Common defects analysis of products and solutions
1. Insufficient filling of the pieces of incomplete pieces of beer, or more cavities when the individual cavity beer is not satisfied.
analysis:
① Improper feed adjustment, lack of material or more material;
② Injection pressure, temperature and time is not enough;
③ The temperature is not enough
④ Low or uneven mold temperature, water design is not reasonable;
⑤ Poor plastic flow;
⑥ Mold design is not reasonable
The design is not reasonable, including the flow channel turning more resistance large; plastic parts too thin; poor exhaust system; flow channel without cold or cold well is not enough; multi-cavity mold cavity excessive number of non-balanced feed or The location of the gate, the wrong form or the lack of quantity.
2. Flash edge (Pioneer): plastic products edge, insert joints and thimble bit extra thin wings appear.
analysis:
① Mold manufacturing accuracy is poor: Including poor FIT mold, insert with poor precision, thimble holes and other large gap;
② Mold design unreasonable:
Unqualified position, resulting in pressure imbalance;
Improper gate position, there bias the flow, resulting in a lack of material, while out Phi Feng;
Lateral parting mechanism design is unreasonable, clamping force is not enough, or due to the line with the inserts straight body caused by wear and tear;
Poor mold exhaust, sub-type surface is distraction under high pressure and so on.
③ Beer clamping force is not enough;
④ Injection process conditions (transfer machine) improper: over-pressure, over-temperature and feeding amount is too large.
3. Silver grain (commonly known as water, including surface bubbles and internal bubbles)
analysis:
When the plastic is full of water vapor, decomposition gas, solvent gas and air, the product surface along the stream direction to form a series of silver luster such as needle-like or mica flake, this part of the gas if only left in the plastic wall , A bubble is formed.
① Water vapor: water vapor from the plastic should be drying material (hygroscopic plastic such as PA, PC, ABS, PPO and PSF, etc. must be drying material), and sometimes water vapor also comes from the cavity.
② Material temperature is high, poor quality plastic and shear stress is too easy to produce decomposition gas.
③ When the plastic mixed with different kinds of plastic, silver sometimes also produce.
4. Shrinkage depression: the surface of plastic parts due to internal contraction of the pit.
analysis:
① Bad packing, uneven cooling, wall thickness or bone width is too large, the insert is not preheated.
② Wall thickness as uniform as possible.
③ In key areas (such as thick-walled parts) set up cooling waterways to enhance the cooling water temperature and flow control.
④ To ensure that the clamping force, not due to lack of material leakage due to flash.
⑤ Gating system design should be reasonable.
5. Weld Line
analysis:
① Melt shunt convergence due to the material temperature dropped, or because of the local part of the glue is too thin, resulting in poor fusion junction, there are traces or reduce the intensity of weld lines to reduce or eliminate the method and shrinkage dent is basically the same.
② Can change the gate position, size and workpiece wall thickness, weld marks will not affect the appearance of the location.
③ Open the overflow well near the weld line.
6. Transparent parts defects
Silver lines and cracks:
Eliminate pollution (including moisture)
Reduce the material temperature, sub-regulation
Increase injection pressure
Improve runner and cavity exhaust
Shorten the molding cycle
If has been produced, available annealing method to eliminate.
Poor surface gloss:
Cavity type core polishing is not good
Melt premature cooling and hardening, can not completely copy the good and clean mold surface.
Shock (ripple):
The material in front of the contact cavity rapidly condenses and shrinks, and the subsequent frit pushes forward the condensate.
Increase cylinder temperature, especially nozzle temperature, increase injection pressure and speed
Improve mold temperature, improve runner gate size, pay attention to polishing nozzle holes and runners
Improve exhaust to improve the flow rate.
Pan white, fog halo:
Eliminate water vapor
Improve material temperature and mold temperature;
Increase injection pressure and back pressure.
7. Warping deformation
Product design issues:
Uneven wall thickness, the structure is irrational, from thick to thin transition zone and the corners have sharp corners without corner transition, will lead to warping deformation.
Mold Design:
For flat parts, large projected area, to use multi-point gate, or fan-shaped gate gate and slice equation logic;
All parts of the mold should be evenly cooled.
Plastic problem:
Crystalline plastic shrinkage rate is much larger than amorphous plastic, rapid solidification, easy to warp deformed parts (PE, PP, PA, POM, etc.
The same product with different plastics will have different deformation.
Injection process:
Material temperature is too low
Material temperature is too high
Increase the injection pressure, time, speed, if allowed
Guarantee dwell time
Some plastic deformation after the release of plastic parts to be fixtured or tempered.
8. Evaluation of the quality of plastic products, the three indicators
Appearance quality: including integrity, color and gloss;
Size and relative position accuracy;
Use related to the mechanical properties, chemical properties.
9. The cause of product defects
Plastic issues: including plastic quality ingredients and baking materials;
Transfer problems: Including injection pressure, temperature and cycle;
Mold Problems: Including mold design, manufacturing and wear.