What is a hot runner- more info?

Mold-Masters hot half

 

Hot runner technology, introduced to the plastics industry over 50 years ago, revolutionized injection molding processing capabilities by improving molded part quality, enhancing operational efficiencies, reducing scrap and saving money.

A hot runner system is a molten plastic conveying unit used within an injection mold. In other words, a hot runner system consists of heated components (generally via electricity) used inside the plastic injection molds, which brings the molten plastic from the barrel of an injection molding machine into the cavities of the mold. The sizing of hot runner melt channels depends on many factors such as the type of resin, the injection speed, fill rate, and the molded part. A temperature controller (standalone controller or controls from the injection molding machine) heats the hot runner system within the injection mold and the resin inside the machine barrel to processing temperature and injects the resin into the mold. The resin travels through the inlet, down into the manifold which then splits to the various nozzles and through injection points (or gates) into the final mold cavity where the final part is formed. Today’s molds can have anywhere from 1 to over 192 nozzles depending on the plastic parts being manufactured.

Prior to hot runner technology, cold runners were widely used on injection molds. Cold runner molds faced many challenges in conveying the resin from machine barrel to cavities without affecting the flow and thermal characteristics of the resin. With the advancement of resin types and the complexity in mold and part designs, it became more and more difficult to control the molding process via cold runner molds to produce molded parts of acceptable quality.

However, with the introduction of hot runner technology with advanced thermal controls, processing of wider ranges of resin became more practical and convenient to injection molders. Unlike a cold runner mold, the hot runner components are individually heated to ensure the resin maintains the temperature continuously through the mold. The temperature of each hot runner heated component can also be precisely controlled to ensure the process is optimized to the requirements of each type of resin delivering the highest possible part quality. Today, hot runners are capable of producing highly complex parts in a wide range of sizes which are utilized in every industry.

Elements of a Hot Runner

  • Locating Ring – The locating ring aligns the injection mold with the platen of the molding machine. It ensures there is proper alignment of the mold with the machine.
  • Inlet – When resin is injected into the mold, this is the entry port where the resin enters from the injection machine nozzle. Depending on the type of resin and the design of the hot runner the inlet component may be heated in order to optimize the molding process.
  • Manifold – The manifold enables the flow of resin into different nozzles and injection points (gates). Manifolds are normally used where multiple cavities are injected or where more than one nozzle/gate per part is needed. Manifolds are available in a wide range of materials, designs and shapes and are often optimized to improve the molding process using CAE analysis. There are 2 main types of manufacturing techniques, gun drilled and 2 piece brazed. Gun drilled are often ideal for simpler, more economical systems while 2 piece brazed is often favoured when tighter performance criteria is required (balance, faster color change). 2 piece manifolds are also ideal for multi material or multi color molding applications.
  • Nozzles –Nozzles are components where the resin is injected into the cavity through a gate. Depending on the design, nozzles are typically installed into the mold plate with or without a manifold. A wide range of nozzle designs are available, using different materials, in order to achieve the processing characteristics of various resins that best suit the application.
  • Heater Technology – Heater technology is the basis of all hot runner systems and significantly affects molding process and part quality. There are several heating options each with their own pros and cons. Selecting the right hot runner depends on the requirements such as molding process, part performance, reliability and cost. Most common hot runner technologies have heaters with heater bands/plates, paste-in/flex heaters or brazed-in heaters.
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Understanding Differences in Hot Runner Heater Technologies – Manifolds

All hot runner systems need a heat source to operate as designed, however not all hot runner systems are heated by the same methods. The type of heater technology your hot runner system uses can significantly affect molding performance, molded part quality and system cost. No heating method exists that is ideal for every scenario and each one has their own pros and cons but illustrating their differences may help you in understanding how your hot runner system is constructed and provide you with some additional insight on your next purchase. Some hot runner systems may use a mix of heating methods depending on the components of the system and application but for the purposes of this discussion we will focus on manifold heater elements.

The main types of manifold heating methods include Embedded Heat Sources (Brazing, Pasted, Pushed-in) or External Heat Sources (Heater Pads/Plates). Selecting the right heater element is always a careful balance of performance, reliability and cost (both initial investment and operating). Many factors are also weighed including type of industry, part geometry, mold design, part variables and production requirements.

EMBEDDED HEAT SOURCES

Compared to External Heat Sources, Embedded Heaters offer a range of advantages

  • Heater element channels optimized through CAE analysis for enhanced thermal profile
  • Enhanced energy efficiency
  • Helps protect heater elements from physical damage
  • Extended life
  • Generally ideal for small to large symmetrical manifold designs with tight or standard pitch dimensions

Brazed-In Heaters

Brazed-in Heaters generally offer the best performance and reliability making them ideal for achieving the highest molded part quality and long term production. Using advanced CAE analysis, heater channels can be optimized for each manifold to achieve unbeatable thermal balance. Thermal balance of the manifold is a critical variable in achieving excellent balance of fill results and therefore superior part quality.

As the element is set into a recessed heater channel, the greater contact area is much more efficient at transferring and maintaining heat than traditional heater methods and helps protect the element from physical damage. The Brazing process also completely eliminates any air gaps that can lead to heater failure through electrical arcing. Brazed heaters are often made to higher quality standards than other heaters and therefore have a very low failure rate. With a lifespan able to exceed 10 years, they have the ability to outlast well beyond the life of the mold. While brazed heaters require a higher initial investment, this is typically offset by higher quality part production reducing scrap rate, eliminating heater replacement costs and minimized downtime. Part quality aside, the higher the cavitation and longer the production run the more it makes sense to invest in Brazed heaters.

Paste-In

Paste-In heaters are considered to be mid-range heaters. They are more economical than the brazed version however there is a trade-off in performance and reliability. Although the paste-in technique attempts to eliminate air gaps, the method is not 100% so there is a relatively higher risk of heater failure which does occur at a higher rate (vs. Brazed). This production challenge is offset by the potential ability to replace the element in the field, although it’s not always possible. Regardless of the potential for increased downtime, Paste-In Heaters are still a great option for molders looking for performance with a more economical initial system price.

Push-In/Flex Heaters

Push Heaters, like Paste-In heaters, are considered to be mid-range heaters but their design favours faster in-field replacement. Since there is no “pasting” step required it helps minimize any servicing downtime. However, with the elimination of the paste, there is less contact area which can increase energy consumption. The element itself also has a more limited bending radius which can restrict its applications. Available in a wide range of standard lengths, diameters and wattages, Push Heaters are an off the shelf item so sourcing spares globally is also quick and easy.

EXTERNAL HEAT SOURCES

Compared to Embedded Heat Sources, External Heaters offer a range of advantages

  • Lowest cost for more economical up front system pricing,
  • Ability to use multiple heaters to increase number of temperature control zones (ideal for manifolds with long pitch/asymmetrical designs-automotive),
  • Easiest to replace,
  • High standardization allowing for easy global access to spare parts from multiple sources

Heater Plates

By now, you may be wondering what sense it makes to use Heater Plates when there are several “better” options available. Truth is, although Heater Plates would be considered lower performance under the same circumstances as the other options, Heater Plates are a good choice for a completely different type of mold design. Their ideal applications are on molds that benefit from having additional zones of control. Typically this would be large/high pitch/non-symmetrical manifolds (automotive, and large parts for white goods for example).

Evaluated on a larger scale and utilizing CAE optimization analysis it is possible to achieve a good overall thermal profile, better than if a single continuous element had been used for the same application. Also, Heater Plates are the most economical, the easiest and fastest to replace and are a common standard off the shelf component offered by a wide range of global suppliers. While high reliability is always beneficial, automotive molds have a lifespan limited to 3 to 5 years so the lower system price is better positioned to offset some failure related downtime.

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Hot Runners vs Cold Runners: Why You Should Be Using a Hot Runner System

cold-runner-vs-hot-runner-toothbrush

 

Plastic components are in use by every industry and manufacturing these components through injection molding has come a long way. A wide range of equipment options exist depending on your application and capabilities. Generally speaking you have a choice between traditional cold runners or the more advanced hot runners. Each option comes with its own unique sets of pros and cons and so understanding the differences and how they relate to your application could have a big impact on your productivity and overall profitability.

Cold Runners

In a cold runner mold, the molten thermoplastic is injected into the mold which fills the runners that distribute the molten plastic to the individual mold cavities. The cold runner mold then cools the sprue, runner, and gate along with the molded part.

Cold runner molds are certainly more economical to manufacture and can be easier to maintain, however they have several major limitations compared to molds with hot runner systems:

  • Longer cycle time
  • Creates waste (sub-runners)
  • Require additional auxiliary processing equipment (robotics, re-grinding machines/employee labor to remove runners, etc.)
  • Secondary operations (degating, removal of cold runners, re-grinding etc.)

Why Choose Hot Runners

While hot runners often come with a higher upfront cost and require some additional maintenance, their more efficient design can often easily provide a valuable return on this investment. Hot runners significantly overcome the inefficiencies of its cold runner counterpart.

Hot runner systems produce less wasted plastic, have shorter cycle times, use less energy, improve gate quality, use fewer auxiliaries and require less manual labor for runner handling, trimming and regrinding.

Wasted Plastic & Energy

Depending on the part design, the cold runner can equal 50% to 250% of the mold part weight with regrind typically limited to 15% at most, so the remaining 85% is waste or has minimal salvage value. Re-grinding also adds a step in the manufacturing process and could decrease the plastic’s mechanical properties

For some markets, this waste could be much higher. The medical market requires 100% virgin resin, so all of the runner would be scrap. The energy consumption of a cold runner can double due to extra heat, cool and regrind wasted.

For many applications, the wasted runner can double the part cost.

Cycle Time

Cycle time is typically dominated by part cooling, with cooling time being dictated by part wall thickness or cold runner thickness. Even optimized cold runners cause typically 50% to 100% longer cycle times than hot runners.

Hot runners offer higher productivity yields due to significantly reduced process cycle times.

Capital Equipment

Cold runners mold with 3 plate design, trimming equipment, regrinding equipment, added chilling/cooling capacity and metering blender. Hot runners only require a manifold, nozzles and plates as well as a temperature controller, which is reusable.

Managing additional overhead and operational factors such as added chilling capacity and the noise and dust related to grinding scrap runners.

Labor Costs

Cold runner costs include runner handling, trimming, re-blending and scrap. They are prone to occasional stick in molds interrupting overall operation. Maintenance is also required on numerous auxiliaries.

Hot runners are highly automated and are ideally suited to scheduled preventative maintenance.  Interruptions are possible with failed heaters or thermocouples but depending on the hot runner manufacturer, these interruptions can be minimal.

Eliminating the cold runner saves the added labor from runner handling, gate trimming and regrinding.

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Prevent Hot Runner Downtime with Scheduled Maintenance

Preventative Maintenance (PM) is a critical task that aims to help ensure your mold(s) run at peak efficiency by strategically investing in service and maintenance before things go very wrong and get very costly. A well executed PM program will help improve productivity and avoid costly downtime including unscheduled breakdowns. However, the trick has always been in finding the right balance to optimize your operation. Too little service and you could still incur breakdowns, among other issues, and too much maintenance you end up throwing money away.

The frequency of a Preventative Maintenance Program is very specific to individual molds. There are numerous factors that have an influence on the scheduling of PM. Some of the most significant are materials and how the processing equipment is being operated.

Materials being molded play a big part in how often a hot runner mold will require maintenance.  Some molds can go months with very little maintenance while others will require daily cleaning of the “gas” residue that builds-up on the face of the mold. Aggressive materials that contain “fillers” (glass) or are corrosive can prematurely wear hot runner components.  These types of materials require that the hot runner be manufactured using special materials that protect the system in order to maximize the “runtime” between PM’s. If your hot runner was not specified to process this type of resin grade your maintenance schedule may be more frequent.

If a mold becomes hard to start-up, difficult to maintain all cavities or has required a gradual increase in nozzle set-points, there needs to be a full evaluation completed to determine the “wear” on gate components (both in the hot runner & mold). The condition of the gate may be a clue as to the need for PM. On valve gated molds, flash around a valve pin may require valve pin replacement and/or gate replacement or repair. Molds with a thermal gate also experience wear on torpedoes or liners in the gate components. Sometimes a frequency for PM can be set up based on the shot count.

Training personnel on the shop floor on the proper start up & shut down procedures is also an important factor in keeping a mold performing at its best. All hot runner systems require a “soak time” for heat to penetrate through the system. Just because the hot runner controller indicates that the set-point has been reached, doesn’t mean that everything is up to a temperature that allows you to safely start up the mold. Knowing the material & the hot runner system allows you to determine what the “soak time” requirements are for each mold. Heat sensitive materials may degrade if it’s left to sit at a normal processing set-point for an extended period of time.  Degraded material can lead to major hot runner maintenance.

If the hot runner system is “On”, the mold cooling must be “On”. If the mold is valve gated and has individual pistons for each cavity, mold cooling should remain “On” for a period of time after the hot runner is shut down.  This protects the actuator seals from being harmed by the residual heat from the hot runner as it cools. This becomes especially important if running a high temperature engineered resin.

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Hot Runner Balance and the Effects of Shear

For years, natural balance has been the cornerstone of a successful hot runner balance. This means that the melt experiences the same flow length and the same diameter melt channels from when it leaves the machine nozzle until it enters each cavity within the mold.  This approach has served the industry well.

In recent years, much attention has been paid to the effects that shear has on the melt as it flows through a cold runner system. Of specific interest is how shear heated melt is distributed by the cold runner geometry. Research in this field has led to a greater understanding of shear-induced variances as they apply to cold runner systems and led to the introduction of technologies that are aimed to help address molding issues which have irritated molders for years.

It has also led to a greater awareness of the topic by the general injection molding community. While the majority of published research on this phenomenon has been based on cold runner systems, it has naturally called into question the validity of natural balance principles as applied to hot runner systems.

As a hot runner supplier, Mold-Masters has long been aware of the phenomenon of shear-induced variances that can occur within melt channels and the effect that this can have on the balance performance of a mold.

Balance Sensitive Applications

Uniform balance is always desirable. If a mold is significantly imbalanced, it will be difficult to start up and may have a narrow process window. The balance that can be achieved between cavities on a multi-cavity mold will have a bearing on the part to part consistency. That being said, there are some applications that will require a higher degree of balance than others. These will include parts that have a demanding dimensional requirement or parts that will be difficult to eject if they are over packed. Here uniform balance is important to ensure that all cavities are uniformly filled. It is important to recognize applications where balance will be critical.

However, it’s important to recognize that there are some fundamental differences between hot runner system and cold runner system designs. Cold runner systems are more prone to the effects of shear due to their inherent design.

Runner Geometry

It is good design practice to minimize the size of a cold runner. Consequently, in comparison to the hot runner that may be employed for a similar application, the cold runner is small. For a given injection rate (fill time) this means that the shear rates that the material sees in the runner system will be higher in a cold runner system. When you further consider that the shear rate is inversely proportional to the diameter to the power of three, it is obvious that the smaller sized cold runners will have a significantly greater shear rate and consequently accentuate any shear-induced variations.

Another significant difference between a hot and cold runner is that with a cold runner, the effective size of the runner reduces during injection. The first melt to flow into the cold runner solidifies; effectively further reducing the diameter of the runner and further increasing the shear-induced on the melt. The runner continues to reduce in effective size during injection as the runner cools. This is in stark contrast to the hot runner system where the runner wall is maintained at the required processing temperature during the injection molding cycle.

Level Changes

Cold runners are typically restricted to a single face of a mold. This means that a cold runner is typically a ‘single level’ runner. Level changes are more easily incorporated into a hot runner design and can be strategically positioned to assist in uniformly distributing shear-induced variances.

Shear Sensitive Materials

Certain materials exhibit a dramatic change in viscosity in response to shear and in response to temperature change. Such materials will be more susceptible to shear-induced variations than other materials. In order to design the optimum hot runner system and avoid shear-induced imbalances, it is important that the material’s behavior, in response to shear and temperature, is understood.

Summary

In summary, the phenomenon of shear-induced imbalance can occur in a hot runner mold; however, it is much less likely to happen to a significant extent due to lower shear in hot runners compared to cold runners. The phenomenon of shear-induced imbalance is well understood, and its relevance can be anticipated based on the material being molded and critical nature of each application. Hot runner design allows more opportunities to introduce such features as level changes which facilitate uniform distribution of sheared material.

Mold-Masters dedicates its global resources into delivering molds with the best balance performance in the industry. When Mold-Masters technology and decades of experience comes together, anything is possible. Our customers rely on our high-performance capabilities to deliver solutions where others fall short.

Mold-Masters hot runner systems feature iFLOW Manifold Technology, a 2pc brazed manifold where runners are carefully CNC milled utilizing patented melt flow geometry, flow path options, and runner shapes to be able to achieve the best possible results. For instance, iFLOW incorporates curved runner channels, eliminating sharp corners and dead spots, which help overcome the challenges associated with traditional hot runner manifold designs which significantly improves processing results.

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Putting Your Mark on Your Part

Have you ever looked at the bottom of a plastic container and noticed one or more symbols molded into the part? These markings are added at the time of molding with a metal insert placed in the cavity of the mold. When the resin solidifies it bears the mark of the specific insert added. Believe it or not these markings can be extremely important and very helpful for molders and consumers alike as they guide decisions through the life cycle of the plastic part. For the molder, the markings provide key information which can include when the part was made, helping to identify a specific manufacturing lot or batch and ensuring that a reliable quality system exists. For consumers, the markings can show how the finished good can be used and possibly re-purposed through recycling.

High-Temperature Blind Hole Inserts

The use of engineering resins is increasing and since these resins are processed at elevated temperatures, high-temperature inserts are required. One important feature of high-temperature inserts is a blind hole which allows the mold designer to enhance cooling around the location of the insert.

Food Container Inserts

Fast-paced lifestyles and more affordable modern day conveniences, such as microwaves, and dishwashers for example, have changed the food container industry for both the manufacturer and the consumer. Food Container Inserts allow producers to easily identify the material characteristics of the product. These simple pictured images take the guess work out, allowing consumers to quickly visualize appropriate conditions for product use.

Recycling Inserts

As we all know today, green initiatives have become common practice. More and more plastics are being recycled to avoid placement in landfills, ultimately protecting our environment. Through the use of recycling or resin identifier inserts by manufacturers, recyclers can easily sort and recycle post-consumer plastics helping the sustainability of our industry.

The Industry Innovator

The ability to effectively cool the mold is imperative for managing an efficient cycle time. Up until now mold inserts have been an incumbent as they often interfered with the location of the water lines used to cool the mold. Recognizing this gap in performance DME has introduced the first mold insert that is inserted through a blind hole. This added feature allows the mold designer to enhance cooling around the location of the insert and improve the molders productivity. It also eliminates the need to remove the mold when it is time to change the insert. This is a truly major industry breakthrough.

Milacron’s DME brand has enjoyed a leadership position in the supply of mold marking inserts for many years. We offer over 9 styles and hundreds of data combinations suited for manufacturers in all industries. DME is building on this success and ensuring an even brighter future with its launch of its new products expanding the number of applications and improving the productivity of use for its customers.

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Don’t Worry, It’s Cool – The Power of Conformal Cooling

In today’s world of plastic injection, there are several factors driving long cycle times. Thermal control of the mold is the most influential aspect. With the inability to evenly cool an injected part, the cycle times run long, warpage is increased and the end product is plagued with tension and stress which often ends with parts failing quality control.

Conformal cooling technology provides the industry greater thermal control over injection molds. The increased control is accomplished through the manufacture of conformal cooled inserts custom tailored to fit each and every need. Using cooling channels in places and shapes that conform to the geometry of the part being manufactured ensures greater control over these specific, hard to reach areas. Traditional or conventional tooling simply cannot achieve the shapes, paths, and channel geometries possible with conformal cooling.

Having control of both the hot and now the cold halves you have full process parameter control.  Your design solution places cooling (or heating) channels at the optimal distance from the part surface, allowing the mold to maintain a targeted, consistent temperature for complete thermal control.

Conditions sometimes dictate that heating is required within the mold and conformal heating channels operate in tandem with conformal cooling channels as well. Conformal heating can assist in maintaining a molten flow front of resin as it enters a hard to fill area of the tool. This takes place much like a hot manifold operates. The heating element, in this case high-temperature oil, will run through channels that follow the shape of the part to increase surface temperature of the mold. As the resin passes through, it still maintains the melt temperature needed to properly flow and fill tight areas, such as an automotive speaker grille.

Shown here (on the left) is an example of an insert that originally contained conventional cooling channels. Beneath the image showing the circuits you can see the thermal effect the resin has on the insert in question. To the right you will see the counterpart with conformal cooling channels to address the key warm areas of the mold insert. Beneath the channel image again you can see the thermal effect on the insert. Side by side comparison shows the conformal channels provide much greater thermal control and reduced delta when used with injection molding.

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The Importance of Precise Hot Runner Temperature Control

Hot runners are known to offer many processing advantages. However, to maximize your productivity and production quality, maintaining precision temperature control is a critical component for these systems to work as designed. Maintaining precise temperature control is known to affect part quality and processing as temperature directly impacts processing variables associated with the Resin Characteristics and Hot Runner System.

RESIN CHARACTERISTICS

All thermoplastics degrade under elevated temperatures. A well designed hot runner system eliminates hot spots from its design and precise temperature control will help to ensure temperature uniformity of the system during processing. Temperature uniformity is important because it allows you to bring the overall system temperature closer to the lower processing temperature limit. The greater the heat history of the polymer, the more the properties of the polymer will have been weakened.

Additionally, as the plastic melt is forced along the hot runner channel under pressure, it is subject to shear which also generates additional heat. Precise temperature control becomes especially challenging when processing shear sensitive or highly viscous polymers and additives. Otherwise polymer properties will deteriorate and part quality will be affected.

HOT RUNNER SYSTEM

In a multi-cavity system, natural flow balance means the same flow length, same channel diameter and the same number of turns from the machine nozzle to each mold cavity. In conjunction with temperature uniformity across the entire system, this leads to uniform filling and back pressure conditions in each cavity, uniform part quality and the widest processing window. Where changes in material or injection parameters exist (like temperature) these changes will cause quality problems such as poor weight consistency.

The hot runner and mold cut-out are dimensioned so that all hot runner components are perfectly aligned at the specified operating temperature. To allow for heat expansion, sliding or rotational pressure seals are used between hot runner components. If excessive temperature variations exist in the system, it can cause leakage or even component fatigue and/or failure. The nozzle center axis must remain in an absolutely fixed position, in exact alignment with the gate at processing temperature.

Fast Response is Crucial

Injection molding is a cyclical process. The hot runner must maintain accurate and uniform temperature conditions through both the heating (injection) and cooling (hold) phases of the molding cycle. Since the gate is the most critical areas of the hot runner, it is essential for the TC to accurately measure gate temperature. For quick and accurate response to temperature over or under swinging, closed-loop temperature control is required for each and every nozzle. The quality of the molded part is directly related to temperature control response efficiency.

Unlock your Operations Full Potential

Mold-Masters offers precision temperature control through our comprehensive line of advanced TempMaster Hot Runner Temperature Controllers. They have the ability to optimize the performance of any hot runner system.

All TempMaster hot runner temperature controllers feature APS Technology which maintains set point for precision temperature control of 1 to over 500 zones. APS is a proprietary Auto-Tuning algorithm that continuously monitors, learns, predicts and automatically adapts to process variables every 20mS.

 

Benefits include:

  • Precise 1°F Control Accuracy
  • Superior System Reliability
  • Enhanced Part Quality & Gate Vestige
  • Improved Part Consistency
  • Reduced Scrap
  • Lower Power Consumption
  • Maximized Profit Margins
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Cost Effective Injection Molding Tips from a Design and Engineering Firm

Injection molding is one of the most popular and effective manufacturing processes, because it is capable of producing high quality parts in large numbers, and generally very quickly. In a nutshell, injection molding is when a material (generally plastic) is heated until pliable, forced into a mold made for a specific purpose, allowed to cool and harden, and then ejected from the mold. Depending on how the mold is made (and what material is being injection molded), this process can be repeated over and over in order to create large numbers of a given product. Although popular and effective, injection molding is not a cheap process; projects typically cost between $10,000 and a few hundred thousand dollars to manufacture. Let’s look at some ways to ensure that cost effective injection molding is a reality for your project.

Tips for cost effective injection molding 

Make sure you’re using the right material. Did you know that there are hundreds of plastics (let alone other materials) that can be injection molded? It’s important to consider what function you want a particular piece to accomplish, and which material is most appropriate to make that happen. Does a piece need to be pliable or rigid? Will it be exposed to heat or extreme temperature deviations? How does Factor of Safety affect the materials required for design? It’s a common mistake to assume that a state-of-the-art, top-of-the-line material is the right one to utilize, but if its good qualities aren’t pertinent to your project, then they are essentially useless – and may cost more money overall. For instance, why use a 40% glass filled nylon when polyethylene would do the trick just as well? The best material for injection molding is the one that best fits your requirements and is not simply the better material overall.

Identify where processes can be consolidated. There are a lot of secondary processes involved in producing a part from scratch. Such processes (like custom inserts, label printing, painting, etc.) can prove to be time consuming, as they require extensive setup – and in injection molding, time is money. All those extra costs – and the time that could have been saved with better production management – ultimately drive the part price up. The best practice is to try to combine all of these processes into one single robust process.

Be selective when choosing who does the injection molding. Like most industries, the injection molding industry is full of small, mid-size, and large companies. One or the other may be more appropriate depending on your project. Smaller companies will generally offer more flexibility and lower costs, whereas prices may be driven up with large companies due to higher overhead, higher salaries, and sometimes more advanced technology. In general, it’s best to choose a company that has experience molding your type of product, as it will save time during the research and development part of the project. Remember that bigger and more expensive does not necessarily equal better quality.

Consider bulk production. Molding operations are rarely personal projects or projects that will produce small numbers. In the research and development phase alone, some projects produce hundreds or thousands of prototypes, as many benefits come from extensive testing and feedback. When the product moves into the production phase, it is even more important to be able to mold as many parts in one shot as possible. Molds for production should also have as many cavities as possible without compromising the quality of the parts produced. In a competitive market, a product must be the best it can be while also being affordable. That is why it is advisable to produce as many parts as possible at one time – because it spreads the setup cost out over more parts, thus leaving you with a lower price per piece. You can now sell your product in a competitive market. 

Is the mold design optimized for cost effective injection molding? In mold design, as in bulk production, it is beneficial if you can produce as many parts as possible in a single shot. For mold design, it is also very important to be able to eject the plastic product quickly and to be ready for the next shot without wasting movements. Rods, an air blast, or a plate are typically used for the ejection stage of injection molding. Every second in the injection molding process translates into money, so it is critical to minimize the mechanisms of molding to as few and as fast as possible. A design and engineering firm that is familiar with the nuances of injection molding will create parts that will lend themselves to optimized mold design.

Optimize product design and materials. You can save a considerable amount of money, especially in material consumption, with an optimized product design. Using ribs and gussets to reinforce a product, for example, will save on material consumption, as well as ensuring that the product has uniform wall thickness that is neither too thin nor too thick. Incorporating adequate draft is also essential, as it allows for quick ejection of the product from the mold, saving time and money. If there is a need for a mechanism in the product, there are quite a few to choose from. Many can be incorporated into the molding process without the need for secondary processes or machining. Some mechanisms, such as living hinges, take advantage of the properties of the material that was used to mold the plastic part. These mechanisms can be made directly from the molding process versus spending extra time and money on other processes, such as stamping.

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5 Different Design Methodologies in Solidworks

Five design features in Solidworks that every design engineer should know

Designing in Solidworks starts with a 2-dimensional sketch. From a 2D sketch one can create 3-dimensional objects using built-in tools called “features.” Features are simply different ways of converting 2D outlines into 3D objects. Two of the most common tools (methods) for doing this are extrusions (the “extrude” feature) and revolutions (the “revolve” feature).

  1. Extrusions: The Extrude feature takes a 2D sketch in the x-y plane and gives it thickness or depth by developing it linearly in the z-axis. For example, a sketch of a circle would be extruded into a cylinder. A sketch of a square would be extruded into a rectangular block (or a cube in the event the thickness were made to be the same as the x and y dimensions).
  2. Revolutions: solidworks tips for design engineersThe Revolve feature takes a 2D sketch in the x-y plane and gives it thickness or depth by rotating it about one of the two sketch axes (i.e. the x or y axis). A commonly known item that demonstrates the utility of the revolve feature is a pawn from the game of chess. An otherwise extremely intricate piece to design, the revolve feature allows the designer to develop a 2D profile which is rotated about the vertical axis for 360 degrees and easily completes the part.

Although extrusions and revolutions are some of the most common features used to design parts in Solidworks, they are nowhere near the only available options. Here are three more features that help round out a basic inventory of design tools:

  1. Sweeps: The designer can create parts using multiple sketches on perpendicular planes. One sketch will act as the profile and the other will act as the path. The profile sketch is dragged along the path to create the 3 dimensional object. The sweep feature is very effective for things like handles or pipes.solidworks tips for design engineers
  2. Surfaces and Lofts: Surfaces typically work similar to sweeps in that they utilize profile and path sketches but they also introduce guide curves. Guide curves act as a second path of sorts in the event that the surface is not going to be symmetric about the path. Surfaces are great for things like handles or nozzles. Additionally, surfaces are hollow by default (the designer simply applies a thickness to the shape which is different than most solid parts). Lofts are typically used to connect different pieces into a single part by using mathematical equations that blend the curves between parts according to the designer’s inputs.
  3. Sheet Metal: Sheet metal drawings are the most effective way to design parts that are actually manufactured by sheet metal forming (adding flanges and bends to a flat “sheet” of metal).solidworkstips.png

In truth, even these five features are only the beginning. There are a great many other tools to design and refine the design of various parts such as patterns (linear and circular are very common), holes, and a built-in toolbox for off-the-shelf (OTS) components. When determining which tools and/or features to use in your design, it is often useful to think about how the part will be fabricated once you are finished with the design. Some processes are subtractive (such as CNC), while others, like sheet metal work, manipulate a flat surface in different ways. Sometimes it is easy to buy components from manufacturers that make their Solidworks files available on the web. Sometimes parts are combined via fasteners and in other instances they might be welded together. Solidworks has powerful design tools for all of these decisions and more.

Pro Tip: Once you’ve settled on the right design, think about how you’ll display it to your clientele. What types of files do you want to export when you are finished with your design? The three most fundamental file types are .sldprt (the basic file extension for a part designed in Solidworks), .sldasm (the basic file extension for an assembly of multiple parts designed in Solidworks), and .slddwg (the basic file extension for a Solidworks drawing). But are these the right files to send to a customer?

  1. Sending files to customers: Oftentimes when we send files to a client it will be as a .STP or .STEP file. The interesting thing about this file type is that it doesn’t display the individual features that were used to build the part but rather simply displays the part as a single piece. E-drawings are another good way to send pictures or videos of the design to individuals who do not have Solidworks on their computer. Functional depictions of designs can be exported in multiple formats such as html, .exe (executable files) or .zip.
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