Improvement of the Bidirectional Straightening Device for Feeding in Horizontal Roller Cold Heading Machine

Improvement of the bidirectional straightening device for the feeding of horizontal roller cold heading machine 
In today's continuously developing market economy, the continuous improvement of product quality is one of the key factors for success or failure in market competition. The bearing industry is no exception; the accession to the WTO and the development of international trade have brought us increasing pressure. The production of bearing rollers is a relatively complex process, requiring multiple processes and steps to form a finished roller. In the forming process of the roller, there are many factors that affect its quality. For example, the roller blanks stamped on the cold heading machine often result in inferior products and waste. In response to a series of issues, processors are constantly exploring new ways to produce the highest quality rollers using the most economical means. For instance, when forming bearing rollers on the Z31-25 cold heading machine, in addition to under-pressing, overlapping injuries, pitting, and deformation, there are also cases where the rollers are qualified at the time of stamping but later exhibit elastic recovery of curvature. Analyzing the reasons reveals that the raw materials may not all meet the ideal standards during processing, thus requiring a set of devices for stricter straightening to achieve the best linearity of raw materials to ensure the quality of roller formation. 
1. Process Analysis 
In the production of bearing rollers, there are many quality issues. During the stamping process of forming rollers, under-pressing and deformation of the rollers after pressing often occur. 
(1) Under-pressing As shown in Figure 1, the differences in the thickness and length of the rollers are significant, and the shape differences will also affect the quality after roller formation. The severe bending of the raw materials seriously hinders the pushing effect of the feeding wheel, causing differences in feeding efficiency, leading to under-pressing. 
(2) Deformation of rollers after pressing When the shape of the roller is good after stamping, but it bends again after a period of time as shown in Figure 2, we initially used a unidirectional straightening device to solve this. However, after a period of use, the above problem still occurred. After repeated research, it was found that the unidirectionally bent materials shown in Figure 3 can be modified, while it is very difficult to modify the bidirectionally bent blanks shown in Figure 4, meaning that multi-directional bending severely affects the stamping quality of the rollers. Therefore, we adopted a bidirectional straightening device to straighten the bidirectionally bent blanks, making some appropriate adjustments based on the unidirectional straightening device to create a device suitable for large equipment, thus trial-manufacturing the bidirectional straightening device. 
2. Principle of the Unidirectional Straightening Device 
This device is placed before the feeding wheel of the roller cold heading machine, used to stabilize and straighten the blanks before they are straightened by the feeding wheel of the cold heading machine. Since the straightening by the feeding wheel may not achieve the ideal effect, this device can effectively change the deficiencies and has a significant pre-straightening effect on the unidirectional bending phenomenon shown in Figure 3. 
Its principle: Adjust the handwheel according to the specific situation and degree of bending of the material, so that the moving plate drives the D4 and D5 wheels shown in Figure 5 to move back and forth. Of course, under the condition of achieving the goal, it is not necessary to adjust the wheels too tightly to avoid counterproductive effects, which would prevent the blanks from moving and cause insufficient feeding length, leading to under-pressing; moderate adjustment is sufficient. This device works best on the Z31-13 automatic roller cold heading machine because small equipment processes rollers with smaller diameters, which can curb material bending and the rebound of bending after pressing, and it is still in service in production. 
3. The Emergence and Principle of the Bidirectional Straightening Device 
As we know, the rollers processed by the Z31-25 automatic cold heading machine have a much larger diameter than those processed by the Z31-13 automatic cold heading machine. The unidirectional straightening device has a decent effect on the unidirectionally bent raw materials shown in Figure 3, but it is difficult to straighten the multi-directionally bent raw materials. To effectively achieve the straightening purpose, we attempted to adopt a bidirectional straightening device to change the situation, thus designing a bidirectional straightening device as shown in Figure 6. Its principle is to add another unidirectional straightening device based on the unidirectional straightening device, creating a 90° straightening state, with each adjusting to an average. However, the ideal effect differs significantly from reality, and changes in straightening effects will lead to feeding difficulties, making under-pressing inevitable due to insufficient length. To overcome these deficiencies, we added 204 bearings to each straightening wheel to facilitate the rotation of the straightening wheels. The increased support length may also cause the reference axis to bend, so we used reinforcing ribs in the structural treatment to improve the overall bending strength while reducing the overall weight. After designing and manufacturing, we conducted tests again, and the effects were very significant. 
4. The Effect of Using the Bidirectional Straightening Device 
We chose to conduct tests on the Z31-25 roller cold heading machine, comparing the pressing conditions before and after the use of the bidirectional straightening device. 
From this table, it is clear that there is a significant difference in the effects before and after the use of the bidirectional straightening device, and it is recommended to promote its use to achieve the best economic benefits. According to investigations and analyses, adding a set of bidirectional straightening devices before the feeding wheel in the same industry can effectively improve the bending state of roller raw materials, and similar devices are also used in domestic and foreign equipment tooling. 
5. Conclusion 
The unidirectional straightening device we originally used did not achieve the effect of bidirectional straightening. Therefore, we actively took measures and independently designed and manufactured a set of bidirectional straightening devices, which have shown good results after being put into production. In summary, the bidirectional straightening device is very helpful in the cold forming of many processes in roller processing, reducing waste and alleviating the bending phenomenon of blanks, making it very significant in production.