Extrusion granulating unit is a highly integrated and high-aotumatic control machine line with machine parts,electrical parts and many other devices.

Druing usage,there will be many difficult faults to deal with, this will disturb the normal working of the machines and lower the production efficiency.

Generally speaking, there are four reasons which will cause machine unit stop working during usage:

Main motor system faults

1. main motor torque is too low or too high

2. main motor rotating speed is too low

3. main motor axis temperature is too high

4. main motor surround unit temperature is too high

5. main motor water cooling device exit temperature is too high

6. main motor axis lubricant pump exit flow amount is too low

7. main motor axis lubricant pump exit pressure is too low

8. main motor water cooling device water leaking amount is too much

Driving system faults

1. gear box speed changing pole hold the wrong position. 

2. friction clutch instrument wind pressure is too high.  

3. friction clutch speed difference is too big. 

4. gear box lubricants pump exit pressure is too high.

5. gear box lubricants pump exit oil temperature is too high.

6. friction clutch inner faults etc.

Extrusion screw faults

1.Throttle front and back melting material pressure is too high.

2.Machine head melting material pressure is too high.

3.Sieve front and back melting material pressure difference is big.

4.Starting valve rotating fault.

Underwater cutting system faults

1.Cutting motor temperature is too high.

2.cutting machine rotating speed is slow.

3.cutting machine torque is too high.

4.water shifting fault.

5.water pressure is either too low or too high.

6.water flow is too small.

7.cutting machine screw loose.

8.cutting chamber water valve not shut.

9.cutting machine Hydraulic is too low

10.cutting motor fault

11.cutting blade Hydraulic pressure is too low.

During above faults, some of them are normally appear:

1.main motor system torque is either too low or too high

2.transmission system friction clutch faults

3.extrusion screw melting material pressure either too low or too high

4.underwater cutting system fault

Next we will give solutions according to each specific fault.

Normal faults and solutions:
1.Main motor torque too high

Reasons analysis:

Lubricant system fault,main motor out axis bad position,motor and clutch vibrating will damage the main motor axis, then the torque becomes high. Besides, feeding too much material and melting problems also will cause high torque.

Solutions:

Check and wash the lubricant system regularly, by using vibrating instrument and infrare temperature measurer to record the screw conditions and form a trend chart. If the trend appears not good, then axis should be checked and see if it should be replaced. Check the main motor output axis position and gear box axis position regualrly, the axis position should be checked when first use and after working for 3 months. Check electrical devices to find rotor balance problems;

Vibarting test should be given to the clutch , adjustment should be done when there are problems.

Check the barrel heatinga nd cooling system, make sure the material is heated even. If the main motor power curve and melting pressure curve become larger quickly after starting the machine,feeding capacity should be reduced.

2.Main motor torque is too low

Reasons analysis:

Feeding system fault cause screw idle run will lead to low toruqe.

Solution:

check feeding system and material exit system, clear blocking part.

3.Friction clutch fault

Reasons analysis:

Main motor starting voltage low, friction plate and flake overheat or ageing, friction plate lpw pressure will also cause clutch disconnected.

Solution:

When starting main motor, avoiding electricity using summit.,reduce feeding capacity, restart interval should controlled at least within 30 minutes; summer time when restarting main motor , wait longer or cool the motor by using fans. clean friction plate and flake, if they are in bad condition or appears vitrification, replace them and make sure air pressure is suitable.           

4.High-pressure of melt

Reasons analysis：

Mesh of filter is too much. Polypropylene powder with low melt index and a large quantity of feed. The temperature of every core tube is low, so that materials can not melt completely. The low open hole ratio making materials extrusion blocked and other factors can cause excessive pressure on the melt.

Solutions：

The low mesh filters should be used when produce low melt index products, and increasing throttle opening to reduce the back pressure; the timely replacement of filters, monitoring the quality of the various additives and ash content in polypropylene powder. Reduce the feed load. Under the conditions of ensuring product quality ,raising the temperature of the cylinder ,so that the melt temperature of polypropylene to improve and increase the mobility of materials. After extruder stopped, you should improve the nose temperature and be constant temperature for some time. Finally wash clean-up template thoroughly.

5.Underwater pelletizing system failure

Reasons analysis：

Cutter excessive damage or cutter edge wear. Flow of particle water is too low, cutter vibration is too large, cutter and the templates can not fit tight, materials melt index wave lager which make discharging speed inconsistent, temperature of particle water is too high.All of these above causes will generate underwater pelletizing system stopped, thereby causing the entire unit chain stopping.

Solutions：

After stopping, visual inspection whether the cutting edge have excessive wear or damage.If any should be replaced. Check to make sure whether the particulate water transuded, particle filter and cooler water is blocked. If blocked, it should be manually cleaned up; to check the import and export of particulate water pressure is normal, if irregular, it should overhaul pumps and valves on the pipeline pumps . Check whether the center between the knife and the pelletizing motor is poorest, knives bearing axis units are damaged, whether dynamic balancing of cutter rotor is imbalance. In running process, check four mobile-round of pelletizing car contact between the guide, whether there is space. Control volatile of polypropylene powder, and eliminate vibration which is effected on the cutter and the cutter shaft when it through the template hole. Reduce the temperature of the hot oil of template department to check the temperature distribution of cylinder and template. Whether cooling water’s flow, pressure and temperature is normal; confirmation the time set of " water, knife and materials" to get to the template, it can prevent water particles premature reaching the template to make the template block frozen. After granulator closed head ,it should be rapid to increase feeding capacity to the extruder volume of the set load.

If we compiled the above reasons for failure with the interlocking relationship between the combination of logic into fault diagnosis software, the unit can operate, maintenance and management to provide a fast, intuitive reference and help.