Dual Cone Extruder Workflow - Speed, Temperature, Machine Switching (Actual Production)

Dual Cone Extruder Workflow - Speed, Temperature, Machine Switching (Actual Production)

Author: PVC Maniac

Dual Cone Extruder Workflow - Speed, Temperature, Machine Switching (Actual Production)

The main control block of host's workflow is effect of host feed and speed on current, interaction between host temperature and recipe, and switching skills.

1. Adjust feeding speed according to speed of main machine, and maintain a certain current to maintain plasticizing effect. Basic reference data is up to date.

Example. The current management of mainframe varies greatly for each enterprise. The current control of main motor is determined by storage of materials in viewing window. If current is too high, amount of material in viewing window will increase, and in severe cases, materials will float. The current has a significant effect on shear of material. Reasonably judge product quality to control current perfectly. If you feel that material distribution of components is not good, generally choose high speed and low current. When you feel melt kneading is bad, you can choose high current control. This is also one of main reasons for adjusting formula.

At normal temperature, if melt viscosity is equivalent, use high speed and low current. As a rule, this formula is better. If a strong current is forced, melt becomes relatively thin and soft, which can only be solved by adjusting high temperature. In simple terms, current adjustment method, plasticized material is not dry, output mold hardness is high, and high speed and low current are also used. If material is relatively thin and soft, use low speed and high current. Of course, with a relatively reasonable formula, both high-speed and high-current production is possible, but melting section of a twin-screw cone of embossing generally needs to be lengthened, and range of cutting pitch narrowing should not be too large. The same goes for lead, otherwise heat of shear will be too high.

2. Temperature control, temperature control is generally determined by proportion of calcium powder and production speed.

The relative working temperature without addition of plasticizer is high, and lower content of calcium powder, lower relative working temperature. no regard for stability. The lead and return section temperatures are high, and lead and outlet section temperatures generally determine fineness and softness of melt. In rigid PVC, temperature is not absolute, and I usually use pipe cutting temperature:

190, 195, 175, 165 confluence center 170, flow channel 175, small mill chamber 185, die 205-225.

This temperature is a relatively high power output when starting at high speed. Generally, double cone adopts temperature curve of pendulum (hard). The temperature setting is very obvious to recipe.

One of main sources of temperature is heat, and other is shear heat. If heat of shear is not controlled, material willThe neck is thin and soft. A four-zone high temperature phenomenon is common. The main reason for high temperature in fourth zone is that stabilizer is not strong enough, and heat generated by continuous shearing of material is too great. This can also be solved with lubrication. The more lubricant, lower relative pressure of mold and higher ejection ability. The amount of lubricant and stabilizer has an obvious effect on quality of PVC.

There are four areas by which you can judge whether a formula is good or bad, that is, temperature controllability. The fourth zone is usually air-cooled and should not be too continuous. The air-cooling interval should not be too long, as a rule, it is best to keep an interval of 10-20 seconds. The plasticizing effect of shear heating is better than that of heating. Therefore, temperature control can effectively control processing range of recipe. Conventional processing methods, frequent heating or cooling of air in second zone, less initial lubrication, may increase temperature in second zone or change components of formulation. The problem of high temperature in fourth zone can be solved by increasing content of internal lubricant or stabilizer. The temperature of die head has a significant effect on apparent gloss of product. The temperature range is usually around 15 degrees. If temperature is too high, brightness will decrease after melt expansion rate is exceeded. If temperature is insufficient, material cannot expand and contract properly, lubricant cannot migrate outward under high pressure, and surface brightness cannot be formed.

3. Turning skills on and off, personal habits in using steps:

The cold machine is held at 130 degrees for about half an hour until it reaches specified temperature. When temperature of each area reaches temperature, keep it for 10-20 minutes and then start machine. Check if potentiometers are set to zero. Start synchronously, confirm host and feeding start, and adjust speed synchronously within three to five weeks. Slowly start main motor potentiometer, pay attention to change in current, and adjust supply at same time. When it reaches 500-600 rpm, pause for 1-2 minutes to observe change in current, then increase speed. up to about 800 rpm, make sure current is stable and adjust mold pull. Speed ​​up when job is done.

Turning it off is much more difficult than turning it on. When stopping, reduce engine speed to 800 rpm, or hold at 500 rpm for 10-20 minutes, turn off temperature of each zone, leave exhaust zone and outlet open, and then use a compound stabilizer, generally do not lubricate, evenly add to feed port, useIt is better to join feeder. If you are inexperienced early on and feel when material is out of shape, you can use colored particles as a marker, turn off feed and slowly slow down and stop when you feel material is out. second zone. Turn off temperature of remaining two zones, material will go too far and waste should be high next time machine is turned on. The intersections of cut paste are obvious. If parking material is perfect, cross position of old and new materials will be virtually invisible next time car is turned on. This is standard shutdown trick. The shutdown skill determines boot failure. If material is empty, it will be very difficult to start machine, so plasticization will have to wait a long time. If it is high filling, it is easy to get phenomenon of unplasticized material stuck in mold. Turn off synchronous start button and reset potentiometers to zero. Shut down host.