what is a good plastic part design

Getting products to market fast and on budget are two essential elements in the process of manufacturing. The manufacturing process design talks both makers and injection moulders as the process that could most impact manufacturing outcomes. If plastic injection molders are in the process of designing the part, which includes design development along with mold flow evaluation many cost and time efficiencies can be achieved.

Designing a plastic part to be able to manufacture from the beginning requires a variety of considerations that could eventually have a major impact on the key factors. Although some manufacturers do not account for design changes in their schedules early communication with your molder might reveal certain aspects of a design which can be optimized to improve the efficiency of the production process and performance. Here are some of the most common elements that are discovered in the design process for manufacturing process:

1. Material Considerations

Manufacturers usually select a known kind of plastic that is similar to an application or rely on recommendations from suppliers. Resins chosen this way may be suitable, but they are rarely optimal. Plastic selection is a complex job that requires many factors like:

Temperature: Thermal stress that can be experienced during extreme or normal use conditions, as well as during assembly, finishing and shipping.

Chemical resistance: The results that occur when liquid, solid or gas come in contact with the item.

Agency approvals: Both government and private standards for properties like flame-resistance, heat resistance as well as mechanical and electrical abilities.

Plastic Assembly: Its collaboration with all assembly steps like bonding, mechanical fasteners and welding.

Finish: The ability of the material to create the desired finish such as smoothness, gloss and other values of appearance.

Cost Resin pricing as cost calculation for manufacturing, maintenance as well as assembly and disassembly in order to cut down on the cost of tooling, labor as well as other costs such as finishing.

It is the availability of the resin with respect to the quantity needed for production.

2. Draft

As a fundamental requirement in injection molding draft angles are essential to make it easier for the finished and cooled component come out of a mold. Reducing friction during the release is essential to prevent damage to the parts, create a uniform surface finish and reduce wear and wear in the mold.

Drawing angles is calculated using a degree measurement from the direction of pull. Designing a part with sufficient draft is essential this is why design engineers typically recommend minimum draft angles of 0.5 degrees for core and 1.0 Degree for the cavity. Draft needs for textured surfaces desired and if there are steel shut off surfaces within the tool design.

3. Wall Thickness

For Injection Molding, the Wall Thickness Table Another crucial aspect in the design of parts is the wall thickness. A uniform and consistent wall thickness minimizes the possibility of cosmetic and structural flaws of injection-molded parts.

While typical wall thickness ranges between .04 up to .150 for most resins  that you consult with a knowledgeable design engineer or injection molder to confirm thickness specifications for the material(s) you’re thinking of using for your component.

The measurement of wall thickness is an important element in the design process to avoid making parts that sink, warp or are ultimately ineffective.

4. Ribs design

Injection Molded Ribs design are to strengthen wall thickness of the component without increasing wall thickness and are a vital element in injection molded parts. Particularly for intricate parts, a proper design of ribs should reduce the length of the flow in the mold while ensuring the proper joining of ribs, which will increase durability of your piece.

Since the location and thickness are important in rib design The ribs should not be larger than 2/3 of wall’s thickness, dependent on the material that is used. Using wider ribs may create problems with design and sinking. To prevent this from happening, a design engineer will generally core some of the material in order to limit shrinking and to maintain the strength.

Rib lengths should not exceed 3 times the wall’s thickness as anything more than that could result in the part becoming short or not being able to fill the part completely. The proper position, thickness as well as length of the ribs during the initial stages of design is a crucial aspect to the longevity of the part.

5. Gate Location design

Injection Molding GateA gate defines the place where melts plastic material flows into the mold cavity. While every injection molded part comes with at least one gate, many parts adopt multiple gates. Because gate location affects the orientation of the polymer molecules and how the part will shrink during the cooling process, gate location can either make or break your part design and functionality.Injection Molding Runner and Gate.

For example, if a part is long and narrow and needs to be perfectly straight, the suggestion is to place the gate at the top of the piece. For parts that need to be perfectly round, a centrally located gate need here.

Working on preliminary designs with your engineering team, leveraging their expertise and knowledge in material flow and material flow, will lead to optimal gate placement and the best injection points.

6. Location of the Ejector Pin

Injection Molding Ejector Pins After an injection molding process and ejector pins (located within the B-side/core the mold) provide just the appropriate amount of force to release the part from the mold. Ejector pin placement is generally an unimportant issue in the beginning stages of design. However, the formation of marks and indentations could result from incorrectly placed ejector pins, which is why design and positioning should  consider as early as possible in the process.

The location of ejector pins comes from a variety of aspects, including the draft and texture of the walls, wall thickness and ribs, and also the type of material employed. The review of part designs can confirm that your initial ejector pin location is correct or could provide additional suggestions to improve the production results.

7. Sink Areas

If the material within the area of thicker features, such as ribs or bosses, shrinks significantly more than the material of the wall adjacent to it and sink marks can result in the injection-molded plastic component. The reason is because the thicker parts cool at a slower rate than those with thinner features and the various rates of cooling leave a mark on the adjacent wall which is commonly  sink marks.

Many factors influence sink mark formation, such as the process methods employed in the part’s geometry, tools and material selection. Based on the specifications of the part, it may not be possible to adjust geometry and material selection, but there are many options available to eliminate sink marks.

Depending on the part and the final use and the design of the tooling (e.g., cooling channel design the gate type, gate design and the gate’s size) can influence sink. In addition, manipulating process conditions (e.g., packing pressure, time to pack, length of packing phase , and the conditions) provides a variety of options to minimize sink. Finally, minor tooling modifications such as retrofittable components or process adjustments (e.g., gas assist or foaming) can also be for reducing sink. As a result it is best to collaborate with your injection molder to figure out which techniques can be most effective in reducing sink in your specific injection-molded components.

8. Parting Lines design

Molding Molding Parting LinesParting line location is important to note and plan for the production of more complicated parts or when intricate shapes need.

Part designers and molders tend to evaluate parts differently the design you share with your injection molder can drastically impact the production and functionality of your final product. If parting line challenges are  a variety of solutions to overcome them.

Understanding the significance of the parting line in the initial design is a good first step, but that isn’t the only option. With the help of an CAD program or mold flow analyzer, you might be able identify other locations. Working with a knowledgeable injection molder will keep your part final use in mind and help provide you with the best possible location to separate lines.

There’s no doubt, engaging your plastic injection molder early in the design manufacturability and working closely to a designer in order to identify efficiencies will help get your product on the market faster and within budget. What challenges are you currently experiencing with your design process for plastic parts?

9. Special Features

Parts made of plastic should be a design so that mold tools open and eject the part effortlessly. When a piece comes out of the mold, the two sides an injection mold split in the opposite direction. When special features like shoulder holes, undercuts or holes stop the release and are preventing the release, it is possible to incorporate side actions within the model.

Side actions pull coring in a direction other than the direction of the mold separation. This allows for greater flexibility in the design of the part and, occasionally, can raise the cost of the mold.

Partnering with an experienced plastic injection molder and engineering team is essential to avoid many problems that can occur during the design and development process. When you take these factors in mind during the design process, and align with an experienced plastics engineer, then you’ll be well on your way to getting your product out to the market faster and in the budget you have set.

Steven Cheng, the founder of Topworks Plastic Mold, a China injection molding company with the most complete services, from design to production. Topworks provides customers with a one-stop service for Polycarbonate injection molding and ABS injection molding. The company’s professional team has excellent product knowledge of the plastics industry, which enables it to provide customers with quick responses and high-quality service.

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