Practical Methods for Burr Elimination of 3C Precision Injection Molded Parts
2026-04-27 10:57:17
Injection Mold
Burrs and flash are the most common defects in the mass production of 3C precision injection molded parts. Covering mobile phone shells, keyboard components, mouse accessories, electronic fasteners and other thin-walled precision parts, such products feature strict dimensional tolerances, high appearance requirements and precise assembly coordination. Tiny flash will not only damage surface texture and hand feel, but also cause assembly jamming, button stagnation and dimensional deviation. In severe cases, falling debris may affect the internal safety of electronic products. Restricted by complex part structures, dense rib distribution and strict mold coordination accuracy, the formation of burrs is affected by mold matching, injection molding parameters, material properties and equipment conditions. Combined with actual workshop operation experience, this paper summarizes practical and implementable solutions from multiple dimensions including source control, process optimization and post-treatment improvement, so as to thoroughly reduce burr defects and stabilize production yield.
Ⅰ. Optimization of Mold Structural Accuracy to Prevent Burrs at the SourceHigh-precision grinding and fitting shall be conducted on the cavity, core and parting surface of 3C precision molds to strictly control the fitting clearance and prevent molten material from overflowing through gaps under high pressure. For curved parting surfaces and irregular spliced surfaces, the number of segmented inserts shall be reduced to lower the risk of splicing misalignment. When wear and edge collapse occur on the parting surface after long-term production, surfacing repair and grinding should be carried out in a timely manner to re-fit and polish the sealing surface, avoiding repeated burrs caused by expanded gaps.
Buckles, clamping grooves, tiny holes and side undercuts are widely adopted in 3C products, where sliding blocks, inclined top structures and insert splicing positions become high-incidence areas of flash. It is necessary to adjust the guiding clearance of sliding blocks and the fitting tolerance of inclined tops, and add limiting and wear-resistant structures to prevent offset and misalignment during mold opening and closing. Stop positioning shall be adopted at insert joints to avoid the expansion of splicing gaps under high-pressure injection. The wear loss of all movable forming parts shall be inspected regularly, and the tightness of coordination shall be adjusted timely to put an end to flash at movable joints.
Excessively deep exhaust grooves and insufficient sealing edges are important inducements for edge burrs. The depth of exhaust grooves shall be controlled in accordance with 3C precision production standards. Open exhaust shall be reduced on appearance and assembly surfaces, and auxiliary exhaust shall be realized through tiny gaps of thimbles and inserts. Segmented shallow groove exhaust shall be arranged in non-appearance areas to balance exhaust efficiency and overflow prevention. Thickening the key sealing edges and strengthening local mold rigidity can resist mold expansion deformation caused by high injection pressure and avoid thin-edge flash generated by local expansion.
Ⅱ. Adjustment of Injection Molding Process to Reduce Melt Overflow RisksHigh pressure and high-speed injection are core inducements for burrs of precision parts. Strong fluidity and impact force of molten plastic will easily squeeze open tiny mold gaps and cause overflow. Based on the actual forming requirements of molds, the primary and secondary injection pressure should be appropriately reduced, and the filling speed in the middle and later stages should be slowed down to cut down material flow impact. The clamping force shall be set on demand to avoid long-term ultra-high pressure mold closing, which can not only save power consumption, but also reduce the wear of mold parting surfaces and extend mold service life.
Excessively high plastic temperature will greatly improve melt fluidity and increase the probability of overflow. For ABS, PC, PC+ABS and other common raw materials for 3C products, the temperature of each barrel section shall be strictly controlled to prevent over-temperature plasticization. The mold temperature shall be lowered reasonably to shorten the cooling and shaping time of edge positions and reduce the overflow of diluted molten material. Standardized raw material drying operations can also avoid the decline of melt viscosity caused by moisture decomposition, so as to indirectly alleviate the generation of burrs.
Excessive holding pressure and prolonged holding time will continuously squeeze residual materials into mold gaps and form thick-edge flash. A low-pressure and short-duration holding mode should be adopted to release pressure in time after filling completion. Extending the overall cooling time ensures complete shaping of plastic parts before mold opening and ejection, preventing irregular rough edges formed by extrusion and stretching of soft edges. This process adjustment method is especially suitable for thin-walled shell parts of 3C electronic products.
Ⅲ. Raw Material and Equipment Control to Reduce Hidden InducementsAlthough high-fluidity special raw materials are conducive to thin-wall filling, they are highly prone to flash. Medium and low viscosity materials shall be selected when not necessary to balance filling performance and burr resistance. The proportion of recycled materials shall be strictly controlled. Excessive recycled materials will lead to unstable melt fluidity and uneven heating, resulting in abnormal fluctuations between material shortage and overflow, which will increase defective rates of precision parts.
The parallelism of mold clamping, deviation of oil cylinder pressure and delay of injection response of equipment will cause uneven local stress and instantaneous high-pressure overflow. Regular calibration of machine mold clamping accuracy and balanced clamping force can help stabilize pressure output. Timely maintenance of hydraulic valves and pressure gauges can eliminate abnormal pressure fluctuation. Cleaning carbon deposits and aged rubber materials in screws and barrels can ensure uniform plasticization and avoid abnormal material flow induced local flash.
Ⅳ. Mold Repairing and Fine Post-treatment for Precision Requirements
For stubborn burrs at fixed positions, slight hollowing and edge blunting treatment can be carried out on mold edges to weaken overflow points. Fine polishing and grinding of dead corners such as tiny holes and rib positions can reduce residual glue adhesion and lower the difficulty of later trimming. Targeted mold modification for long-term recurring burr positions can realize long-term defect suppression.
Appearance parts of 3C products are prohibited from rough grinding and surface scratching. Fine sandpaper and professional trimming tools shall be used for light trimming on appearance edges and assembly stop openings. For mass production, low-temperature cryogenic deburring and ultrasonic trimming equipment can be matched to quickly remove tiny flash based on material embrittlement principles. This non-destructive processing method will not cause surface scratches or part deformation, meeting the high-efficiency processing demands of precision small parts.
Ⅴ. Daily Production Control and Standardized ManagementA regular mold inspection system shall be established to check the wear and jamming of parting surfaces, sliding blocks, thimbles and inserts in each shift. Timely cleaning of residual glue, oil pollution and carbon deposits on mold surfaces can maintain good sealing performance. Unified process parameter standards should be formulated to prohibit random parameter adjustment and avoid production chaos caused by blind debugging.
A burr defect account shall be established to record high-frequency defect locations and inducements, so as to carry out targeted optimization on molds and processes. Closed-loop improvement mechanisms can continuously reduce the incidence of burrs. Strengthening the skill training of operators can standardize daily operation habits, reduce human operation errors, and lay a foundation for long-term stable production of 3C precision injection parts.
In actual production, most burr problems of 3C precision injection parts stem from neglected detail control and redundant process parameter settings. Through multi-dimensional collaborative optimization of mold precision, injection process, raw material performance, equipment operation and on-site management, flash defects can be fundamentally controlled. While stabilizing product appearance and assembly accuracy, it can also reduce repeated trimming procedures, cut comprehensive production costs, and improve the comprehensive market competitiveness of electronic supporting parts.
