How to prevent and address carbonization issues in blow molded products in Shanghai (Part 2)

2.2 Disassembly and Cleaning

It is relatively easy to clean the carbides inside the extruder using the in machine cleaning method, but it is difficult to clean the carbides inside the storage type head of Shanghai blow molding equipment.

Because the extruder has a simpler internal structure, the storage type head of Shanghai blow molding processing equipment has a more complex internal structure, and the equipment has been in use for too long, making it more difficult to clean.

In this situation, disassembly and cleaning are imperative. Raise the temperature of the machine head to a sufficient level, then turn off the power and disassemble all assembly parts of the machine head. Clean the plastic melt inside the machine head with a copper sheet, remove burnt carbides with a metal brush, and then polish all assembly parts with sandpaper or a flower impeller before assembly. Although the disassembly and cleaning effect is good, it takes a long time and is labor-intensive, so it is generally not easy to use this disassembly and cleaning method.

3. Preventive measures for carbonization

3.1 Temperature and Time Control

The processing temperature of blow molded products in Shanghai is determined according to the plasticization requirements of raw materials and products, and cannot be too high or too low. Low temperature can lead to excessive load, as well as defects such as water streaks and weld marks on the product's appearance.

If the temperature is too low, the fluidity of the melt will be poorer, which will have a significant impact on the glossiness of the product surface and the filling of the corners; If the temperature is too high, and sometimes there is a temporary shutdown for two hours or even several hours, it is easy to cause carbonization of the molten material inside the machine. In this case, the constant temperature should be between 100-120 ℃, and it is necessary to heat it up to the required temperature before starting up to prevent carbonization caused by sudden temperature rise or long insulation time during shutdown.

3.2 Heating and startup operation control

Usually, a one-step heating method is used, which means that after setting the temperature, the equipment is continuously heated to the set temperature, depending on its size, and then kept at a constant temperature for 1-3 hours before starting up. This method is prone to carbonization of residual plastic inside the machine.

If the step heating method is used and the temperature is raised in stages, the effect is much better. For example, set the temperature to 100 ℃ at the beginning, adjust the temperature to 130 ℃ after constant temperature, and then adjust the temperature to 170 ℃ after constant temperature. Gradually increase the temperature according to the time period until it reaches the desired temperature. Small and medium-sized devices can be turned on once they reach the required temperature, and of course, relevant supporting preparations need to be made in advance. After reaching the required temperature, large equipment needs to be kept at a constant temperature for 1-2 hours before starting up.

When starting up, pay attention to gradually increasing the speed of the extruder from 1 to 5 revolutions per minute, slowly opening the feeding port, and constantly monitoring the current value displayed on the extrusion ammeter. If the load is too large, the constant temperature time should be appropriately extended to gradually increase the temperature. When it can be turned on, it should be turned on as early as possible to prevent residual plastic in the machine from carbonizing in the long waiting time due to sudden high temperature.