Mold Design

The design and maintenance of molds are critical aspects that directly impact the quality, efficiency, and cost-effectiveness of the manufacturing process. Whether it’s creating intricate plastic components or precision metal parts, a well-designed and well-maintained mold is essential for achieving consistent and high-quality production. I want to explore the key elements of mold design and the importance of regular maintenance in the manufacturing industry.
Mold Design: The Foundation of Precision
1. Material Selection:
The choice of mold material is crucial and depends on various factors such as the type of material being molded, production volume, and desired product characteristics. Common mold materials include tool steel, aluminum, and pre-hardened steel. Each material has its own set of advantages and limitations, influencing factors like durability, heat resistance, and cost.
2. Geometry and Complexity:
The design of the mold cavity must precisely mirror the intended shape of the final product. The geometry of the mold is especially critical for intricate or complex components. Computer-Aided Design (CAD) tools are extensively used to create detailed and accurate mold designs, ensuring that every contour and detail of the final product is captured.
3. Cooling System:
Efficient temperature control is essential during the molding process to ensure proper solidification of the material and prevent defects. Mold designers must incorporate an effective cooling system into the mold design, utilizing channels and cooling lines strategically placed to maintain uniform temperatures throughout the mold.
4. Venting and Ejection:
Adequate venting is crucial to allow gases to escape during the molding process. Additionally, an effective ejection system is necessary to release the molded part without damage. Both these aspects are integral to preventing defects and maintaining the integrity of the final product.
5. Tolerance and Surface Finish:
Precision is paramount in mold design. Tolerances must be carefully considered to ensure that the molded parts meet the required specifications. Furthermore, the surface finish of the mold directly affects the appearance and quality of the final product. Proper polishing and finishing of the mold surfaces are essential for achieving a smooth and flawless finish on the molded parts.

One of the most common manufacturing processes for plastic mold design is injection molding. This automated process involves injecting molten plastic into a mold cavity. The mold is then cooled down until the material solidifies, resulting in a finished product with a consistent shape and size. This method is often used for creating many high volume, affordable plastic components from toothbrushes to TV housings. It’s very quick and cost effective compared to other production methods. And to make the production process of high-volume items even more cost effective multi cavity mold design can be utilized to make many of the same components in one shot simultaneously. Such multi cavity molds obviously are a lot more expensive than single cavity molds and only interesting if annual production volumes are upwards of a million.

The importance of mold design on the productivity of a tool is often overlooked in the design of a mold. Several areas in the mold design exist where the molder must work with the mold builder in order to optimize the productivity of the mold. A good standard for mold productivity is saleable parts out of the press per hour. Cycle time and part quality are the critical aspects of saleable parts per hour. The areas of design found to be most important for increased productivity are the sprue bushing, runners and gates, hot manifold, venting, cooling, and ejection. While each of these items is specific to the mold being built, good design for each can contribute to improved part quality and optimum cycle time.

Characteristics Critical to Mold Design
The first and most important area in mold design is the size of the sprue bushing, runners, and gates. This criterion is critical to ensure that the part can be filled stress-free, packed out, and frozen off to obtain the optimum molded part. With the use of mold flow analysis and the previous work of injection molding professionals, the correct size of the sprue bushing, runner, and gates for each material molded can be determined quite accurately. Following the guidelines for these sizes is most important, especially for the gate land length dimension, which should never be greater than 0.050″ and should be as small as practical. Sprue bushings that are too small will create excessive heat and pressure in the plastic. A good starting point is to make the “O” (inlet orifice) diameter the same diameter as the main runner.

Another area that relates to the sprue bushing is the nozzle. Often, molders will change molds without ever looking at the nozzle size and making sure it is matched to the mold they are running. Many times, this will lead to excessive pressures and temperatures of the material. Always matching the nozzle diameter to the sprue bushing “O” diameter is imperative.

Too often the mold maker is left to decide the sizes of the sprue, runners, and gates and only when running the first samples does the molder learn that the sizes are not optimal. Much of this can be resolved beforehand by following the principles of runner and gate design found in the Injection Molding Handbook, as well as other reference materials. Again, runners sized too small affect the heat and pressure of the plastic and runners too large may slow the cycle for cooling time and cause unnecessary regrind.

The following chart can be used as a guideline for runner sizes, depending on part size and the length of flow of the runner. If this data can be determined from mold flow, then that is a better place to start because it uses the rheology of the material being molded.

Gate location and gate size have a large effect on the fill of the part. Gate type and location should be the first determination when designing a runner layout. This is especially true in multi-cavity molds and large parts. Many different types of gates are available to the designer. The one selected should be determined by the part geometry, as well as the effect of the gate type and location on part dimensions, material flow, and part appearance. Most problems such as part appearance, warping, long cycle times, and cycle-to-cycle part variation can be attributed to some degree to the size and location of the runner and gate. A good rule of thumb is to start with the gate at 60 percent of wall thickness for crystalline materials and 75 percent of wall thickness for amorphous materials. Gate width should be two to three times the gate height when using a tab gate.

Hot manifolds, too often, are only available to the custom molder when the customer is willing to pay for them in the initial tool. However, the advantages of hot manifolds to the custom molder, including reduced cost of molding runners and sprues, as well as handling and remolding of regrind, usually pay for a hot manifold within a relatively short period of time. The hot manifold is usually of no cost benefit to the customer, given the way plastic parts are quoted. It should be used to increase productivity for the custom molder through the elimination of regrind. The tendency is to look at the capital outlay of adding a hot manifold in the mold design. Often this makes the tool quote non-competitive.

However, as is usually the case, there is a cost to not doing something. This cost can be determined as the cost of regrind. Regrind is the most expensive material molders use because they have already paid for it, molded it, reground it, and then have to reprocess it. Sometimes it is more difficult to process than virgin material. If the yearly volume of a job is high enough, it is a good investment for the molder to include a hot manifold for the mold, even if it is at the custom molder/s expense.

Venting is a topic that is often neglected by the mold builder or at best is an afterthought. Vents need to be included in the mold design and put into the mold so that they eliminate the hot gases generated during injection. The number of vents should be too many rather than too few. An accepted rule is one vent for every inch of part periphery. However, too often, vents have lands that are too long, not polished, and do not lead to atmosphere. So while the mold may look good, if it is not made properly it really isn/t doing much to eliminate trapped gases. Going to the trouble to install proper vents both for the part and the runners will pay off in increased part quality and decreased cycle times. Many times, parts can be vented at ejector pins, slides, and lifters. Following the raw material suppliers/ recommendation for vent sizes will help eliminate flash. Finally, vents can be neglected when performing mold maintenance; they should always be checked and repaired if necessary.

Cooling takes up the greatest portion of the injection cycle and is as important to part productivity as any other aspect of the molding cycle. The size and location of water lines are critical to optimizing part quality as well as cycle time. The best cooling for the part is to make it as uniform as possible in order to eliminate molded-in stresses and non-uniform shrinkage. In reviewing the mold design, it is important to determine if there are adequate cooling lines that are optimally located to provide the most efficient amount of heat transfer for the parts in the most uniform manner possible. The water line size should be large enough to allow flow that can keep the mold at a constant temperature during molding. The use of quick connects should be specified so that they don/t restrict the flow through the water lines. Making sure each mold half is correctly plumbed so that the mold isn/t simply turned into a water heater also is important. Looping A and B halves together makes it almost impossible to keep each mold half at the same temperature.

Following the resin manufacturers/ recommended mold temperature will help optimize both part quality and cycle times. Including a plan for water flow for each mold half is always helpful to the molder and should be required in the design.

Ejection is dictated by part geometry. This is an area where the part designer and the mold designer need to work together, if possible, to ensure that the part can be ejected easily from the mold. Unfortunately, this cooperation is not always possible. Adequate draft and the elimination of any unnecessary undercuts are both extremely important to ejecting the part without distortion or stress marks. Guided ejection also is important in mold design. This feature is worth the cost in savings of damaged pins and uneven wear on ejector pins.

In more complex molds, the relationship between the ejector pins and other moving parts, such as slides or lifters, must be carefully checked so that there is no interference. Using the largest possible ejector pins is recommended to alleviate stress marks. More complicated ejector systems, such as two plates and accelerated knockouts, are used often and with great success. What/s more, most of the mold base suppliers have components that make these systems fairly economical and easy to build. The most productive ejection system is one that operates automatically. However, this is not always possible. Through the use of automation, molders have been able to develop systems that interface extremely accurately with the ejector system and do not require operators.

So many more points can be made about the importance of good mold design in relation to part productivity. But if these basics are followed, mold makers will be well on their way to making a productive mold. It is always amazing to see the same mistakes being made when there is no good reason for it, and it always seems to be at the expense of the molder. All of the above items affect the size of the processing window for making good parts. By optimizing these design features, the molder is given the best conditions possible for productively processing quality parts.

What do the cap on your water bottle, strap on your smartwatch, and frame of your sunglasses all have in common? If they are all made out of plastic then they were all injection molded. Injection molding is a manufacturing process that has been around for over a century. In that time, the process and technology have made tremendous advancements. Similarly, mold design techniques and solutions have needed to evolve to match the technology and market needs. In the early days collapsible cores, conformal cooling, and advanced CAD softwares were beyond anyone’s wildest dreams. Today these are all standard tools in a mold designers toolbox, however, the only way these tools are useful to a mold designer is for them to gain the knowledge on how to use them. Even a simple tool, like a hammer, is just a paper weight to an individual who doesn’t know how to swing it.

we believe 3D printed mold tooling is the next big advancement in injection molding. While printed mold tooling certainly isn’t something new to the industry, it has not been widely adopted. Anecdotally, we hear all too often that someone tried out printed mold tools years ago and they just didn’t work. And historically, 3D printed tools were not made from the right materials and/or printed on the right hardware to hold up in a mold press. I dove deep into the application to understand exactly what inputs are needed to be successful. While standard inputs like material properties and printer quality are a major focus, less obvious inputs like the mold design itself has turned out to be a key contributor to successful or unsuccessful molding outcomes. One very basic principle that has guided us is that printed molds are fundamentally different from traditional steel molds. Steel molds are made out of metal while printed molds are made from a photopolymer. As a result, in order to be successful with a polymer based mold, different design strategies must be implemented.

Before plastic injection molding tooling, our team works on mold design. Mold deisgning determines minute factors such as the angles and wall thickness. The texture of the mold and the measurement as per the precision are also important.

The direction the line of draw

The direction of the line of the draw is important because it directly impacts how the two halves of the mold sit together. This decides the final product, so the direction of the draw should be pre-decided in injection mold tooling.

Amount of texture

The texture is decided by the design of the part. Ideally, there is the need for a certain texture because it helps with the grip of a delicate part. However, we can also provide molding tools with a glossy finish to give a smooth appearance.

Angle issues

Harsh angles like 90 degrees are not preferable at close proximity to the parting line. We resolve all of these problems during the design process. The mold tooling needs to go smoothly for better production capacity.

Temperature control within the tool

please do not need to worry about temperature control. the tool temperature resistant is a good choice, so that the fluid does not damage the tool during the molding process.

Wall thickness

The wall thickness should always be uniform across the entire part. Because the fluid, when inserted, can cool evenly without causing warping or inconsistent setting. The medical device verification and validation depends on how it dries, determined by wall thickness.

Filler requirements

You should know the core characteristics of the filler you are opting for on the basis of strength and durability. the supplier should offer contract medical manufacturing to help the clients add several services as per need.

Now that you know what injection molding is and its processes, let’s show you some tips that’ll guide your production.

They include the following:

1. FOCUS ON MATERIAL SELECTION:
We cannot emphasize enough that the material you opt for in creating your injection molding products is important. Using the right material will ensure that you design a finished product with the highest quality.

What’s more, a product with remarkable quality will tend to last longer. It’ll also save you the cost of production since you won’t have to waste extra material to recreate these products or replace damaged parts.

Therefore, dedicate the time, energy, and research needed to choose the right material that will be most suited for your components.

On the other hand, it is worth noting that there is a range of materials and each of them reacts differently to the injection molding process.

Thus, you need to know what to expect ahead of time in terms of cooling rates, minimum wall thickness, shrinkage, and durability.

2. ADD TEXTURE INTO YOUR DESIGN:
Textured products give your designs more appeal, which is quite common to find several products featuring it.

Accordingly, there are two approaches you can adopt to adding textures into your injection molded projects. The first is adding the texture using a specialized mold that includes these textures as the product is molded.

On the contrary, there’s the alternative of waiting after the injection molding process before adding the texture.

Now the first option will save you time and money since there are really no secondary texture processes to go through.

Therefore, if you choose to go that route, here’s what you can do. Opt for etched or milled molds that will help in creating the textured product.

3. COLLABORATE WITH AN ENGINEER:
Did you know that collaborating with an engineer can save you the time, energy, and extra resources that may be required to create your components?

An engineer or specialist in the field has advanced knowledge on injection molding, as well as, the intricacies of mold design. This extensive knowledge, therefore, makes it easy to enhance the design of your components.

It will ensure that you get molds and components feature the qualities you’ve already mapped out.

That being the case, it’s now left for you to search for a reputable engineer in the field who will be able to offer comprehensive services.

The engineer or professional company you settle for will be able to answer your queries or concerns you have regarding the injection molding process.

4. CONSIDER THE PRODUCT’S WALL THICKNESS:
It may be useful to reduce the product’s wall thickness in a bid to save money. The same can be said about aiming to streamline the injection molding process.

However, while aiming to gain these benefits, you also have to ensure that these parts are not too thin. If they are, you’ll end up with a finished product that is weak or unreliable.

Therefore, it’s useful to consider shrinkage and also create designs with the right wall thickness. It’ll ensure that you end up with a successful part and even save you money in the long run.

These are the tips for injection molding design and they should guide your design of parts that’ll stand the test of time.

The design process will reduce the wastage of resources and, therefore, save you money.

And remember, there’s a reputable engineer you should also fall back on to get professional help in your design process. This engineer will steer you on the right path if at any point you’re making mistakes that could pose grave consequences to your final product.

Therefore, give these tips your utmost consideration.

Injection molding isn’t a simple process, and as many of us know, it can sometimes take quite a bit of trial and error to get your injection molding designs just right. And while every new design requires several iterations between initial conception and production, there are several things you can do now to increase the chances of your design becoming a successful product.

Focus on material selection: The materials you use for your injection molding products are essential when it comes to the cost of production and the quality and durability of the finished product. Make sure that you devote plenty of time, energy and research to finding materials that are most suitable for your components and will result in the highest quality finished products. Different materials respond differently to the injection molding process and it’s important that you know what to expect when it comes to shrinkage, minimum wall thickness, cooling rates, and durability.
Incorporate texture into your design: There are many different ways to create texture in injection molded projects. Some manufacturers choose to add texture after the injection molding process has been completed, but it’s possible to create a textured product with a specialized mold. Etched or milled molds are effective at creating a textured product. By incorporating texture into your mold design, you can save time and money that would otherwise be spent on secondary texture processes.
Think about wall thickness: Reducing wall thickness can save you money and streamline the injection molding process, but going too thin might leave you with a part that’s weak or unsuitable for its intended purpose. Factor in shrinkage and create designs with wall thickness that will result in the most successful part possible.
Work with an engineer: Without extensive knowledge of injection molding and the intricacies of mold design, it’s difficult to optimize the design of your components. Working with an engineer who specializes in injection molding is the best way to achieve molds and components that have all of the qualities you want. Look for a reputable engineer who can provide you with comprehensive services and answer any questions you have about the injection molding process

If you’re looking to hire an expert in mold design, you may be looking for certain skills or keywords on resumes to indicate their level of proficiency in the field. An expert level designer should have at minimum five years of proficient design experience, at least 5 years of experience in injection molding, and a minimum of 10 years in a manufacturing and molding environment. Beyond those years of experience, they should have some of these skills included in their experience:

1）Problem solving – You can expect that every design will have a problem, whether that is something small or large enough to require a complete redesign. The expert level designer will have the experience to minimize the risks on every design and find a solution to every problem as it arises.

2）Plastic part design – Molding plastic is similar to molding other materials, but it does have unique characteristics that make it a challenge for some designs to mold easily. An expert in plastic mold design will know what changes to suggest for smaller and higher tolerance parts, or for products based on industry standards. An expert will be able to design for automotive products, overlay products, or for the medical industry without the need to restudy standards and criteria to achieve certification.

3）Software design – There are a handful of design software that will create molds. AutoCAD, Unigraphics, SolidWorks, and Pro-E are the dominant software packages used, and all are similar in their function. An expert may have knowledge of all mentioned, but will most likely be very fluent in the software used frequently. Most designers learn on one or two of the software packages and then hone their skills using each repetitively in day to day activities. Designers should also be able to create a replacement part database for maintenance teams to keep the molds in service and quickly repair as needed. That may be a list in a spreadsheet with 2D drawings as a guide, or separate parts designed in the same software for the mold.

4）New product development – Mold design is just part of a product lifecycle. Every part starts as an idea, then moves to a 3D design, and then into the physical mold creation. The designer should participate in the mold creation to ensure their design is translated to the mold and their concept will actually work in trials and production. The development cycle is more than just watching parts come out of a mold. It’s investing in what does and doesn’t work, then correcting and improving for the future.

5）CNC knowledge and setup – Most molds are created via Computer Numerical Control (CNC) software and machines. While having a deep knowledge of programming CNC machines and cut paths isn’t required, understanding the basics of software to generate them should be a standard requirement. Expert mod designers should be able to understand the concepts, speak the language, and help the tool creators turn the design into a physical mold.

6）Mold Flow Analysis – An expert mold designer should be able to assist or complete a flow analysis on their design to determine how well it will produce parts. These analyses will attribute to faster cycle times due to optimized molding processes, reduce the overall mold test cycles, and reduce your delivery time for parts. While it can be an added cost to the development process, the designer can complete the analysis quickly and offer suggestions to increase capability and productivity that will benefit the mold and product in the future.

7）ISO Standards – An expert mold designer should be up to date on the latest International Standards Organization (ISO) guidelines that the part design and production facility is incorporated under. The product may be required to undergo testing per ISO standards to prove compliant for overseas distribution. In that case, the designer may need to adjust the part or mold design to incorporate extra features to support testing and documentation for verification.

8）Knowledge of GD&T – General Dimensioning and Tolerancing (GD&T) outlines tolerances on a given part and product that are not specifically noted. The criteria for the tolerance is set under a general set of rules based on the industry the part is designed for or a governing set of guidelines such as Mid-America Machining engineering standards, ASME 14.5 GD&T, ANSI 14.5M, or ANSYS standards. An expert mold designer should know basics of GD&T and be able to investigate any additional requirements for a given industry or product design.

9）Knowledge of CMM – A Coordinate Measurement Machine (CMM) is able to measure parts based on a set of datum coordinates or points for verification of size. CMM machines are commonly used in the development of the molds to verify parts meet the design and tolerances, and then on a certain frequency during production of the product. An expert designer will have the basic understanding of the CMM machines and how it is utilized for verification, plus be able to help coordinate and design checking fixtures for the product or part the mold produce.

Whether you have a new part, are updating an existing one, or changing the manufacturing process, it’s important to design for manufacturing. The short and long-term cost/timing implications can be large if you’re not designing a component with the manufacturing process in mind. you should learn about everything from the injection molding process, to design tips for various part details.

hope that you are better informed and can use this knowledge to optimize your components for plastic injection molding. If you’re designing a plastic part, we highly recommend to work with an excellent mold engineering company. they can leverage years of experience, a network of suppliers, in-house injection mold design, mold building, and injection molding to make your product come to life quickly and efficiently.

Qualities of a good mold design company:
1) Reputation and past performance are critical. Ask the potential designer to give references and samples. Anyone can make unfounded claims of experience, but a referral from a reputable source is most valuable. This might make it hard for a qualified engineer just starting out, but the risk is not worth taking.

2）Availability is paramount. Check to see if he is easy to contact. It might simply be by telephone, but, more and more, people use things like Skype, Facebook, Twitter, and, of course, old fashioned email. Do some tests to see how available he really is. You certainly do not want to be waiting around for hours or days to get a response.

3）Flexibility is a must. Given the fast paced environment of the plastic injection molding manufacturing process, the mould design company must be quick to adapt to changes, updates, emergencies and such.
Follow-up service can make or break a job. It is one thing to make a one-off injection mold design, quite another to be there for support when you need answers after the initial job is done.
Timeliness is extremely important, given today’s very short delivery dates. If your mold making company has 8 weeks to build a mold and 2 of them are used up in design, you might need to look for a different mould design company to do your work. Of course, complex tools take longer, but the timeliness of the project starts with the mold designer.

4）Ease of communication can make everyone’s life much easier. What if you cannot understand the accent, or he does not have a good command of your language? It is hard enough to communicate about slides, ejector pins, cores, cavities, shut-offs, mold flow, gates, runners and hot runner systems without having the barrier of language.

5) Price, ahh yes, price. The last thing you want to do is choose a mould design company based on price. There are always cheaper deals on almost everything, but you generally get what you pay for. If you want to be totally frustrated and lose money, then place your order with the lowest bidder. On the other hand, if you need a good design and not a premium product, you should not spend money unnecessarily on extras that you do not need.

Injection-molded parts can feature complex geometries, and offer product designers a fair amount of design flexibility. The only caveat is that product teams must design their parts around the specific requirements of injection molding.
It’s very challenging to make design adjustments after the part has already been manufactured. As such, product designers must design the plastic part perfectly for injection molding to reduce the risk of issues with the tool design, achieve the best results, and reduce costs. To design clean, functional parts, start with these three injection molding design best practices:

1） The number one rule of injection molding part design is managing the thickness of the mold. Non-uniform walls can cause the part to warp as the thermoplastic material cools down or cause sink marks to occur. Recommended wall thicknesses vary depending on the plastic used. For example, polyurethane (PUR) has a recommended wall thickness of 0.080 inch to 0.750 inch, while polystyrene (PS) has a much smaller range of 0.035 inch to 0.150 inch. A good rule of thumb is to keep any given mold’s wall thickness between 1.2mm and 3mm.
If the part is designed to include different thicknesses, product designers should make the transition between them as smooth as possible. This ensures that the molten plastic flows evenly inside the mold cavity. A chamfer or fillet that is 3x as long as the difference in thickness should do the trick.
Thick sections in an injection mold design can cause warping, sinking, and other defects, but sometimes they’re necessary for complex geometries. Product designers can include thicker sections in their molds while adhering to wall thickness limitations by hollowing these sections out. Including ribs in the part strengthens the hollow sections and provides stiffness.
Rib thickness varies depending on the thermoplastic used, but ribs should always be less than two thirds of the main wall thickness. If the rib is too thick, it will cause sink marks on the outer surface

2）Undercuts are features that prevent the injection-molded part from being ejected cleanly from the mold without any structural damage. Undercuts can come in a variety of forms — holes, cavities, or areas where alignment is not perpendicular to the mold’s parting line. A product designer’s best bet is to avoid undercuts altogether. They always make the injection mold design more expensive, complicated, and labor-intensive than necessary.
Still, there are a few design tricks to handle undercuts. The simplest way to fix an undercut is to move the parting line of the mold such that it intersects with the undercut. However, this tip is only applicable for designs with undercuts on the outside of the mold.
Bumpoffs, or stripping undercuts, are an option if the feature and material are flexible enough to expand and deform over the mold during ejection. The bumpoff should be far away from the mold’s support structures and have a lead angle between 30 to 45 degrees.
As a last resort, side-actions or lifters can fix undercuts when the mold cannot be redesigned to avoid undercuts. Side action cores are perpendicular inserts that slide in and out of the mold as it opens and closes.These mechanisms drive up cost and complexity significantly. Even with these solutions, it would behoove designers to steer clear of undercuts altogether and eliminate undercuts during prototyping.

3）Draft angles are design considerations that make it easier to cleanly eject an injection-molded part from the mold. This might sound like a non-essential design feature, but drafts are critical to manufacturing functional injection-molded parts. Drafts help prevent the part from becoming damaged upon release, lower production costs, accelerate production timelines, ensure a uniform surface finish, and provide a slew of other benefits. Without draft angles, product teams risk damaging their expensive molds and producing a large number of rejectable parts.
Drafts should be accounted for early in the design process. Draft angles will vary according to a number of factors related to the part, including wall thickness, wall depth, material, and any applicable shrink rates, texture, or ejection requirements. It’s best to apply as much draft angle as possible. Product designers should include one degree of draft per inch of cavity depth to start, adjusting for the aforementioned factors as necessary.
Even if it looks like draft might negatively impact the performance of the part, it’s always better to have draft than to not have draft. Parts can be designed with a minimum of 0.25 degrees of draft, generally, but the smallest degree of draft possible will depend on the part’s unique geometry and material.

Injection molding is a high-precision manufacturing process that injects molten plastic into a carefully designed mold, where the plastic cools and hardens into the specified part or product. The piece is then ejected from the mold, either as the final product or as a near-final product that is sent on for secondary finishing.

The injection mold consists of two parts: the mold core and the mold cavity. The space that these two parts create when the mold is closed is called the part cavity (the void that receives the molten plastic). Depending on production needs, “multi-cavity” molds can be designed to create multiple identical parts (as many as 100 or more) during the same run.

Designing the mold and its various components (referred to as tooling) represents a highly technical and often complex process that requires high precision and scientific know-how to produce top-quality parts with tight dimensions. For example, the proper grade of steel must be selected so components that run together do not wear out prematurely. Steel hardness must also be determined to maintain the proper balance between wear and toughness. Waterlines must be well-placed to maximize cooling and minimize warping. Tooling engineers also need to calculate gate/runner sizing specifications for proper filling and minimal cycle times, as well as determining the best shut-off methods for tooling durability over the life of the program.

During the injection molding process molten plastic flows through channels called “runners” into the mold cavity. The direction of flow is controlled by the “gate” at the end of each channel. The system of runners and gates must be carefully designed to assure even distribution of plastic and subsequent cooling. Proper placement of cooling channels in mold walls to circulate water are also essential for cooling to create a final product with homogeneous physical properties, resulting in repeatable product dimensions. Uneven cooling may result in defects called “hot spots”—areas of weakness that affect repeatability.

In general, more complex injection-molded products require more complex molds. These often must deal with features such as undercuts or threads, which typically require more mold components. There are other components that can be added to a mold to form complex geometry; rotating devices (using mechanical racks and gears), rotational hydraulic motors, hydraulic cylinders, floating plates, and multi-form slides are just some examples.

Before you start a new mold design, the particular plastic mold designer should be owning the next data .
An unambiguous totally comprehensive injection molded parts drawing
Specifications of the moulding material, consisting of grade and color
The moulding machine technical specs
All the estimating details which includes any kind of blueprints
The global market size of the injection molding industry was $139 billion by 2018, expected to reach $233 billion by 2023 with a CAGR of 10.9%. In the interim, the injection molding industry directly relies on mold design. If the design is up to the mark, the product will prevail in the market. Similarly, mold design is a leading factor that defines the quality of the final molded part.

The perfect mold design also ensures the proper investment of money while bringing the wastage to the lowest level. Existing prototyping techniques such as 3D printing consider early testing of design ideas where the whole part can be modeled before constructing costly tooling.

There are many factors to consider for injection molding, but the part design and tool design are two of the most important.Getting them right could mean lower entry cost, high production quality, shorter cycle time, and quick assembly. Getting them wrong, on the other hand, can be very costly indeed.

Wall thickness
The thinner it is the easier the injection molding process. Parts with thin wall thickness cool faster, weigh less and use less plastic per part. This means shorter cycle times, resulting in more parts produced per hour and lower production cost.

Wall thickness must be consistent to reduce if not eliminate warping. If consistency is hard to achieve due to design limitations, the change in thickness should be done gradually. The use of a coring method will help eliminate such problems, while adding gussets will reduce warping.

Ribs
Instead of increasing the thickness of the wall, ribs are often used to increase the bending stiffness of a part, which is a result of an increase in the moment of inertia.

Also, its orientation must be perpendicular to the axis where bending may occur, and the corners at the point of attachment must be rounded.

Sharp vs curved corners
Sharp corners in your design will cause molded-in stress from the resin flow. A stress riser may also form during application. But round corners do the opposite, reducing stress concentrations and fracture. For effective injection molding, the inner radius should be, at least, similar to the thickness of the walls.

Draft angle
When molded parts are hard to eject, drag marks or ejector punch marks can occur. To facilitate faster ejection, a draft angle of 1°- 2° should be applied to all walls parallel to the parting direction of the clamping unit. In case design considerations do not allow draft angles, the use of a side action mold may be required.

Bosses
Bosses are where fasteners, such as screws, are attached or threaded inserts are accepted. They basically facilitate registration of mating parts. Good bosses should not have thick sections that will result in sink and voids in injection molded parts.

Ribs should be used to isolate bosses placed near a corner

Textures and lettering
It is possible to incorporate textures and lettering to a part, whether as an aesthetic addition or for branding purposes. Texturing is also an effective way to hide surface defects and other imperfections on a molded part. Like anything involved in designing for moldability, there are guidelines to textures and lettering as well.

The extra draft must be added to textures and letters with a limited depth. This will facilitate part removal without dragging or leaving marks. Generally, texture must have a depth of 1.5° min. per 0.025mm (0.001 inch) in addition to the normal draft.

Undercuts
These are a piece of the design that blocks the mold keeps it from sliding away along the parting direction. It is either external (protrusion) or internal (depression). Unless absolutely necessary, external and internal undercuts must be minimized. If needed, a feature should be redesigned. Otherwise, tooling costs will increase because external undercuts require side cores, while internal undercuts require internal core lifters.

Inserts
These plastic parts provide a place where fasteners, such as screws, can be placed and replaced many times over, allowing for longer cycles of assembly and disassembly. This is especially true with inserts made of brass. Insertions are usually installed in injection molding parts using ultrasonic insertion, thermal insertion, or molded-in.

Injection mold design tips
A good design must be practical. The mold maker must be able to produce the components in a logical, orderly manner to make money. Often, close tolerance dimensions are specified when a much looser tolerance could have easily done the job.
Take an ejector pin plate, for example. Everyone knows that the thickness is basically irrelevant, but usually the dimension given is a close tolerance size. An experienced toolmaker will just ignore the tolerance and proceed, but nowadays, with the specialization of tasks in the shop, a less skilled operator would waste precious time holding an unreasonable tolerance.
The 3D geometry must be clean. The fast pace of mold making today makes it essential to have efficient, reliable software. The days of vague sketches, or toolmakers making up the design as they go are long gone. There are many excellent companies that offer high end software programs for designing molds, dies, and just about any kind of tooling you can imagine.
CNC machines need clean geometry to run properly. If the design is sloppy and the translation of different software messy, the end result will show it. Plus, the operator will have a much easier time running the programs with clean geometry.
The design must be clear in it’s function. It is maddening for a plastic injection mold maker to spend hours deciphering what the designer means. Information that is assumed or omitted can delay the construction by days and cause unnecessary errors. Why should a toolmaker spend time looking up information that was right in front of the designer at one time?
It is always much easier to include notes or details that show what is required than to search it out later on. Once the design is in process, and the information is available, why not simply give the mold maker the same information? For example, a 3D drawing can visually clarify many questions.

Injection mold design tips
A good design must be practical. The mold maker must be able to produce the components in a logical, orderly manner to make money. Often, close tolerance dimensions are specified when a much looser tolerance could have easily done the job.
Take an ejector pin plate, for example. Everyone knows that the thickness is basically irrelevant, but usually the dimension given is a close tolerance size. An experienced toolmaker will just ignore the tolerance and proceed, but nowadays, with the specialization of tasks in the shop, a less skilled operator would waste precious time holding an unreasonable tolerance.
The 3D geometry must be clean. The fast pace of mold making today makes it essential to have efficient, reliable software. The days of vague sketches, or toolmakers making up the design as they go are long gone. There are many excellent companies that offer high end software programs for designing molds, dies, and just about any kind of tooling you can imagine.
CNC machines need clean geometry to run properly. If the design is sloppy and the translation of different software messy, the end result will show it. Plus, the operator will have a much easier time running the programs with clean geometry.
The design must be clear in it’s function. It is maddening for a plastic injection mold maker to spend hours deciphering what the designer means. Information that is assumed or omitted can delay the construction by days and cause unnecessary errors. Why should a toolmaker spend time looking up information that was right in front of the designer at one time?
It is always much easier to include notes or details that show what is required than to search it out later on. Once the design is in process, and the information is available, why not simply give the mold maker the same information? For example, a 3D drawing can visually clarify many questions.

There are thousands of designers who design injection molded parts but there is an elite group within this large community who can actually design parts for injection molders. Injection molded product design evolves through many phases of development before all the parts are ultimately documented and released to a molder for production. This last step in the development process is the most critical, since design changes or corrections can no longer be made without significantly adding cost or project delays.Unfortunately, plastic part design mistakes will be uncovered only after first article parts are inspected and evaluated by the project team. Even with today’s sophisticated mold flow simulation, 3D CAD interference checks, rapid prototyping and numerous other development tools, it is impossible for anyone to predict every potential problem for an injection molded part. However, there is a very simple, low-cost method for minimizing potential problems and virtually ensuring perfect parts. It’s called partnering with your molder.

One of the greatest challenges for any designer faced with designing an injection molded part is providing enough clearance in the design for tolerance variation. Tolerance variation depends upon several variables, including materials, process control and tool design. Acceptable tolerance ranges in a design will vary greatly from one molder to another. It’s imperative that designers discuss reasonable critical tolerance specifications with a molder and consider options for possible mold revisions, if required. This may require certain design features to be intentionally designed with extra clearance, which will later be tightened by removing steel from the mold. No one wants to add steel with welding to remedy interference problems. Molders may offer a number of suggestions for maintaining tight tolerance control, including post machining, fixturing and gate locations.

The biggest challenge in injection molding is the process of designing a mold. There are almost no limits to your creativity,but you can do the designs in clever and less clever way from a manufacturing point of view. Plastic manufacturers highlight this aspect as the most crucial part of injection molding. There will be no successful plastic part designs for injection molding if there is no perfect mold from where it is formed. The biggest factors to designing a mold are part and mold design. Getting these factors right means faster production, better quality and reduced costs while having them wrong could substantially affect these production aspects in a negative manner.

Before formal mold design, the following datas or documents are usually available:
1. Part’s design data (2D/3D)
2. Mold design and production standards;
3.Design and manufacture contract;
4. Other
To fully understand the above information, unclear details must be confirmed by the customer.

The correct injection mold design has the following benefits:
Quick mold setup
Faster cycle time
Quality parts
Low scrap rate
High productivity
Long mold life
Long life of the molding machine
Improve employee morale
Unfortunately, many mold designs have some fundamental flaws that prevent the injection molding machine from reaching higher productivity levels.

First-rate mold design team always designs products and molds in strict accordance with your design standards. Let you know that these designs belong to you, they will even use your standard title block. After all, these are your projects and should really be designed to your expectations.

Injection molding is a highly precise manufacturing process that injects molten plastic into a well-designed mold where the plastic cools and hardens into a specified part or product. The workpiece is then ejected from the mold either as a final product or as a secondary product near the final product.

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