Small bore probe
1. Inspection of valve ports of automatic transmissions
Valve bodies of automatic transmissions are complex parts with multiple cylindrical valve ports. Examples of vale body components are shown in Figure 1.
Figure 1. Component of a valve body of an automatic transmission
The valve ports in these valve bodies range in diameter from about 5 mm to 25 mm and in length from about 20 to over 100 mm. The diameter of a valve port can change in discrete increments along its length and the valve ports are intersected by multiple slots that segment each valve port into short cylindrical segments. The cylindrical surfaces are diamond turned and are highly reflective. Defects in the valve ports can consist of pores, chatter, delamination, metal flakes and other machining defects. These components are difficult to inspect on a production line using alternative inspection techniques.
The IOMS small bore probe can be used to scan the entire surface of a valve port in 10 seconds or less. Software analyzes the data from the probe to determine whether a valve port has an acceptable or defective surface finish. The result of the analysis is indicated by a red or green light on the front panel of the computer monitor.
Additional graphs displaying the surface finish are a feature that can be used as needed to aid human visualization. The graphs display circumferential angle from 0 to 360 degrees along one axis, depth into the cylinder in mm along the second horizontal axis and relative detected laser intensity along the vertical axis. Examples of these graphs are shown below. Figure 2 shows a valve port with acceptable surface finish, Figure 3 shows a valve port with excessive porosity and Figure 4 shows a valve port with both chatter and porosity.
Figure 2. Acceptable surface finish
Figure 3. Excessive porosity
Figure 4. Example of chatter
These graphs are three dimensional and can be rotated by the observer to obtain the best view of the component surface finish.
2. Inspection of tapped threads
In addition to inspecting smooth diamond turned surfaces for surface flaws, our probes can inspect tapped threads for proper thread count, thread spacing, pitch and thread defects such as crossed threads and other flaws. An example of a scan of the entire surface of a threaded part is shown in Figure 5.
3. Comparison of internal surface structure with a master part.
Some cylindrical parts may have detailed internal surface structure. Our probe can rapidly scan the interior of these parts and compare the surface pattern of the part with that of a CAD drawing or a master part. A scan of a part with internal surface structure is shown in Figure 6.
Figure 6. Graph of the interior of a cylindrical plastic part
4. Detecting valve seat defects
If the tool machining the seating surface of a valve seat develops a chip in its cutting surface it will not cut a smooth surface on the part. Instead, a ridge will be created by the void in the surface of the cutting tool. This ridge can prevent the valve from properly seating causing the cylinder to loose compression. These ridges on the surface of the seating surface may be almost microscopic and could be very difficult to detect visually, yet could still have an effect on engine performance. Our probe is able to detect a ridge if one is formed on a valve seat surface. This is shown in Figures 7a and 7b that show the probe signal from a defective surface (7a) and from a surface with an acceptable surface finish (7b).
Figures 7. (a) Signal from defective valve seat surface (b) Signal from acceptable valve seat surface
The signals shown are single line scans across a valve seat. The defective surface has a dip because the ridge on the seating surface scatters incident light and prevents some of it from returning to the probe and being detected by the detector in the probe. Using this probe it is also possible to scan the entire seating area of a valve seat. The probe can quickly identify when a cutting tool tip has become chipped so that it can be quickly changed and not produce additional defective engine heads.
5. Determination of part concentricity
Some parts are designed to be concentric along the same cylindrical axis. An example is the valve seat and valve guide of an engine head. Our probes are sensitive to angular alignment and can tell whether parts are properly aligned within a fraction of a degree relative to the probe axis. By measuring the alignment of each component relative to the probe as the probe passes through both components, the concentricity of the components to each other can be determined.