Injection Molding Wall Thickness Guidelines and Design Specifications

Table of Contents

There are many plastic injection-molded products around us with uniform wall thickness, like household items, consumer electronics shells, automotive inner decorative parts, medical device plastic shells, etc.

To plastic product engineers, this is one of the fundamental rules of plastic injection molding, and ignoring it can lead to sink, warp, short shot, and faulty or non-functional parts. Yet the functional and structural requirements of most consumer plastics, medical, laboratory, aerospace, defense, and industrial products often give product designers little consideration for the wall thickness.

So, when launching mold projects, mold engineers must analyze the plastic part design and achieve consistent walls and features with slight adjustments to geometry and materials. The TDL mold factory engineering team has 4 product design engineers and 23 mold design and manufacturing engineers. Can help customers design products and, from the perspective of mold manufacturing, adjust product design issues so that products can be produced smoothly.

How to design the wall thickness of injection molded products?

The plastic injection molding process and application requirements have essential restrictions on the wall thickness of the plastic parts. 

When designing products, product design engineers should consider more than just the application of plastic products. But meeting the requirements of the relatively consistent wall thickness of injection molded products (leading to easy injection formed and smooth production) is particularly essential. Therefore, there must be specific value requirements for the molding wall thickness when injection molding products with different plastic raw materials. 

It is easy to produce bubbles, shrinkage holes, and depressions if the plastic wall is too thick. It also increases the cost due to the excessive use of materials. It brings certain difficulties to the injection molding process, such as prolonging the molding time (hardening or cooling time). It is unfavorable to improve production efficiency. Does it mean it is easier to fill the plastic product if the wall thickness is thin? The answer is NO. The flow resistance of the molten plastic in the mold cavity will be large if the plastic wall is thin, especially for complex or large plastic parts, which are difficult to form. Also, the wall thickness is too thin, and the strength of the plastic parts is also poor.

Generally speaking, the plastic wall thickness should be thicker for large products, and for small products, it should be thinner. Under this basic rule about the wall thickness of the plastic parts, the thickness must be uniform. Otherwise, the shrinkage will be uneven during the molding, and cooling process, which will not only cause bubbles, depressions, and warpage but have significant internal pressures inside the plastic parts. For general products, most wall thicknesses take 1.0-2.0. In addition, the plastic wall thickness should be designed as uniformly as possible. In the case of unavoidable circumstances, the indicated area can be appropriately thicker or thinner.

Avoiding acute angles at the junction of thick and thin walls when designing plastic parts. The transition should be relaxed, and the thickness should gradually decrease along the plastic flow direction, not be changed suddenly.

Figure 1

The principle is no shrinking and being able to fill the plastic product. Generally, a plastic wall thickness of less than 0.3 will be difficult to fill. But it is fine to fill with soft plastic and rubber even though the wall thickness is only 0.2-0.3.
Then, the plastic designer should also think that the plastic parts should have a particular work intensity, save materials, and lower manufacturing costs in product molding production.

For example:

Figure 2

Design Specifications for Plastic Structures

Material Selection:

One of the most important considerations with wall thickness is which material to use for your project. With hundreds of materials, deciding on the right one can take time and effort. You can view available resins grouped by the family with recommended wall thickness ranges and detailed information on material properties, tensile and impact strength, and maximum operating temperatures online.

ABS: high fluidity, low cost, suitable for parts that do not require high strength (parts that are not directly impacted and do not withstand structural durability in reliability tests), such as internal support brackets (keyboard brackets, LCD brackets) ), etc. Electroplated components are commonly chosen ABS materials, such as buttons, side keys, navigation keys, electroplated decorative parts, etc. At present, Chimei PA-757, PA-777D, etc., are commonly used.

PC+ABS: good liquidity, good strength, and moderate price. It is suitable for parts with high rigidity and high impact toughness, such as frames, shells, etc. Commonly used material code: Bayer Bayblend T85, T65.

PC: High strength, expensive, and poor liquidity. It is suitable for high-strength shells, buttons, transmission frames, lenses, etc., which require high-strength—commonly used material codes such as Teijin Panlite L1250Y, PC2405, and PC2605.

POM: POM has high stiffness and hardness, excellent fatigue resistance and wear resistance, small creep, and water absorption, good dimensional stability, and chemical stability, good insulation, etc. Commonly used in pulleys, transmission gears, worm gears, turbines, transmission parts, etc., widely used material code such as M90-44.

PA: is tough and absorbs water, but becomes fragile when the water evaporates completely. Commonly used in gears, pulleys, etc. For key gears subject to greater impact, the material usd for injection molding will need an additive to make it strong. Material code such as CM3003G-30.

PMMA: has excellent light transmittance. After 240 hours of accelerated aging, it can still transmit 92% of sunlight, transmit 89% of light after ten years outdoors, and transmit 78.5% of ultraviolet rays. It has high mechanical strength, certain cold resistance, corrosion resistance, good insulation performance, stable size, easy to injection molding, and brittle charactor. It is often used in transparent structural parts with specific strength requirements, such as lenses, remote control windows, light guides, etc. Commonly used material code such as Mitsubishi VH001.

Considering the most important attributes of the finished plastic product:

1. Does it need chemical or ultraviolet light (UV) resistance?
2. Will the molded plastic part be subjected to direct flame or extreme temperatures?
3. How strong must the plastic injection molded part be, and will it need to flex under load?
4. Does it need stable physical properties and is safe for the human body, especially for medical mold/molded parts projects?
5. If for the food industry, does the plastic should be FDA-grade?
6. What about environmentally friendly?
7. Does it need to biodegrade or accept the application of recycled materials?
8. If color is important, can the plastic components be painted, or colorant be added to the resin before injection molding?
9. What about opacity? Some plastics have good optical properties, others not so much.
10. Will the plastic product be used in an electromagnetic environment?
While all of these factors are being weighed, refer back to the recommended wall thickness. Obviously, materials only make good candidates if they can be injection molded to the dimensions and geometry needed for your plastic product project while still meeting the engineering requirements. Once you’re close to selecting a material, contact TDL mold engineers, and we will advise you directly or contact an expert at one of our material suppliers.

Plastic wall thickness chart of commonly used thermoplastic.

ABS0.045 in. – 0.140 in.
PC+ABS0.035 in. – 0.140 in.
Acetal0.030 in. – 0.120 in.
Acrylic0.025 in. – 0.500 in.
Liquid crystal polymer0.030 in. – 0.120 in.
Long-fiber reinforced plastics0.075 in. – 1.000 in.
Nylon0.030 in. – 0.115 in.
Polycarbonate0.040 in. – 0.150 in.
PolyesterPolyethylene0.025 in. – 0.125 in.0.030 in. – 0.200 in.
Polyphenylene sulfide0.020 in. – 0.180 in.
Polypropylene0.025 in. – 0.150 in.
Polystyrene0.035 in. – 0.150 in.
Polyurethane0.080 in. – 0.750 in.
PMMA0.032 in. – 0.256 in.
POM0.018 in. – 0.126 in.
PSU0.038 in. – 0.178 in.

For example, nylon 6/6 flows well, is good for injection molded thin-walled parts, and has excellent impact resistance, but you might have rejected it because of its average strength and lack of resistance to heat. Adding glass-fiber filler to the resin makes the nylon much stronger and far more heat resistant. Glass fiber also reduces the risk of sinking in the wall thick sections but may lead to warp in the thin areas, depending on material flow during the plastic injection molding process.

In some cases, you might be directed to a completely different material family:

Polycarbonate is a common material used in designing optical components, but acrylic is often a better choice on thick parts, as it’s less likely to experience sink, voids, bubbles, and poor part detail.

Optical-grade liquid silicone rubber (LSR) offers superior light transmission and product clarity, and allows designers to break the rules of thick and thin, even with very fine part features.

A styrene-like material known as K-Resin is often a good substitute for ABS or polycarbonate in large structural components.

Liquid crystal polymer (LCP) is another glass-filled material that’s strong but can “go thin” when needed.

Again, there are hundreds of materials and thousands of ways to adjust, blend, or fine-tune them to produce the desired results. More information can also be found on the TDL materials blog page. TDL is a plastic injection molding factory, and we have rich experience in plastic product manufacturing. We can provide suggestions if you need help with choosing material for your product.

Principles of Plastic Part Thickness Design

1. Proper wall thickness will reduce the risk of cosmetic defects in plastic parts. The thickness of each section part of the plastic product should be as uniform as possible. And the thickness difference should be controlled within 25% of the basic wall thickness. The minimum wall thickness of the entire part should be at least 0.4mm.

2. The thickness of the shell in the thickness direction should be 1.2~1.4mm as much as possible, and the side thickness should be 1.5~1.7mm; the thickness of the outer lens support surface should be 0.8mm, and the minimum thickness of the inner lens support surface should be 0.6mm. The wall thickness of the typical battery cover is 0.8~1.0mm.

3. The thickness difference of the connection plastic wall between the thick and thin should be slight; Walls in any plastic-molded part should be no less than 40 to 60 percent of adjacent walls. Arc transition should be adopted at the junction between each wall, and all should fit within recommended thickness ranges for the selected material.

4. When choosing the product’s wall thickness, attention should also be paid to the material flow and fill properties because the flow length of the melt during injection will decide the wall thickness. When the process is long, the wall thickness should be slightly larger. The flow length calculation of the melt is shown in the figure 4-1 below.

Figure 4-1

When the product’s wall thickness is 2.5mm, the length of the melt flow for different raw materials is shown in the figure 4-2 below.

Figure 4-2

5. On the basis of satisfying the functional strength and reasonable structure of the product, the wall thickness of the product should be reduced as much as possible to save materials and reduce the manufacturing cost of the product. But the thinnest part should be at least 0.6 ~ 0.9mm, generally taking 2 ~ 5mm.

6. The product’s wall thickness should consider the raw material’s viscosity, which can be calculated and selected according to material properties. The minimum wall thickness requirements for materials with high viscosity will be more significant. Different viscosity will influence the fluid flow, as shown in figure 6-1.

Figure 6-1

7. The wall thickness value is selected according to the injection molding process conditions for different raw materials. It can be selected with reference to the value range in table 7-1 below.

Table 7-1

Product structure design

Maintaining a uniform plastic wall thickness is critical in injection molded part designs. Uniformity prevents abnormal shrinkage that causes sinking, warping, and twisting. It will also manage pressure better, preventing the injection-molded plastic products from cracking. Good injection molding goes a long way toward making parts more cost-effective.
In addition to optimizing product wall thickness, product structural design is also crucial. Good product design can help reduce product surface defects, enhance product performance, and obtain more beautiful and durable plastic parts.

Design Guidelines for Optimum Plastic Part Structure

1. Part geometries, such as long unsupported spans, sharp internal corners, and poorly designed bosses, should be avoided, regardless of wall thickness.

2. Use ribs to strengthen tall walls where needed. In order to ensure the strength and rigidity of the plastic parts without thickening the walls of the plastic parts, it is preferable to increase the number of reinforcing ribs rather than increase their wall thickness. Because design the reinforcing ribs in the appropriate parts of the plastic parts can not only avoid the deformation of the plastic parts, but in some cases, the reinforcing ribs can also improve the plastic flow in plastic part molding.

Rib Design Example:

Figure 2-2-1

3. Sharp external corners are fine, but should design a radius on inside corners—part design permitting—makes them stronger and alleviates the stress that creates warp.

4. Bosses should follow molding design guideline rules of properly designed walls of 40-60 percent of the surrounding area to avoid sinks.

  1. When designing the boss, the product designer should consider whether the plastic wall thickness will shrink.
  2. To increase the boss’s strength, additional ribs can be added around it. Refer to Figure 2-4-1 for the width value of the rib.

Figure 2-4-1

For example:

Figure 2-4-2

See Figure 2-4-3 and Figure 2-4-4 for how to improve the shrinkage of the boss: the plastic wall of the boss before the improvement is too thick, and it is easy to shrink; after the improvement, it will not shrink.

5. Principles of Plastic Part Hole and Boss Design

The distance between holes should generally be more than two times the diameter of the hole.

The distance between the hole and the edge of the plastic part should generally be more than three times the diameter of the hole. If it is limited by the design of the plastic part or used as a fixing hole, the edge of the hole can be reinforced with a boss.

The design of the side holes should avoid thin-walled sections, otherwise, sharp corners will occur, which may cause hand injury and short shot.

6. 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.

The main points of the draft angle

There is no certain criterion for the size of the draft angle, most of which are determined by experience and the depth of the product. In addition, the method of molding, wall thickness, and choice of plastic is also considered. Generally, for any side wall of the molded product, a certain amount of draft angle is required to remove the product from the mold. The size of the demolding slope can vary from 0.2° to several degrees, depending on the surrounding conditions. Generally, 0.5° to 1° is ideal.

The following points should be paid attention to when selecting the demolding slope:

  • Take the direction of the inclination. Generally, the inner hole is based on the small end, which is in line with the drawing. The inclination is obtained from the expanding direction. The shape is based on the big end, which conforms to the pattern.
  • Like the below image.draft angle design
  • Where the precision of plastic parts is high, a smaller demoulding slope should be selected.
  • For higher and larger sizes, a smaller draft angle should be used.
  • If the shrinkage of the plastic part is large, a larger slope value should be selected.
  • When the wall thickness of the plastic part is thick, the molding shrinkage will increase, and the demolding slope should adopt a larger value.
  • In general, the draft angle is not included in the tolerance range of plastic parts.
  • The demoulding slope of transparent parts should be increased to avoid scratches. Under normal circumstances, the demolding slope of PS material should be greater than 3°, and the demolding slope of ABS and PC material should be greater than 2°.
  • The side wall of the plastic parts with leather grain, sandblasting, and other appearance treatments should be added with a demoulding slope of 3°~5°, depending on the specific bite depth and required draft angle for reference. The deeper the bite depth is, the larger the demolding slope should be. The recommended value is 1°+H/0.0254° (H is the biting depth). For example, the pattern drafting slope of 121 is generally 3°, and the pattern demoulding of 122 is generally 3°. The slope is generally 5°.
  • The slope of the insertion surface is generally 1°~3°.
  • The draft angle of the shell surface is greater than or equal to 3°.
  • Except for the outer shell surface, the draft angle of the other features of the shell is 1° as the standard draft angle. In particular, it can also be taken according to the following principles: the draft angle of the reinforcing ribs below 3mm is 0.5°, 3~5mm is 1°, and the rest is 1.5°; the demolding angle of the cavity below 3mm is high. Take 0.5° for degrees, 1° for 3~5mm, and 1.5° for the rest.

Design of screw boss

1 The two shells are usually fixed using screws and snaps, and the screw posts usually also play a role in positioning the PCB board.

2 The design principle of the screw boss for self-tapping screws is: its outer diameter should be 2.0~2.4 times the outer diameter of the screw. In the design, we can take: outer diameter of screw boss = 2 × outer diameter of the screw; inner diameter of boss (ABS, ABS+PC) = outer diameter of screw -0.40mm; inner diameter of boss (PC) = outer diameter of screw -0.30mm or -0.35 mm (can be designed according to 0.30mm first, and then modify the mold and add plastic thickness after the test fails); the distance between the screw boss surfaces of the two shells is 0.05mm.

3 The values of screw boss for different materials and screws are shown in Table 8.3-1 and Table 8.3-2.

Table 8.3-1

Table 8.3-2

4 The torque values used in the assembly and testing of standard self-tapping screws (10 times) are shown in Table 8.4-1.

Table 8.4-1

The design of the seam

The role of the seam

  1. The touch between the inner space of the shell and the outside will not be direct, which can effectively block the entry of dust/static electricity, etc.
  2. Positioning and limit of the upper and lower shells.

Matters needing attention in the design of the shell mouth

  1. The mating surface should have a demoulding draft angle of >3~5°, and the end should be chamfered or rounded to facilitate assembly.
  2. For the fitting of the rounded corners of the upper shell and the lower shell, the R angle of the matching inner corner should be larger to increase the gap between the rounded corners and prevent mutual interference at the rounded corners.
  3. The direction of the seam is designed, and the seam at the end with the stronger side wall should be designed inside to resist external force.
  4. For the design of the seam size, the convex edge thickness of the outer seam is 0.8mm; the convex edge thickness of the inner seam is 0.5mm; B1=0.075~0.10mm; B2=0.20mm
  5. Design size of art line: 0.50×0.50mm. Whether to use an art line can be carried out according to design requirements

3. Requirements for the difference between the top shell and the bottom shell.

Figure 9.3-1

After assembly, at the stop position, if the top shell is larger than the bottom shell, it is called top shell scraping; if the bottom shell is larger than the top shell, it is called bottom shell scraping, as shown in Figure 9.3-1. The acceptable surface scraping is less than 0.15mm, and the acceptable bottom scraping is less than 0.10mm. No matter how it is made, the mismatch will exist. It is only a question of the size of the gap. Try to make the top shell of the product assembly larger than the bottom shell, and reduce the mismatch of the surface shell and bottom shell.

The design of the snap-fit

Key points of snap-fit design

  1. Quantity and position: the snap-fit position at the corner should be as close to the corner as possible;
  2. Structural form and positive and negative snap-fits: the convenience of assembly and disassembly should be considered, and the production of molds should be considered;
  3. Pay attention to prevent shrinkage and weld marks at the snap-fit;
  4. For the snap-fit towards the inside of the shell, the movement space of the slider/angle lifter is not less than 5mm;

2 Common snap-fit design

  1. Usually, the upper cover is provided with a hook for running the slider, and the lower cover is provided with a hook for the angle lifter. Because the upper cover has more ribs than the lower cover, and the wall of the upper cover is often deeper than the lower cover, the angle lifter gets limited space for demoulding, so the slider will be better.
  2. Selection of decorative line (art line) for the upper and lower covers at the below image.

Figure 10.2-2-1

3. The hook should be close to the corner. Otherwise, the corner will get a warpage easily.

Figure 10.2-3-1

4. The distance between the snap-fits should not be too far. Otherwise, it will be easy to open the seam.

Design of decorative parts

Precautions for the design of decorative parts

  1. When the size of the decorative parts is large (greater than 400mm²), the width of the adhesive position around the shell and the decorative parts should be larger than 2mm. When assembling decorative parts, use a fixture to press the decorative sheet, the pressure is greater than 3kgf, and hold the pressure for more than 5 seconds.
  2. When the size of the decorative parts on the outer surface is large (greater than 400mm²), it can adopt other technology such as aluminum, plastic shell spraying, and stainless steel, and the electroforming process is not allowed. Because the electroforming process is only suitable for appearance parts with small areas and fine patterns. The area is too large to achieve good flatness, and the wear resistance is very poor.
  3. When designing electroplating decorative parts, the plastic casing assembly groove should be without through holes if the distance from the internal main board or electronic device is less than 10mm. Otherwise, it will be very difficult for ESD. If the decorative parts must be snap-on, the shell will have through holes, as the clip position cannot be electroplated, so the clip should be covered with a shielding film.
  4. If the decorative parts are on both sides of the main unit, the surface shell inside the decorative parts and the bottom shell rib should be designed in direct contact, and the decorative parts cannot be used to ensure the strength of the assembly.
  5. Whether there is ESD risk should be considered when designing electroplating decorative parts.
  6. Electroplated decorative parts with a diameter of less than 5.0mm are generally designed to be bonded by double-sided tape or loaded at the back and are not intended to be snapped fit.

Selection of decorative hypotenuse angle of electroplated parts

If the decorative hypotenuse of the electroplating parts is required to be a mirror-polished side, the hypotenuse angle in Figure 11.2-1 should be as a>45°. Otherwise, this side will be a black appearance in actual effect, and there will be no good mirror effect. The B value is set according to the ID design requirements.

Figure 11.2-1

Design of electroplated plastic parts

The plastic electroplating layer is generally composed of the following layers, as shown in the following figure 11.3-1:

Figure 11.3-1

  1. The thickness of electroplated parts will be controlled at about 0.02mm according to ideal conditions, but in actual production, there may be a maximum thickness of 0.08mm, so we should pay attention to the assembly design of electroplated parts. The thickness of the coating layer is in μm. Generally, the lower limit of the thickness of the coating layer is indicated. If necessary, the thickness range of the coating layer can be marked.
  2. If there is a blind hole design, the depth of the blind hole should preferably not exceed half of the aperture and not require the color of the bottom of the hole.
  3. It is necessary to use a suitable wall thickness to prevent deformation, preferably more than 1.5mm and less than 4mm. If it needs to be made very thin, a reinforced structure should be made in the corresponding position to ensure that the deformation of electroplating is within a controllable range.
  4. The surface quality of plastic parts must be very good. Electroplating cannot cover up some injection molding defects and usually makes these defects more obvious.
  5. It is best to use ABS material as the base material. The adhesion of the film after ABS electroplating is better, and the price is relatively low.
  6. Key design

Button design

From the analysis of the actual operation situation, combined with the knowledge of ergonomics, when operating one button, the buttons near around cannot be affected,  so the distance between the surrounding buttons should be considered as follows:

  1. In the vertical separation button, the distance between the centers of two adjacent buttons a≥9.0mm
  2. In the horizontal row of buttons, the distance between the centers of two adjacent buttons b ≥ 13.0mm
  3. For the convenience of operation, the minimum size of the commonly used function keys is: 3.0×3.0mm

Figure 12.2-1

The design gap between the button and the panel base is shown in Figure 12.2-1:

  1. The size of the button skirt is C≥0.75mm, and the gap between the button and the tact switch is B=0.20mm;
  2. The matching gap between the clear button and the base body is A=0.10-0.15mm on one side;
  3. The matching clearance between the painted button and the base body is A=0.20-0.25mm on one side
  4. The swing direction clearance of the seesaw button is 0.25-0.30mm, which needs to be simulated according to the size of the switch; the design matching clearance in the non-swing direction is A=0.2-0.25mm;
  5. The rubber oil is 0.15 mm thicker than ordinary oil, and 0.15 mm should be added on one side to the design gap of regular painting, such as the gap between the rubber oil painted button, and the base body is 0.3-0.4 mm;
  6. The matching gap between the surface electroplating button and the base body is A=0.15-0.20mm on one side;
  7. The height of the button protruding from the panel is shown in Figure 12.2-2:

The height D=1.20-1.40mm of the ordinary button protruding from the panel, generally 1.40mm;

For buttons with large surface curvature, the height D between the lowest point of the button and the panel is generally 0.80-1.20mm.

Figure 12.2-2

Knob design

1 Knob size requirements

Knob size requirements are shown below.

Figure 13.1-1

2 Distance between two knobs

The distance between the two knobs: C≥8.0mm.

Figure 13.2-1

3 Design clearance between the knob and corresponding fittings

  1. The design of the knob and the corresponding fittings should match the unilateral clearance of A≥0.50mm, as shown in Figure 10.3-1;
  2. The design of the electroplating knob and the corresponding fittings should match the unilateral clearance of A≥0.50mm;
  3. The rubber oil is 0.15 mm thicker than ordinary oil and needs to add 0.15 mm to the design clearance of ordinary painting.
  4. The height of the knob protruding from the panel base or the highest point of the trim is 9.50≥B≥8.00mm.

Figure 10.3-1

Design of rubber stopper

  1. Plastic mold for TPU plug;
  2. The rubber stopper needs to be designed with a disassembly port (≥R0.5 semicircle);
  3. All plugs (especially IO plugs) cannot have a thin thickness of 0.4mm because it is easy to deform after being inserted several times;
  4. The opening at the earphone of the shell is 0.3mm larger than the one side of the earphone socket (PLUG); the gap between the shape of the earphone plug and the host shell is 0.05mm on one side;
  5. The part where the earphone plug is inserted into the earphone holder is designed with a “+” rib shape. The depth of the earphone holder is 2.0mm, the width of the rib is 0.8mm, and the unilateral interference between the outer contour and the circumference of the phone jackhole is 0.05mm. The top surface of the “+” rib is inverted with R0.3 rounded corners, which is convenient for insertion;

Lens design

Common Materials for Lenses (LENS)

  1. PMMA: lens (LENS) commonly used PMMA material. Good light transmittance ≥91%, high surface hardness, good weather resistance, not easy to oxidize and crack. The surface hardness can reach above H without hardening and above 3H after hard coating.
  2. PC: The transmittance of PC is above 88%, and the lens has good toughness and impact resistance. However, its surface hardness is low. After injection molding, the surface hardness is generally about 4B. After hardening treatment, the hardness is only about HB. Lenses are easily scratched during use.

Design gap between the lens (LENS) and panel.

  1. The matching gap between the lens and the front shell is A=0.10mm, as shown in Figure 15.2-1.
  2. The area where the double-sided tape is attached should have a gap of B=0.10mm, as shown in Figure 12-1.

Figure 15.2-1

The design of the matching position of the touch screen and the plastic cover

Figure 16-1

Figure 16-2

Precautions for the design of the plastic cover at the corresponding position of the touchscreen

  1. The distance (periphery) between the plastic cover window’s edge and the touch screen’s action area is 1.50-2.00mm, usually 1.50mm. See Figures 16-1 and 16-2;
  2. During 3D modeling, the outer dimension of the touch screen is determined according to the maximum tolerance size of the design drawing, and the matching plastic size only needs to leave a gap of 0.15mm on one side of the outer dimension of the touch screen;
  3. To prevent the touch screen from being squeezed and twisted due to deformation, it is necessary to use EVA with appropriate elasticity and strength between the touch screen and the plastic cover, the touch screen and the TFT screen as well, to absorb shock. The thickness of the EVA before compression is 0.50-1.00 mm. The thickness can be maintained at 0.30-0.50mm after compression.

TDL is a plastic injection mold factory and a reliable China mold maker. We have rich experience in plastic product design and mold manufacturing.

TDL Clever Tweaks Can Help Strengthen Walls for Customers.

Even if the right combination of material attributes can’t be found, don’t despair. Some clever edits to part geometry go a long way to alleviate internal stress and potential weakness produced by less than optimal wall thickness. Parts shaped like dumbbells or sewing bobbins are perfect candidates for coring, which eliminates large cross-sections of material similar to removing wedge-shaped slices of an apple, but the strong core is left in place. This is a great way to avoid sinks, reduce material usage and make parts lighter but just as strong (possibly stronger). And parts like box lids that have tall, thin walls can be reinforced with gussets, so long as the relative wall thickness of the supporting material follows the 40 to 60 percent rules mentioned previously. This also eliminates the chance of shadowing, which occurs when one section of the part cools down faster than others.

TDL Plastic mold, a professional mold manufacturer and injection molding factory, helps customers design plastic products and manufacturing. TDL plastic product designers and mold engineers work together to solve the issues about wall thickness and product design for injection molding.

Design for Manufacturability Offers Feedback

TDL team makes quotations for customers’ mold projects. Before launching the mold project, we will make DFM about the project and send it to customers. Be sure to review the accompanying design for manufacturability (DFM) analysis, which provides feedback to improve the moldability of your part. Overly thick or thin areas will be color-coded based on nominal wall thickness and recommendations on draft angle changes. Parting lines, ejector and gate locations, undercuts, side actions, and the need for hand-loaded inserts are also displayed. If deemed necessary, a flow analysis can be performed to analyze pressure points around gate areas and to identify potential knit lines. As always, contact us at or if questions or concerns emerge about plastic product design or mold projects.


Gary Liao

Gary Liao

Gary Liao is the Engineering Manager of TDL Company and has more than 20 years of mold design experience.

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