Cracking, including filamentous workpiece surface cracks, crazing, top white, cracking and because parts stick mold, stick-runner or trauma caused by the crisis, according to a release time diversity cracking cracking cracking and applications. The main causes of the following aspects:
(1) The working pressure is too large, too fast, the more filling material, injection, dwell time is too long, too much stress can cause cracking.
(2) adjusting the speed and pressure of the mold to prevent the rapid releasing strong drawn products cause cracking.
(3) due to increase mold temperature, make parts easy to stripping, appropriate to reduce the material temperature to prevent decomposition.
(4) prophylaxis of welding marks, plastic degradation caused by low mechanical strength and cracking.
(5) appropriate use of mold release agents, pay attention to the mold surface adhesion often eliminate aerosol and other substances.
(6) The article residual stress, can be carried out immediately after forming annealing to eliminate stress and reduce the formation of cracks.
(1) To the top of the balance, such as the number of mandrel, the cross-sectional area should be sufficient, stripping slope should be enough, the cavity surface must be smooth enough to prevent the external force so that it leads to the top of the residual stress concentration and cracking.
(2) parts structure can not be too thin, the transition part arc transition should be adopted to avoid sharp corners, chamfers cause stress concentration.
(3) minimize the use of metal inserts to prevent different inserts and parts increased stress caused by shrinkage.
(4) deep bottom parts of the release should set the appropriate air intake tract, preventing the formation of vacuum.
(5) the sprue gate large enough to feed when not enough time to solidify the release, so easy to mold.
(6) the sprue bushing and nozzle engagement should be prevented from leaving chilled drag material stuck to the fixed mold parts.
3. Material aspects:
(1) renewable materials content is too high, resulting in low strength parts.
(2) the humidity is too large, resulting in the emergence of the top of the steam cracking of some plastics and chemical reactions, reducing the strength.
(3) the material itself is not suitable for processing environment or poor quality, contamination can cause cracking.
4. Machine: the plastics injection molding machine capacity should be appropriate, too small plastics insufficient and not fully blended brittle, degrades too large.