Cast film line technology sharing-extruder motor and gearbox

Nantong Sanxin Plastics Equipment Technology Co.,Ltd started to make cast film line since 2000. Sanxin has been experienced in this field, and is willing to share the technologies. Today we will talk about the extruder motors and gearbox. 

There are single screw and twin screws. The twin screw extruder is not used so often like single screw extruder. It is normally used for PVB glass adhesive film line and one-step breathable film line. So we only introduce the single screw extruder and gearbox.

Extruder:

Single screw extruder motors mainly include DC motors, AC motors, and permanent magnet motors. The advantage of DC motors is the high torque. The machine would be stable when starting at low speeds. For some materials with poor fluidity, the customer still prefers DC motors. But DC motors require frequent maintenance of carbon brushes, it may cause some troubles.

The most often used DC speed regulator is PARKER.

Compared with DC motor, the AC motor is more common for cast film lines. The advantage of AC motors is the low maintenance frequency.

There are lots of brands for AC frequency converter, such as SIEMENS, ABB, INOVANCE, YASKAWA, DELTA, EMERSON and so on. There are many series levels of frequency converters, different series with different functional capacity and different price. It is common for frequency converters to be more expensive than AC motors.

Permanent magnet motors was used for cast film line since several years ago. It is not so common like AC motors. For some materials with high melting point, permanent magnet motors can perform well (but still not so good as expected). The energy consumption is similar compared with using normal motor. That’s why it is not common used in cast film line.

Here we take example of CPP film line to calculating the motor power. The single screw extruder power as below:  

φ55 extruder: 37KW.

φ60 extruder:37/45KW.

φ75 extruder:55KW.

φ80 extruder:55KW.

φ90 extruder:75/90KW.

φ100 extruder:90/110KW.

φ110 extruder:132KW.

φ120 extruder:132/160KW.

φ150 extruder:160/185KW.

φ160 extruder:160/185KW.

φ180 extruder:200/220KW.

The above motor power is only for reference. The actual power is decided by many factors, such as capacity requirements, plasticization,  MFR, L/D ratio, screw structure, the clearance between screw and barrel , temperature setting, pressure and so on.

It’s not that the motor power higher the better. When the machine is stably running, the best motor working efficiency is 60%-80%.

Gear Box

The requirements of gear box for single screw is not so high as twin screw. The life of the gearbox is very long if properly maintained. 

The gear and shaft parts of the gearbox are made of high-strength alloy steel, carburized and quenched. It is equipped with thrust blocks with high load-bearing capacity.

For the cast film lines, the reduction ratio is used to be 8:1、10:1、12.5:1、14:1、16:1、18:1、20:1. For EVA film line encapsulating solar cells, the reduction ration can be 40:1 and even higher.

The gearbox installation is usually to be horizontal and vertical.

The users should pay attention to below points while using gearbox.

50. Water cooling: Ensure the water cooling continuously and stably. If workers accidentally close or reduce the water valve, long term operation will affect the lifespan of the gearbox. During normal operation, slight temperature is allowed, but if the gearbox is very hot, then we must pay attention to it and find the reasons and solutions. 
50. Change the lubricating oil timely: There is oil gauge scale on the gearbox. Check it regularly and ensure the lubricating oil within the appropriate range. If the lubricating oil falls below the lower limit for a long time, the service life will be greatly reduced.
50. Thrust bearing maintenance: maintain it regularly since it will become wear and tear after long term working. 

There is another part to share with everyone, which is the connection part between extrusion motor and gearbox. There are two main connections: belts and couplings.

Usually belts are used if motor and gearbox installed in opposite directions. The advantage of the belt is easy to replace, but the change frequency is higher than coupling.

The advantage of coupling is small error. Once the screw locks and extrusion motor no stop, the coupling will be damaged firstly. Compared with extrusion motor and screw, the coupling cost is much more lower. While the coupling is consumable, it must be changed after long time working, it is not east to exchange.

Coupling is more often used than belt.

Oil inspect of the gear box                Coupling core

If you want to learn more about cast film line, don’t hesitate to contact us.