Benefits And Limitations Of Injection Molding
Injection molding is an established manufacturing technology with a long history, but it’s constantly being refined and improved with new technological advancements.
Below is a quick rundown of the key advantages and disadvantages of injection molding to help you understand whether it’s the right solution for your application.
Benefits of injection molding
Injection molding is the most cost-competitive technology for manufacturing high volumes of identical plastic parts. Once the mold is created and the machine is set up, additional parts can be manufactured very fast and at a very low cost.
The recommended minimum production volume for injection molding is 500 units. At this point economies of scale start to kick-in and the relatively high initial costs of tooling have a less prominent effect on the unit price.
Almost every thermoplastic material can be injection molded. This gives a very wide range of available materials with diverse physical properties to design with.
Parts produced with injection molding have very good physical properties. Their properties can be tailored by using additives or by mixing together different pellets to achieve the desired level of strength, stiffness or impact resistance.
This means that hundreds of identical parts can be produced every single hour.
Limitations of injection molding
Design Guidelines For Ribs
Recommended Rib Parameters
Rib features help in strengthening the molded part without adding to wall thickness. In some cases, they can also act as decorative features. Ribs also provide alignment in mating parts or provide stopping surfaces for assemblies. However, projections like ribs can create cavity filling, venting, and ejection problems. These problems become more troublesome for taller ribs. Ribs need to be designed in correct proportion to avoid defects such as short shots and provide the required strength. Thick and deep ribs can cause sink marks and filling problems respectively. Deep ribs can also lead to ejection problems. If ribs are too long or too wide, supporting ribs may be required. It is better to use a number of smaller ribs instead of one large rib.
Minimum Radius at Base of Ribs
A fillet of a certain minimum radius value should be provided at the base of a rib to reduce stress. However, the radius should not be so large that it results in thick sections. The radius eliminates a sharp corner and stress concentration. Flow and cooling are also improved. Fillet radius at the base of ribs should be between 0.25 to 0.4 times the nominal wall thicknesses of the part.
Draft Angle for Ribs
Spacing Between two Parallel Ribs
Team Rapid Mfg Co Ltd
TEAM MFG is a rapid manufacturing company who specializes in ODM and OEM starts in 2015. We offers a series of rapid manufacturing services such as rapid prototyping services, CNC machining services, injection molding services, pressure die casting services etc to help with designers and customers’ low-volume manufacturing needs. In the past 10 years, we assisted over 1000+ customers to launch their products to market successfully. As our professional services and 99% accurate delivery which keeps us the most favorable in our clients lists.
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Fusion 360 Design For Injection Molding
By Matt Perez
A ‘metal Safe’ Approach Can Save Time And Money When You Have To Modify Your Part Design For Injection Molding
The whole purpose of prototyping is to allow yourself the option of tweaking your modelâthickening a wall, adding a rib, placing text or a logoâbefore locking in a final design for production. For injection-molded plastic prototypes, tweaks can entail the creation of a whole new mold. A new mold may be quite affordable if your parts are being made by Brazil Metal Parts, but if the change can be made by modifying the existing mold, your cost will be even lower.
There’s one critical fact to remember if you want to be able to modify your part by modifying the original mold. It is relatively easy to remove metal from an existing metal mold. Adding metal, on the other hand, can be difficult or, for all practical purposes, impossible with Shunjing injection molding. To look at this from the part perspective, you can add plastic, but you can’t take it away.
Saving Time, Money
Designing with this in mind is called “steel safe” or “metal safe,” and doing so can save you both money and time when you have to modify your design. For example:
- You may be able to thicken a wall, but making it thinner requires remaking the mold.
- You can add featuresâbosses, raised text, ribs, pins, etc.âbut you can’t remove them.
- You can reduce the diameter of a hole by adding plastic around the perimeter, but you can’t increase the hole size.
- Similarly, you can eliminate holes, but you can’t add them.
A Feature-By-Feature Review
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Stack Height & Opening Stroke
Estimate the stack height of the mold and compare it with the minimum and maximum stack-height ratings of the machine. A mold that has a stack height less than the machines minimum closed daylight rating can easily be corrected by adding rails or risers to the back of the moving-platen clamp plate. Some molders have platen spacers available for their machines for this very purpose.
Conversely, assume you are quoting a single-cavity drink tumbler. The mold is relatively small, as is the projected area. But the stack height and the required mold-opening stroke are huge. If the molds stack height plus the required mold-opening stroke exceeds the machines rated maximum open daylight rating, or if the required mold-opening stroke exceeds the machines clamp-stroke rating, you have a problem. Three-plate, cam-action, stack and various other types of molds often require large opening strokes. For these reasons, the mold may need to go into a larger machine.
Popular Blow Moulding Design Considerations Photos
Ad At Surplex you will find used machinery and industry equipment at best prices. Also the neck must often be reamed and sized to produce the finished part. Blow moulding design considerations.
Blow Moulding Design Considerations, There are many factors to consider for injection molding but the part design and tool design are two of the most importantGetting them right could mean lower entry cost high production quality shorter cycle time and quick assembly. The process consists of three steps. Design must take this limitation into account.
Blow Molding Manufacturing Design Considerations Blow molding Extrusion Blow Molding is a manufacturing process that forms hollow thermoplastics. A male mold is generally less expensive than a female mold. Injection blowing and ejection. This is because each mold half will expand to forms its own wall.
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Uniform Wall Thickness To Avoid Warping
Warping is one of the most common defects of injection molding. As thermoplastic cools, it shrinks if one part of the object cools faster, it will shrink more quickly, resulting in permanent deformation.
Warping can usually be avoided by using a uniform wall thickness across the entire design. Ribs and other structures can be used in areas that need additional support, but make sure that the ribs are the same thickness as the walls.
For easy cooling, always use the thinnest possible thickness for your design. This will help prevent sink marks, which are caused by uneven internal cooling. 1-millimeter and 3-millimeter thickness are recommended.
Corners often cool faster than walls, so remember to round all edges in your design. Use an internal fillet with as wide of a radius as possible so that the thermoplastic can flow smoothly through the mold.
Design And Secondary Operations
When you upload your CAD model to some injection molders, such as Protolabs, you receive a free design for manufacturability analysis of your molded part design. In it, undercut areas are clearly defined, along with other moldability concerns. Parts should have sufficient draft angles to assure easy part ejection from the mold. Wall thicknesses should be uniform and comply with the resin manufacturers min./max. thickness recommendations. Ribs should be used to support large flat areas. Internal corners should be radiused, thick sections cored out to prevent sink, and fine finishes used only where needed.
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Why Dfm Is Important For The Injection Molding Process
Beyond just estimating manufacturing costs, your injection molder should be using DFM principles to reduce the costs of components, reduce the costs of assembly, reduce the costs of supporting production, and to identify the impact of DFM decisions on other factors throughout the entire design and production process.
Another reason for selecting a molder that uses DFM principles is the increasing complexity of plastic injection molded parts. Consideration of tolerance, draft angles, undercuts, and more, need to happen in the design stage in order to achieve the quality/cost requirements of customers.
Ways To Sidestep Undercuts In Molded Parts
Undercuts on injection-molded parts are features that prevent those parts from being ejected from the mold they were made in without damage. With straight-pull molds, undercuts include any protrusions, holes, cavities, or recessed areas in the part where alignment is not perpendicular to the molds parting line. If possible, the best way to deal with undercuts is to eliminate them in the design.
Some examples include the threads on an injection-molded fastener, a hole running the length of a plastic hose barb, a slot for a power switch in the side of a smartphone case, an angled boss on the exterior of a hydraulic manifold, and the locking tabs on the base of a taillight lens.
There are many more such parts, all of which require a little molding magicor at least some minor design modifications.
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With Precise Tooling And High
Stratasys Direct has decades of experience in all phases of tooling, including part design, tool design, material sciences, post-processing and project management. Capabilities include injection molding, pad printing, silk screening, painting, EMI/RFI shielding and light assembly.
For streamlined operations, we offer Fast Track tooling, an operation that delivers parts in as little as ten days at volumes of 25 to 1,000 units.
Whatever the project, industrial designers, engineers and product designers may face some challenges when designing for injection molding. The following details three mistakes designers should avoid for successful injection molded parts.
Surface Finishes And Spi Standards
Surface finishes can be used to give an injection molded part a certain look or feel. Besides cosmetic purposes surface finishes can also serve technical needs. For example, the average surface roughness can dramatically influence the lifetime of sliding parts such as plain bearings.Injection molded parts are not usually post-processed, but the mold itself can be finished to various degrees.Keep in mind that rough surfaces increase the friction between the part and the mold during ejection, therefore a larger draft angle is required.
The Society of Plastics Industry explains several standard finishing procedures that result in different part surface finishes.
|Suitable for non-cosmetic parts, such industrial or hidden components.|
When selecting a glossy surface finish, remember these useful tips:
- A high glossy mold finish is not equivalent to a high glossy finished product. It is significantly subject to other factors such as plastic resin used, molding condition and mold design. For example, ABS will produce parts with a higher glossy surface finish than PP. To find the recommended material and surface finish combination visit the appendix.
- Finer surface finishes require a higher grade material for the mold. To achieve a very fine polish, tool steels with the highest hardness are required. This has an impact on the overall cost .
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Molding Defects Often Caused By Process Problems
Some molding defects may be difficult or costly to address. Others can be prevented by adjusting the molding process, without the need to redesign the mold tooling or replace other production equipment. You can typically avoid these defects relatively easily simply by adjusting the flow rate, temperature or pressure of your mold.
Introduction To Injection Molding For Mass Production Of Custom Plastic Parts
Although 3D printing is the technology used for prototyping custom plastic parts, injection molding is the technology used for mass manufacturing.
Unless your electronic product will be marketed solely to DIYers and electronics hobbyists its going to need an enclosure. Most likely this enclosure will be made of plastic.
Injection molding is going be a big part of your journey to market. Regardless of your technical background you at least need to understand injection molding at a basic level.
Many entrepreneurs are surprised to learn that while the electronics will likely be the most expensive to develop, the plastic enclosure will be the most expensive to scale to manufacturing.
This is primarily due to the high cost of the injection molds. In fact, mold cost is one of the biggest expenses when taking a product from concept to market.
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Get Frames To Make The Mold
The first step in our injection molding setup is to create a mold. We will use epoxy to create our mold. Epoxy is actually a two-part liquid. It is initially in liquid form, but it can then be poured into a mold or frame. It then solidifies and hardens.
You need to get a frame in which you can pour the epoxy to make your molds. You will need two frames for two molds. Moth these molds will clamp against each other. Each mold will make one section of your injection molded part. You can buy a frame for making your epoxy mold here.
You can always make your own frame, but that will add a significant amount of time to the whole process. If you really want to make your own frame, then make sure that the frames have a cavity for the epoxy to pour itself in and that they also have alignment pins so that the two frames line up correctly. The link we posted above is for a set of frames which have the alignment pins and the cavity.
Designing Parts For Injection Molding
Injection molding can be used to create a variety of complex plastic parts. This article outlines some important design considerations for the manufacturing process, from wall thicknesses to draft angles and beyond.
Injection molding can be used to create a variety of complex plastic parts, from food packaging to functional mechanical systems.
Nonetheless, the injection molding process is a fine art, and engineers must follow certain design rules and principles when designing parts for injection molding. If a part is not designed with the mold and plastic injection process in mind, it may not perform to the best of its abilities. In fact, it may not perform at all.
This article outlines some of the most important design considerations for injection molding, from wall thicknesses to draft angles to embossed text. By following these few simple rules, your parts will come out of the mold in perfect shape, ready for their end use.
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Are All Injection Mold Shops The Same
Not all injection mold shops are created equal. Specialties exist here just as they do in other types of manufacturing. While there are plenty of shops that do a bit of everything without having a predominant specialty, there are also many injection molding shops that have specialties.
What these specialties are varies. It could be working with a specific material or group of materials, molding parts with unique features, handling production at a certain level of volume, or even something else. When you begin searching for a company to take care of the injection molding for your project, try to find one that specializes in what you need. General injection molding shops are typically fine, but an injection molding shop with a known specialty may be a better choice.
One: Injection Molded Part Design
First things first. We start by designing your part so that it meets your products needs in addition to being effective, safe, user-friendly, and attractive. Of course, thats standard product design fare. However, designing injection molded parts involves a number of unique considerations, including:
Plastic part design techniques. These industry-standard techniques incorporate strategic, functional, and technical requirements as well as stress-reduction best practices.
Material selection. Each individual material is best suited to different applications. Selecting the right material for your injection molded part can spell the difference between success and failure.
Design tolerances. Depending on your products unique specs, application, and environment, you will need to anticipate and define a set of specific manufacturing tolerances for your injection molded parts.
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Tip #: Fit Multiple Parts In One Mold
As we saw in a previous section, fitting multiple parts in the same mold is common practice. Usually, 6 to 8 small identical parts can fit in the same mold, essentially reducing the total production time by about 80%.
Parts with different geometries can also fit in the same mold . This is a great solution for reducing the overall cost of assembly.
Here’s an advanced technique:
In some cases, the main body of 2 parts of an assembly is the same. With some creative design, you can create interlocks points or hinges at symmetrical locations, essentially mirroring the part. This way the same mold can be used to manufacture both halves, cutting the tooling costs in half.