Prototype Tooling Can Help Reduce Time and Cost

Prototype Tooling Can Help Reduce Time and Cost

prototype tooling

Developing & producing injection-molded products follows a proven process

The process for launching a product that includes injection molded components has been continuously developed for decades, and most commonly includes the distinct phases seen in the graphic below.  Each phase builds on the last, generating additional information necessary to bring a high-quality product to market in commercially relevant volumes and at an acceptable cost.  Prototype tooling plays an important role in this process.

product development & launch timeline

The time, energy, and expense associated with each phase is of course highly dependent on the design and functional parameters of the desired product, but for the sake of our discussion, we can employ the oft-used rule of thumb that the time and cost of making changes to a product is roughly 10X that of the previous step.  While this is clearly a gross oversimplification for any complex product, it does serve to illustrate a few key points that are relevant to product designers, project managers, and business unit executives: 
1) More information earlier in the project reduces risk
2) Earlier identification of design and manufacturability problems reduces overall project cost
3) Changes are much less expensive earlier in the process

Skipping steps must save time and money, no?

Injection molding process cost impactIt may seem logical to think that skipping steps in the process would reduce the time and cost of bringing a product to market.  Certainly there are examples of this, perhaps a simple bottle cap that has only minor changes in lettering or texture from previous versions, where the molder has sufficient experience to go directly from CAD design to production tooling. 

However, for most complex designs, say for an ergonomic consumer product with unique features, past experience, simulation, and rapid prototyping might not provide sufficiently accurate predictions of how the product will appear, what critical dimensions will be held, or how it will function when molded in the production material.

Rectifying problems in production tooling is difficult, expensive, and time consuming

Once a design for a high productivity steel injection mold has been completed and mold production starts, the costs to make changes becomes much more expensive simply due to the time and effort it takes to make even minor, much less major, changes to the tool.  Additional CNC, EDM, benching, and texturing time add up quickly.  The very nature of hardened tool steel, especially if it has been highly polished or textured, makes it difficult to modify.  Compounding this is the time it takes to remove the tool from the press, return to the mold making department (if in house) or transport to an external mold maker for modification.  All of this can easily add up to weeks of delay even with minor modifications, especially if the production tool has been sent to another country for molding operations. 

How does investing in prototype tooling save money? 

Firstly, let’s define prototype tooling, since it means different things to different people.  In the case of Xcentric, it means high quality injection molds produced with state-of-the-art CNC equipment and finished by master mold makers.  The mold material is a premium grade of aluminum developed specifically for injection mold applications.  You can read more about the Xcentric mold making process here.


Xcentric prototype injection molds help our clients save money in the following ways

  1. Reduce the cost of making corrections to injection molded components during validation and pre-production
  2. Reduce the cost of exploring design and material options

As noted above, the costs of making changes to a production tool are many multiples of making changes to prototype tooling.  In the case of a multi-cavity production tool, the costs are similarly multiplied should a change be required in the design of the tool or part.  Secondly, if there are still open questions about the design of the component including material choice, the cost of doing this experimentation in hardened steel is typically prohibitive.

Validating or correcting early in the process is extremely valuable

In the case of Xcentric, we typically turn around injection molded projects in under 13 business days, and upon request for certain products in under five business days.  Even if done sequentially, this is time well spent because this activity is completed so early in the project.  Problems can be identified and corrected weeks or months before the same issues would have been uncovered in production tooling.  While it is fully understood that there is not a 1:1 correlation between the performance of some aspects of prototype tooling versus production tooling, particularly related to high cavitation fill balancing, feedback on dimensional issues, material behavior, shrinkage, warp, sink, splay, and aesthetics can all be gathered in the desired production material in an Xcentric prototype mold.

The graphic below illustrates the standard process versus a process imagined to save time by skipping prototype molding.  Important points to note are: the time to a) recognize and b) correct for problems is weeks earlier, and depending on the severity of the change required, the overall project time can be shorter even including making changes to the prototype tooling.

Reducing product launch risk is even more valuable

By identifying and addressing production issues early in the process, project managers help to de-risk the overall project by giving themselves enough time to react.  Executive management and down-stream customers do not typically respond well to learning just before the originally scheduled product launch that there are delays due to production tooling that may push back launch by several weeks.  It is generally accepted that significant delays in new product introductions in many industries have a huge deleterious effect on the total net present value of the product launch.  Inevitably the questions come like “Why wasn’t this caught earlier?”  One difficult to explain answer is “Budget for prototype tooling was eliminated.” (that would have been a small fraction of the cost of the production tool changes and product introduction delay).  In this light it is fair to say that prototype tooling is a valuable insurance policy to help reduce the risks associated with new product introductions.   

Key takeaways about the money and time saved by prototype tooling

Including the process step to validate designs, identify improvements, and avoid downstream problems using prototype injection molding has been proven on innumerable projects to save both time and money.  Learning and correcting early in the process pays dividends for project risk mitigation.  Ultimately it is all about bringing the best possible product to market as quickly as possible, which happens to be Xcentric’s mission.

When To Choose Injection Molding Manufacturing

When To Choose Injection Molding Manufacturing

injection molding

Injection molding: one of the most important manufacturing processes

It may sound hyperbolic to state that injection molding is one of the most important manufacturing processes, without which the daily lives of people in industrialized countries would be completely different. But the evidence in terms of our common experience with the products in our homes, offices, restaurants, hospitals and more, suggests very strongly that if injection molding were not available, we would have less varied, less functional, and more expensive products around us.

Injection molding is by far the most effective and economical process for high volume complex plastic component production.

In this blog you’ll learn how to determine whether it is the appropriate manufacturing process for your application by examining: 3 factors of the product being produced: 1. material, size, and complexity, 2. manufacturing economics, and 3. prototypes and low-volume production.

Injection Molding Factor 1: Material, size, and complexity.

Material

The most important parameter when considering injection molding is the material requirement: the application must demand a thermoplastic or thermoset material that can be molded in a closed tool.  For the purposes of this blog, we will focus on thermoplastic materials which are much more common than thermosets, except in certain electrical, chemical, and thermal applications.

Today the choice of thermoplastic resins is enormous and encompasses a broad range of mechanical, chemical, physical, aesthetic, and economic characteristics that make them suitable for everything from toothbrushes to car bumpers.

Moldable polymers can be practically the full spectrum of colors, may be flexible or stiff, extremely strong and tough, and may have excellent chemical resistance.  However, it is the incredible combination of these properties that a single polymer can exhibit that makes them the material of choice for so many injection molding applications[1].

Size

The next factor to evaluate when considering injection molding is the size of the component to be produced.

On the small end of the spectrum there are micro-molded components used in medical devices that weigh a few tenths of a gram and easily fit in a 5x5x5mm cube.  On the other end we find components for agricultural equipment weighing more than 100kg with maximum dimensions well over 1500mm.

The majority of injection molded components, measured in billions per year, are caps, closures, disposable / single use products, toys, and personal electronics to name a few applications, which generally weigh in the 1-500g range.

Statistically, the world produces billions of molded plastic components per year, even excluding packaging such as beverage bottles.

-plasticsinsights.com


Complexity

The degree of geometric complexity further influences the choice of manufacturing process.

Injection molding can produce components with thousands of features, complex textures, combinations of materials in different locations in the same component, and molded-in metallic components in the exact same time it would take to mold a completely plain, featureless, single material, similarly sized component.

While there are some geometric limitations based on the physics of a molten liquid polymer filling a metal mold, solidifying, and then cooling pre- and post-ejection from the mold, the geometric possibilities are, for all intents and purposes, limitless.

Injection Molding Factor 2: Manufacturing economics – how to evaluate value

Following material properties, component size, and complexity, the design engineer needs to consider the manufacturing economics of the application.

In its simplest form, manufacturing economics is the exercise of maximizing the rate of value creation versus invested capital (including direct material and labor expenses, as well as tooling and equipment investments).  Or seen another way: minimizing the fully burdened manufacturing cost per component.

For a given capital expenditure, the rate of production of complex polymer components by injection molding can be many multiples of other means of forming the same geometry. This is where injection molding dramatically separates itself from other processes.

Doing a bit of back-of-the-envelope math for our telephone handpiece cover, let’s say we have our hypothetical factory floor with a CNC mill, an industrial 3D printer (as distinct from a desktop 3D printer), and a standard production injection molding machine lined up ready to start production.

An average CNC mill for a component this size new would cost $100-$150k, the industrial 3D printer $50-75k, and the injection molding press including a four-cavity steel mold $175k ($75k of which is the mold).

Ignoring the extra cost of automated fixturing and robotics needed to run production volumes in CNC machining, and eliminating the time required to unload and post-process 3D printed parts, the following table suggests the relative production performance of injection molding:

Manufacturing Process Comparison:
CNC Milling vs. 3D Printing vs. Injection Molding
Example: manufacturing a plastic office telephone handpiece cover.

One could CNC mill an office telephone hand piece cover from a block of the desired ABS, which would take, at best, tens of minutes per part and would not have the required surface texture.

Or, this same hand piece could be 3D Printed in an ABS material with similar, but different, properties and have compromises in surface finish and dimensional accuracy at the rate of a few per hour.

Lastly, a hand piece could be injection-molded every 20-30 seconds with exactly the desired material properties, surface finish, and geometry. For even higher production rates, multi-cavity injection molding tools would be used to increase the effective production rate.

Injection Molding

So, in this very simplified example we can see that the relative economics measured in invested capital relative to production rate (CAPEX / PPD), is substantially better than our hypothetical printer and CNC mill.  If the example component had been the same size but much simpler geometry, then the mill might improve to being only 1/5th as economical (which would still not be viable).  Or if the part were substantially smaller, then the 3D printer might also close to within 2-3X the CAPEX/PPD range of molding.[1]

Injection Molding Factor 3: Injection molding for prototype and low-volume production

The traditional injection molding tool manufacture and molding process is rarely the correct choice for prototype and low volume production expressly due to the cost and lead time as noted in our example telephone hand piece.

However, this is precisely where Xcentric delivers enormous value to our customers by helping them bring their plastic products to market on time, on budget, and with lower risk.

Proprietary Process Engine: From CAD to Production, Faster

Technically, how we do this is to provide the component in the right quality at the right time for the current product development phase of the customer’s project.  So, if the customer needs one or two parts for form-and-fit testing at the beginning of the project and the material does not matter, 3D printing is likely the solution.

If the customer requires the component to be in the polymer that will be used in production and have the same geometry and mechanical properties as the production article for testing or initial launch production, then we select injection molding.

Xcentric, however, has developed a rapid injection molding proprietary process engine that reduces the time to design, manufacture, and try-out injection molding tools down to a few days.  This is orchestrated by our proprietary XMBM expert system supporting our team of experienced mold makers and molders.  Secondly our mold manufacturing process is optimized for high-quality aluminum tooling, which helps us to be extremely efficient.  This allows Xcentric to deliver injection molded components in the customer’s choice of polymer in quantities as low as 25 parts in under 15 business days, and for some components in under five (5) business days [3].

Low volume production, for the sake of argument defined as under 10,000 units per year, can easily be accommodated with the same aluminum tools we use for 25 prototype parts.  When production volume increases, the tools would be designed for automated operation, adding cost and lead time, but still far below traditional hardened steel tooling due to the efficiency of our in-house tool production technology.

Today, Xcentric is often supplying a customer with prototypes and preproduction parts in semi-automated aluminum tooling for testing and early market entry, and then transitioning directly into automated aluminum production tooling producing over 250,000 parts for the same project.  This seamless transition saves time and is economical for the customer, and ultimately allows the customer to get their product to market in volume earlier than with steel tooling.

Injection molding is currently by far the most effective process for high volume complex plastic component production.  The benefits of injection molding for producing complex components from myriad polymers at high rates with low waste make it essentially the only viable manufacturing process choice for most polymer parts used in consumer, medical, automotive, and many industrial applications.

[1] Given the scope of the materials topic, details about thermoplastics will be covered in a separate dedicated article.
[2] This scenario already suggests a production rate that is beyond current 3D printing technologies when post processing and surface finish are factored in.
[3] Some limitations in project type and additional fees apply for expedited projects.

How is a rapid injection mold made?

How is a rapid injection mold made?

We are frequently asked how we manufacture injection molds, and more specifically how do we do it so quickly. To answer this, it helps to put our services into context. The cost and time required to produce traditional high-volume production injection mold tooling are a consequence of needing to maximize productivity and minimize per part costs for large production volumes. Very high volumes and high production rates dictate hardened steel tooling with full automation, multiple cavities, and advanced runner and cooling systems. Such tools are complex, time consuming to produce and test, and even more difficult to modify once in operation. However, when the customer requires a few hundred injection molded components on a tight delivery schedule, and the rate of production is not required to be high, a completely different mold production approach can be employed. This is what Xcentric has been perfecting for over 20 years.

Rapid Injection Mold Tool
Xcentric helps our clients beat their time to market requirements by rapidly creating custom injection mold tools thousands of times each year.

Understanding customer requirements is the foundation for every successful injection mold project

From the very outset of every client engagement, we strive to understand the full context of the project we are producing molded components for, to be sure we are addressing the customer’s primary needs and are making the best decisions for the mold design. For example:

  • What is the end use of the product?
  • What do the components we are molding do?
  • Will components be used for form, fit, function testing?
  • Is the project only a model for a coming trade show?
  • Are the components intended as end-use production parts?
  • How was the requested material chosen and what were the requirements?
  • Do the components need to have a high-quality surface finish or special texture?
  • Will the customer need 25 components in a few days or 250,000 over the next few months? 

Understanding and acting on the answers to each of these questions are the foundation of a successful injection molding project.

Translating requirements into fast action

Once we have gathered the requisite contextual information, our engineering and design team initiates an extremely tightly managed process of converting requirements and 3D CAD data into a mold proposal. Even at this early stage the project is already being managed by our proprietary design and production expert system XMBM to assure efficient execution at every stage downstream. This is essential, in that it assures that everything quoted can be designed, machined, and molded efficiently to meet our very short delivery timelines. Mold design engineers take into consideration the specific characteristics of the molded polymer, the required production volume and rate, and per part cost objectives of the customer. Using our proprietary design engine, the mold designer then completes the mold design in a matter of hours. Yes, hours, not days or weeks. This is possible because our designers can draw on decades of experience and an enormous library of existing solutions that can be quickly deployed, saving time and reducing variability from project to project. There are no shortcuts, simply a very efficient means of getting to a mold design solution.

Form follows function when designing an injection mold

Even within the sub-category of prototype and low volume injection molding, there are many choices to be made on specifically how each mold is to function. In the case of very simple low volume components in a forgiving material, the mold would be a simple single cavity open and close design. When undercuts are required the designer will consider current and future production volumes to decide if the tool will be automated or include hand-loaded inserts for these features. The use of hand-loaded inserts reduces the cost and production time of the mold, but generally increases the per part cost due to manual tending of the molding machine. Finally, in the case of complex geometries, including inserts and overmolded features in multiple materials, the full spectrum of design concepts will be deployed to balance product needs with cost and delivery time constraints. In the end, everything that can be molded in a complex high rate production mold can be molded in an Xcentric mold, and even in these cases our design process only requires a few hours for even the most complex designs. Again, a combination of great people, streamlined processes, and our unique expert system makes this possible.

Design validation in electrons not metal

Following initial mold design, our team performs mold flow analysis to reduce the likelihood of problems in the molding process. Depending on the complexity of the molded component, this can be a simple filling simulation all the way to complex warpage and shrinkage analysis, fiber orientation estimates for filled polymers, and other factors. Catching issues and collaborating closely with our clients at this stage to resolve potential problems leads to better products and higher on-time-delivery rates. Although we are quite nimble in rectifying problems that arise in the molding process, it is far easier and more efficient to do this when the mold is still in CAD and not in the press. Ultimately the completed mold design is reviewed with the client for approval prior to production.

From CAD to CAM, preparing for production

Once the mold design is complete, the process starts to really accelerate. The individual components of the mold (core, cavity, inserts, actions, ejector pins, etc.) are designated for their respective manufacturing process: CNC machining, EDM (electrical discharge machining), grinding, and manual machining. As with all prior steps, our expert system manages the flow of each of these components to their designated recipient in the appropriate order and quality so that the CAM team can be as efficient as possible. In many cases the g-code for simple components has already been produced during the design phase, but for more complex molds the CAM team will further optimize cutter path selection to assure best possible production rate and surface finish. Semi-automated cutter path planning and validation helps us save time, reduce variability, and increase the quality of all mold components. Typically designs are transferred from initial customer CAD through to completed g-code ready to mill within a day. That is moving quite fast in the injection molding world.

Hitting the production floor to make the injection mold

Transferring CAM information to the production floor again relies on the scheduling engine of our proprietary expert system. Depending on the component or EDM electrode to be machined, an appropriate three or five axis mill will be scheduled and the matching stock material selected and delivered to the milling machine. To maximize efficiency, stock mold materials, machining routines, cutters, and supporting processes are all predetermined and controlled to work in concert. This again follows the philosophy that controlling the end-to-end process details from quoting to design to manufacture yields repeatable high-quality results on a very compressed time scale. Likewise, minimizing the “dead time” between each step in the mold manufacturing process saves hours in every project, which in the case of our average project represents a meaningful percentage of the total time on task, allowing us to deliver fast. So, it is not that we necessarily machine faster, and we certainly do not cut corners, since doing so will only slow us down later in the mold finishing stage, it is that we plan and execute well.

The expert finishing touches complete the injection mold build process

Production of high-quality injection molds will always demand the personal attention of expert mold makers. At Xcentric we have a team of highly talented and hugely experienced mold makers who finish and test every mold to assure proper functioning of the mold and to achieve the desired surface finish of the molded components. This is part engineering and part artistry and cannot be rushed.  So, all of the efficiency we build into the prior mold production steps assures that this team has enough time to do the mold finishing process properly. Naturally we do everything possible to maximize the mold surface finish quality coming out of CNC and EDM so that manual finishing or laser texturing is less difficult. Finally, the various components of the mold are all brought together in the assembly department where the functional mold is built up and tested prior to delivery to the molding department.

Now let’s do that a few thousand times a year

So, you now have a brief glimpse into how we make an injection mold efficiently for prototypes, limited production volumes, or even production parts in the hundreds of thousands. But how do we do this consistently over and over and deliver all of this, including the molded components, in less than fifteen business days? No mystery, it is again great people, clever processes, and a unique expert system orchestrating a highly complex process in a way that is designed for repeatable success, even with the huge variability in customer and product requirements from project to project. This is what makes Xcentric truly exceptional in the injection molding world.     

How to Eliminate Knit Lines In Injection Molding

How to Eliminate Knit Lines In Injection Molding

Knit lines are formed when two or more plastic flow fronts collide and solidify or “knit” together during the molding process.

Overall, injection molding is a relatively simple process. A thermoplastic resin is heated to its melting point and injected into the cavity of an injection mold to produce a specific part geometry. The part is cooled in the mold until it reaches a temperature where it is solid enough to be ejected.

Knit lines most commonly occur around holes or other obstructions to the melt flow such as bosses. A boss is a feature with a hole that designed for a threaded fastener. A gate is an area where the resin is injected into the cavity.

Some thermoplastic resins with lower flow rates such as ABS and filled resins are more prone to having knit line issues. There are approximately 85,000+ thermoplastics available in the marketplace. Within the vast material options available, there are approximately 40 polymer blends or families.

While the presence of knit lines does not always compromise the structural integrity of the plastic part, they are almost always a cosmetic issue.

Changing the injection profile parameters – modifying the fill time for instance – may cause the knit line to move to a more favorable location.

Material selection, part design, tool design, and process parameters all also affect knit lines.

How to eliminate Knit Lines

  • Select resins that are less susceptible to knit line formation.
  • Change the boss or gate locations.
  • Thicken part walls to slow down the resin cooling process however be careful not to make them too thick that it causes sink marks.
  • Place knit line causing features farther from the edge of parts when the design allows for it to do so.

Do you have a question regarding knit lines? Send your design to one of our Technical Specialists for review at 586-598-4636 or sales@xcentricmold.com.

Plastic Molding Processes: Know The Basics

Plastic Molding Processes: Know The Basics

4 Plastic Molding Processes

We are frequently asked about different plastic molding processes and how each effect the process of part design and production. In this post we explain the basics of 4 plastic molding processes: plastic injection molding, blow molding, rotational molding, and vaccuum molding.

Plastic Injection Molding

Xcentric Mold specializes in plastic injection molding for low-volume and protyping. Injection molding is one of the most versatile manufacturing processes. It is used for producing simple and complex plastic parts for nearly every industry.

The injection molding process involves injectiong molten material into a mold. The, material is fed into a heated barrel, mixed (using a helical shaped screw), and injected into a  mold cavity. Finally, the material cools and forms the plastic part.

Not all materials heat (or cool) the same.

When designing for plastic injection molding, material selection is a critical for success. After all, materials do not all perform the same – during or after the injection molding process. To achieve the intended fit, form, and function of your part design, work with your supplier to choose the optimal material.

The injection molding process can be performed with a host of materials including: plastic, metal (for which the process is called die-casting), glass, elastomers, confections, and most commonly, thermoplastic and thermosetting polymers.

Common examples of plastic injection-molded parts include medical equipment and medical devices, automotive, marine, industrial, agriculture, aerospace and tight tolerance parts.

Other Molding Types

Below are some molding types which are not specialties of Xcentric Mol. However we may be able to provide you with recommendations of other suppliers who can assist you.

Blow Molding

Blow molding is a specific manufacturing process by which hollow plastic parts are formed and can be joined together. In general, there are three main types of blow molding:

  • Extrusion blow molding
  • Injection blow molding
  • Injection stretch blow molding

The blow molding process begins with melting down the plastic and forming it into a parison or in the case of injection and injection stretch blow molding (ISB) a preform. The parison is a tube-like piece of plastic with a hole in one end through which compressed air can pass.

The parison is then clamped into a mold and air is blown into it. The air pressure then pushes the plastic out to match the mold. Once the plastic has cooled and hardened the mold opens up and the part is ejected.

Common examples of blow molding products include bottles, containers and other hollow shapes.

Rotational Molding

Rotational molding is comprised of a heated hollow mold which is filled with a charge or shot weight of material. It is then slowly rotated (usually around two perpendicular axes), causing the softened material to disperse and stick to the walls of the mold. In order to maintain even thickness throughout the part, the mold continues to rotate at all times during the heating phase and to avoid sagging or deformation also during the cooling phase.

Common examples of rotational molding include parts larger than 2’ such as containers, utility carts, storage bins, car parts, tanks (oil, septic, water) and leisure products such as kayaks.

Vacuum Molding

Vacuum molding is a process by which a sheet of plastic is heated until it becomes pliable, stretched onto a single-surface mold and forced against the mold by a vacuum to create a shape.

This process can also include thick-gauge thermoforming, a type of vacuum molding, that is known for producing a variety of products including disposable cups, containers, lids, trays, blisters, clam shells, and other products for the food, medical, and general retail industries.

Common products produced with the vacuum molding application include industrial containers and crates, pallets, exterior door panels, plastic totes, plastic trailers, passenger cabin window canopies for winged aircraft, and lawn mower hoods.

Would you like additional information about the plastic injection molding process and its capabilities?  Contact our Application Engineers today at 586-598-4636 or sales@xcentricmold.com.

Wall Thickness Guide For Plastic Part Design

Wall Thickness Guide For Plastic Part Design

Wall Thickness Guide For Plastic Part Desgns

Our wall thickness guide will come in handy when you’re designing plastic parts for the injection molding process. Regardless of industry or application, designing plastic parts can be a challenge. Investing time early in process to optimize your design for manufacturability can help to save time and money.

Top 5 design tips for optimal wall thickness

Maintaining uniform wall thickness throughout your plastic injection molding part design is critical.  Without uniform wall thickness, many issues can occur such as sink, warping, short shot (meaning the material in tool does not fill correctly), and cosmetic imperfections.

  • A 10% increase in wall thickness provides approximately a 33% increase in stiffness with most materials
  • Walls should be no less than 40%-60% that of adjacent walls
  • Core out all unneeded thickness and wall stock
  • Sharp internal corners and long unsupported part spans should be avoided
  • Use ribs as stiffening features and supports to provide equivalent stiffness with less wall thickness

plastic injection molding

Material Selection

Selecting the proper material for your part design has a significant impact on wall thickness.  How the part is expected to perform and under what conditions will play a considerable role in material selection.

There are thousands of materials available to choose from.  Material properties not only effect wall thickness but also effect strength and durability.  Below are some recommended wall thickness guidelines with some common materials.

wall thickness

For further information, please visit our material selection guide.