What's the difference?!

Remember the puzzles of two similar pictures which have slight differences between the two? When I was younger, we would receive Reader's Digest magazine and each edition often included one of the puzzles. I loved and hated these puzzles at the same time. Maybe those puzzles are to blame for inconsistencies in manufacturing processes driving me absolutely up a wall even today.

The key processes in manufacturing a PCD reamer are brazing, clearing, and cylindrical grinding along with the supporting processes of low pressure sand blasting, final inspection, balancing, part marking, and packaging.  

Clearing has been accomplished most often by using a wire erosion process.  With the advancement of laser technology, the laser ablation option is becoming more prevalent for its speed and its ability to cut through high diamond content PCD segments without creating the “valley” we discussed in a previous article (see https://www.dhirubhai.net/pulse/whats-your-grade-pcd-shawn-farley/ )

Use of wire erosion involves using a wire to cut along the full width of the PCD tip.  The result is the cut is consistent, straight, and the relief follows the angle of the wire.  See the included picture, "Photo A," of a tool manufactured using wire erosion to complete the clearing process. Note the uniform finish generated along the PCD table and the carbide wafer.

However, using a laser process does create its own risks due to the different method to cut through the PCD segment.  A laser clearing process relies on the beam to cut through the PCD tip in a series of passes with each pass cutting a few tenths of a millimeter deeper into the PCD and carbide layers.  As you can see in the attached picture, "Photo B," the layers are clear when the PCD tip is viewed at 50x magnification.  These layers are easily seen at even 20x magnification as well.  

It is important to state that both processes can and will produce a high-quality tool if there is a clear understanding of the strengths of each process and, likewise, the risks that accompany the two methods.  With wire erosion, the ability to properly transition the reliefs is critical especially around the chamfer or radius areas.  When using a laser to clear, the ability to eliminate any high spots, no matter how small, around the same transition of the chamfer or radius areas is critical.  The challenge is the raised areas are difficult to locate.  They often cannot be found using automatic optical final inspection methods.  The manufacturer must know of the possibility for the high spots to exist and develop programming strategies to mitigate the risk.

"This is great to know, but how does that apply to my situation?" 

This is a great question that you, the customer, must understand.

The answer to this question relates to a previous article on consistency (see https://www.dhirubhai.net/pulse/consistency-first-step-shawn-farley/?trackingId=WGy1Pp7uDiihyVbvatmpng%3D%3D ).  If your supplier of PCD reamers switches back and forth between the two methods of clearing described above, they need to notify you they are making these changes. More importantly, are they proactively explaining to you why they are making this change before manufacturing your tools? Any change to a process often results in the need to re-qualify to your customer.  Consistency is the key to having repeatable manufacturing processes and this is a critical step in the manufacturing of your high precision PCD tooling.

Any questions on the clearing processes and more information on what to look for, send a message.  We will be happy to explain and show you how to inspect for yourself.