How to Setting and Alignment Twin Screw Barrel ( Parallel and Conical)?

Date:2022-11-09 Author:hcscrew

Twin screw extruder machines with conical/parallel twin screw barrel require the correct setting up and alignment of the twin screw barrel to maximize their service life. Furthermore, twin screw alignment and set-up are closely related to the quality of the products produced by the extruder.

With years of experience serving twin screw extruder users, we’ve learned that, in addition to selecting a good screw barrel with the correct screw structure, setting up and aligning the screw barrel is also very important. How do we install and commission a new twin screw barrel set? HUACHEN Screw, a leading Chinese manufacturer of twin screw barrel for extrusion, describes how twin screw barrels are set up and aligned.

How to Setting and Alignment Twin Screw Barrel ( Parallel and Conical)? by huachen screw barrel factory — New parallel twin screw barrel manufactured by HUACHEN Screw

What is conical/parallel twin screw barrel?

There are a number of advantages of using conical or parallel twin screw barrel, including uniform plasticisation and mixing, high output, stable quality, wide adaptability range, long service life, and direct injection of PVC powders. A twin screw extruder relies on this component as its core. Conical twin screw extruders can extrude various thermoplastics, especially when equipped with twin screw barrels and corresponding forming heads. In addition to extruding PVC powder directly into plastic products such as pipes, plates, sheets, rods, films and profiles. The extruder can also modify and pelletize various plastics. It is possible to achieve melt plasticisation at low temperatures using a conical twin screw extruder.

Key point for twin screw barrel alignment

Two key points need to be considered during the alignment of the twin screws and barrel. 1. Check and adjust the screw barrel’s axis to the extruder gearbox’s center height. 2. Screw barrel must be horizontal to the center of the gearbox and level to the ground and must be the same height as the center of the gearbox.

Preparation of the screw barrel alignment tools

A set of magnetic meters (0-5 mm range), a plug gauge, an outside diameter micrometer (0-25 mm range (0.1-1 mm thickness), copper rod, and a number of shims of the appropriate size.)

Conical twin screws alignment

1) Insert A SINGLE conical twin screw into the barrel separately. Reconnect the screw barrel to the gearbox. Connect the screw to the gearbox output shaft with a coupling. Each twin screw handle needs to be pushed back until it reaches the limit position of the coupling.

2) Use the connection flange of the screw head as a reference to position the magnetic gauge holder. Set the percentage gauge thimble against the screw head end point and zero it.

3) Use a brass rod to pry the screw forward. Measure the movement of the screw from back to front.

4) The axial runout of the single conical twin screw in the barrel should be between 4 and 4.5 mm. Adding or subtracting shims at the screw ends adjusts this if necessary.

5) Once again, insert both TWO conical twin screws into the barrel, and reconnect it to the gearbox. Fit the coupling between the screw and the output shaft of the gearbox. And then turn the screw backwards to the coupling’s limit position.

6) Place the percentage gauge thimble against the end point of the head of one of the conical twin screws and zero it. Pry the measured screw forward with a brass rod, ensuring the other screw doesn’t move. The screw should have a combined axial clearance of between 1.2 and 1.5 mm when measured forward. Repeat the measurement to ensure accuracy.

7) Measure the forward play of the other screw in the same manner. By adding or subtracting shims from the ends of the two screws, the forward play between each screw is ensured to be within 0.1 mm.

8) Once the above adjustments have been made, push the two screws back to their limit positions. Using a plug gauge, measure the radial clearance between the screw head and the screw barrel. Make sure the radial clearance is between 0.3 and 0.4 mm. This refers to the overall clearance, which is 1/2 on one side.

Parallel twin screws alignment

1) Place the two parallel twin screws in the screw barrel together. Reconnect the screw barrel to the gearbox. Connect the screw to the output shaft of the gearbox and push the screw back to the limit position. Screw flights on the head of parallel twin screws should be within 3mm of the barrel’s end face.

2) Set the percentage gauge thimble against the end point of one parallel twin screw and zero it. Make sure the other parallel twin screw does not move. Take a brass rod and pry the screw forward. Measure the screw’s forward movement with an overall axial clearance of 1.2-1.5 mm. Repeat the measurement to ensure accuracy.

3) Measure the forward play of the other parallel twin screw in the same way. Adjust the forward play between the two screws by adding or subtracting shims from the ends.

4) Once the parallel twin screws have been adjusted as described above, return them to their limit positions on the gearbox shaft. With a filler gauge, measure the radial clearance between the parallel twin screw head and barrel. Radial clearance should be between 0.3 and 0.4 mm. This refers to the overall clearance, which is 1/2 on one side.

Test run twin screw barrel on the extruder

1) After setting up the heater bands and heating oil tube, check and tighten the screw and barrel bolts once again. Then, raise the temperature to normal working temperature. Ensure that neither end of the screw has leaks in its sealing parts.

2) Install the connecting frame, mould and other components. Follow normal procedures for starting the machine.

3) Start the equipment power-up procedure. First, run the machine at 0 to 5 RPM. Also, observe the screw and barrel for any abnormal friction or vibrations.

4) It is recommended to set the temperature and speed ratios slightly higher than normal when feeding the machine for a trial run. By doing this, we will be able to induce plasticity. As soon as over plasticization is discovered. The twin screw barrel must be gradually reduced in temperature and speed. Plasticization should continue until it reaches a stable state.

5) If there are black lines on the extruded PVC profile or pipe, stop the machine immediately. Take out the screw and inspect the flights for friction marks. In cases where the marks are small, they can be polished on site. In the event of abnormal wear, return the product to the factory as soon as possible.

A routine maintenance check for twin screw barrels

1) Routine maintenance on twin screw extruder equipment

The material to be processed should not be allowed to carry foreign objects. A hopper or barrel should not contain metal or gravel. It is also important to prevent foreign objects from falling into the barrel when the vent port is opened. The extruder should be kept warm after it has warmed up, and it should only be started after it has been gently driven. Screws should be started at low speeds and idled for no more than two minutes at a time. Before increasing the speed, the feeder should be fed in a starvation manner.

It is recommended that oil and lubricating oil be replaced after every 4000 hours of operation. Check the carbon brushes of DC motors once a month and replace them if necessary. It is recommended to purge the electric control cabinet once a month. It is important to check and record the wear on the screw and barrel every three months. If a drop in extrusion output or deterioration in plasticisation occurs in the normal production context, and when production cannot resume even after alignment the screw barrel clearance etc., it is necessary to consider whether to replace the screw and barrel with a new one. Annually inspect the extruder gearbox’s gears, bearings, and oil seals. When a machine is down for a prolonged period of time, it should be protected from rust and dirt.

Summary

The above content is the correct steps to setting and alignment parallel or conical twin screw barrel . If there are more questions about the acceptance of the barrel screw, welcome to write to contact Brilliance screw.

About the twin screw barrel Factory: HUACHEN

HUACHEN Screw has been a leading manufacturer of twin screw barrel in Zhoushan Jintang since 1993. As one of the leading companies in designing and processing parallel and conical twin screw extrusion spare parts screw barrel, HUACHEN Screw can provide its customers with a wide range of services, including drawing rebuilding, design, modification, and customized screw barrels. Our company has also successfully exported and supplied screw barrels to customers worldwide.

>>Learn more about our company

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