“Aftermarket” Bending Sections

There were two new bending section manufacturers at the FIME expo in Miami Beach last week. I had an opportunity to evaluate an unknown model from China under magnification. It was a similar design to a GIF-160 with a combination of four wedge bands and alternating scissors (see nomenclature blog).

 

Upon initial inspection it looked pretty good. The bands were a good thickness and firm to the squeeze. Their edges were smooth and rounded. And the movement was extremely free.

Under magnification, it was another story. When doing an inspection, you look for things that ‘stand out’, and everything stood out on the inside of this bending section. The first thing I noticed was the two bands which were subjected to expansion. It appears this was accomplished by forcing a mandrel larger than the bands Internal Dimension into it until the ID desired was obtained. This technique scrapped the walls and deposited all of this metal finings at the end of the expansion area. There were lots of metal shards to break off later to do damage to the delicate internal components later on.

The next problem was with the rivets to connect each band. These allow the bands to swing freely. But the rivets were machined to produce too much movement. The extra-long step down and long shaft means the internal heads stick up into the elements too far to grab the elements as they move back and forth as the bending section articulates ‘P’ and then “DOWN”. The outer rivet heads will grab and eventually destroy the fine wires of the mesh. Another rivet problem was with the thin size of the internal rivet heads. Several were already ‘pulling through’ and in need of replacement. Most of the outer rivet heads were fractured. Much like a chisel head mushrooms and fractures after being hit by a hammer too many times, it becomes a danger from the fractured edges flying off with the next impact. As these rivets are twisted and stressed, the fractured pieces of the heads will crack off and become a shredding force to the elements.

It appears that all of the ears of the bands were worked by hand since each one shows different scratch patterns. Scratches left to hamper the free movement if the rivet lengt problem is ever corrected. The ears should mate up with two smooth flat surfaces gliding against one another, not scratch to scratch.

The last defect in assembly is the eyelets and how they are attached. It appears the eyelet was dipped into the brazing paste and then heated by torch into place. So the brazing is on and all around the eyelet. And it is already peeling off. Peeling from both the band surface and surrounding the eyelet. They did file the brazing off of the inside of the eyelet which left a scratchy surface to accelerate the wear on the angulation wire. The big problem is if the brazing is already peeling, usually indicating poor surface preparation, how will it keep the eyelets in place during use. You cannot braze to a surface covered in machining oil just like you cannot paint over a kitchen wall where cooking oils have splattered. And where will the peeling brazing go? That’s right, to mix in with the internal elements to do destruction there. Pieces of free floating metal are always suspect when unknown damage is discovered in the distal end. Internal components move as much as five inches as a colonoscope articulates from full ‘UP’ to full ‘DOWN’ within the bending section.

Once again, it proves the old adage, “You get what you pay for”. The unsaid portion of that statement is “If you pay a little now, you can expect to pay many times more latter down the road”.

There will certainly be a lot more unknown; fluid leaks, electrical shortages and damaged light guides when these aftermarket bending sections hit the market.

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