How To Repair Polydur Plastic

Posted on: Nov.23th, 2018| By Judy, WayKen Project Manager

The advantages of plastic injection molding for manufacturing parts methods include fast production speed, high efficiency, automation of operation, shapes, and size flexibility. Moreover, the injection molding products are accurate in size, easy to exist replaced, and the mold parts tin can exist formed into complex shapes. This eco-friendly method is suitable for the molding processing fields such as mass production and circuitous shape products.

However, although the operators are familiar with specific machines and the operational skills in the molding process of plastic parts, the various rapid injection molding defects on mold pattern and materials are inevitable. The commodity aims to plastic injection molding bug and solutions, mainly as follows:

Analyze the causes of these problems generated from raw materials, plastic parts or mold pattern, molding processes, etc., and propose related solutions.

one.Brusque Shots

Brusk shots are a phenomenon in which the mold cavity cannot exist completely filled.

Causes: (1) Dice temperature, material temperature or injection pressure and speed are too depression (2)Uneven plasticization of raw materials (3)Poor exhaust (4) Bereft liquidity of raw materials (5)The part is as well thin or the gate size is too pocket-size (6) Polymer melt is prematurely cured due to unreasonable structural design

Remedies: Material: Use more fluid materialsMold design: (1) Make full the thick wall before filling the sparse wall to avoid the retentiveness phenomenon. (ii) Accordingly increase the number of gates and runner size to reduce the procedure ratio and flow resistance (3) The position and size of the exhaust port should be properly set to avoid the phenomenon of poor exhaust.

Machine: (one）Check whether the bank check valve and the inner wall of the material cylinder are seriously worn (two) Bank check if the feeding port has fabric or whether it is bridged.

Process: (1) Increase injection pressure and injection speed to enhance shear heat (2) Increment the corporeality of injection (iii) Increment fabric cylinder temperature and mold temperature

2. Air Traps

Air traps is that air is trapped in the crenel to create bubbling in the part.

Causes: It is caused by the air being unable to escape from the parting surface, the ram, or the vent when the two melt fronts meet.

Remedies: Structural design: Reduce thickness inconsistency and endeavor to ensure uniform wall thickness

Mold design: (ane) Add a vent at the last filled place (2) Redesign the gate and runner system

Process: (1) Reduce the injection speed of the last stage (2) Increment the mold temperature

three. Brittleness

Brittleness is that the plastic part is easily cracked or broken in some place

Causes: (1) Dry conditions are non suitable; utilise excessive recycled materials (2)Injection temperature setting is wrong (3) The gate and runner arrangement settings are not appropriate (4) The melting mark strength is non high

Remedies: Textile: (1) Prepare advisable drying conditions earlier injection molding (2) Reduce the apply of recycled materials and increase the proportion of raw materials. (3) Employ loftier-strength plastic. Mold design: Increase the size of the principal runner, co-operative runner, and gate

Machine: Choose a well-designed spiral to brand the temperature distribution more compatible during plasticization

Procedure: (1) Reduce the temperature of the material cylinder and nozzle (2) Reduce dorsum pressure, screw speed and injection speed (3) Increment the material temperature and injection pressure level, ameliorate the melting strength

iv.Burn Marks

The burn marks are that the gas in the cavity cannot exist removed in time, resulting in blackening at the end of the catamenia.

Causes: (1)The air in the crenel cannot be removed in time. (2) Material degradation: overhigh melt temperature; overcast spiral speed; improper design of the runner organisation

Remedies: Mold design: (1) Add an exhaust organization to a place where the exhaust gas is hands generated (two) Increase the size of the runner organisation

Process: (ane) Reduce the injection pressure and speed (2) Reduce the barrel temperature (3) Bank check if the heater and thermocouple are working properly.

5.Flash

It means that excess plastic is present on the mold parting or ejector office.

Causes: (1) Bereft clamping strength (2) The mold has defects (3) The molding conditions are unreasonable (4) Improper design of the exhaust system

Remedies: Mold design: (one)Reasonably design the mold to ensure that the mold can be closed when the mold is closed (2) Cheque the size of the frazzle port (3) Cleaning the mold surface

Machine: Set the machine of the appropriate size process: (ane) Increase the injection time and reduce the injection speed (2)reduce the barrel temperature and nozzle temperature (three) Reduce the injection pressure and pressure

half dozen.Delamination

It refers to the surface of the part that can be peeled off layer by layer.

Causes: (one) Mixing other incompatible polymers (2) Excessive release agent used during molding (three) resin temperature is inconsistent (4) Excessive moisture (5) The gate and the flow path have abrupt angles

Remedies: Material: Avert incompatible impurities or contaminated recycled materials mixed into the raw materials Mold design: Chamfer all runners or gates with precipitous angles

Process: (1) Increase the barrel and mold temperature (2) Appropriate drying of the material earlier molding (3) Avoid using too much release agent

7.Jetting

A spray trace caused by the cook flowing also fast, generally serpentine.

Causes: (1)The gate size is too pocket-sized, and information technology is facing the product surface with a large cross-sectional area (ii) Filling speed is as well fast

Remedies: Mold pattern:(1) Increase the gate size (2)Change the side gate to the lap gate (3)Increase the stop pin in front of the gate

viii.Flow Lines

Flow lines are molding defects that are wavy on the surface of the production known as a kind of frog leap acquired past the slow flow of the melt.

Causes: (1)Mold temperature and the material temperature is as well depression (two) Injection speed and pressure is besides slow(3) The size of flow channel and gate is likewise small (4) Due to the structure of the product, the acceleration is besides big when the filling flow is acquired.

Remedies: Mold design: (1) Increase the size of the cold well in the menstruum channel (2) increment the size of the runners and gates (three)Shorten the size of the primary channel or switch to the hot runner

Process:（1）Increase the injection speed （2） Increase injection pressure level and pressure （3） extend the pressure holding time （four）Increase the mold temperature and material temperature

ix.Fog

A cloud-like discoloration occurs near the gate. The reason is the cook fracture.

Causes: If the gate is as well pocket-size or the cavity at the glue is also sparse, the flow rate of the cook is large, the expanse of the break is pocket-sized, the shear rate is big, and the shear stress is often increased so that the melt condom breaks and the fog shift occurs.

Remedies: Moldflow simulation. It is possible to predict the temperature, shear rate, and shear stress of the melt passing through the in a higher place narrow zone. Moldflow by and large provides an upper limit for the temperature, shear charge per unit, and shear stress of various plastic materials. Moldflow engineers can brand adjustments based on the assay results to find the advisable gate size and cavity wall thickness at the glue inlet to eliminate fog.

10.Streaks

Streaks are those in which water, air, or char is distributed in the management of menstruum along the surface of the role.

Causes: (1)The moisture content in the raw materials is too high (2) Air is trapped in the raw cloth (3) Polymer deposition: the material is contaminated, butt temperature is too high; bereft injection volume

Remedies: Mold pattern: Check if the exhaust position is sufficient Process: (ane) Cull the right injection molding machine and mold (2) When switching materials, clean the one-time materials completely from the butt (3) Improve the exhaust organisation (iv)Reduce melt temperature, injection pressure or injection speed

11.Sink Marks

Information technology is a miracle in which the surface of the part is concave at the wall thickness.

Causes: (i) Injection pressure or holding pressure is too low (ii)The property time or cooling fourth dimension is besides short (iii) Melt temperature or mold temperature is as well high (iv) Improper design of the structure of the parts

Remedies: Pattern: (i) Corrugated surface on the surface where dents are like shooting fish in a barrel to occur(2)Reduce the thick wall size of the workpiece, minimize the aspect ratio, and the next wall thickness ratio should exist controlled at 1.5~2, and try to make a smooth transition. Redesign the thickness of the ribs, counterbore, and ribs. Their thickness is generally recommended every bit 40-80% of the basic wall thickness.

Process: (1) Increase the injection force per unit area and pressure (two) Increment the gate size or change the gate position

12.Weld Lines

The weld lines refer to the surface defect caused by the 2 streams beingness welded together.

Causes: If there are holes, inserts, or multi-gate injection molding methods in the fabricated parts or the wall thickness of the parts is uneven, weld lines may be generated.

Remedies: Material: Increase the fluidity of plastic melt Mold Design: (1) Change the position of the gate (2) Add a venting slot Process: (1) Increase the cook temperature (two) Reduce the corporeality of release agent

13.Warpage

The well-nigh difficult trouble to solve in the design and production of plastic parts is the warpage.

Causes: (1)Mold structure: pouring, cooling system and ejection system (2) Production structure: plastic parts wall thickness changes, with curved or asymmetrical geometry, ribs and Dominate cavalcade design is not reasonable (3)Production process: the plastic parts are not fully cooled, and the injection and pressure holding curves are unreasonable (four)Plastic materials: plastic materials have, no added fillers, the size of the shrinkage.

Remedies: (1)The mold temperature is unstable. Provide cooling/heating balanced mold (2)Irregular department thickness Redesigned production shape and size according to resin characteristics

At WayKen, we have encountered many similar plastic injection molding issues and solutions in some cases of prototype injection molding. In order to create injection molding products for our customers, we extremely have injection molding machine parts details and injection molding pace by step to eye before manufacturing parts and during the injection molding process.

Source: https://waykenrm.com/blogs/plastic-injection-molding-problems-and-solutions/

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