Plastic products Warpage

Molds:

Improper (1) or an insufficient number of gate location.

(2) the top of the improper position or article discontinuity.

Technological aspects:

(1) die, cylinder temperature is too high.

(2) injection or the injection pressure is too high too fast.

(3) the holding time is too long or too short cooling time.

Raw materials: phthalocyanine pigments can affect the degree of crystallinity of polyethylene deformation caused by products.

Product design:

(1) uniform wall thickness, wall thickness changes suddenly or too small.

(2) improper product structure modeling.

Dimensionally unstable

Equipment:

(1) feeding system is not normal.

(2) back pressure instability or temperature instability.

(3) failure of the hydraulic system.

Molds:

(1) gate and runner size uneven.

(2) the cavity dimensions are not allowed.

Technological aspects:

(1) The mold temperature cooling circuit caused uneven or improper mold temperature control unreasonable.

(2) injection pressure is low.

(3) injection dwell time is not enough or there are fluctuations.

(4) high cylinder temperature or the injection cycle is unstable.

Raw materials:

(1) change the batch, the resin properties have changed.

(2) Material particle size erratically.

(3) a large amount of moisture.

(4) Replace the aid of influential law contraction.

White steam cracking

Mold: the top of the organization is poor.

Technological aspects: (1) lower cylinder temperature or mold temperature is low. (2) a high injection pressure. (3) long dwell time.

Raw materials: (1) lubricants, release agents, or the amount is too inappropriate. (2) grades, grades do not apply.

Product design: product design is unreasonable, leading to local stress concentration.

Delamination

Technological aspects: (1) barrel, nozzle temperature is low. (2) back down. (3) for PVC plastics, the injection speed is too low or the mold temperature may also cause delamination.

Raw materials: (1) raw material contamination or foreign matter. (2) Different plastic mix.

In the process of injection molding, there are still many problems. For example

www.plastic-injectionmoulding.com http://www.listfree.org/156810-how-to-solve-the-plastic-injection-molding-process-in-a-blooming-problem.html

Plastic parts Gloss bad

Equipment:

(1) feed shortage.

(2) the timing of refueling tube is not clean.

Molds:

(1) gate is too small or too thin runner.

(2) the difference between the surface roughness of the cavity.

(3) Exhaust bad or mold temperature is too low.

(4) No cold well.

Technological aspects:

(1) uneven heating barrel, barrel temperature is too high or too low.

(2) pre-plastic backpressure nozzle is too small or too low.

(3) the injection speed is too large or too small.

(4) plasticized uneven.

Raw materials:

(1) Not dried material.

(2) containing a volatile substance.

(3) The excessive amount of aid or release agent.

Stripping difficulties (gate or plastic parts tightening in the mold)

Equipment: ejection force is not enough.

Molds:

(1) releasing structure is unreasonable or improper location.

(2) stripping slope is not enough.

(3) The mold temperature is too high or bad ventilation.

(4) runner cavity wall or surface roughness.

(5) the inlet nozzle and the mold match against posts or nozzle diameter greater than the diameter of the inlet.

Technological aspects:

(1) cylinder temperature is too high or too injection volume.

(2) injection pressure is too high or long dwell and cooling time.

Raw materials: lack of lubricant.

In the process of injection molding, there are still many problems. more information www.injectionmoldchina.com http://cnmoulding.livejournal.com/21497.html

Plastic products Discolor

Causes discoloration is multifaceted, it is:

Equipment:

(1) The equipment is not clean. Dust or other dust deposited on the hopper so that contaminated material discoloration.

(2) thermocouples, temperature control device or heating system disorder caused by the temperature control failure.

(3) barrel obstructions, easy to promote degradation of the plastic; cylinder or screw slot card metallic foreign body, constantly grinding the plastic color.

Molds:

(1) mold venting is bad, the plastic is adiabatic compression, at high temperature react violently with oxygen, burn plastics.

(2) mold gate too small.

(3) feed or in-mold lubricants, release agents too. Necessary regular cleaning cartridge, remove the plastic heat resistance worse than antistatic additives.

(4) the nozzle orifice, sprue and runner size is too small.

Technological aspects:

(1) screw speed is too high, pre-plastic backpressure too.

(2) the barrel, the nozzle temperature is too high.

(3) injection pressure is too high, too long, the injection speed is too fast for the products and discoloration.

Raw materials:

(1) the material is contaminated.

(2) moisture and volatile matter content.

(3) a coloring agent, additive decomposition.

Spots or liquor

The main reason for this defect in equipment and raw materials:

Equipment

(1) barrel has charred material.

(2) barrel cracks.

(3) a screw or plunger wear.

(4) near the hopper dirty.

Molds:

(1) oil cavity.

(2) penetrate the oil from the top of the device.

Raw materials:

(1) raw material dirty.

(2) lack of lubricant.

Charred Obscure

Equipment: After injection of heat-sensitive plastic, barrel or nozzle not clean material mat have resulted in poor exhaust injection begins.

Molds:

(1) Exhaust poor.

(2) improper or small gate gate location.

(3) of the cavity local resistance, so that the exhaust gas stream resulting slow convergence difficulties.

Technological aspects:

(1) barrel, the nozzle temperature is too high.

(2) pre-plastic injection pressure or back pressure is too high.

(3) injection injection period is too long or too fast.

Raw materials:

(1) uniform particles, and containing the powder.

(2) high volatile content of the feedstock.

(3) lubricants, release excessive amount.

more information 

www.plastic-injectionmoulding.com http://zymoulding.livejournal.com/5781.html

Plastic products Fragile

Products frangible large part is due to the stress caused. Many causes brittle hair products, are:

Equipment:

(1) barrel are dead or obstacles, easy to promote melt degradation.

(2) machine plasticizing capacity is too small, plastic barrel in plastics is not sufficient; too much capacity plastics machinery, plastic barrel by the shear heat and time is too long, plastic easy to aging, so that products become crisp.

(3) the top of the device is tilted or unbalanced, dry top small cross-sectional area or improperly distributed.

Molds:

(1) gate is too small, you should consider adjusting the gate size or the addition of auxiliary gate.

(2) shunt is too small or improperly configured, a reasonable balance should be arranged or increased shunt size.

(3) mold caused by poor molding cycle unusual structure.

Technological aspects:

(1) barrel, nozzle temperature is too low, raise it. If the material is easily degradable, it should raise the barrel, nozzle temperatures.

(2) reduce the pre-plastic screw back pressure and speed, so that the material slightly loose and reduce degradation of plastic due to overheating caused by shear. (3) The mold temperature is too high, stripping difficulties; mold temperature is too low, plastic premature cooling, poor weld fusion, easy to crack, especially high-melting plastics such as polycarbonate even more so.

(4) cavity core have appropriate stripping slope. When stripping the core difficult to raise the temperature of the cavity, shorten the cooling time; when the cavity impunity, to reduce the cavity temperature, prolonged cooling time.

(5) minimize the use of metal inserts, such as Polystyrene hematocrit cold brittle plastic, but can not join the insert molding.

Raw materials:

(1) raw materials mixed with other impurities or doped with inappropriate or excessive solvent or other additives.

(2) Some plastics such as ABS, etc., in the damp heat condition can occur with moisture catalytic cracking reaction, the occurrence of large parts of the strain.

(3) plastic recycling too many times or recycled materials content is too high, or in the machine barrel heating time is too long, can cause brittle parts. (4) The plastic itself is poor quality, such as molecular weight distribution of a large, non-uniform structure containing ingredients rigid molecular chain possession excessive; or contaminated, poor additive pollution, dust and other plastic doping impurity contamination is caused by brittle the reason.

Product design:

(1) products with sharp corners prone to stress cracking, or the thickness of the gap very different parts. (2) product design too thin or too hollow.

In the process of injection molding, there are still many problems. more information www.chinamoldmaker.org http://chinamoldmaker.blogspot.com/2015/07/plastic-products-fragile.html

Plastic products Swelling and bubbling

Some plastics molding after releasing soon in the back of the piece of metal inserts or swelling and bubbling in the thickest part of the special, which is released under the effect of gas expansion cooling due to the incomplete hardening of plastic, including pressure caused.

Solution:

(1) reduce the mold temperature, mold extend time.

(2) reduce material drying temperature and processing temperature; lower filling rate; reduce the molding cycle; reduce flow resistance.

(3) improve the packing pressure and time.

(4) to improve products or thick wall thickness variation in the situation.

Production slow

(1) plastic high temperature, long products cooldown. Barrel temperature should be lowered to reduce the screw speed or back pressure, adjusting temperature of each barrel is good.

(2) mold temperature is high, the impact of stereotypes, and cause card, clip articles and downtime. We must focus on strengthening the cooling channels. (3) molding time unstable. It should be automatic or semi-automatic operation.

(4) a barrel for the lack of heat. Plasticizing capacity should be used to strengthen the preheating of the machine or materials.

(5) to improve the conditions of machine production, such as oil, fuel, clamping force and so on.

(6) nozzle drool. Should control the barrel and nozzle temperature or replaced with self-locking nozzle.

(7) the part thickness is too thick. Mold should be improved to reduce the wall thickness.

Backpressure: When feeding, the screw in the opposite direction retrograde added pressure on the molten plastic;

Back pressure effect:

1. To improve the plastics melt kneading effect;

2. Increase the temperature of the molten plastic;

3. Increase the density of the molten plastic;

4. promote uniform plastic colors;

5. The exhaust gas within the molten plastic;

Low voltage protection: refers to a protective device for mold resistance when clamping generated, which can make the mold when pressed by the smallest foreign object damage, reduces die losses. The working principle is the distance from clamping in the mold clamping pressure is set low to a certain time, when the mold clamping encountered foreign body in this process. Plastic or due to insufficient lubrication within a set time is less than the high-pressure lock When the switching point, the machine will generate an alarm, and the mold is opened;

Hot runner system leak-Analysis:

1. The support pad is too low. Under the influence of the injection pressure, the flow channel plate and hot mouth creating a gap resulting from drooling.

2. The support pad is too high. Support pad into the top mold base plate, this prevents leakage of plastic flow channel between the nozzle plate and the heat, but in the role of injection pressure and clamping pressure manifold is pushed to one side, resulting in leakage of plastic.

3. The center pad is too high. Manifold empty frame on the center pad, plate and hot runner nozzle from creating a gap caused by drooling.

4. The center pad is too low. Injection pressure in the injection molding machine, the center pad collapsed manifold bent, causing leakage of plastic.

5. hot mouth highly uneven. Lowest thermal drooling mouth easily.

6. spacing the screws and manifold or hot mouth too much. Manifold and heat seal the mouth is not enough, resulting in leakage of plastic.

7. The locating pin high. Manifold empty frame on the positioning pin, plate and hot runner nozzle from creating a gap caused by drooling.

8. hot mouth too long. Hot mouth no room for expansion and generate pressure on the heat loss of the role of the mouth of the ring, resulting in leakage of plastic. 9. The seal is too high or too low. Ring approximately 0.3 mm pre-compression, high cause manifold easily deformed, easy to drain the hot glue on the plane of the mouth. There is no initial clamping force is too low, after heating the hot runner system leak glue.

10. The hot mouth locate the installation location of the error. Shen head hot mouth or on the front frame in a mold insert on the front mold core die rather than leave the front, hot mouth by the time the injection pressure or thermal expansion mouth, clamping pressure error will force the front-Hui , resulting in leakage of plastic.

In the process of injection molding, there are still many problems. For example

www.cnmoulding.com  http://cnmoulding.over-blog.com/2015/07/improve-the-quality-of-injection-molding-causes.html

Dent (collapse pits, flat shape)

Plastic cooling caused due to hardening shrinkage depressions, mainly in the thick position, ribs, chassis, insert nut on the back places.

Equipment:

(1) feed shortage. Screw or plunger wear serious, melt leakage occurs during injection and holding pressure, reduce the filling pressure and quantity, resulting in insufficient melt.

(2) the nozzle hole is too big or too small. Too small, easy to plug the feed channel, the radio will force small is too large, filling difficult.

Molds:

(1) gate is too small or too narrow runner or too shallow, low flow channel efficiency, resistance, melt prematurely cooling. The gate can not be too big, or lose the shear rate, high viscosity material, the same can not make the full article. Gates should be set up in the thick portion of the article. Set up the necessary flow path has sufficient capacity cold well can exclude cold material into the cavity so that the mold filling continues. Point gate, gate gate length of the needle must be controlled in 1mm or less, otherwise the plastic solidification in the gate fast, pressure is passed; increase the number of point gate or gate position to meet the actual needs as necessary; when the flow When the road is long and thick, it should be set in the exhaust gas flow path groove edge, reducing the barrier effect of the stream of air.

(2) Multi-runner mold to adjust the gate speed filling, preferably symmetrical open gate.

(3) The key parts of the mold cooling channels should be effectively provided to ensure cooling of the mold to eliminate or reduce shrinkage play very good results.

(4) The entire mold should be without a glitch and reliable clamping sealing, can withstand high pressure, high speed, low viscosity melt filling.

Technological aspects:

(1) increasing injection pressure, holding pressure, injection time extended. For mobility plastic, high pressure will produce flash caused the collapse pit material should be appropriately reduced temperature, lower front barrel and nozzle temperature, melt into the cavity to reduce the volume change, easy coldset; high viscosity for plastics, should increase barrel temperature, make filling easy. Contraction in the gate area should extend the dwell time.

(2) increase the injection speed can more easily make the full article and to eliminate most of the contraction.

(3) thin-walled parts mold temperature should be increased to ensure the smooth flow of material; thick parts mold temperature should be reduced in order to accelerate the curing of skin stereotypes.

(4) in the mold parts to extend the residence time of the cooling, to maintain a uniform production cycle, increase back pressure, screw front retain a certain cushion, etc. are conducive to reducing shrinkage.

(5) low-precision products should be allowed to die early out slowly cooled in air or hot water, it can not affect the use of depression gentle contraction. Raw materials: raw materials too soft prone to depression, an effective method is to add a nucleating agent in plastics to accelerate the crystallization.

Product design: product design should be uniform thickness, to avoid changes in wall thickness, such as polypropylene plastic shrink greatly, when the thickness variation exceeds 50%, instead of the best of the area with thick ribs.

more information www.injectionmoldchina.com  www.plastic-injectionmoulding.com

Burrs (flash)

Also known as flash overflow, overflow edge, and so on, mostly in the mold closing position to score, such as: the parting surface, slide the slip position, insert the gap, porosity, etc. rams. Bur not resolved will be further expansion, thereby forming a partial imprint mold trap collapsed, causing permanent damage. Cracks and pores inserts ejector burrs also stuck in the mold of the article, the impact of the release.

Equipment:

(1) Machine genuine insufficient clamping force. When selecting the injection molding machine, clamping force rated machine to be higher than projected longitudinal tension injection molded article formed in the injection area, or will result in expansion mode, the occurrence of burrs.

Poor (2) adjust the clamping device, the toggle mechanism does not straighten, or left and right or up and down to produce uneven mold, mold parallel phenomena can not be achieved while the mold is closed and tight one side and the other side not of tight situations the occurrence of burrs during injection.

(3) The mold itself parallel poor, or not inserted parallel or not parallel template, or rod uneven force distribution, deformation unevenness, which will cause mold does not close and produce flash.

(4) loopback badly worn only; spring nozzle spring failure; cylinder or screw wear too much; the feed inlet cooling system failure caused by a "bridge" phenomenon; inadequate set-cylinder injection quantity, the cushion is too small, etc. may cause flash repeatedly, the importance of timely repair or replacement of parts.

Molds:

(1) mold parting surface accuracy is poor. Activity templates (such as plate) deformation warping; parting surface stained with foreign matter or mold frame surrounding protruding skid printing glitch; old die earlier flight because of fatigue side extrusion leaving the cavity surrounding the collapse.

(2) mold design unreasonable. The creation of the position of the mold cavity through partial, unilateral mold tension will make the injection occurs, causing flash; plastic good liquidity, such as polyethylene, polypropylene, nylon, etc., in a molten state low viscosity, easy access to activities or fixed slit, the higher requirements of the mold manufacturing precision; in without compromising the integrity of the product should be placed on the quality of the center of symmetry, the product thick part of the material, while the lack of material can be prevented with the burr side situation; when the product or near the center of the shaped hole, open side gate is customary in the hole, in the larger injection pressure, resulting in insufficient mold clamping force if the force is not enough to support this part of slight warping flash, such as when the mold side with active members on its side of the projected area is also affected by the molding pressure, if the support is not enough can also cause flash; sliding core with bad accuracy or fixed core and cavity installation position shift The formation of burrs; poor exhaust cavity in the mold parting line grooves or exhaust vent is not open ditch is too light or too dark or too large will cause foreign body obstruction by flash; for multi-cavity mold should be attention to the shunt closing gate design is reasonable, otherwise it will cause uneven force filling produce flash.

Technological aspects:

(1) injection or the injection pressure is too high too fast. Because of the high speed, the mold opening force increases lead to flash. To be adjusted according to product thickness injection speed and injection time, thin products use high-speed rapid filling, after filling into the note no longer; thick products use low-speed filling and let the skin before reaching the final pressure is generally fixed.

(2) caused by excessive charging flash. It is noteworthy that not to prevent excessive sag injected melt, so depressed may not be "filled", and flash it will appear. Application of this case to extend the injection time or dwell time to resolve.

(3) barrel, nozzle temperature is too high or the die temperature is too high will cause the plastic viscosity decreased, increased mobility, resulting in flash in the case of fluid into the mold.

Raw materials:

(1) plastic viscosity is too high or too low may occur burrs. Low viscosity plastics such as nylon, polyethylene, polypropylene, etc., should increase the clamping force; absorbent plastic or water-sensitive plastic at high temperatures will significantly reduce flow viscosity, increase the likelihood of burrs, These plastics must be completely dry; incorporation of recycled materials too many plastic viscosity will decline, if necessary, to supplement the residence ingredients. Plastic viscosity is too high, the flow resistance increases, resulting in back pressure so that the cavity pressure increase, resulting in insufficient clamping force and produce flash.

(2) particle size uneven plastic materials will increase quantity of flux, parts or complaints, or flash.

more information www.plastic-injectionmoulding.com  www.injectionmoldchina.com