As an experienced industrial designer, especially for a mold designer, when he or she designs a plastic part, the wall thickness need to be considered carefully,On the premise of meeting the requirements of product use function and injection molding, the designers should know how to design a minimum wall thickness, because during injection molding process, The thinner the wall, the faster the part cools, so that we can save cycle times, then save part costs, of course, thinner parts weight less, for every part, we can save the amount of the plastic, in a big order， the amounts of the plastic are saved.
What is the suitable wall thicknesses of an injection-molded part? I think, generally it ranges from 2 mm to 4 mm (0.080 inch to 0.160 inch), for some plastic material, because of special requirement, The wall thicknesses can be designed as 0.5 mm (0.020 inch) without any molding problem.
Injection molded parts can have a shell-like structure with molded surfaces and supports. Examples of these supports include walls, ribs, and gussets.
Wall thickness in injection molded parts generally ranges from 1 to 5 mm. The recommended thickness depends on the plastic material, the part’s requirements, and factors such as mold flow. For the best results, a part’s walls should be fairly consistent — that means avoiding designs with widely different walls thicknesses.
Note, however, that walls are tapered. In other words, a wall doesn’t have the exact same thickness from the base to the top. Typically, the base of the wall is slightly thicker and tapers at a draft angle of at least 0.5 degrees. Without draft, parts won’t eject cleanly from the mold and are susceptible to damage, so applying a draft angle to vertical walls and surfaces is critical.
What is the Significance of Wall Thickness in Product Design?
During product design, the significance of wall thickness is about reducing material usage while improving part quality and production speed.
Reduced Raw Material: Optimal wall thickness can reduce the amount of plastic needed and the weight of the molded part — in many cases, thicker walls can be replaced with thinner ones.
Part Quality: Designing injection molded parts with wall thickness problems can result in defects like sinkholes, warping, and short shots. These problems increase rejection rates and, ultimately, the total cost of your parts.
Production Speed: Thicker walls take longer to cool than thinner walls, but adequate cooling is critical for injection molding success. Consequently, wall thickness affects cooling rates and, ultimately, injection molding cycle times.
What is Uniform Wall Thickness?
Uniform wall thickness does not necessarily mean that every wall must have the same exact thickness. Some thickness variations are acceptable within limits. Generally, the thickness of a wall should be no less than 40% to 60% of adjacent walls because when thickness transitions aren’t gradual, part defects such as warping occur. Also, note that ribs and supporting walls do not need to be the same thickness as the main walls.
How to Design for Uniform Wall Thicknesses
Typically, injection molded parts are designed using CAD (Computer-Aided Design) software and those designs follow specific DFM (Design for Manufacturing) principles. Most modern CAD packages have a powerful set of tools with features that assist with the design of parts for injection molding. These features make it easy to modify wall thicknesses and to apply draft angles.
Selecting the Optimal Wall Thickness
For injection molding plastics, optimal wall thickness is given as a range of measurements in inches (in) and millimeters (mm). However, these numbers are a broad range — for best results, you need to work with a skilled injection molding manufacturer, like First-rate Mold Company, who can provide you with DFM feedback and insights gleaned from experience.
What is the Minimum Injection Molding Wall Thickness?
Minimum injection molding wall thickness refers to the thinnest wall recommended for a given type of plastic. There are several factors to consider when specifying this dimension. For example, it’s important to define the expected loads to which the part will be subjected — cosmetic parts are exposed to different loads than one used as a push-button. Some designers start by using the lowest possible wall thickness for the selected material, then perform a finite element analysis (FEA) using previously-defined load cases. The results of the FEA will provide a good indication of whether the thickness of the wall is sufficient. If the wall is too thin, you can adjust its thickness or select a different material. 1 mm is usually the thinnest that part walls get, although minimum wall thickness can be thinner for some materials
What is the Maximum Injection Molding Wall Thickness?
Maximum injection molding wall thickness refers to the thickest wall that is recommended for a specific type of plastic. There are several factors to consider when specifying this dimension. In general, excessively thick walls are not recommended because they often result in part defects. Sometimes, however, thicker walls are needed because of high loads exerted on the part, thermal insulation requirements, or simply to make the part feel heavier and more substantial.
Most injection moldable plastics have an upper limit which, if exceeded, can cause issues such as underfilling, warping, and excessive dimensional deviations. However, as a general rule, the maximum wall thickness should be limited to 5 mm. As with minimum wall thickness, the maximum wall thickness is a function of the plastic material being molded.
Choosing the Correct Wall Thickness for Injection Molding
Choosing the optimal wall thickness for an injection molded part can be a balancing act between part cost, strength, cycle times, and other factors. To effectively balance all of these requirements, it takes expert knowledge and real-world experience.
When you ask First-rate Mold Company for an injection molding quote, you’ll receive free DFM feedback. And, the report doesn’t merely indicate whether or not your part can be injection molded — you’ll receive recommendations about how to improve your design to accelerate production and be less expensive to mold.
Notice how the walls of these household items are all relatively uniform? This is one of the fundamental rules of plastic injection molding, and ignoring it can lead to sink, warp, and inaccurate or non-functional parts. Yet the functional requirements of consumer, medical, aerospace, and industrial products often leave designers little consideration for the material flow and fill properties of plastic, both of which are at least partially determined by wall thickness.
To achieve uniform wall thickness, let’s start with the basics:
Recommended wall thickness in injection molding design
Proper wall thickness will reduce the risk of cosmetic defects in plastic parts.
Walls in any plastic-molded part should be no less than 40 to 60 percent that of adjacent walls, and all should fit within recommended thickness ranges for the selected material.
Part geometries such as long unsupported spans, sharp internal corners, and poorly designed bosses (not the person in the corner office who signs paychecks), should be avoided, regardless of wall thickness.
Use ribs for strengthening tall walls where needed.
Sharp external corners are fine, but placing a radius on inside corners—part design permitting—makes them stronger and alleviates the stress that creates warp.
Bosses should follow molding design guideline rules of properly designed walls of 40-60 percent of the surrounding area to avoid sink.
Finally, follow recommendations on draft angles—1 degree of draft per 1 inch of cavity depth is a good rule of thumb—and keep draft consistent throughout the workpiece to prevent internal stresses that lead to warp and curl.
Choose Materials with Wall Thickness in Mind
One of the biggest considerations with wall thickness is which material to use for your project. With literally hundreds of materials to choose from, deciding on the right one can be challenging. You can view available resins grouped by family with recommended wall thickness ranges along with detailed information on material properties, tensile and impact strength, and maximum operating temperatures online.
While thick walls offer additional strength, there are some advantages to engineering thinner walls. In fact, the longer a production run, the more benefits that can be gained by keeping a part thin and light, so maintaining optimal wall thickness is particularly important for high-volume injection molding projects. Keeping walls as thin as possible allows for:
Resistance to warping during the cooling process
Reduced costs due to less material usage and faster manufacturing
Reduced overall weight for ease of handling, management, and shipping
Quicker cooling cycles for shorter, more efficient production run time
Wall thicknesses are not subject to any restrictions, but generally, the goal is to create the thinnest wall possible while taking into account the part’s structural requirements and overall size and geometry. The flow behavior and material qualities of the resin should also be considered.
Wall thickness is defined as the distance between one surface of the 3D model and its opposite surface. It is the required thickness that a 3D model should have. Since many 3D printing problems are caused by inappropriate wall thickness, it is important that the wall thickness of the 3D model is assigned correctly.
Maintaining uniform wall thickness allows for the most uniform flow of the plastic through the part, allowing the best processing. Also, plastics are essentially poor heat conductors. By maintaining a uniform wall thickness, the part will cool as uniformly as possible.
Determining the best wall thickness for each part is a balancing act. It must have great mechanical strength so that the part can support the intended load of any additional parts in an assembly. A good design must also prevent oddities like strength-reducing bubbles that could occur inside the wall if the part is too thick and a material that doesn’t have the proper flow properties is chosen. Any experienced design engineer with a background in plastics should be able to assist a customer with part design to avoid costly mistakes later in manufacturing.
Consistent wall thickness is critical during the cooling process in injection molding; if some sections of a part are thinner than others, the part may be vulnerable to warping, cracking, twisting, and overall failure. Uniform wall thickness minimizes both shrinkage and residual stress in the final part.
please examine an injection mold design on the computerIf completely uniform walls simply aren’t an option, gradual thickness variations are essential to maintaining design stability. Wall thickness variations in high-mold-shrinkage plastics should never exceed 10%, even with gradual transitions to accommodate for potential stress concentrations.
Uniform wall thickness also allows for the most efficient, uniform flow of resin through a tool for ideal processing. Variations in wall thickness cause molten polymers to take preferential flows, leading to air trapping, unbalanced filling, and weld lines.
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