![\"Injection](\"https:\/\/chiggofactory.com\/wp-content\/uploads\/2025\/05\/Injection-Molding-Process-1024x484.png\")
<\/figure>\n\n\n\nInjection molding is one of the most cost-effective manufacturing process<\/a> for producing high volumes of identical plastic parts. In this process, polymer pellets are first melted and then injected under pressure into a mold. Once the plastic cools and solidifies, the mold is opened, and the part is ejected. The cycle then repeats, often in as little as 15 to 60 seconds, depending on part size and mold complexity. In comparison, CNC machining or 3D printing might require minutes to hours to produce the same geometry. <\/p>\n\n\n\n This process offers high repeatability, tight tolerances, and excellent design flexibility. It is widely used in mass production projects all around you, including car dashboards, plastic containers, mobile phone housings, bottle caps, and even everyday toys. The main limitations are the high initial costs of mold design and manufacturing, as well as longer lead times\u2014from initial design to production\u2014which typically take at least four weeks.<\/p>\n\n\n\n Almost all thermoplastic materials<\/a> can be injection molded, and some thermosets and liquid silicones are also compatible with the process. Additionally, their properties can be tailored by adding fillers and additives (e.g., glass and carbon fibers) or by blending different pellets (e.g., PC\/ABS blends) to achieve the desired appearance and functionality. Below is an overview of commonly used injection molding materials:<\/p>\n\n\n\n To ensure that parts are produced consistently, with minimal defects, and at the lowest possible cost, designers should follow some established guidelines. The following sections outline the key considerations when designing parts for injection molding:<\/p>\n\n\n\n Wall thickness affects the mechanical performance, overall cost, and appearance of your injection molded part. There are two wall thickness terms that designers need to understand:<\/p>\n\n\n\n Whenever possible, maintain a uniform wall thickness in your part. This promotes even cooling, resulting in more consistent shrinkage, and helps reduce stress concentrations, deformation, and other injection molding defects .<\/p>\n\n\n\n Uniform wall thickness does not necessarily mean that every wall must have exactly the same thickness. Rather, it emphasizes minimizing large variations between neighboring wall sections. Generally, the thickness of a wall should be no less than 40% to 60% of adjacent walls. When thickness variation is necessary for functional or structural reasons, transitions should be gradual\u2014using chamfers or fillets with a length at least 3 times the difference in thickness\u2014to avoid abrupt changes in flow or cooling that could lead to part failure.<\/p>\n\n\n\n Nominal wall thickness refers to the target or average thickness of a part, and it serves as the starting point for design. A proper wall thickness helps ensure sufficient part strength and reducing material waste. It also lays the foundation for mold design, processing parameters, equipment setup, and material selection.<\/p>\n\n\n\n Walls that are too thick increase the risk of shrinkage and deformation. They also require more material and longer cycle times\uff0cdriving up production costs. On the other hand, walls that are too thin may can solidify too quickly or trap air, leading to short shots\u2014defects caused by incomplete mold filling.<\/p>\n\n\n\n To avoid these issues, always keep wall thickness within the recommended range for your chosen material. Below is a list of the recommended wall thicknesses for common plastic resins:<\/p>\n\n\n\n Sharp corners tend to concentrate stress, make demolding more difficult, and accelerate wear on the mold surface. Material can accumulate or cool unevenly at these sharp transitions, resulting in flow lines or other defects. In addition, sharp corners often require the use of EDM (electrical discharge machining) to form the mold, which raises tooling costs.<\/p>\n\n\n\n The best practice is to use rounded corners. General design guidelines are as follows:<\/p>\n\n\n\n \u25aa Use an internal radius of at least 50% of the wall thickness (minimum 25% if space is limited). The parting line is the seam formed where the two halves of the mold meet. It typically appears on the surface of the molded part and is an unavoidable feature in injection molding. The placement of the parting line affects mold complexity, production efficiency, and the final appearance or functionality of the part.<\/p>\n\n\n\n An intuitive idea might be to place the parting line straight down the middle of the part. But this is not always possible\u2014or even practical. In reality, the parting line should be positioned strategically to balance visual appeal, function, and mold complexity. For example:<\/p>\n\n\n\n Draft is the angle applied to vertical surfaces of an injection-molded part to allow for smooth ejection from the mold. Without adequate draft, the part would tightly contact the mold surface, risking excessive force during ejection. This can lower part quality, lead to scrap parts, and may even result in damage to the tooling.<\/p>\n\n\n\n Many CAD software programs make it easy to add draft angles, but it\u2019s best to apply them in the final stages of the design to prevent unnecessary complexity. When determining the appropriate draft angle, following factors must be considered:<\/p>\n\n\n\n Different plastics have different flow characteristics, which affect the required draft angle. Materials like polypropylene (PP), polyethylene (PE), and polystyrene (PS) generally have good flow properties and low viscosity. For these materials, a draft angle of 1\u00b0to 3\u00b0is typically sufficient. In contrast, thermosetting plastics like epoxy and phenolic resins often require larger draft angles (3\u00b0or more) to ensure smooth ejection.<\/p>\n\n\n\n Draft is related to the surface texture and smoothness of your injection molded parts. Smoother finishes require less draft, while heavier textures require more. For example:<\/p>\n\n\n\n \u25aa For smooth finish, a draft angle of about 1\u20132\u00b0is generally sufficient. During injection molding, the texture from the mold is transferred to the part\u2019s surface. The type of product you are designing will influence your choice of mold finish. Industry organizations such as the Society of the Plastics Industry (SPI) and the Society of German Engineers (VDI), as well as companies like Mold-Tech (MT) and Yick Sang (YS), have established standardized classifications for polished and textured mold finishes. These standards help guide the selection of proper draft angles based on surface finish requirements.<\/p>\n\n\n\n The surface finish chart below lists the recommended draft angles for the most common finishes.<\/p>\n\n\n\n <\/p>\n\n\n\n Set your draft angles with the way the mold opens\u2014the mold\u2019s \u201cdraw\u201d direction. Otherwise, the part can stick to the half that holds the ejector pins and won\u2019t release properly. In addition, be sure to apply draft not only to all vertical walls but also to any features like holes or bosses.<\/p>\n\n\n\n For example, imagine a rectangular part with four through\u001eholes. If the holes are drafted toward the cavity, the part may remain stuck there after molding. Instead, drafting them toward the core side\u2014where the ejector system lives\u2014so the pins can push the part out cleanly.<\/p>\n\n\n\n Ribs and gussets are both used to reinforce localized structures and improve part stiffness without increasing the overall wall thickness.<\/p>\n\n\n\n Ribs are slender, wall\u001elike protrusions that extend from a part\u2019s surface\u2014often across broad, thin\u001ewalled areas or inside box\u001eshaped features\u2014to distribute loads evenly and improve overall stiffness. To ensure effective rib design, follow these best practices:<\/p>\n\n\n\n \u25aa Rib thickness should be 40\u201360% of the main wall thickness. Gussets are small triangular or trapezoidal plates placed at the junction of walls, bosses, or ribs to strengthen local high\u001estress points. Best practices for gusset design include:<\/p>\n\n\n\n \u25aa The gusset should usually be about one-third to one-half as thick as the wall it\u2019s supporting. Bosses are cylindrical features designed to receive inserts, self-tapping screws, or pins for assembly or mounting. It can be also viewed as circular ribs that contribute to the overall structural strength. Freestanding bosses should be avoided. Always connect them to adjacent walls or surfaces using ribs or gussets rather than being fully integrated into the wall itself.<\/p>\n\n\n\n When designing bosses, remember the following:<\/p>\n\n\n\n \u25aa Place bosses where structural integrity or fastening strength is needed ,such as at screw locations. Undercuts are recessed or overhanging features that create an interlock between the part and one or both mold halves, preventing clean ejection along the mold opening direction. Common examples include hooks, snap-fits, holes, grooves, and side slots that are perpendicular or transverse to the mold\u2019s parting direction.<\/p>\n\n\n\n While undercuts are sometimes necessary for mechanical function or assembly fit, they typically require additional tooling\u2014such as sliding cores, lifters, or cams\u2014which increase mold complexity, cycle time, and manufacturing cost. Improperly designed undercuts can cause ejection difficulties, part distortion, excessive wear, or tool failure.<\/p>\n\n\n\n Some design guidelines for undercuts are as follows:<\/p>\n\n\n\n \u25aa\u202fAvoid undercuts whenever possible by modifying the geometry, reorienting the part, or shifting the parting line so that features align with the mold\u2019s pull direction and eliminate recesses. Text and symbols (e.g., part numbers, logos, recycling marks) are commonly embossed or debossed on molded parts for traceability, branding, or regulatory compliance. Here are some helpful tips:<\/p>\n\n\n\n \u25aa Use raised (embossed) text rather than recessed (engraved) when possible, as engraved text requires more complex mold tooling, accelerates tool wear, and increases cost\u2014especially for high volumes or intricate designs. Injection molding tolerance defines the allowable deviation of a part\u2019s dimensions from its nominal design. In design, tighter tolerances should be applied to critical features, such as assembly interfaces, sealing grooves, and locating holes, as these directly impact fit and functionality. For non-critical dimensions, such as the width of non-load-bearing surfaces, looser tolerances can be used to reduce manufacturing costs.<\/p>\n\n\n\n There are two common tolerance levels:<\/p>\n\n\n\n During design, dimensional tolerances must be adjusted according to material shrinkage. Different plastics have different shrinkage rates\u2014semi\u001ecrystalline materials (e.g., PA, PP, PE, POM) shrink more than amorphous materials (e.g., ABS, PC, PMMA). Although shrinkage is generally predictable, slight variations in resin formulation or processing conditions (like melt temperature) can influence the final part size. As part size increases, shrinkage variation becomes more pronounced. Depending on the material, you should expect a shrinkage\u2010related tolerance of roughly \u00b10.002\u202fin\/in (0.05\u202fmm\/mm).<\/p>\n\n\n\n Tolerance stack\u001eup analysis must also be considered in multi\u001epart assemblies, because even if each individual feature (e.g., a hole) is within its specified tolerance, cumulative variation can lead to misalignment\u2014especially when multiple holes across different parts need to align for fasteners to pass through.<\/p>\n\n\n\n Note that mold tolerances also influence final part quality. Standard mold machining tolerances are around \u00b10.005\" (0.13\u202fmm), but tighter tolerances may be required for high\u001eprecision parts. Additionally, molds experience wear over time, which can lead to dimensional drift. It\u2019s important to plan for tool maintenance and refurbishment to maintain consistent part quality during long\u001eterm production runs.<\/p>\n\n\n\n Part design and mold design are closely linked in determining the success of an injection molded product. As part design focuses on geometry and functionality, mold design translates those requirements into a manufacturable tool. The following section outlines the fundamental aspects of mold design:<\/p>\n\n\n\n The mold tooling consists of a standard mold base, cavity and core inserts, and any moving components (slides, lifters, ejector plates, etc.). The mold base provides the rigid framework\u2014holding guide pillars, support plates, and the ejection system\u2014while the cavity and core inserts define the part\u2019s shape. Together, they control how precisely and consistently each part is molded.<\/p>\n\n\n\n A good mold design should:<\/p>\n\n\n\n \u25aa Use a standard base (e.g., DME or HASCO) for cost\u001eeffective sourcing and easy replacement of worn components. Gates are the entry points through which molten plastic flows into the mold cavity. Their size, shape, and placement have a great impact on part appearance, structural strength, and the presence of molding defects such as flow marks and weld lines.<\/p>\n\n\n\n \u25aa Larger parts need larger gates to maintain pressure and flow rate for complete filling. Gates can be categorized by trimming method\u2014manual or automatic\u2014and certain types are better suited to specific part geometries. Below picture shows the common examples of the gates.<\/p>\n\n\n\n \u25aa Edge Gate (Standard Gate):<\/strong> Rectangular cross\u001esection along the parting line; ideal for flat or rectangular parts; can be tapered for better flow. \u25aa Submarine (Tunnel) Gate:<\/strong> Angled entry below the parting line; auto\u001ebreaks during ejection for minimal blemish. The runner system guides molten plastic from the sprue to the gates and into the mold cavities. The runner design impacts material flow, cycle time, and part quality\u2014especially in multi-cavity or family molds. An efficient runner system ensures that molten plastic flows evenly to all cavities. Balanced flow prevents defects such as dimensional variation, short shots, and weld lines. Uneven distribution can also cause localized overheating or underfilling, which affects both strength and surface finish.<\/p>\n\n\n\n The shape and size of the runner channel directly impact flow behavior and processing efficiency. Full-round runners reduce pressure loss but increase tooling complexity, while trapezoidal or semi-circular runners are easier to machine but less efficient. Oversized runners waste material and slow cooling; undersized ones restrict flow and may cause incomplete fill. In multi-cavity molds, runners should be symmetrical and evenly distributed to ensure each cavity fills simultaneously.<\/p>\n\n\n\n There are two main types of runner systems:<\/p>\n\n\n\n The runner system must be designed in coordination with the gate and cooling systems. A well-optimized layout reduces cycle time, improves consistency, and supports efficient, high-quality molding.<\/p>\n\n\n\n Ejector pins are used to push the molded part out of the cavity once it has solidified. Their placement and design significantly affect part quality, ejection efficiency, and mold life. Design recommendations are:<\/p>\n\n\n\n \u25aa Position ejector pins on non-cosmetic surfaces, such as near the parting line. The cooling system maintains mold temperature to control shrinkage, cycle time, and final part quality. Channels should be routed for uniform cooling, with tighter spacing (3\u20135\u202fmm from the cavity) around thick sections. Ensure cooling lines do not conflict with gates, runners, or ejection hardware. Proper channel diameter (typically 6\u201310\u202fmm) and balanced manifolds further improve thermal consistency and shorten cycle times.<\/p>\n\n\n\n Now that you have a clearer understanding of how injection molding design impacts manufacturability, performance, and cost, it's time to move forward. Once your design is ready, Chiggo offers a free DFM (Design for Manufacturability) analysis along with your request for quote. This analysis helps identify potential issues or risks related to mold making and injection molding.<\/p>\n\n\n\n What\u2019s next? Creating a prototype<\/a> can help validate your design decisions before tooling begins. Chiggo is here <\/a>to guide you through each step of the injection molding journey, ensuring a smooth transition from design to production.<\/p>\n","protected":false},"excerpt":{"rendered":" This article provides practical design tips for injection molding to help mitigate common mistakes, improve product quality, and reduce costs by avoiding expensive mold changes and rework.<\/p>\n","protected":false},"author":2,"featured_media":3264,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"inline_featured_image":false,"footnotes":""},"categories":[11,17],"tags":[],"class_list":["post-3261","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-manufacturing-process","category-inject-molding"],"yoast_head":"\nMaterial Selection<\/h2>\n\n\n\n
Material<\/strong><\/strong><\/td> Characteristics<\/strong><\/strong><\/td><\/tr> Polypropylene (PP)<\/td> Ultra\u2011low density and cost, excellent flow and chemical resistance; low stiffness and poor UV\/oxidative durability.<\/td><\/tr> Polyethylene (PE)<\/td> Chemical resistance, available in HDPE\/LDPE for strength or flexibility; low rigidity and poor adhesion. <\/td><\/tr> Polystyrene (PS)<\/td> Very rigid and dimensionally stable; easy to mold; brittle with low impact strength.<\/td><\/tr> Acrylonitrile Butadiene Styrene (ABS)<\/td> Tough and impact\u001eresistant, good surface finish and moldability; moderate heat resistance, poor long\u001eterm weatherability. <\/td><\/tr> Acetal (POM)<\/td> High stiffness, low friction and water uptake, excellent dimensional stability; limited high\u001etemperature performance. <\/td><\/tr> Acrylic (PMMA)<\/td> Optically crystal\u001eclear, UV\/weather\u001eresistant, high rigidity; brittle and prone to stress\u001ecracking.<\/td><\/tr> Nylon (PA)<\/td> Excellent toughness, wear and fatigue resistance, high strength; hygroscopic (moisture uptake) requiring drying and design compensation.<\/td><\/tr> Polybutylene Terephthalate (PBT)<\/td> Strong, stiff with low moisture absorption and good electrical insulation; moderate shrinkage\u2014needs proper gating.<\/td><\/tr> Polycarbonate (PC)<\/td> High impact strength, natural transparency, wide temperature range; sensitive to stress\u001ecracking, needs uniform wall thickness.<\/td><\/tr> Polyether Ether Ketone (PEEK)<\/td> Exceptional chemical\/thermal resistance and mechanical strength; very expensive, requires specialized molding. <\/td><\/tr> Thermoplastic Elastomer (TPE)<\/td> Rubber\u001elike flexibility and soft\u001etouch feel, good chemical\/weather resistance; lower load\u001ebearing capacity. <\/td><\/tr> Thermoplastic Polyurethane (TPU)<\/td> Outstanding abrasion resistance and elasticity, good load\u2011bearing; can stick in mold\u2014needs optimized draft and release.<\/td><\/tr> PC\/ABS<\/td> Balanced toughness and heat resistance with easier moldability than PC and better stability than ABS; moderate chemical resistance.<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n Part Design Considerations<\/h2>\n\n\n\n
Wall Thickness<\/h3>\n\n\n\n
\n
![\"transition](\"https:\/\/chiggofactory.com\/wp-content\/uploads\/2025\/05\/transition-at-section-of-non-uniform-wall-thickness-1024x341.png\")
<\/figure>\n\n\n\n\n
Material<\/strong><\/td> Recommend Wall Thickness\uff08in\uff09\u00a0\u00a0<\/strong><\/td> Recommend Wall Thickness\uff08mm\uff09\u00a0<\/strong><\/td><\/tr> Acetal (POM) <\/td> 0.030\u20130.120 <\/td> 0.76\u20133.05 <\/td><\/tr> Acrylic (PMMA) <\/td> 0.025\u20130.500 <\/td> 0.64\u201312.70 <\/td><\/tr> Acrylonitrile butadienestyrene (ABS) <\/td> 0.045\u20130.140 <\/td> 1.14\u20133.56 <\/td><\/tr> Nylon (PA) <\/td> 0.030\u20130.115 <\/td> 0.76\u20132.92 <\/td><\/tr> Polybutylene Terephthalate(PBT) <\/td> 0.080-0.250 <\/td> 2.032-6.350 <\/td><\/tr> Polycarbonate (PC) <\/td> 0.040\u20130.150 <\/td> 1.02\u20133.81 <\/td><\/tr> Polyether Ether Ketone (PEEK) <\/td> 0.020-0.200 <\/td> 0.508-5.080 <\/td><\/tr> Polyetherimide (PEI) <\/td> 0.080-0.120 <\/td> 2.032-3.048 <\/td><\/tr> Polyethylene (PE) <\/td> 0.030\u20130.200 <\/td> 0.76\u20135.08 <\/td><\/tr> Polyphenylsulphone (PPSU) <\/td> 0.030-0.250 <\/td> 0.762-6.350 <\/td><\/tr> Polypropylene (PP) <\/td> 0.035\u20130.150 <\/td> 0.89\u20133.81 <\/td><\/tr> Polystyrene (PS) <\/td> 0.035\u20130.150 <\/td> 0.89\u20133.81 <\/td><\/tr> Thermoplastic Elastomer(TPE) <\/td> 0.025\u20130.125 <\/td> 0.64\u20133.18 <\/td><\/tr> Thermoplastic Polyurethane (TPU) <\/td> 0.025\u20130.125 <\/td> 0.64\u20133.18<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n Corners<\/h3>\n\n\n\n
\u25aa Make the external radius equal to the internal radius plus the wall thickness.
\u25aa The internal and external corner radii share the same center point.<\/p>\n\n\n\n![\"Corner](\"https:\/\/chiggofactory.com\/wp-content\/uploads\/2025\/05\/Corner-design-in-injection-molding-1024x403.png\")
<\/figure>\n\n\n\nParting Line<\/h3>\n\n\n\n
![\"parting-line\"](\"https:\/\/chiggofactory.com\/wp-content\/uploads\/2025\/05\/parting-line.webp\")
<\/figure>\n\n\n\n\n
Draft<\/h3>\n\n\n\n
![\"Draft](\"https:\/\/chiggofactory.com\/wp-content\/uploads\/2025\/05\/Draft-angle--1024x403.png\")
<\/figure>\n\n\n\n\n
\n
\u25aa For parts with light or moderate textures, a draft angle of 3\u20135\u00b0is usually required.
\u25aa For heavy textures, a draft angle of at least 5\u00b0is needed.
\u25aa A general rule of thumb is to add 1.5\u00b0of draft for every 0.001\" (0.025 mm) of texture depth.<\/p>\n\n\n\nSPI Standard<\/strong><\/strong><\/td> Draft (\u00b0)<\/strong><\/strong><\/td> Mold Tech Texture<\/strong><\/strong><\/td> Draft <\/strong>(\u00b0)<\/strong><\/strong><\/td><\/tr> A-1<\/td> 0.5<\/td> MT-11000<\/td> 1.0<\/td><\/tr> A-2<\/td> 0.5<\/td> MT-11010<\/td> 1.5<\/td><\/tr> A-3<\/td> 0.5<\/td> MT-11020<\/td> 2.5<\/td><\/tr> B-1<\/td> 1.0<\/td> MT-11030<\/td> 3.0<\/td><\/tr> B-2<\/td> 1.0<\/td> VDI Texture-PC<\/strong><\/td> <\/td><\/tr> B-3<\/td> 1.0<\/td> VDI-18<\/td> 1.0<\/td><\/tr> C-1<\/td> 1.5<\/td> VDI-24<\/td> 1.5<\/td><\/tr> C-2<\/td> 1.5<\/td> VDI-33<\/td> 3.0<\/td><\/tr> C-3<\/td> 1.5<\/td> YS Texture<\/strong><\/td> <\/td><\/tr> D-1<\/td> 2.0<\/td> YS\u202f1xx<\/td> 1.0<\/td><\/tr> D-2<\/td> 2.5<\/td> YS\u202f3xx<\/td> 4.0\u202f\u2013\u202f5.5<\/td><\/tr> D-3<\/td> 3.0<\/td> YS\u202f5xx<\/td> 6.0\u2013\u202f12.0<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n \n
Ribs and Gussets<\/h3>\n\n\n\n
![\"ribs-and-gussets\"](\"https:\/\/chiggofactory.com\/wp-content\/uploads\/2025\/05\/ribs-and-gussets.webp\")
<\/figure>\n\n\n\n\n
\u25aa Rib height should not exceed three times the wall thickness.
\u25aa Apply a draft angle of 0.5\u00b0\u20131\u00b0 to aid mold release.
\u25aa Add a fillet at the rib base with a radius of 0.25\u20130.5\u00d7 the wall thickness.
\u25aa Space each rib at least four times its own thickness from nearby vertical features (other ribs, bosses, or hole edges) to provide extra cooling room and prevent hot spots.<\/p>\n\n\n\n![\"Ribs](\"https:\/\/chiggofactory.com\/wp-content\/uploads\/2025\/05\/Ribs-design.png\")
<\/figure>\n\n\n\n\n
\u25aa A gusset should never be taller than the boss or rib it\u2019s reinforcing. In fact, you often only need the gusset to be about 30\u201350% of the height of that boss, which is enough to provide support in most cases.
\u25aa Apply a draft of 0.5\u00b0to 1\u00b0to ensure smooth ejection.
\u25aa Use generous fillets at the gusset base to reduce stress concentration and improve plastic flow; a radius of 0.25 to 0.5 times wall thickness is generally appropriate.
\u25aa Place gussets symmetrically when used in pairs and avoid overcrowding.
\u25aa Maintain a gap of at least 2 to 3 times the gusset thickness from adjacent features to ensure uniform cooling and prevent molding defects.<\/p>\n\n\n\nBosses<\/h3>\n\n\n\n
![\"attach](\"https:\/\/chiggofactory.com\/wp-content\/uploads\/2025\/05\/attach-bosses-to-a-side-wall-or-to-the-floor-with-ribs-or-gussets.webp\")
<\/figure>\n\n\n\n
\u25aa For self\u001etapping screws, size the boss OD to about 2\u20132.5\u00d7 the screw\u2019s major diameter.
\u25aa Limit boss wall thickness to \u2264\u202f60% of the adjoining wall to avoid sink marks or voids.
\u25aa Add a fillet at the boss base to improve melt flow and reduce stress concentration.
\u25aa Oversize the hole diameter slightly to compensate for plastic shrinkage and ensure a proper fit after molding.<\/p>\n\n\n\nUndercuts<\/h3>\n\n\n\n
![\"example-of-undercut\"](\"https:\/\/chiggofactory.com\/wp-content\/uploads\/2025\/05\/example-of-undercut.jpg\")
<\/figure>\n\n\n\n
\u25aaUse bump\u001eoffs or flexible zones for shallow undercuts in soft, non\u001ereinforced materials\u2014ideally high\u001eelasticity thermoplastics (e.g. TPE\/TPU grades or specialty nylon elastomers). Avoid PP\/PE unless the undercut height is \u2264\u202f0.3\u202fmm with very thin walls. Provide a 30\u00b0\u201345\u00b0 lead\u001ein chamfer and add 0.5\u00b0\u20131\u00b0 draft on the bump\u001eoff face to ensure smooth ejection.
\u25aa If undercuts are necessary, keep them minimal, localized, and placed on a single side to reduce the need for multiple side actions.
\u25aa Incorporate proper draft angles (typically \u22651\u00b0) and generous radii around undercut features to ease ejection and reduce stress on both the part and the mold.<\/p>\n\n\n\nText & Symbols<\/h3>\n\n\n\n
\u25aa Consider embossed text with a height of 0.5 mm.
\u25aa Choose simple sans-serif fonts (e.g., Arial, Helvetica) to improve readability, ensure consistent plastic flow, and reduce tool wear.
\u25aa Use a uniform stroke thickness and a minimum font size of 20 points (approximately 7 mm in height).
\u25aa Avoid placing text near thin walls, sharp corners, ribs, or high-cosmetic surfaces, as these areas are more prone to defects, sink marks, or ejection issues.
\u25aa Orient text perpendicularly to the parting line or in the mold\u2019s draw direction to simplify machining and prevent distortion during ejection.<\/p>\n\n\n\nTolerances<\/h3>\n\n\n\n
\n
Mold Design Basics<\/h2>\n\n\n\n
Mold Base and Cavity Layout<\/h3>\n\n\n\n
\u25aa Maintain proper plate thickness and guide\u001epillar size to withstand injection pressure and ensure alignment.
\u25aa Lay out cavities and cores for easy access\u2014inserts should be removable for cleaning, maintenance, or replacement without dismantling the entire mold.
\u25aa Balance cooling channels around each cavity to keep temperature uniform and minimize warping or shrinkage variation.
\u25aa Include adequate draft and ejection space so parts release cleanly and cycle times stay short.
\u25aa For new products, a single\u001ecavity mold is often the fastest and most cost\u001eeffective way to validate the design. Once the design is finalized, you can move to multi\u001ecavity or family molds to scale up production.<\/p>\n\n\n\nGates<\/h3>\n\n\n\n
\u25aa Position gates at the part\u2019s thickest section to promote uniform fill, control shrinkage, and minimize defects.
\u25aa Place gates in low\u001estress, low\u001evisibility areas whenever possible, since they leave small vestiges and can weaken the part.
\u25aa Use multiple gates on large or complex parts to balance flow and prevent short shots.
\u25aa Since gates leave a small vestige, locate them on the parting line for easy trimming and minimal visibility.<\/p>\n\n\n\n![\"Gate](\"https:\/\/chiggofactory.com\/wp-content\/uploads\/2025\/05\/Gate-Types-1024x341.png\")
<\/figure>\n\n\n\n\n
\u25aa Fan Gate:<\/strong> Wide, flared opening for large or thin\u001ewalled parts; minimizes shear and improves filling balance.
\u25aa Tab Gate: <\/strong>Edge\u001egate variant with a small tab to absorb shear and heat; suited for shear\u001esensitive materials.
\u25aa Diaphragm Gate: <\/strong>Circular gate around the core for concentric flow; excellent balance but difficult and costly to trim.
\u25aa Ring Gate:<\/strong> Continuous ring around the core for even radial filling; used in tube\u001eshaped parts.
\u25aa Spoke Gate:<\/strong> Ring\u001egate variant with radial ribs; good for symmetrical tubular parts but maintaining concentricity is challenging.
\u25aa Film (Flash) Gate:<\/strong> Very thin, wide gate for large\/thin parts; ensures uniform fill but leaves a long vestige that needs manual trimming.<\/p>\n\n\n\n\n
\u25aa Pinpoint Gate: <\/strong>Small, direct gate inside the parting line; ideal for high\u001eflow materials and cosmetic parts; common in multi\u001ecavity or precision molds.<\/p>\n\n\n\nRunner System<\/h3>\n\n\n\n
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Ejector Pins<\/h3>\n\n\n\n
\u25aa Avoid placing pins on thin-walled or angled areas that may deform under ejection force.
\u25aa Locate pins in mechanically strong areas of the part to ensure it remains intact during ejection.
\u25aa Material choice matters\u2014sticky resins may require more ejection force, while softer plastics benefit from larger or more numerous ejector pins to spread the load and prevent deformation.
\u25aa The number and type of pins depend on factors such as part geometry, draft angles, and wall thickness. For instance, parts with edge or fan gates may need additional pins for balanced ejection.
\u25aa Ejector pins must be made of high-strength, wear-resistant materials to ensure long-term durability.<\/p>\n\n\n\nCooling System<\/h3>\n\n\n\n
Work with Chiggo for Expert and Prototype DFM Feedback<\/h2>\n\n\n\n