We are currently in the middle of a medical device project which involves grinding a standard 15 degree trocar tip on 1.1mm stainless steel wire (316LVM) K-wire. We are having issues with a burr along one edge of the trocar tip. We noticed this burr early on and we have been troubleshooting it. I wanted to make this post in case it could help other manufacturers who are troubleshooting grinding problems.
The standard trocar tip angle we see is 15 degrees. The 15 degrees is measured from the angle of one face of the tip against the center line of the wire. We have done 8 degree angles for sharper tools and 45 degree angles for a less sharp tools. If you are looking at the end of the wire, the trocar tip is divided into 3 – 120 degree angles.
We set up our program to start by grinding off the tip. We grind off about .005″ of material at the edge of the wire. We can only do this on projects in which the wire is larger than the final product and we have excess material that we can waste. Having excess material also allows us to use a sensor for automatically loading the wire. If we don’t have any access wire to use, it is difficult to use the sensor because the leading tip may not be precise.
One Pass at the Tip
We started out our grinding program just taking one pass at the tip i.e. grinding all three tips of the trocar in a single pass along the grinding wheel. This is when we first noticed the burr. We have done grinds in the past and only done a single pass and we had no problems.
Verdict: Did not work
Where does the burr come from?
The edge burr is coming from stainless steel material getting pushed to the side during the grind process and having no where to go. It pushes out over the angle of and offset trocar angle.
Slow down the Grind
For the next attempt, we tried to slow down the grind. We kept with a single pass. Our hope was that by slowing down the grind it would give the material more time to be ground away instead of getting pushed aside.
Verdict: Did not work
Two passes at the Tip
For the next attempt, we kept the grind slowed down and we added a second run across each face of the trocar tip. Our hope was that the second run across the tips would help clear away the burr from the first grind.
Verdict: Helped a little, but did not work
Three passes at the Tip
For the next attempt, we kept the grind slowed down and we added a third run across each face of the trocar tip. Our hope was that the second run across the tips would help clear away the burr from the first grind.
Verdict: Helped a little more, byt did not work
Redressing the Wheel
We are using the wheel dress from a previous project which has a radius dressed into the wheel. The plan is to create a dress a square coming out of the wheel, do you think this will help? We will let you know. We have one more project which needs the radius and then we will try it out
If you are having difficulties with a grinding project, don’t hesitate to reach out. It is what we do all day long. Our engineers are available to help.