues along the way. In fact, as much as 80-percent of manufacturing costs can be determined by design decisions.
