Plastic product design is a type of product design that we often encounter when designing. When designing structure of plastic products, in addition to meeting basic functional requirements of product, it must also meet requirements for ease of injection molding. Some general points to pay attention to when designing plastic structures,
Starting today, I'll share some general considerations that I think you need to keep in mind when designing plastic products in installments. Today we will first analyze most basic point: calculation of wall thickness.1. Wall thickness of plastic parts
When designing a plastic product, wall thickness is first factor to consider. The wall thickness of product determines mechanical properties, appearance, complexity of injection molding and cost of product. Therefore, pay special attention. The calculation of wall thickness of product should reflect following three principles:
- The wall thickness of individual parts should be moderate
We know that plastic products can only be produced by injection molding. Due to characteristics of plastic materials and injection molding process, wall thickness of plastic parts must be in a suitable range, not too thick and not too thin. thin If too thick, it will increase flow resistance in injection molding and make it difficult to fill mold cavity; if it is too thick, it will increase injection cooling time of part and injection molding cycle (each time main wall thickness is doubled, cooling time is increased by 4 times), injection molding The injection molding efficiency is low, and wall thickness is too thick, which also leads to shrinkage surface of part, air bubbles (the wall thickness is too thick, external cooling rate is high, and internal cooling rate is low), warping (due to uneven cooling, part creates a bending moment, which causes deformation), and other quality defects.
It is recommended below to select a wall thickness value for frequently used materials (the manufacturer may have slight differences if it cannot be generated)
PE material: minimum wall thickness: 0.9 mm, maximum wall thickness: 4.0 mm
PP material: minimum wall thickness: 0.6 mm, maximum wall thickness: 3.5 mm
PA material: minimum wall thickness: 0.6 mm, maximum wall thickness: 3.0 mm
PS material: minimum wall thickness: 1.0 mm, maximum wall thickness: 4.0 mm
AS material: minimum wall thickness: 1.0 mm, maximum wall thickness: 4.0 mm
PMMA material: minimum wall thickness: 1.5 mm, maximum wall thickness: 5.0 mm
PC material: minimum wall thickness: 1.5 mm, maximum wall thickness: 5.0 mm
PVC material: minimum wall thickness: 1.5 mm, maximum wall thickness: 5.0 mm
ABS material: minimum wall thickness: 1.5 mm, maximum wall thickness: 4.5 mm
POM material: minimum wall thickness: 1.5 mm, maximum wall thickness: 5.0 mm
2. Minimize part wall thickness
The basic principle of determining wall thickness of a part is to make wall thickness as small as possible in order to ensure structural strength of part, as well as smooth assembly and production. However, be careful not to cause some problems because wall thickness is too thin, such as wall thickness is too small to resist demoulding force during injection molding;
The wall thickness is too thin to withstand blocking force during assembly;
3. The wall thickness of parts should be as uniform as possible
The ideal distribution of wall thickness of part is that thickness of part is same in any part of part,
But in most cases, products we develop cannot fully meet this requirement, and we can only try to be as uniform as possible. Because uneven wall thickness causes uneven cooling and shrinkage of parts, resulting in defects such as surface shrinkage of parts, internal pores, warping of parts, and large dimensional deviations. According to requirements above, I have listed a few typical design ideas to make wall thickness same for your reference (I am not an art graduate, hand painting is too rough, please forgive me)
For parts with a hole in middle of disk, wall thickness can be machined as shown in figure below. The design on left is most unreasonable.
Detail with a hole in middle of disk
For porous parts, you can refer to following figure to determine wall thickness, which not only reduces material, but also provides strength to part.
We all know why holes on plastic parts are always accompanied by a BOSS post. In fact, this is a way to intelligently solve problem of wall thickness. But holes we see on board mostly don't have boss posts,
This is a feature of plastic material, so special attention should be paid to design.Welcome to follow us, thanks for your support.