The main forms of injection molded spacers
One of the main types of injection molding spacers is the flat spacer. This flat spacer is uniformly thick and primarily used to separate different chambers or components within a plastic part, ensuring independent operation without interference. The thickness of a flat spacer is determined by the required separation and structural strength, typically ranging from 0.5 to 3 mm. For example, a 1 mm thickness is used within an electronic device housing to separate the battery compartment from the circuit board compartment without adding significant weight. Flat spacers can be designed as either integral or modular. Integral spacers are molded integrally with the main body of the plastic part, offering high strength and suitable for small parts, such as those within mobile phone charger housings. They are injection molded simultaneously with the housing, eliminating the need for subsequent assembly. Modular spacers, attached to the plastic part via clips or screws, are suitable for larger parts or where removable components are required, such as toolbox spacers. A snap-on design allows for adjustable separation space based on tool size. The edges of flat spacers should be rounded (R0.5-R1 mm) to prevent sharp edges from scratching internal components or operators. This also facilitates melt flow during injection molding and reduces stress concentrations.
Stepped spacers are another common design. Their surface features height differences, creating a stepped structure. They are suitable for plastic parts requiring layered placement of components, effectively utilizing space and achieving separation at varying heights. The step height difference for stepped spacers is typically 2-10mm, determined by the thickness of the components being placed. For example, spacers in instrument housings are designed with three steps, with height differences of 5mm and 8mm, respectively, to accommodate circuit boards, displays, and batteries. This provides clear separation and facilitates wiring and assembly. Each step surface of a stepped spacer must maintain a flatness tolerance of no more than 0.1mm/m to ensure a stable placement of components. For example, the flatness of the stepped surface should be controlled within 0.05mm/m to prevent display deviation caused by tilting the display. Step transitions should be beveled or rounded, with a bevel angle of 30°-45° and a radius of 1-2mm. This facilitates melt filling and enhances the strength of the transition, preventing cracking caused by stress concentration. Stepped spacers are often used in car center consoles and the internal structures of household appliances, and can achieve orderly arrangement of multiple components in a limited space.
Grid spacers, composed of a network of crisscrossing ribs, offer lightweight yet high strength. They are primarily used in applications requiring ventilation, heat dissipation, or lightweight construction. The ribs in these spacers range from 1-3mm wide and 5-20mm apart, designed to meet strength and ventilation requirements. For example, the heat dissipation spacers on the bottom of laptop computers feature ribs 1.5mm wide and 10mm apart. This provides support for internal components while ensuring air circulation, increasing the heat dissipation area by over 50% compared to flat spacers. Reinforced nodes are installed at the intersections of the ribs. The node diameter is 2-3mm larger than the rib width, for example, a 2mm rib with a 5mm node diameter. This strengthens the intersections and prevents fracture under stress. Grid spacers are typically made of reinforced plastic (such as PP + 30% GF) to increase the rigidity of the ribs. At the same weight , their flexural strength is 40% higher than that of standard plastic spacers. They are suitable for separating components within automotive engine compartments and can withstand high temperatures and vibration.
Spacers with through-holes are a specialized design. They feature a varying number of through-holes, creating separation while allowing fluid or signal flow. They are suitable for applications requiring both connectivity and separation. The diameter and number of through-holes are determined by flow requirements. For example, spacers in hydraulic valve blocks have through-holes with diameters of 5-10mm, and their number corresponds to the oil flow path. This separates oil chambers of varying pressures while ensuring the flow of fluid along the intended path. The edges of the through-holes should be chamfered or countersinked, with a 1×45° chamfer to prevent turbulence or excessive resistance during fluid flow. For example, chamfering the through-holes in hydraulic system spacers can reduce pressure loss by over 20%. Spacers with through-holes must ensure precise alignment with adjacent component holes, with a coaxiality tolerance of no more than 0.1mm. For example, for spacers used in pipe connections, the coaxiality between the through-holes and the pipe fittings should be controlled within 0.05mm to prevent leakage. These spacers are widely used in hydraulic systems, pneumatic components, water treatment equipment, and other fields, providing both separation and connectivity.
Elastic spacers are flexible spacers made of elastic materials (such as TPU and silicone) that provide cushioning, sealing, and shock absorption, making them suitable for applications requiring vibration isolation or sealing. Elastic spacers range in thickness from 1 to 5 mm with a shore hardness of 60 to 80A, depending on the cushioning requirements. For example, spacers inside precision instruments use 3mm thick TPU with a shore hardness of 70A. This not only separates components but also absorbs external vibrations, protecting instrument accuracy. Elastic spacers are typically combined with rigid plastic parts through overmolding or insert molding. For example, a waterproof spacer in a mobile phone case is first injection-molded into an ABS shell, followed by overmolding of a TPU elastic spacer around the edge to achieve a waterproof seal with IP67 rating (waterproof after immersion at 1 meter for 30 minutes). The surface of the elastic spacer can be designed with micro-ridges or textures to increase friction or sealing area. For example, 0.5mm high ridges on the sealing spacer improve fit with the mating surface and enhance the sealing effect. Elastic spacers are widely used in electronic equipment, medical devices, automotive seals and other fields, and are important components for achieving functional isolation and protection.
