Posted by PDI on | Comments Off on Plastic and Rubber Molding 101: Materials, Manufacturing Processes and Applications
Plastic and rubber molded parts are everywhere, and are produced from an extensive array of materials. While the complete list contains hundreds of varieties, they fall into four basic categories: thermoplastic, thermoset, rubber and silicone. Each group has its unique set of characteristics, advantages, and applications. Due to the differences in their material properties, they also require different fabrication processes. Let’s dive in!
What Are Thermoplastics?
Thermoplastics are polymers that soften and become moldable once heated, then harden once cooled. Thermoplastics are the most widely used materials due to their extreme versatility and recyclability. They are known for being durable, and offer a wide range of properties due to the many polymers available. These include Polyethylene (PE), Polypropylene (PP), Polyvinyl Chloride (PVC), Polystyrene (PS), and Nylon.
Molded thermoplastics may be worked using a few different methods: injection molding, blow molding, and extrusion. Injection molding involves heating plastic pellets to a molten state, injecting it into a mold cavity under high pressure, then allowing it to cool and solidify.
Blow molding is an entirely different process. Here, a tube-like piece of plastic, known as a parison, is inflated with air inside a mold to form hollow parts like bottles and containers. (It’s interesting to note that the parisons themselves are created by injection molding or extrusion.)
With the extrusion process, plastic pellets are melted then forced through a die to create continuous shapes. They are then cut to the required length.
Thermoplastic Applications
Chances are, if you’re thinking of a plastic component, it’s likely made from thermoplastics. They are used in countless commercial and consumer applications. Here are a few common ones:
Injection Molding – automotive parts, packaging, electronic enclosures, medical components, and many household items.
Blow Molding – bottles, containers, tanks, sporting goods (baseball bats), decorations, and other consumer items.
Extrusion – pipes, sheets, films, and profiles.
Thermosets
Thermosetting plastics, simply known as thermosets, are polymers that undergo a chemical change when heated, thus forming a rigid structure. Once set, they cannot be remelted or reshaped. When compared to thermoplastics, they are usually more stable, but also more brittle. Typical materials include Epoxy, Phenolic, Melamine, Urea-formaldehyde, and Polyester resins.
Thermoset molding processes involve the polymerization of the resin in the mold, which permanently sets it. Common manufacturing methods include compression molding, transfer molding, and injection molding designed specifically for thermosets.
With compression molding, a pre-measured amount of material, often in the form of powder or preform, is placed into the heated mold. It’s closed, then heat and pressure are applied to harden the material.
Transfer molding is similar to compression molding, but the material is preheated in a chamber before being transferred to the mold.
Finally, thermoset injection molding is very similar to thermoplastic with one key difference: the material undergoes a chemical reaction while curing, rather than just cooling down.
Thermoset Plastic Applications
Due to their unique characteristics, uses for thermoset plastics are a bit limited, but do excel for certain ones. In addition to adhesives, coatings, and composite materials, they are used for the following:
Compression Molding – Electrical components, automotive parts, appliance housings, and large industrial parts.
Transfer Molding – Precision parts, electrical components, automotive parts, and industrial equipment
This process involves shaping rubber materials, which can be either natural or synthetic rubber (elastomers). Rubber has high elasticity and abrasion resistance with good tensile strength. These properties vary based on the type used, which include Natural Rubber, Neoprene, and Nitrile Rubber.
Common processing methods include compression molding, transfer molding, and injection molding. While these are similar to what is done for thermoplastics and thermosets, the process usually involves vulcanization. Here, the rubber is cured through heat and pressure usually with the addition of sulfur or other curatives to enhance durability and elasticity.
Molded Rubber Applications
Applications for rubber rely on its unique characteristics, they include:
Compression Molding – Seals, gaskets, large industrial parts, and tires.
Injection Molding – High-precision parts, seals, gaskets, and automotive components.
Transfer Molding – Electrical components, O-rings, seals, and more complex rubber parts.
Silicone
If you’re thinking, “Hey. Wait. Isn’t silicone a type of rubber?” – you’d be absolutely correct. However, silicone is processed a bit differently than other rubber types, and has earned its own category as a result. Silicone is widely known for its high heat resistance, flexibility, and biocompatibility.
Silicone also utilizes several processes including Liquid Silicone (LSR) Injection Molding, Compression Molding and Transfer Molding.
LSR Injection Molding is a specific yet simple process that uses liquid silicone rubber. It is poured into a heated mold, then cures quickly, taking the shape of the mold cavity. Compression molding uses High Consistence Silicone Rubber (HCR), often in sheets or preforms, which is placed into a heated mold cavity. Pressure is then applied to cure the silicone. Transfer Molding for silicone is similar to plastics: the silicone is preheated in a chamber then transferred to the mold cavity through a system of runners and gates, where it cures under heat and pressure.
Silicone Applications
Silicone is optimal for any product that require flexibility, heat resistance and/or biocompatibility. Common uses include:
LSR Injection Molding – Medical devices, kitchenware, baby products, and automotive parts.
Compression Molding – Seals, gaskets, and large silicone parts.
Transfer Molding – Complex silicone parts with fine details.
Posted by PDI on | Comments Off on Plastic Injection Molding 101: An Overview
Plastic injection molding is a complex fabrication process used to create countless products we engage with daily. This includes everything from the keys on your keyboard, buttons on your toaster, or gears grinding away under your car’s hood. Plastic injection molded parts are everywhere. Today, we’ll take a closer look at injection molding, the process, and its advantages.
What is Plastic Injection Molding?
Plastic injection molding starts with a mold that contains impressions of the part or assembly that is being fabricated. The mold is then injected with melted plastic, which takes the shape of the mold, and cools down to create the solid component.
The process has been around since the early 1870’s (or late 1860’s or even earlier depending on who you ask) when the earliest molding machines were made and patented. Back then, injection molding was used to make common items such as combs, buttons, and other small parts.
The Injection Molding Process
Design – the process begins with part design, which includes material selection and part prototyping.
Die/Mold/Tool Making – once designs and prototypes are approved, production dies are made. For high-run jobs, multi-cavity molds may be used to produce multiple parts at once. This brings efficiency by cutting down run time, which reduces part cost. Intricate parts and assemblies may require more advanced tooling in addition to complex molds, such as jigs and other work holding and processing solutions.
Material Introduction – raw plastic material, typically in the form of pellets or granules, is fed into a hopper. This material can be conventional plastic, or engineering resins for more demanding uses. These include glass-filled, carbon-filled, PTFE (Teflon) filled Thermoplastics. This all depends on the functional, operational, and aesthetic requirements of the parts being molded.
Melting – the plastic moves into a heated barrel where it melts and mixes uniformly.
Injection – the molten plastic is then pushed into a closed mold cavity at high pressure, ensuring it is completely filled.
Cooling – the plastic then cools and solidifies into the desired shape.
Ejection – the mold opens, and the cooled finished part is pushed out by ejector pins.
Inspection – certain plastic molding suppliers, such as PDI, will utilize inline part inspection to help ensure part quality. With this critical step, an image of the finished part is taken, compared to a reference image, and is either accepted, or, sadly, pushed into the reject bin. (But don’t be too sad, that part will get a second chance here at PDI, since we recycle all excess plastic inline!)
Assembly (if required) – more complex components or assemblies will go through further automated or manual steps for assembly or packaging.
Repeat – the plastic injection molding cycle then restarts, ready to produce the next batch of parts, until the order is ready to ship.
Why Choose Plastics for your Component or Assembly?
Plastic injection molding, and the materials used, offer many properties making it ideal for part fabrication:
Versatility – plastics come in a wide range of types allowing you to tailor material selection to your specific requirements. Specific properties include strength, flexibility, heat resistance, corrosion, and chemical resistance.
Durability – thermoplastics, or engineering resins, in particular can withstand significant wear and tear, making them suitable for long-lasting parts. Properties for certain materials are comparable to metals.
Lightweight – when matched up against metals, thermoplastics offer significant weight reduction, critical for weight-sensitive applications like aerospace and automotive.
Cost-Effective – injection molding allows for high-volume production at a relatively low cost per part.
Design Flexibility – the process allows engineers and product designers to create complex shapes with intricate details, allowing for innovative product design.
The Future of Plastic Injection Molding
Molding has come a very long way in a century and a half. Time and technology have been good friends to the process. It went from a rather basic, manually driven production method with few material selections, to one that can be fully automated, with an extensive menu of materials available. As technology continues to advance, injection molding will continue to evolve. We can expect to see:
More Sustainable Materials – biodegradable and recyclable plastics are gaining traction for a more eco-friendly future.
Multi-shot Molding – fabricating parts with multiple materials and functionalities within a single mold, rather than high quantities of the same exact part at once.
Continued Advancement in Automation and Monitoring – Increased automation and real-time process monitoring for enhanced efficiency and quality control.
Plastic injection molding is an indispensable and flexible manufacturing process that has stood the test of time. It is used in practically every industry today to produce simple to intricate parts that range in size, complexity, material, and use. Leveraging the many benefits of injection molding can help manufacturers increase efficiency and product evolution, thus making manufacturers more competitive and profitable.
Want to see if Plastic Injection Molding is right for your part fabrication needs? Contact us today, we’re happy to see if we can help reduce current part cost, or produce new ones.
Injection molding dies, or injection molds, are the heart of molding process. It’s crucial for buyers to source them from reliable, trusted, quality-driven suppliers. They have a big decision to make: to build their molds in China, or closer to home in the USA. Often, this leads to questions about quality versus cost and delivery. This requires closer consideration, as each option has its own features, benefits, and disadvantages. Let’s explore insourced vs outsourced injection mold die production.
Advantages of Building Injection Molds in China
There are several benefits to working with China for your mold production needs. It should come as no surprise the biggest reason manufacturers choose China is cost savings. China’s lower labor costs and favorable material prices can significantly reduce mold development expenses. Another factor is China’s large manufacturing base – it’s no secret that China boasts a large fabrication industry, which includes injection molding. This gives access to a vast network of molding suppliers with rapid production capabilities. Further, many Chinese mold manufacturers can handle high-volume orders and tighter timelines.
Disadvantages of Building Injection Molds in China
The benefits of cost savings and other advantages we discussed do come at a price. One big challenge is the communication barrier, due to language and cultural differences. This barrier could lead to misunderstandings and project delays. Also, concerns still linger about quality and consistency, which could lead to rework and revisions. This all adds up to unwanted delays and cost increases. Also, as with outsourcing anything, there are intellectual property (IP) risks. IP protection in China can be less robust, increasing the risk of unauthorized duplication or use of your designs. Violations also harder to litigate should something go very wrong. Finally, shipping from overseas adds additional time, expense, and the increased risk of logistical disruptions.
Advantages of Building Injection Molds in the USA
There are many reasons to have your molds made in the USA. Quality is the big one. As a rule, US-based mold manufacturers often follow stringent quality control standards and processes, reducing the likelihood of defects, and associated delays. Another considerable advantage is that overall collaboration is easier, despite potential time-zone differences. Domestic production allows for much better communication and collaboration overall with the mold maker, simplifying iterations. As for intellectual property concerns, the USA provides stronger legal frameworks to protect your IP and designs. Another obvious advantage is that domestic suppliers tend to offer quicker lead times with relatively simple logistics when compared to overseas options.
Disadvantages of Building Injection Molds in the USA
Well, you already know the big one: higher total cost. There’s no need to elaborate on that one any further. Also, while there are many established and capable mold makers here in the States, some may have less capacity for larger-scale orders, which could affect lead times.
So, Which Is the Right Choice?
The decision depends on your company’s priorities, production needs, and project specifics. Ultimately, it all boils down to considering cost vs. quality, complexity, and IP sensitivity. Your goal is to find a good shop that will do the job on time, within (or close to) budget, while fully respecting your IP requirements.
Generally speaking, it is cheaper to produce molds overseas, and quality has come up over the years. Also, you can consider a hybrid approach: have the die made overseas, but use a local die maker for any required modifications or fixes. We encourage you to keep an open mind when evaluating and making the choice.
Regardless of where you decide to have your injection molding dies made, there are a few things we strongly recommend that you always do:
Communicate your needs and expectations very clearly. it’s better to over-explain, than underexplain. Don’t leave room for the supplier to make assumptions.
Obtain and actually check references. It’s important to vet your suppliers as well, overseas or domestic. Get references. Follow up on them. Talk to the mold-makers customers. Conduct online research on the brand and its reputation. A little effort here could go a long way at minimizing the risk of working with a new mold maker.
Show up! For larger jobs or longer term engagements, consider a visit and walkthrough of the manufacturer’s facility. Pay attention, and ask questions while you are there.
Injection molds are crucial investments. Be sure to carefully weigh the pros and cons against your specific requirements to help ensure a successful outcome.
Are you leveraging mold flow simulation software to optimize your molds and injection molding process? You should be. Here’s why: injection molding is a complex process, and is subject to threats such as warping, uneven cooling, material defects, and much more. Historically, these challenges were only discovered through trial and error, leading to costly mold reworks, part design changes, and process modifications; all resulting in frustrating production delays. Wouldn’t it be great if you could foresee and resolve these problems before they occur? You can thanks to plastic mold flow simulation software.
This technology has been hailed as a game-changer for the injection molding industry. This powerful software allows users to virtually replicate the entire molding process, from filling the mold cavity to the final cooled part. This enables designers and engineers to optimize material choice, process settings, cooling efficiency, and other critical production aspects. There are many benefits to leveraging this technology, including:
Reduced Development Time and Costs – by identifying issues in the design phase, prior to production, you can avoid mold revisions and production delays. The process allows you to optimize your molds for efficient filling, consistent part quality, and minimal material waste before the mold is even made. A good mold is expensive, so you need to get it right the first time!
Improved Part Quality – the software helps predict and prevent common defects such as warpage, shrinkage, and air traps. By solving these issues on screen, you’ll get parts that have consistent dimensional accuracy and aesthetics with superior mechanical strength.
Easier Design Optimization – simulation software provides the ability to optimize part design beyond simply preventing defects. It helps achieve better part functionality. By visualizing flow within the mold, you can optimize gate location and size for balanced filling. It also allows you to predict warpage and shrinkage when cooling, so the design or mold dimensions can be adjusted to help assure that the final part meets functional tolerances and dimensions when cooled.
Enhanced Innovation – if you’ve ever wanted to improve your part design, you already know the factor that slows you down: fear! Will the proposed new material work? Will modifications to part geometry disrupt the process? These questions and more can be answered with simulations. They give you the freedom and flexibility to optimize process factors, without the fear of failing.
Improved Production Efficiency – by maximizing your mold design and process considerations through simulation, you can benefit from faster cycle times, and higher yields, along with reduced energy consumption, defective parts, and waste. Keep in mind that in addition to geometry and material, the software takes many other factors into account such as pressure and flow rate.
Wait – This Sounds Too Good to be True!
It’s true: mold flow and process simulation has indeed been a game changer. But, as will all technological innovation, it’s not perfect. It’s software. One drawback is that it assumes that everything is perfect such as the mold, the machine, the material, and environmental conditions. In reality, these things are subject to imperfection and variation. For instance, materials can have viscosity issues, which will change the flow properties. A brand new machine will function much better than say a twenty- or thirty-year-old machine. Another key factor is heat, which plays a huge role in part cooling and mold design. While the software may consider certain thermal factors, it doesn’t know all of them. The bottom line here is that there are real-world drawbacks, and it’s up to the manufacturer to be aware of these and to compensate for them accordingly.
If you are not employing this impressive cost-saving technology yet, why wait? If budget is a concern, you can simply work with a plastic injection molding shop, such as PDI, that includes simulation as a value-added service. In doing so, you’ll optimize your part quality and consistency, while reducing mold and material costs and waste. All adding up to reliable components and a healthier bottom line.
Have a question about mold flow simulation or want to see how you can benefit? Contact us today.
There are three aspects of plastic part design that are often overlooked, but crucial for manufacturing success: surface finish, texture, and draft angles. Understanding and optimizing each is critical for fabricating consistent, high quality plastic components efficiently.
The first question that comes to mind: if these are so important, why are they often overlooked? We’re glad you asked! The reason is that these attributes are a function of the fabrication process, rather than the end product’s design and function. They fall under the umbrella of designing for manufacturability. So, it’s easy to see why these can be underappreciated by design engineers. But by doing so, they risk having issues and inefficiencies with part production. All of which leads to waste, extended turn-times, premature mold wear, and part quality issues.
Let’s take a look at surface finish, texture, and draft angles more closely, and how they relate to each other:
Surface Finish – refers to the finish of the part’s surface. Finishes fall into categories: smooth or textured. Smooth finishes may be either glossy or matte, and provide a clean elegant look. Textured finishes include grain finishes, stippled finishes, or others that provide grip, hide imperfections, or produce a certain aesthetic.
Surface finish is influenced by several factors including mold material, processing parameters, part material, and ejection mechanisms. Molds made from polished steel yield smoother finishes, while textured molds create specific surface patterns. Mold temperature, injection pressure, and cooling time can impact surface quality. As for the part material, different plastics have varying gloss levels, shrinkage rates, and flow properties, all of which affect the final finish. Finally, ejector pins and core pulls can leave marks if not designed optimally.
Texture – helps enhance the look, functionality, and performance of the finished component. Common options include leather-like, pebble/sandblasted, geometric patterns, and micro textures. Leather-like finishes enhance aesthetics, functionality, and performance. Pebble or sandblasted textures are durable and hide scratches. Geometric patterns provide functional grip, but may also be used for decorative purposes. Finally, micro-textures are ideal for parts where glare reduction or wear resistance is desired. Note that fine textures might require more intricate mold designs. One last thought on texture: textured molds can be more expensive to manufacture.
Draft Angles – often referred to as just “draft”, these are tapers in the mold that help release the part without damaging it. Optimizing draft is important for many reasons. Failure to do so could lead to visible scratches or steps on the finished component, which ruins the desired finish. It’s important to understand that surface finish and texture directly affect the required draft angles. Deeper textures require larger draft angles to avoid surface tearing during part removal.
Designing for Success
Remember, just because your plastic part looks perfect on screen, doesn’t mean it’s ready for optimal production. The key is to balance functionality and aesthetics by selecting surface finishes and textures that complement the product’s function and desired look while considering their impact on draft angles. Collaborate closely with mold designers and part fabricators to ensure optimal draft angles for achieving the desired surface finish within budget and feasibility constraints. Don’t hesitate to prototype and test parts to verify draft angles and surface finish quality before committing to full-scale production. The added cost will be worth it in the long run.
By understanding the intricate relationship between surface finish, texture, and draft angles, you can design and efficiently manufacture high-quality plastic parts that meet functional, aesthetic, and quality requirements.
Have questions about designing your parts for optimal manufacturability?
Keeping your plastic injection molds properly maintained is crucial to the long-term success of any molding program. When doing so, you will drive down costs, reduce downtime, and keep deliveries on schedule, all leading to better profitability. Today, we’ll take a deeper look at the benefits of proper mold maintenance, and dive into some tips on how to keep your injection molds properly maintained and functioning.
Benefits of Proper Mold Maintenance
Improved Quality – Proper mold maintenance will lead to higher quality products by preventing defects such as flash, sink marks, and warpage.
Increased Lifespan – A well-maintained mold can last for many years, saving money on replacement costs.
Reduced Downtime – Mold breakdowns can cause significant downtime, depending on the extent of the damage. Turn times could be substantially extended as a result, leading to weeks or even months in the event a new mold may be required. Preventing mold breakdowns with a solid maintenance program will help keep production running smoothly and on schedule.
Improved Efficiency – A well-maintained mold will operate more efficiently, leading to faster cycle times and increased production output. As an added bonus, scrap rates will be reduced as well. This is good for your bottom line, and the environment.
Tips for Maintaining Your Plastic Injection Molds
Before we jump in, let’s keep in mind that in almost all contract molding arrangements, the molding facility is responsible for maintaining and storing the injection molds. Since you are ultimately at their mercy, it’s important to make sure they have proven (and well- documented) maintenance procedures in place.
Maintenance broadly fits into three categories as follows:
Preventative Maintenance – is performed on a regular schedule to help prevent problems before they occur. This typically includes cleaning, lubrication, and inspection of the mold. More on that in a minute.
Corrective Maintenance – is done to repair problems that have already occurred. This usually consists of repairing damaged parts, replacing worn components, and adjusting mold settings.
Predictive Maintenance – uses technology to monitor mold performance and identify potential problems before they occur. This can help to prevent costly repairs, unplanned downtime, and extend the lifespan of the mold.
We recommend performing preventive maintenance on a monthly or quarterly basis, depending on the types of mold, material, and production schedule. This should include:
Cleaning the mold regularly to remove debris and buildup.
Lubricating the mold to help prevent wear and tear on the moving parts.
Inspecting the mold for damage. The idea is to catch small problems before they turn into much bigger ones.
Keeping a maintenance log that tracks the mold’s history and to help identify trends that may indicate potential problems.
At PDI, we inspect every mold for wear and damage after each run, regardless of run time. The maintenance plan is dictated by how many cycles it has endured. For instance, if the run was short, it will undergo a simple cleaning and greasing. Longer runs will undergo a complete cleaning, including disassembly and sonic cleaning. More complex molds that have endured higher runs will go through this as well, but may also have components such as gears changed.
Proper storage is as important as a good maintenance program. Molds should be stored in dry, climate-controlled environments. Remember, moisture and steel don’t mix!
Let’s face it: plastic injection molds are costly investments. So, just as you would do with you car, or any other big-ticket mechanical item, make sure injection molds are properly maintained and stored. Be sure to work with a shop that’s protecting your investment. Doing so will lead to improved efficiency, predictable delivery times, fewer headaches, and the best part: increased profits.
When it comes to creating prototype molds for injection molding, choosing the right material is crucial. Two common options for prototype mold construction are aluminum and soft steel (P20). Today, we’ll compare these two materials to help you make an informed decision. For the purposes of today’s discussion, we’ll be talking about “late stage” prototype molds. These are molds that are likely to be used for medium to high volume production runs, not just to knock out a few early-stage prototypes.
Durability/Production Life – P20 steel, although a soft steel, is stronger and more durable than aluminum. It will certainly endure a higher number of injection cycles as result. Further, steel’s strength means better mold integrity over time. Since aluminum is softer, molds made from it are more likely to deform eventually, requiring either repair or replacement, depending on how severe the deformity is.
Heat Conduction – aluminum dissipates heat quickly and efficiently, meaning reduced cooling time during the injection molding process. Steel holds heat longer, leading to extended cooling times, which could lengthen production time. Also consider the required melting point of the material being molded. For those that require higher values, steel is the way to go.
Machinability – since aluminum is a softer material, it’s generally easier to machine than steel. This is particularly useful if changes still need to be made to the mold before putting it to work on longer production runs. However, when it comes to high precision, steel would be the better choice.
Part Geometry/Size – since steel can be more easily machined to high precision, and is durable, it works much better for parts with complex geometries, especially over longer runs.
Cost – we saved the best for last. In fact, if we started with the cost aspects, you might not have read this all the way through! As you could probably guess, a domestically sourced aluminum mold is going to be less expensive than a steel mold. No doubt about that. But I’m going to share a valuable secret with you: if you source a mold from a quality oversees mold maker in China, there is little difference in the cost between an aluminum and steel mold. This is simply since labor costs are much lower. While there is still a difference in the cost of the material itself, and it takes longer to machine P20 steel, the differences become negligible when considering the final cost of the mold.
I know what you’re thinking – what about shipping and tariffs? Don’t they wipe out the reduced labor cost advantage? The answer is no. In fact, molds sourced overseas still typically cost about half, saving tens-of-thousands of dollars, even after the extras are added to the price. They are also able to produce them quickly, negating the longer shipping distance. And quality? That’s always going to be a concern. No matter where you source from, you’ll still need to do your homework to make sure you are working with a reputable supplier that has a documented quality program in place.
Who Wins, Aluminum or Steel?
So, what to choose? In most cases, an outsourced mold made from P20 steel will be your best decision. When price is essentially off the table, why wouldn’t you want a mold that’s more durable, will maintain its integrity, and can handle considerably more injection molding cycles? Sure, there are exceptions where locally sourced aluminum molds are a better choice, such as earlier stage prototyping. For some jobs where there are ITAR or other domestic sourcing mandates at play, there’s no choice. Otherwise, if you’re getting ready for mid-high volume/repeat production runs, we recommend an outsourced P20 steel mold. It will last longer, and have a lower lifetime cost.
Not sure which material is best for your mold?
Contact us, we’re happy to help you make the right selection!
With plastic injection molding, there are two types of mold configurations that may be used: standard self-contained molds and modular insert molds. Today, we’ll compare the key aspects of both types.
Self-Contained and Modular Insert Molds – Defined
Let’s start with a definition for each. Self-contained molds consist of all components integrated into a singular unit or a mold frame. These include the core, cavity, and other necessary components within a single base. Conversely, a modular insert mold is comprised of separate interchangeable components. The primary parts are the frame and the mold itself, which gets inserted into that frame.
Part Complexity
Self-contained molds are custom-made and, therefore can facilitate more complex part designs. When compared to modular insert molds, self-contained ones allow for intricate cavities, cores, and cooling channels.
There are some limits to what modular insert molds can handle. They can’t facilitate complex
operations involving for example gear assemblies. However, some insert molds can support
cam actions (side action).
Tooling Lead Times
Since self-contained molds are typically designed and fabricated from scratch, they take longer to produce. Conversely, insert mold frames are readily available, and while the insert itself does take some time to make, it’s much less than what’s required to build an entire self-contained mold from scratch.
Longevity
In the world of injection molding, longevity translates to cycles. In other words, how many impressions can be made in that mold before it needs to be replaced? Note that, regardless of configuration, longevity also depends on various factors including material and maintenance. Self-contained molds tend to outlive insert molds, as they are usually comprised of higher-quality materials.
Cost
Conversations around cost are rarely simple these days, and this topic is no exception. Let’s start here: self-contained molds have higher tooling costs due to their custom nature. Modular insert molds are lower in cost since they have interchangeable inserts, thus reducing the need for mold frames. Remember, with insert molds, you are essentially paying for the “guts” of the mold, and not the entire assembly including the frame, helping to keep a lid on tooling costs.
If design changes are made, insert molds win again. However, keep in mind that self-contained molds generally last longer, and the lifetime cost may be lower than an insert mold. Similarly, if only specific hi-wear components of the tooling need to be replaced over time, insert molds offer more flexibility since the entire tool doesn’t need to be rebuilt.
Before we wrap up, we need to talk about part volume. Let’s put tooling costs aside for a
moment. If the injected component is a high-run part, in the hundreds of thousands, then the
price of the components themselves will be lower with a multi-cavity self-contained mold. This
allows for multiple pieces to be made at one time, which significantly reduces cycle time and its
associated costs.
Which is Best?
So, what will it be, self-contained mold or modular insert? It depends. For instance, we have a customer who supports the aviation market, but their parts are simple and are ordered in short runs. Perfect for modular insert molds. Conversely, we have an automotive customer with an uncomplicated part, but we use a self-contained mold. If you’ve read this far, you know why – it’s a high-volume run (500,000+) produced with a multi-cavity mold.
While some jobs may use either, in the end, the decision will rely on the requirements of the job, including volume, complexity, frequency of design changes, and related considerations.
Scientists estimate that there are 5 trillion tons of plastic in the world’s oceans. FIVE TRILLION!* It’s hard to wrap your head around that number, isn’t it? Couple that with the ever-increasing global demand for plastic, and the oil it is derived from, and you have a perfect storm. Thankfully, plastic is recyclable. Today we’ll look at some approaches to plastic recycling, and dive into the benefits of sustainable injection molding.
First, let’s consider the use of plastics during the plastic injection molding process. For parts to be formed, molten material must travel through channels known as runners into the mold’s cavities. Once the parts have set, the plastic strip-like pieces formed within the runners, ironically also known as runners, have served their purpose. This excess plastic may be as much as 50% of the job’s material usage! That creates a tremendous amount of plastic that’s ripe for recycling.
How Do Injection Molders Recycle Plastic?
A robotic arm picks up the runners, and feeds them into the grinder for in-line recycling.
There are several ways a manufacturer can handle this excess material. In many cases, they will simply collect it, and send it out for recycling. A third party will take the plastic, which will eventually be recycled. To complete the cycle, the fabricator may buy recycled plastic to use as raw material for production. While this does help conserve resources, the processes to properly recycle plastic are complex, costly and demand more natural resources.
Alternatively, plastic shops may recycle in-house. There are two main methods of doing this:
They collect the excess material during production, then send it to another part of the facility for regrind and reuse.
In modern automated shops, like Plastic Design, the material is collected, reground and reused in-line, as part of an extremely efficient plastic injection process.
So, why go through all this effort to recycle plastic?
Resource Conservation
It’s pretty simple. Using recycled material helps conserve valuable natural resources such as oil. By keeping waste out of landfills, the manufacturer is contributing to a circular economy, giving materials a second life.
Waste Reduction
Keep in mind that about half of the material used in the plastic injection molding process doesn’t make it into the finished components. By capturing and recycling this plastic, significant amounts of waste are avoided, along with the costs it takes to handle, store and dispose of it. Putting less waste into the environment results in a much more sustainable manufacturing process.
Cost Reduction
While recycled plastic tends to cost more than virgin material, utilizing an optimal in-line recycling process actually drives material costs down. This is due to the many operational efficiencies it brings, across many departments. Think about it for a moment – it costs nothing to ship material that’s already in the building. There’s less handling required on the shop floor, thanks to automation. Since little disposal is required, associated fees are greatly reduced as well. The purchasing team also has less buying to do. There’s less raw material to stock, which means lower carrying costs.
Most industries can benefit from working with injection molders that are committed to a sensible recycling program. There are certainly some exceptions, such as the medical field or others that have strict requirements aimed at avoiding contamination. Otherwise, recycling plastics within the injection molding process brings many benefits to manufacturers, the environment, and, yes, the bottom line.
Can You Benefit from Using Recycled Plastics?
We’ve helped lots of brands reduce their carbon footprint and help keep plastic injection molding prices in check. Contact us now to see how we can assist you.
There’s one question that comes up in practically every call we have with prospects and customers lately. You’ve probably guessed it already: “How can we reduce cost?”
It’s a fact. Every buyer wants to pay less for their injection molded parts, but without sacrificing quality. Thankfully, for many jobs, this is achievable if you know where to look. But you must be careful to preserve the part’s quality and integrity in the process, otherwise it could cost you in the long run. As the old saying goes, don’t be penny wise but pound-foolish.
There are several areas worth examining to help reduce injection molded part costs. These include part and tooling design, material, and manufacturing process considerations. Let’s take a look at these to see how successful cost reduction can be achieved:
Part and Tooling Design
The first place to start is with part design. Ultimately, your goal is to simplify the part wherever possible, Or, as we say here in the shop, KISS, or keep it super simple. Technically speaking, this translates to simplifying the geometry, minimizing undercuts, and eliminating unneeded features. When design is properly optimized, less material will be consumed and cycle time reduced. Less design complexity leads to lower tooling costs.
Additional cost saving opportunities may be found in the tool design and construction. Optimizing cooling channels, or conducting a mold flow analysis to identify areas for improvement. You should also consider options for using standardized mold components. By optimizing the gating system and cooling channels, you may be able to further cut cycle time and reduce material waste.
Are You Using the Best Material?
Material selection presents another potentially large opportunity for cost reduction. In our experience, the material is often over-spec’d. For instance, it is not unusual to see a job that calls for a resin that is say $10 or $20/lbs., when it could be made from a commodity material costing just a few dollars per pound. For medium and larger runs, this adds up to significant savings. Of course, you must be certain that the new material still meets the required specifications and operating conditions for the part. But there is no benefit in over specifying, it is sort of like installing stainless steel muffler on the Yugo.
Process Considerations
To keep production costs in check, it is critical to be sure that the process is optimized during process development stage. Reducing cycle time has a major impact on part cost. It is also a good idea to routinely revisit and verify that your process is at its optimum, study quality data, and eliminate any sources of waste or defects.
Automation and Robotics to the Rescue!
Another cost-saving process enhancement is to utilize automation and robotics when possible. As we explored in our previous blog, automation brings many cost-cutting benefits. It is especially useful when complex assemblies may be faithfully produced with the help of reliable automation. This reduces labor costs, material waste and cycle time.
Don’t Forgot About the Economies of Scale!
When practical, consider ordering in larger volumes. It is a simple principle. As run size increases, unit cost decreases. When coupled with reliable forecasting, this could lead to healthy savings. Don’t have a lot of space to store components that you don’t need yet? Many shops will offer stocking programs to help with warehousing. Though do keep in mind that carrying inventory is not free, so consider these costs when weighing against the benefits of longer production runs.
As you can see, there are plenty of ways to reduce injection molded part costs. It all comes down to reducing labor costs and cycle time while increasing process efficiency. As we mentioned earlier though, please be cautious. While saving money is certainly a good thing, you don’t want to sacrifice the part’s required properties in the process, especially for mission or safety-critical applications.
Want to see if we can help you reduce molded part costs?
Molded thermoplastics may be worked using a few different methods: injection molding, blow molding, and extrusion. Injection molding involves heating plastic pellets to a molten state, injecting it into a mold cavity under high pressure, then allowing it to cool and solidify.
Thermosetting plastics, simply known as thermosets, are polymers that undergo a chemical change when heated, thus forming a rigid structure. Once set, they cannot be remelted or reshaped. When compared to thermoplastics, they are usually more stable, but also more brittle. Typical materials include Epoxy, Phenolic, Melamine, Urea-formaldehyde, and Polyester resins.
This process involves shaping rubber materials, which can be either natural or synthetic rubber (elastomers). Rubber has high elasticity and abrasion resistance with good tensile strength. These properties vary based on the type used, which include Natural Rubber, Neoprene, and Nitrile Rubber.
will utilize inline part inspection to help ensure part quality. With this critical step, an image of the finished part is taken, compared to a reference image, and is either accepted, or, sadly, pushed into the reject bin. (But don’t be too sad, that part will get a second chance here at PDI, since we recycle all excess plastic inline!)
There are three aspects of plastic part design that are often overlooked, but crucial for manufacturing success: surface finish, texture, and draft angles. Understanding and optimizing each is critical for fabricating consistent, high quality plastic components efficiently.
Texture – helps enhance the look, functionality, and performance of the finished component. Common options include leather-like, pebble/sandblasted, geometric patterns, and micro textures. Leather-like finishes enhance aesthetics, functionality, and performance. Pebble or sandblasted textures are durable and hide scratches. Geometric patterns provide functional grip, but may also be used for decorative purposes. Finally, micro-textures are ideal for parts where glare reduction or wear resistance is desired. Note that fine textures might require more intricate mold designs. One last thought on texture: textured molds can be more expensive to manufacture.
Improved Quality – Proper mold maintenance will lead to higher quality products by preventing defects such as flash, sink marks, and warpage.
When it comes to creating prototype molds for injection molding, choosing the right material is crucial. Two common options for prototype mold construction are aluminum and soft steel (P20). Today, we’ll compare these two materials to help you make an informed decision. For the purposes of today’s discussion, we’ll be talking about “late stage” prototype molds. These are molds that are likely to be used for medium to high volume production runs, not just to knock out a few early-stage prototypes.
Heat Conduction – aluminum dissipates heat quickly and efficiently, meaning reduced cooling time during the injection molding process. Steel holds heat longer, leading to extended cooling times, which could lengthen production time. Also consider the required melting point of the material being molded. For those that require higher values, steel is the way to go.
In the world of injection molding, longevity translates to cycles. In other words, how many impressions can be made in that mold before it needs to be replaced? Note that, regardless of configuration, longevity also depends on various factors including material and maintenance. Self-contained molds tend to outlive insert molds, as they are usually comprised of higher-quality materials.
Scientists estimate that there are 5 trillion tons of plastic in the world’s oceans. 
There’s one question that comes up in practically every call we have with prospects and customers lately. You’ve probably guessed it already: “How can we reduce cost?”