One of the most unique types of injection molds is unscrewing molds. Unscrewing molding is a unique injection molding process with mold technology that includes movement and rotation to produce threaded components. Some plastic parts such as caps and closures with detailed threads cannot be removed using standard knock-off methods. After they are molded, parts need to be carefully unscrewed from mold to avoid damaging the threads.

The unscrewing molds are part of everyday use, which may cause you to think that you won’t need to spend much time considering the required design. To demonstrate the wide use of this particular mold type, the following is a shortlist of the types of products that use unscrewing molds in the design:

• Bottle and milk caps

• Condition and shampoo lids

• Prescription medication bottles

• Medical supplies

• Sprinkler and showerheads

• Screws, nuts, and bolts

Here’s How It Works:

• First, the plastic is injected into the tool. After the plastic has cooled, the threaded core starts to unscrew. The unscrewing mechanism works off of a rack and pinion and is powered by a hydraulic cylinder.

• The rack turns three sets of gears which then retracts the threaded core into the ejector box.

• Once the threaded core is fully unscrewed, the mold opens and the ejector system pushes a stripper plate forward to eject the part.

• After the part is fully ejected, the hydraulic cylinder reverses, screwing the threaded core back into the molding position, and the process repeats.

What factors need to be considered?

When you need one of these types of plastic molds, there are several things you have to determine to make sure you get the right fit for your product and budget.

Volume

The volume of the product will probably determine many different aspects of the final product, including the thread count, the size of the part, and the type of material that will be used during production. While other factors are important, the design of the various unscrewing molds is more complex and costly than many of the other types of molds.

Ease of Removal

The ease by which an unscrewing mold should be removed from the final product is an important factor to consider in the design. Water bottles have only a few threads, sometimes only two or three because they need to be easy to remove. To ensure that the tops do not fall off easily, the threads are spaced out a bit more. An unscrewing mold on a medical device will likely need a lot of threads that are evenly spaced and very difficult to pull off of the device. The material required for these two vastly different uses is affected by how easily the part should be removed from the product.

The Threads

The number of threads is going to vary based on the final product. Water bottles do not require a high thread count because they are relatively light and should be easily removed. If the unscrewing mold is for a plastic part under the hood of a car, it needs to have a higher thread count to be more durable. The number of threads required plays a large role in the final cost of production, so it needs to be tested to ensure it meets the needs of the final product.

Applications and Maintenance

High volume, reliable unscrewing plastic injection molds are some of the more complex plastic injection molds that can be manufactured. Unscrewing plastic injection molds are typically utilized for high volume applications where threaded plastic parts are needed for items such as:

ㆍBottle caps

ㆍShampoo bottles

ㆍPharmaceutical Supplies

ㆍAutomotive parts

ㆍNuts and bolts

ㆍCosmetics packaging

ㆍMedical Supplies

ㆍConsumer goods

ㆍSprinkler heads, lawn & garden parts

ㆍContainer lids

Most threaded plastic parts on standard plastic injection molds are not easy to remove using standard knock-off techniques. Therefore more complex unscrewing plastic injection molds must be utilized to prevent the threads on threaded plastic parts from being damaged while the parts are coming off of the plastic injection mold.

Because these threaded plastic parts are typically needed in high volume applications for items such as bottle caps or cosmetics packaging, the unscrewing plastic injection mold most operate at a high speed to reduce cycle times thus reducing part costs. The unscrewing plastic injection molds must also be high quality and reliable to operate for a large number of cycles while only needing routine preventative maintenance.

WIT MOLD is a very professional mold design and mold maker located South of China, certified ISO2009:2015 international quality standard. Reach out to us for a Rapid Quote to take advantage of this new offering for your internally threaded plastic parts.

What Is Tolerance?

The tolerance stated in the plastic injection mold is an engineering requirement. In basic terms, they are allowable variants to the initial dimensions of the parts or the base dimension. As it is impossible to generate a product that purely abides by the base measurements, some leeway obtains factored into the design of items.

This margin ensures that all measurements for molded products fit the setting up demands. For example, you may wish to produce products with a size of 2.8 mm. Nevertheless, attempting to produce them might end up with some of them gauging 2.6 mm.

What tolerances do is to establish minimum as well as optimum values for the production process in a way that ensures the product fits. In this case, the reduced limit can be evaluated 0mm while the ceiling is readied to 0.3 mm. By doing this, you are assured products whose diameters range between 2.8 mm and also 3.1 mm.

The important of tolerances

Generating plastic parts for your products calls for that their measurements fit perfectly. It’s very easy to offer dimensions for the type of components you want; obtaining them to have similar measurements to your requirements is a virtually impossible venture to achieve.

The type of making procedure you go for also has a terrific bearing on the high quality of completion product. Injection molding is among the most effective processes you can experience with standards like hubbub 16901 to name a few, but it’s still unable to produce parts with the right fit.

The only escape of such a scenario where it’s impossible to get an exact suit is to leave area for some distinctions in dimension. They don’t need to be major; they simply require not interfere with the item style. This is where tolerances are available in.

What Influences Tolerance?

The kind of polymer utilized throughout the creation of your items substantially identifies whether the tolerances are within acceptable limitations. As distinct polymers obtain injected into the plastic mold, they cool as well as shrink at different prices.

Despite the fact that these shrinkage rates can be quickly represented, completion product will certainly have different tolerance ranges and also discrepancies from the acceptable varieties. The array is a dimension of the difference between the biggest as well as tiniest measurements of measurements in the created batch.

Various other aspects that figure out tolerance consist of the style of the product, the intricacy of the style along with the atmosphere the injection molded parts will certainly be running in.

Minimum/Good Tolerances for Plastic molds

The great, or rather, minimal tolerances are established by the plastic polymer you choose to use for your products. These tolerances also can be found in various forms. For one, there are dimensional, straightness/flatness, and also hole diameter tolerances. They are also divided right into business tolerances and precision tolerances, which are greater in price.

Considered that an injection-molded physical tightening is a result of the cooling, the facet of temperature level decrease is influenced by various other aspects as well. They include the thaw thermal reading, the cooling price, the thickness of the part, the dimensions of eviction, as well as much more.

Furthermore, a section of the molded product that is thicker than an additional will certainly experience even more shrinking. All these variables are since even though it is possible to forecast the behavior of the plastic polymer you wish to be molded; the material will never ever act as anticipated 100% of the time.

The polymer concerned might likewise experience warpage. This is particularly real with parts that are non-uniform as they shrink at various rates in comparison to components that have uniform wall surface thickness. These non-uniform components can happen whenever the part’s design has a concern.

The final words

WIT MOLD has become one of the best molds in the industry because we combine the essence of the latest technology with proven traditional methods.

With an expert team composed of experienced and knowledgeable experts, we are able to complete custom orders for Custom Plastic Molds and parts that may exceed the capabilities of our competitors. We are also unremittingly committed to improving customer satisfaction, which includes providing comprehensive end-to-end quality assurance for every product we produce.

There are a variety of manufacturing methods used to create products using plastic polymers, including two-shot injection molding, compression thermoset molding and extrusion. While all of these are viable manufacturing processes, there are several advantages to this process that make it the top choice for many plastics manufacturers. The process is relatively simple; one material is injected into a mold in order to make the initial section of the product, followed by a second injection of a secondary material that is compatible with the original material. There are three good reasons many manufacturers use this method of manufacturing plastics or polymers.

Advantages of two-shot injection molding

Two-shot injection molding is cost-effective

The two-step process needs only one machine cycle, rotating the initial mold out of the way and putting the secondary mold around the product so that the second, compatible thermoplastic can be inserted into the second mold. Because the technique uses only one cycle instead of separate machine cycles, it costs less for any production run and requires fewer employees to make the finished product while delivering more items per run. It also ensures a strong bond between the materials without the need for further assembly down the line.

Enhanced product quality

Two-shot injection molding enhances the quality of most thermoplastic items in several ways:

ㆍImproved esthetics. Items look better and are more appealing to the consumer when they are crafted of different colored plastics or polymers. The merchandise looks more expensive if it utilizes more than one color or texture
ㆍImproved ergonomics. Because the process allows for the use of soft-touch surfaces, the resulting items can have ergonomically designed handles or other parts. This is particularly important for tools, medical devices, and other hand-held items.
ㆍIt provides for a better seal when silicone plastics and other rubbery materials are used for gaskets and other parts that require a strong seal.
ㆍIt lets you combine both hard and soft polymers for outstanding comfort and utility for even the smallest of products.
ㆍIt can greatly reduce the number of misalignments when compared to over-molding or more traditional insert processes.
ㆍIt enables manufacturers to create more complex mold designs using multiple materials that can’t be effectively bonded using other processes.
ㆍThe bond created is exceptionally strong, creating a product that is more durable, more reliable, and with longer life.

Versatility

Product manufacturers favor a wide range of applications for two-shot injection molding, including automotive interior parts, medical equipment, tools, and toys. It allows manufacturers to combine various materials and colors to create a strong and attractive final product. Some materials can be effectively combined with this process, including silicone and thermoplastics, nylon and thermoplastic elastomers, or hard nylon and soft-touch materials.

Two-shot injection molding can solve your company’s product production difficulties. An experienced plastic manufacturer can guide you from concept to finished product and ensure a cost-effective solution.

Producing an assembly with multiple components

Compared to other methods of plastic molding, two-shot is ultimately a more cost-efficient way of producing an assembly with multiple components. Here’s why:

Part Consolidation: Two-shot injection molding reduces the number of components in a finished assembly, eliminating an average of $40K in development, engineering, and validation costs associated with each additional part number.

Improved Efficiency: Two-shot molding allows multiple components to be molded with a single tool, reducing the amount of labor needed to run your parts and eliminating the need to weld or join components after the molding process.

Improved Quality: Two-shot is carried out within a single tool, allowing for lower tolerances than other molding processes, a high level of accuracy and repeat-ability, and reduced scrap rates.

Complex Moldings: Two-shot injection molding allows for the creation of complex mold designs that incorporate multiple materials for functionality that cannot be achieved through other molding processes.

Disadvantages of two-shot injection molding

1) High tooling costs and long setup lead times. Up-front costs are high due to the design, testing, and tooling required. There is the initial design and prototyping (probably via CNC or 3D printing), then the design of a prototype mold tool to produce replicas of the part in volume. Lastly, and only after extensive testing during both stages, you can finally inject mold apart.

2) Part design restrictions. Plastic parts must be designed with injection molding consideration and must follow the basic rules of injection molding, for example:

Avoid undercuts and sharp edges as much as possible

Use uniform wall thicknesses to prevent inconsistencies in the cooling process resulting in defects like sink marks.

Draft angles are encouraged for better de-molding.

Don’t forget, because tools are typically made from steel or aluminum, it can be difficult to make design changes. If you need to add plastic to the part, you can make the tool cavity larger by cutting away steel or aluminum. But in order to take away plastic, you need to decrease the size of the tool cavity by adding aluminum or metal to it. This is extremely difficult and in many cases might mean scrapping the tool (or part of it) and starting over.

Also, the weight and size of the part will determine the tool size and necessary press size. The larger the part, the more difficult and expensive it will be.

3) Small runs of parts can be costly. Due to the complexity of tooling, and the necessity to rid the machine of all previous material before the next product can be made, the setup time can be quite lengthy. Therefore small runs of parts have traditionally always been thought of as too expensive to injection mold.

We are an injection mold manufacturer. If you are interested in our products, please feel free to contact us.

Thermoplastics and thermosetting plastics are two separate classes of polymers that are widely used in the process of injection molding to create products of various types. Both these categories of plastics possess different properties and characteristics. Hence, choosing the right category of polymer, between the two, is of paramount importance to achieve the expected results when used in applications.  Most of the injection molding service providers usually receive a question from their clients about the differences between thermoplastic and thermoset molding process. Here, in this post, let’s see thermoset & thermoplastic injection molding comparison.

Defining Thermoplastic and Thermosets

Before we go deeper into the topic, it is important to understand the two terms thermoset and thermoplastic. Let’s first find out what are thermosets and thermoplastics.

What are Thermosets?

Thermoset plastics “set” after they cure and are generally stronger than thermoplastic materials. Initially, the polymer is a liquid or soft solid, which becomes rigid later when cured. Owing to their high mechanical and physical strength, resistance to heat, corrosion, and mechanical creep, thermosets are used in a variety of applications. A few amongst the common thermoset materials used in the injection molding process include alkyds, epoxy, phenolic, polyimides, thermoset polyester, and so on.

What are Thermoplastics?

In contrast to thermoset, thermoplastics liquefy and become pliable when heat is applied. Thermoplastic polymers can be reheated and reprocessed many times, which is impossible when it comes to thermosets. Usually stored in the form of pellets prior to the molding process, these categories of polymers can withstand multiple re-shaping without causing any damage to the material. They possess high strength, shrink-resistance, flexibility, high-Impact resistance, and chemical resistant, among others. A few amongst the common thermoset materials used in the injection molding process include ABS, nylon, PET, polypropylene, polyethylene and TPE, among others.

Difference between Thermoset & Thermoplastic Injection Molding

The way thermosets are molded differs with respect to thermoplastics in several aspects and both the categories require varied treatment during the injection molding process. Let’s check a few differences when molding thermosets and thermoplastics.

Where and How They’re Used

The differences inherent to thermosets and thermoplastics make them uniquely suited for differing applications.

Appliance fabrication may require a thermoset such as epoxy — the material’s high-impact resistance, microbial resistance, and general inert properties are ideal in the kitchen and cooling environment. Conversely, a thermoplastic such as polyethylene makes a great packaging film, since the material shrinks and conforms to the packaging when heated.

As a general rule, thermosets are often affiliated with manufacturing and utilities — appliances, electrical applications, and anything else involving heat that may otherwise warp thermoplastics. Thermoplastics, on the other hand, are broadly diverse and used in everything from aerospace fabrication to consumer goods and toys. The nature of the polymer used depends on the final application.

Now that you know how thermoset injection molding differs with respect to thermoplastic injection molding. With the information provided in the post, you would be able to make a judgment on the type of polymer category you should opt to produce molded parts. However, just knowing the differences between the materials won’t be enough, instead you would need an injection molding service provider who can mold your parts as per the right specifications provided. Partner with leading injection molding companies like WIT MOLD who own a comprehensive working knowledge regarding thermoplastic vs thermoset molding.

If you need a plastic part molded with extreme precision—for example, to ensure there’s no air leak between two molded sections or to be certain there’s no visible seal gap line—you likely require precision molding. The difference between a typical injection molded part and a precision molded part is the tolerance, or acceptable range of variation in dimension: While the majority of injection molded parts have a tolerance of +/- .005″, precision molding holds tolerances between +/- .002″ and +/- .001″ (or less, in some cases).

Let’s say, for example, you’re planning to manufacture a military projectile. In order for the projectile to fit properly in the firearm, handle the acceleration when it’s launched, and explode on impact, it requires very high precision.

If your application requires precision molding, you can’t leave anything to chance—so you’ll want to ask yourself the following three questions before you begin the process:

1. Have you selected a plastic material with low shrinkage?

The plastic material you select for your part makes a big difference in whether you’ll be able to do precision molding. For example, polypropylene has a shrinkage range of +/- .014″ to +/- .022″, with an average of +/- .018″. This is a wide range for shrinkage, which makes hitting a specific tolerance extremely difficult. If you’re molding a toothbrush (which commonly uses polypropylene), dealing with shrinkage isn’t a big concern, as the toothbrush will function appropriately regardless of whether it’s slightly bigger or smaller than its counterparts. Acrylonitrile butadiene styrene (ABS)—another common thermoplastic polymer—has a much narrower shrinkage average of +/- .006″. That gives you a much better chance of hitting a tighter tolerance, but it still won’t reach the +/- .001″ or +/- .002″ tolerance needed for a precision part.

One way to hit high tolerances with your plastic material is to add glass or another filler resin (like carbon fiber or mica) into the material. This can minimize shrinkage and warp by providing more structure in the material. For example, if you include long glass fibers in a polymer material, the part will shrink more perpendicular to those fibers.

2. Have you determined which areas of the mold require precision?

Because precision molding is more expensive than typical injection molding, be certain which aspects of your part require tight tolerances—and whether those tolerances can be achieved through injection molding—before moving forward. For example, a surgical handle may only require precision for the piece that will connect with a pin, not the entire handle. Identifying your precision requirements from the get-go ensures you’ll get what you need without wasting money. In the case of the surgical handle, your injection molding partner may advise you to add the tolerances you need through tooling after the injection molding process is complete.

3. Can the mold manufacturer you’ve selected tool with high precision?

The process of creating plastic parts with tight tolerances begins with a high-precision mold. If each plastic part you create is not identical, you won’t have a precise product—and a precise mold ensures there’s no variation for each part. Because of this, it’s extremely important to select a mold manufacturer who understands the slow, steady process of building a high-precision tool. Keep in mind that selecting a mold manufacturer that specializes in rapid tooling is likely not your best option, as the goal of rapid tooling is to finish the mold quickly—but not necessarily precisely.

Let’s get your precision molding project started

We have years of experience in precision molding, and would love to answer any and all of your questions. You can either contact us with those questions, or, if you’re ready to get your project started now, simply contact us and request a free quote.