How To Polish Bending Marks Out Of Inconel Tube

A customer recently asked us how to polish bending marks out of inconel tube. This included a range of tubes from 25 to 51mm in diameter and with a number of different bend formations. Critical to this task was that the wall thickness was not reduced significantly. The Garboli LPC 300 demo machine was perfect for the job.

How Aggressive a Belt Can We Use?

The coarser the belt the faster the rate of cut. But for this application preventing too much stock removal was critical, therefore the aero engine user of these inconel tubes put process restrictions on which abrasives could be used.  The belts had to be aluminium oxide and no coarser than 180 grit.

Process

Initial trials to polish bending marks out of the inconel tubes were conducted with our Garboli demonstration machine. The machine was fitted with the premium 180 grit JF4Top Aluminium Oxide belt. JF4top belts use premium white aluminium oxide and contain coolants & grinding aids – ideal for working on inconel.  JF4top is also a very flexible belt material. To increase the flexibility further we conducted this trial using belts with a wave-cut edge.  The wave-cut edge increases the operators ability to manoeuvre the workpiece easily as the tube is passed through the machine and removes the risk of leaving chatter marks around the tube.  Especially useful when working with tubes of different shapes and sizes as we were!

As you can see, the JF4T belts were able to consistently sand the bending marks out of the inconel tubes to leave a clean, bright finish without removing too much material from the tube.

Before                                                                 After

 

Our next stage included switching belts to the Surface Conditioning belt.  This allows you to work deep into the bends of the work piece to reduce some of the deeper bending marks and other remaining surface damage.

Below is the difference before the tube had gone through the Garboli machine and after the two belts were used on the workpiece.

 

Hints and Tips:

1.  Work out how you will feed the tube through the machine before you do it for real!  This is especially useful when you are working with an unusual shaped tube.
2. Keep the heat down.  Inconel really does not like being worked at high temperature.
3.  Set the Garboli machine to run at the right speed.  Working on the Inconel tubes we set the machine at 22 m/s.