Author: Julie Hillis

How to Choose the Proper Plastic

If you’re looking to become a plastic molder, the two main things you should consider are your plastic injection molds and the materials you’ll use to create parts. Before setting out to have your mold designed and made by Quality Mold Shop, you should consider the purpose of the part you plan to create.

Choosing the Right Plastic for the Right Job

Different plastics have different properties, making some more suitable for certain jobs than others. If you take a look around you, noticing different things made from plastic, you’ll notice how similar plastics are always used to make similar products.

Your laptop case, for instance, will always be made from a hard plastic rather than a soft one. If you examine the properties of the plastic used to make laptop cases, you’ll notice that the plastic doesn’t really give way or bend easily. It’s hard, yet it’s durable enough to not break or crack easily if it gets a light knock. The lid on your lunch box, on the other hand, isn’t hard like that. It’s a soft plastic that easily bends and gives way. This can help it to stretch a little over the lunch box container, creating a stronger seal.

If you used a hard plastic to make a lunch box lid, it wouldn’t stay on the container as securely. And if you used a soft, bendable plastic to make a laptop case, it wouldn’t protect the hardware inside the computer from light knocks.

In both cases the plastic used was picked carefully based on the function of the part that’s being made. This is what makes plastic such a popular material for manufacturing, its versatile. But that versatility comes in the form of different polymers. After looking into plastic injection molding and different types of plastics available, you’ll see that laptop cases are most often made of plastics like ABS (acrylonitrile butadiene styrene), while lunch box lids are made from materials like polyethylene.

Practical Considerations

Of course the ultimate function of a molded plastic part will be an important consideration when choosing the right polymer for the job. But how will you know what factors to consider in order to choose a plastic with the right properties?

Here are some of the practical things to consider when choosing what material to use for your plastic parts.


Some polymers are just more expensive than others, so the market value of your final product will have a big impact on your choice of polymer. The raw material could cost you anywhere from less than a dollar per pound, to as much as $50 dollars if you need a specialty material. So obviously the possible price fluctuation is huge.

And it goes without saying that you simply can’t use a polymer that costs $50 per pound as a raw material, if your final product will requires a pound, but will only cost $40. That’s an oversimplified example, but it drives home the point that cost is vitally important when choosing what plastic to use.


Some products don’t need to be very durable at all, while other products are expected to last as long as a lifetime. You’ll know how durable you expect your product to be before having a mold made, and so you should choose a plastic that can live up to these expectations.

People don’t expect disposable plastic cutlery to be particularly durable, but a reusable plastic cup should be made of plastic that won’t easily crack like its disposable counterpart.

Another essential part of choosing a durable material is its resistance to temperature. A simple plastic like polyethylene isn’t very temperature resistant. So while it’s a good plastic for everyday objects, it won’t perform well under somewhat more extreme temperatures. While hot conditions isn’t good for the material, cold conditions also negatively affect its plasticity. Meaning that a part made from polyethylene can actually break or shatter below freezing point, losing its ability to flex.

Part Design

The shape of the part you want to make will influence the polymer you choose. Simple shapes can be made using almost any polymer, but if the part you want to mold will have more holes, depressions, ribs and gussets, you have to pick your polymer more carefully. Not all plastics can be as easily shaped as others.

And while aesthetics isn’t necessarily the most important thing to consider, it’s also something that will influence your decision. Getting a plastic with high gloss, or one that will be good for making a part with a matt effect might be important to you.


Some parts are meant to be able to bend a lot without cracking, while others are made not to bend. It goes without saying that any part that will have to flex a lot, should be made from a plastic that can handle this kind of tension without snapping and breaking. But some parts are meant to stay securely in place under pressure without flexing or giving way, and these parts should be made from harder, yet durable plastics.

The best way to know what plastics will be a good fit for your project is to talk to professionals. Follow the advice from both the engineers working to make your molds, and a chemical engineer. After all, the best way to get it right the first time is to not base your choices on guessing games, but to rely on sound professional advice.

Want to know how to source automotive plastics? Looking for a plastic molder?

How to Design the Perfect Plastic Part

Used to deliver top notch exactness parts everywhere volumes and low costs, plastic injection molding offers adaptable answers for a scope of uses.

While this procedure offers a few one of a kind advantages over other generation forms, the achievement of an injection shaped part relies on upon its mold; with the correct outline, durable, quality plastic parts can be made reliably and effectively. Poor outline can prompt to expensive and tedious preparing botches.

With a specific end goal to advance the viability of high-volume injection molding and boost the exactness and nature of your parts, a few key plan components ought to be considered before proceeding onward to creation.

Divider Thickness

You can reduce — and even eliminate — most injection molding part defects by taking the time to lay out a smart wall-thickness design. The key is to ensure that the thicknesses of all walls are as uniform as possible, as molten plastic will seek out the path of least resistance (in this scenario, larger wall areas), leaving smaller wall areas potentially unfilled.

Rib Design

Ribs are utilized to fortify the quality of a high-volume injection molded part. Ribs ought not surpass 70% of your parts divider thickness, be that as it may, nor should they fall under half of divider thickness; both situations can bring about soaking in the surface of your part. Additionally, make sure to give careful consideration to the tallness of the ribs, their area, and their level of draft for simplicity of discharge.

Boss Design

Bosses are part features serving as one component of a larger product that requires assembly. During assembly, bosses can serve as anchor locations for screws, pins, or other fasteners. These components have width and height recommendations similar to those of ribs. Pairing bosses and ribs, especially in corners, can strengthen your part and significantly reduce chances of sinking.

Corner Transitions

In high-volume plastic injection molding, parts with outrageous or unexpected geometric elements can be inclined to defects — liquid plastic streams in the easiest course of action, and brutal points can obstruct that development. At whatever point conceivable, all corners and divider creases ought to be bended, with coordinating inside and outside spans. Smooth corner moves take into consideration better plastic stream.

Weld Lines

Weld lines — otherwise called weave or merge lines — happen when two plastic streams, or two areas of a solitary stream, meet. They happen most ordinarily around gaps or different hindrances, with the plastic stream isolating to pass them and afterward returning together a short time later. Each plastic infusion formed part has weld lines: the objective is to plan your part so weld lines happen in areas that don’t trade off your part’s quality or respectability.

Gate and Vent Placement

The gate of a large-volume injection mold is the point at which molten plastic exits the mold’s runner and enters the part cavity. Both the type of gate you choose and where you choose to place it can substantially impact your part’s quality. Vents, which allow air to escape from the mold as plastic rushes in, are similarly important; when positioned properly, vents can help minimize weld lines.

How do hybrids utilize eco-plastics?

The whole point of a hybrid is to be eco-friendly, so why would the manufacturers lean to more eco-friendly plastics? Of course that is easier said than done; what of the crash safety? There may finally be a breakthrough in the eco-plastics world.

With about 250 pounds (113 kilograms) of plastic in the average car, the auto industry is doing its part to fill the world’s trash heaps. When that average car outlives its usefulness, all that fossil-fuel-based plastic ends up in one of two places: either recycled into other plastic parts, releasing tons of carbon dioxide in the process, or spending anywhere from a few hundred to a few thousand years in the average landfill, where it proceeds to take up space and leach harmful chemicals into the air, soil and water supply.
Read More Here

Resin Casting: Going from CAD to Engineering-Grade Plastic Parts

Resin Casting: Going from CAD to Engineering-Grade Plastic Parts

Plastics are so versatile; some of them are stretchy, while some are tough as bricks; some are crystal clear, and others come in any color you can imagine; some can perform in high temperatures, and yet others can stop a bullet.

Synthetic polymers play a role in almost every single commercially manufactured item on the planet. Plastics are not just ubiquitous, but extremely versatile: some of them are incredibly stretchy, while some are hard as nails; some are crystal clear, and others come in all colors of the rainbow; some can survive extreme temperatures, and yet others can stop a bullet mid-flight.
Read More Here

From Pest to Bioplastic

From Pest to Bioplastic

Using a natural component to make plastic is nothing new, but using animal matter is a whole new level of creativeness. There is more than one person looking into making plastics out of animals, specifically other marine life.

The Chinese mitten crab, an invasive species from East Asia, gets its name because it looks like it’s wearing a pair of furry mittens on its claws. But it’s not so cute. The crab negatively impacts native wildlife in Europe and the U.S., where it’s labeled an “injurious species.”
Read More Here

Plastic Injection Molding Process

Plastic Injection Molding Process

The plastic injection molding process is adaptable, making it versatile enough to produce anything from a simple plastic cup to car and laptops parts. While there are some alternatives to injection molding – like 3D printing and spin casting – injection molding remains the most reliable way to produce plastic goods. Because of this, injection molding is still the technique most often used to produce plastic goods in the 21st century.

But what is injection molding exactly? What does the typical injection molding process look like? And what exactly is it that makes injection molding so much more adaptable (and hence more versatile) than other options?

What Is Plastic Injection Molding?

Plastic injection molding is a technique used to shape plastic in the form of the object you’re aiming to produce. During the injection molding process, thermoplastic polymers are injected into a mold cavity. To do this, pellets of a material are heated so they can be injected into the cavity in a liquid state. This hot liquid is then left to cool in the mold so the part can properly set. Once one part is ejected from the mold, another cycle can promptly begin.

Although injection molding can also be used for metals and glass, it’s a particularly popular production process for manufacturing plastic parts.

The steps in an injection molding process cycle include clamping, injection, cooling and ejection.

During clamping, the injection mold is prepared for a cycle by tightly clamping the two halves that form the mold cavity into place. This ensures that the molded part will have a smooth appearance and ideally the molded part should have almost no line where the different halves came together, as this shows that the mold might not be clamping tightly enough.

Once the mold halves are clamped together, the mold is ready to form a part. Before the polymer is injected into the mold, the pellets are heated to form a liquid. The liquid polymer is then injected into the mold through a nozzle. This is the injection stage of molding process, which is the second stage in a four stage cycle.

Next, the part is left to cool in the mold for a predetermined amount of time. The cooling stage can take anywhere from a few seconds to a few minutes depending on the polymer being used to produce a part. While some polymers need hardly any time to cool at all, others can take a few minutes. It all depends on the part being produced.

Once a part has cooled, the injection mold is opened and the part is ejected from the mold. The mold will clamp again and prepare for its next cycle.

Because manufacturers know how long the cycle on their molds are, they can accurately predict the amount of parts a mold will produce every hour. This helps manufacturers know exactly how many parts they’ll be able to produce every day, week and month with a fully functional mold.

Why Is Plastic Injection Molding So Popular?

As mentioned above, plastic injection molding is a very predictable process. This predictability also makes the process dependable, as injection molding companies will know exactly how many parts they can expect from every mold they own.

Based on the amount of parts each mold is able to produce, manufacturers can calculate how many molds they need to in order to produce enough parts for their production line to operate at its intended capacity.

It should also be possible for manufacturers to estimate the amount of parts they can produce with a mold during its entire lifetime, making it easier to calculate whether or not a mold will generate enough income to cover its own costs with profit added.

All this is fine and well, but for injection molds to be reliable and predictable they must be maintained according to a maintenance schedule.

Unfortunately, some manufacturers run their molds till they break down. This might be because they’re just inherently stingy, but often times it was recommended to them by financial advisors in their company. The problem is that finance and engineering are worlds apart.

As mold manufacturers, we know that regular mold maintenance can extend the lifetime of your molds and help them operate optimally at all times. Yes, mold maintenance is an expense, but it’s not one you can cut to save money. If molding plastic parts is an integral part of your business, the condition of your molds in undoubtedly important. Cutting on maintenance by working molds till they break down will hurt your company.

It’s ironic that predictability, which is one of the advantages of injection molding, isn’t considered by many molders when overworking their molds. Fact is, a mold that works till it breaks down can’t always be repaired, and the halt in production from the broken mold can’t be scheduled because you won’t know for certain when it will break down.

When looking at it like that, it’s hard to understand why working a mold till it breaks could be considered a viable way to save money. Perhaps it’s time that molders look further into the issue of maintenance to establish what really works best.

But apart from the predictability of plastic injection molding, the process is also very versatile. Thousands of polymers can be used for injection molding purposes, and injection molds can be adapted for different uses. Which is why the process is as effective for the automotive industry as it is for the medical industry. With micro-molding technology, injection molding can even produce even very small parts with surprising accuracy.

To conclude, injection molding is popular mainly because no other manufacturing process allows manufacturers produce a lot of parts in a relatively short amount of time, all while maintaining the desired level of part integrity.

What are eco-plastics?

What are eco-plastics?

When thinking of plastic “ earth friendly” isn’t on the list. From trash pollution, to length of deterioration, to recycling; plastics aren’t normally in on the favorable side of the earth talk. If we could fix the problem at its source, what plastics are made of, we can make them more eco-friendly. But how something would last in a situation where the plastic is being used for long periods, and will be outside a lot in the weather such as automobiles?

Most of us have understood for years that plastic is an environmental no-no. It’s fuel based, requires lots of energy to produce and it clogs up landfills for what might as well be forever. It’s difficult to imagine a plastic we can buy without guilt. And whether eco-plastics fit that bill depends on how “green” you want to be.
Read More Here

Can we ever replace plastic?

Can we ever replace plastic?

In our lives we are surrounded by plastics; phones, car parts, water bottles, food containers, computers, honestly almost everything has some form of plastic component. With almost everything we touch being made out of some form of plastic or another, it’s hard to imagine our lives without plastics. Will we ever be able to get rid of our plastic dependence?

The downsides to plastic are certainly no secret. For starters, it’s often a nonbiodegradable, petroleum-derived product. Factor in toxins, wildlife endangerment and difficult recycling, and the plastic industry has quite a public relations problem on its hands. But that’s only half the story.
Read More Here

Identifying Unknown Plastics

Identifying Unknown Plastics

Even if the plastic you have isn’t labeled which type of plastic it is (though it should) there is ways to tell what type you have. Though the variety of possible plastic materials is essentially infinite, the familiar SPI recycling codes are the typical way to identify plastics. Knowing what plastics are used in other projects can help you find the plastic you are looking for in your own project.

The burn test, as it’s known, correlates a plastic sample’s composition with a set of observable properties including…
Read More Here

Are food-based plastics a good idea?

Are food-based plastics a good idea?

When thinking of plastics and food we normally think “Plastic food container” while “Plastic making material” is probably the last thing on our minds. Using foods to produce plastics will help the eco friendliness of plastics. But how would such plastics preform in the long run?

Food-based plastics, made out of everything from corn to sugarcane, have rapidly grown in popularity over the past several years. Packaging materials, gift cards, cell phone casings — all can be made from these eco-friendly materials.
Read More Here