How to adjust screw clearance of conical twin screw extruder
The conical twin-screw extruder is the main equipment for producing plastic profiles. When the profile is produced, the twin screw rotates outward in the barrel in different directions. The size of the screw gap not only affects the plasticizing effect of the material, but also affects the quality of the product, sometimes causing machine failure, and even leading to scrapping of heart parts such as the barrel and screw. The screw clearance adjustment method starts with the process and strictly controls the process quality to ensure the quality of the whole machine.1. Main technical parameters of screw clearance:
1. Radial clearance of screw: SJZ60/130—0.15～0.36mm;
2. Axial clearance of screw: the clearance is equal before and after;
3. Rolling gap: small end: 10mm, large end: 1.5mm.
2. Operation method:
1. Pre-inspection: Detect the axial clearance of the screw on a special inspection tool to find the axial correspondence between the two screws. The main purpose of the pre-inspection: by checking the backlash of the adjacent thread of each section in the inspection tool and adjusting it to make the two sides of the minimum gap consistent, that is, the twin screw is fixed one, the other is in the center position, measured and recorded The relative back-off amount is used as the basis for onboarding. Specific method: Install the twin screw into the planed barrel, then install the double hole flange and the distance ring, and start to adjust the twin screw gap.
A. Push the left screw (right-handed screw) to the end, and now move backward 5mm, the half key is facing upwards, and lock the screw with a 531 pitch ring;
B. Turn the right screw (left screw) gently to carry the interference, and use the dial indicator magnetic seat to find the middle position of left and right rotation;
C, then push forward and pull the right screw back to verify whether the middle position is consistent.
D. Find the center position and lock with 5.31 retaining ring.
E. Measure and record the gap on both sides of each section (take the left screw as a reference), and record the front and back side gaps.
f. Conclusion: When the screw is reasonable, the relative retraction amount "L" at the "center" position is measured. The left-hand screw (right) is L-5 worse than the right-hand screw, allowing this relative value to be maintained in the barrel of the extruder , X=2(L-5).
2. The screw clearance adjustment on the main machine:
Will be measured on the inspection tool, the twin screw is installed in the extruder barrel, the left end is adjusted according to the required gap, the small end gap is adjusted, d=0.15～0.36mm, excluding the amount of retreat, only the d value is maintained.
A. Use a distance ring to lock the left screw (half key upward), measure the amount of retreat, and record.
B. Turn the right screw, use the magnetic seat and dial indicator to find the center position, measure the difference between the amount of retraction L2 and the amount of retraction of the left and right screws, and record.
Note: L2-L1=L-5 means the axial clearance of the twin screw is equal.
C. Lock the left-hand screw (one on the right) with 5.31 distance ring, and make the standard on the two distance rings of double screw and double hole flange.
D. Axial marking (painting)
E、Angle mark (underline)
F. Check the results on the front and back inspection tools at the feeding port and check to see if they are consistent. The front and rear backlash of the right screw at the center are recorded.
3. Eliminate the gap at the rear end of the screw and adjust the thickness of the pad
a. Pull out the right screw (left-hand screw), install the adjustment pad on the left screw (right-hand screw), double-hole flange (without coupling), push the barrel straight, use four nuts to lock the distribution box and the barrel tight.
B. Use the top screw flange to compress the screw head, completely eliminate the gaps in the distribution box, measure the amount of retreat, and compare the records to calculate the difference.
c. Use the same method. You can eliminate the gap by compressing the right screw, measure the amount of retreat, and calculate the thickness of the adjustment pad for processing;
4. Record the following data and store it in the product file:
A. Side clearance at the feed opening (front and rear)
B. Clearance at the small end (left and right)
C, the amount of retreat on the little end (left and right)
Three, operation essentials:
The axial correspondence of the screw detected by the inspection tool must be kept in the normal production barrel.
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