Yongdeli Machinery values feedback of customers and will supply technical support. Here we offer solutions to some problems that our customers maybe encountered when they use our machines. At the same time, thank you very much for your long-term favor to our products.

1. Core bar is easy to loose.
Solution: On one hand, reduce middle connection. On the other hand, take two different turning directions to screw threads.

2. The fixed bolts of slide board (which is on the surface of mainframe run way) are easy to break.
Solution: When designing mainframe run way, make slide board thicker. Firstly, use bigger screws.

3. The mandrel is easy to break when rolling small tubes.
Solution: Assemble guide rod to the mandrel. At the beginning of rolling, the rolling speed accelerates to normal speed stably.

4. Why do the above problems occur when rolling tubes and how to solve them?
Solution: Because the cylinder spring pressure of the front chuck (chuck of the rolled tube) may not be adjusted properly. The spring of the front chuck should be adjusted well.

5. When rolling Φ57×3.8 to Φ25×2.5 tube, the tube will beat if feeding amount increases.
Solution: It depends on rolling material. For example, 304 tube is faster, so the speed should be slower. The tube will fold if rolling speed is faster.

6. Mandrel breaking
Tools will wear during the rolling period. The service life of the pass is several dozen times longer than the mandrel. So the pass will wear after producing a few tons tubes. If mandrels come from different factories, deformation curve will not match, thus the distribution of the deformation section will be unequal. Under such circumstance, wall reduction may be too concentrated. It makes the stress on some part of the mandrel too concentrated. Mandrel will break when the stress is too large.

I. Solution
(1) Make sure dies are matching.
(2) Check pass carefully if test the quality of mandrel. Measure the wear amount of pass with gauge to decide the excircle processing amount of the pass. If some part of the pass was worn concentratedly, it indicates the compression in the front of the mandrel is not enough (or the excircle mandrel is small), which caused concentrate deformation. So decide to change the mandrel or the pass carefully when grinding. In a word, avoiding concentrate wearing.

Ⅱ.Other factors resulting in mandrel breaking
1. The location of mandrel is not correct when adjusting.
2. Too much feeding amount.
3. Wall thickness of tube billet section is seriously unequal.
4. Heat treatment of tube billet extension direction is not equal, which causes too much performance deviation.
5. Lubrication of tube billet inner wall is not good.
6. Steel sticks on the surface of mandrel.
7. Mandrel is badly worn.