Plasticizing of injection molding machine
components, here refers to: screw, plastic tube, plastic head, aprons, the rubber gasket.
When working in the injection molding machine, plastic components like the wheel of a motor vehicle, as long as a start, is under pressure, impact, friction, extrusion.
For the same tyres, driving on flat road, skilled pilot operation, often can prolong the service life of tires.
And often more uneven, sandstone in the road, with frequent emergency braking action, will soon be ground flat tire surface decorative pattern, scrap.
So often to ensure the injection molding machine is in good condition, it is necessary to clear the use performance of injection molding machine, understand the performance and quality of material plastic, plastic injection machine using the management work, to reduce the failure rate, reduce maintenance costs and prolong the service life of purpose.
Generally speaking, the influence of the injection molding machine plasticizing system service life has the following several aspects: 1.
Mechanical wear some modified plastics added minerals, glass fiber, metal powder, etc. , the presence of these materials, in the process of plasticization and injection processing, will accumulate over a long period of screw, three small and plastic tube for uniformity of mechanical wear and tear.
Can grind to nitride layer, chromium plating layer.
After wearing the gap in the screw and melt tube increase, reduce the plasticizing effect, increasing the glue leakage flow, reduce injection efficiency, reduces the machining accuracy.
So, in order to minimize wear and prolong the service life of plasticizing components, processing should be appropriate increase in temperature, reduce the screw rotation speed.
Choose chrome plated or with double metal solution, can more effectively prevent fraying.
Mechanical fatigue and overload operation machine staff work habitually set temperature, habitually set high speed high working pressure, the plasticizing component performance degrade gradually.
Processing PC, PA plastic when, for example, in the temperature do not meet the requirements, the plastic viscosity is very big, if forced sol action at this moment, must increase the pressure of sol, increase sol torque, and thus increases the stress fatigue of the screw.
At the same time, because the plastic melt viscosity is very big, must carry on the injection molding processing must be increasing injection pressure and injection speed, increased the impact of the three small and load, speed up the wear and fracture stress.
Human factors (
Including the error or illegal operation, etc. )
With metal impurities mixed together into the melt in the plastic tube, due to the squeezing effect, make the screw screw, screw groove, aprons, gluing washer produce different degree of wear and tear caused by injection molding processing is not stable, easy to produce black spots and black stripes phenomenon;
Artificial add wrong plastic, the high temperature plastic to the setting of the melt in the barrel temperature, cause sol screw torque is too big, make the screw produces stress fatigue;
Cold start, it is a kind of anxious psychology and irresponsible working attitude.
In sol barrel temperature temperature or just meet, do not meet the set requirements of residual material in pipe, absorbed in its outer heat from hot coil temperature is higher, and the inner temperature is still very low, so the cold start when the screw torque is large, make the screw produces stress fatigue, serious twist off the screw quickly, twist off the plastic head and the aprons.
Into sol cylinder metal impurity, most is with broken material to bring in.
So, should check the blade damage of the crusher, found the blade wear should be replaced immediately.
The other side should be regularly check clean hopper of the magnet.
When the adsorption of metal debris surrounding the magnet saturation for the outer layer of the iron adsorption force will be weakened, even if is to absorb, also is easy to flow to plastic washed away, together into the sol in the cylinder.
The correct assembly, debug and replacement parts is also very important, if the cylinder assembly sol fashion enough tight, can appear when sol or shoot rubber screw touched sol drum phenomenon, cause the screw or sol cylinder wear.
So, should be regularly check equipment technical status, refer to the manufacturing of parts for abnormal phenomena.
Damage the long-term use of high back pressure caused by wrong technique sol, accelerate the plasticizing three small wear.
This situation occur in the use of toner, due to dispersion of pigments hard so he USES the way of increasing back pressure.
For the high viscosity of plastic, used when sol sol quickly, make the screw produces stress fatigue;
For high temperature plastic, especially the plastic of adding glass fiber, also shall not use the sol method.
Chemical erosion corrosion of metal material is iron.
Common corrosion plastic are: flame retardant plastic, acid plastic, PVC plastic, etc.
Screw, plastic tube and the flange is corrosion, the surface have some pits, rough surface, the flow resistance of melting large injection molding machine work.
Some material easy to adhere to the surface, resulting in decomposition carbonization.
Severe corrosion to the screw and melt, cylinder clearance leakage flow increases, the lower the injection efficiency.
Both flame retardant plastic and acidic glue, plastic processing at high temperatures can decompose the acidic gas, when the plastic melt are easy to coking and stick to the metal.
Conclusion plasticizing components should be chosen on the one hand, stainless steel or chrome plated surface;
Other aspects should use as far as possible in the production and processing low back pressure, low temperature and low shear process, reduce the degradation of plastic;
The third aspect, as a result of the above plastic thermal sensitivity, high temperature or heating time is too long is easy to cause degradation plastic decomposition and carbonization, so should be avoided in the process of production and reduce human cause downtime.
If need downtime, should first to reduce the temperature, close brake material, molten material from the sol tube done, switch to PP or PS material washing sol cylinder to stop.
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