3 Deburring Process Solutions for Engine Parts Sealing Ring Groove

In the CNC machining service, Tuofa CNC machining takes the cylinder head fuel injector bushing bottom hole as an example to analyze the deburring process of the ring groove part. By comparing the effect and stability of various deburring processes, the deburring process suitable for mass production lines is determined. After process testing and batch processing verification, it has good results and completely solves the burr problem in the sealing ring groove.

 

 

 

Analyze the sealing structure of engine parts

 

The sealing ring groove is a commonly used sealing structure for engine parts, which plays an important role in ensuring the sealing of engine parts such as the water cavity and oil circuit. The typical seal ring groove structure (see Figure 1) includes the bottom hole ring groove of the cylinder head injector bushing, etc.

 

Figure 1 Typical seal ring groove structure

 

During the production process, it was found that there are many burrs (see Figure 2) generated during the processing of the ring groove, and the sealing ring and other components will be scratched during the assembly process, resulting in seal failure and water leakage in the inner cavity of the cylinder head.

 

 

Figure 2 Burrs at the ring groove

 

The mechanics of Tuofa CNC machining have achieved deburring effect to a certain extent by adding chamfering to the ring groove. However, affected by factors such as the manufacturing accuracy and wear of the grooving tool, increasing the chamfer cannot completely remove the burrs in the ring groove. For this reason, some experts and engineering technicians have studied and explored the methods and technologies of deburring engine parts.

 

In this paper, taking the ring groove part of the cylinder head injector bushing bottom hole as an example, the deburring process of the ring groove part is studied, the effect and stability of different deburring processes are compared, the deburring process suitable for mass production lines is determined, and the complete elimination Quality hidden dangers caused by burrs, reduce process reject rate and improve product quality.

 

Deburring process design

 

According to the characteristics of the burr on the ring groove and the current situation of the production line, and considering the cost and efficiency of the process method, the following three deburring process methods are analyzed and determined to be tested.

 

1. The process of combining ordinary reamer and floating tool holder

 

The structure of the floating deburring reamer is shown in Figure 3, which is mainly composed of a floating handle, an extension rod, and a reamer. The specific use method is to install the reamer in the floating tool holder, the tool has a certain floating space during processing, and the cutting edge removes the burr during the floating process.

 

Figure 3 Structure of floating deburring reamer

 

2. Process of combining emery abrasive bars with floating tool holders

 

The structure of the emery abrasive bar deburring tool is shown in Figure 4, which is mainly composed of a floating handle, an extension rod, and an emery abrasive bar. Among them, the emery abrasive bar is a commonly used manual deburring tool, but the manual operation workload is large, the production efficiency is low, the consistency of the deburring effect is not good, and it is difficult to adapt to the mass production requirements. After the emery abrasive bar is transformed, it is matched with the floating tool holder to realize the automatic deburring of the equipment.

 

Figure 4 Structure of diamond abrasive bar deburring tool

 

3. Spring blade deburring process

 

The structure of the spring-pressed deburring tool is shown in Figure 5, which is mainly composed of a cemented carbide blade, a pin shaft, a spring blade, a clamping pressure strip, a screw, a tool shank, and a tool body. The blade can rotate around the axis, and the elastic force generated by the spring sheet ensures that the cutting edge presses the edge of the ring groove (burr part of the workpiece) during the cutting process, and the burr is removed at a fixed point. Figure 6 shows the actual type of tool with the spring plate pressed and the blade rotatable.

 

Figure 5 Spring-pressed deburring tool

 

1—Cutter body 2—Toolbar 3, 4—Screw 5—Tightening pressure strip 6—Spring piece 7—Pin shaft 8—Cemented carbide blade

 

 

Figure 6 Spring-loaded, rotatable blade tool 

 

 

Deburring process test verification

 

Taking the diesel engine cylinder head with the bottom hole of the injector bushing φ30H7 and the groove φ35.4H9 as the test workpiece, different deburring process schemes are verified. Before the test, observe and record the burr in the sealing ring groove of the test workpiece, and there are obvious burrs on the outside of the groove. Figure 7 shows the burr of the incision site photographed by the endoscope.

 

Figure 7 Burr at the incision part photographed by the endoscope

 

Before the test, the bottom hole φ30H7 of the test object was measured and recorded, and the bottom hole diameter was qualified.

 

During the test and verification process, check and adjust the machine tool according to the regulations to confirm that the deburring tool is installed correctly, the fixture is positioned accurately, the clamping is reliable, and the program and parameters are correct.

 

 

Deburring effect with the ordinary reamer

 

First, use a 29.99mm reamer for the test. The workpiece is positioned and clamped in the fixture, the machine tool runs automatically according to the program, and 10 workpieces are processed continuously. After processing, it was found that the burrs in the sealing ring grooves of 10 workpieces were all removed, but 8 of the workpiece bottom holes were cut twice. After measurement, the local diameter of the bottom holes was out of tolerance. The analysis determined that the φ29.99mm deburring reamer destroyed the finished bottom hole. The diameter of the reamer was ground down to φ29.96mm, φ29.93mm, and φ29.90mm in turn, and 10 workpieces were machined for testing. It was found that there were two main results:

 

① The burrs in the groove of the sealing ring were removed, and the bottom hole was processed for the second time. , but the deburring reamer destroyed the finished bottom hole.

 

② The bottom hole is intact, but the burr removal is not complete. Deburring by the combination of the reamer and the floating handle has the problem of secondary processing of the bottom hole or incomplete removal of the burr. This method is not suitable for mass production.

 

 

Deburring effect with emery abrasive bar

 

According to the experience of deburring with a reamer, the test was carried out using a φ29.96mm emery abrasive bar. The workpiece is positioned and clamped in the fixture, the machine tool runs automatically according to the program, and 10 workpieces are processed continuously. After processing, it is found that the burrs on the outside of the sealing ring groove of the 10 workpieces have been removed; Grinding marks with emery abrasive bars. After measurement, the surface roughness of the bottom hole is qualified, the diameter of the bottom hole is qualified, and the bottom hole is not damaged.

 

Further observation of the deburring effect of the sealing ring grooves shows that there are a small number of burrs on the inside of the sealing ring grooves of 10 workpieces (see Figure 8). According to the observation, photographing and recording of the burr in the sealing ring groove of the test workpiece before the test, as well as the structural characteristics of the emery abrasive rod, it was analyzed and confirmed that during the deburring process using the emery abrasive rod, part of the outer burr was pushed to the inner side of the sealing ring groove.

 

Figure 8 Burrs on the inner side of the seal ring groove

 

Using the process scheme of combining the emery abrasive bar and the floating tool handle for deburring, there is a problem the emery abrasive bar pushes the outer burr to the inner side of the sealing ring groove, and this method is not suitable for mass production. 

 

 

Deburring effect with spring blade

 

When the spring blade tool is used for deburring, the action sequence of the machine tool and the tool is: when the machine tool spindle is not rotating, the tool enters the middle of the sealing ring groove → the machine tool spindle rotates → the machine tool spindle advances, removes the burr on one side of the sealing ring groove → the machine tool spindle retreats, removes the burr Burr on the other side of the sealing ring groove → the tool returns to the middle of the sealing ring groove → the machine tool spindle stops → the tool exits the workpiece.

 

The spring-blade tool deburring scheme is adopted. Since the requirements for the machining program are different from those of the previous two schemes, a new machine tool operation program is compiled, and the program and parameters are debugged and tested. Experiments were carried out using a spring-blade tool with a theoretical machining diameter of 30mm. The workpiece is positioned and clamped in the fixture, the machine tool runs automatically according to the program, and 10 workpieces are processed continuously. After processing, it was found that the large burrs in the sealing ring grooves of 10 workpieces were removed, but there were still small burrs on the edge of the chamfer. The secondary burr generated at the larger chamfer is shown in Figure 9.

 

Figure 9 Secondary burrs generated at larger chamfers

 

According to the observation of the burr in the sealing ring groove of the test workpiece before the test, the photographing record, and the characteristics of the spring blade tool, it was analyzed and confirmed that the reason for the incomplete deburring effect of the sealing ring groove of the 7 test workpieces was that the blade did not reach the chamfering edge. Work stopped, resulting in small secondary burrs on the chamfered edge. If the engineering process is increased, the length of the chamfer will exceed the requirements of the drawing, which is not conducive to sealing.

 

According to the first round of testing, re-prepare the workpiece without chamfer at the groove of the sealing ring for testing. Before the test, observe and photograph the burrs in the sealing ring groove of the test-cut workpiece.

 

Using a spring blade tool with a theoretical machining diameter of 30mm, 10 workpieces without chamfering in the groove of the seal ring were continuously machined. After processing, use an endoscope to observe the grooved parts, and the burrs in the groove parts of the sealing ring of 10 workpieces are completely removed. The deburring effect without chamfering at the groove is shown in Figure 10.

 

Figure 10 Deburring effect without chamfering at the groove

 

Dissect the test piece (see Figure 11) and observe that there are no burrs on the outside and inside of the sealing ring groove, and the effect is good.

 

Figure 11 Anatomy of the trial cut

 

Comparing the workpieces before and after deburring, it is found that the following conditions have also occurred in the test-cut parts while the burrs are being removed.

 

1) The edge of the ring groove is formed with a chamfer of 0.3-0.5mm and the contour is uniform, which meets the requirements of the pattern. The size of the chamfer can be controlled by changing the spring in the tool, which is acceptable.

 

2) Two scratches are formed on the hole wall, which can be observed visually. When touched by hand, it is as smooth as the place without scratches; the hole wall is measured with a high-precision three-coordinate scanner, and the value of the scratches does not fluctuate. After analysis, the two scratches are the traces left by the tool when the tool is fast-forwarding and rewinding. They are the traces left by the contact between the spherical head of the blade (see Figure 12) and the hole wall. It is a normal phenomenon, not scratched. There is no touch feeling in the anatomical inspection, the air tightness test is carried out with the bushing, there is no air leakage, the aperture is checked, and the aperture does not change before and after deburring. Based on the above factors, it can be judged that the scratch is a normal phenomenon, and the workpiece is not scratched, which is acceptable.

 

Figure 12 Blade spherical head

 

 

Batch processing verification

 

According to the test results of the deburring process, the process method of the deburring tool with a spring blade is applied in the production line. Continuous batch production of 300 parts, good and stable deburring effect. 

 

 

 

Conclusion

 

Aiming at the burr problem in the sealing ring groove of engine parts, three deburring process schemes are designed and verified by experiments. The test procedures are reasonable. According to the process test and batch processing verification results, the deburring effect of the spring blade tool deburring process method is good, and the burr problem in the sealing ring groove of the engine parts is completely solved.

 

 

 

CNC Expert Reviews

 

According to the burr characteristics of the sealing ring groove and the production line condition, Tuofa CNC machining proposes three deburring processes for testing and comparison. Taking into account the cost and efficiency of burr removal, the process method of deburring with a spring blade tool was finally adopted, which achieved good results in batch processing.

 

The article has strong practicability and wide application. The engineers of Tuofa CNC machining have very keen observation ability can analyze and improve some details in the processing process, and completely solve the burr problem in the sealing ring groove of engine parts.