Newbie Question about Insert Usage

[jeremyray25]

Guys I work at a machining facility. Lately, we have ran into excessive insert usage on one of our lathes.

I have verified speeds and feeds.
I have checked for proper seat of insert to tool head.

What other items do I need to look at? Any help is much appreciated.

Thanks.

[mc_n_g]

Ok this may seem a little smart a$$ but...
I liken this to "I have a car and it does not run right"

CNC or manual? material being cut? Size of lathe? Type of insert? Breaking inserts? Wearing inserts? Chipping inserts?

People can only reply based upon the information you provide.

[jeremyray25]

sorry for the lack of information. I was and am looking for a general (not specific) list of items to check. For instance, good work support, good coolant flow, proper feeds and speeds.

I am using a carbide insert on a vertical lathe. I am a new hire so I don't know alot about the process, but it is my understanding all of the engineering work has been performed to find adequate insert type, feed, speed, # of passes, etc. Until two days ago, everything was normal. Now the inserts are breaking, not just wearing.

I guess my question is: what variables could cause tool breakage? I am just looking for a list of items to check.

[leggazoid]

Check if the machine has been crashed. Don't just ask the operators. Check turret alignment (both angular and turret alignment with z-axis). Check headstock alignment.

[mc_n_g]

General quesitons to ask for the 'investigation'. Use the answers to try to pinpoint a potential problem.
Is the stock from the same supplier and the same batch?
Are the inserts from the same box or batch? Were they recently purchased?
Are the inserts breaking at the same place in the routine? Is the routine new? Has it been run in a simulator to test the routine?
Are the breaks in the carbide always the same spot (maybe bad batch of inserts) like near the hole or chip groove?
Is the stock from a new vendor? Maybe there is something wrong with it? Their grades may be mismarked?

Have you tried to cut something soft like aluminum in the lathe and check for dimensional tolerances (sort of what leggazoid is referencing)

[leggazoid]

It could be something as simple as a bad tool offset causing too big a cut resulting in a broken insert.

[PixMan]

Unfortunately, once an insert is broken the opportunity for failure mode analysis is already gone. How many workpieces did the inserts used to make before failure, and what was the criteria for changing them? (Time in cut, surface finish gone bad, size lost or ??)

How repeatable are the current failures? If the insert breaks after 5 pieces the first time, then goes 40, then 2...you have a mechanical problem of some sort.

Has the material changed? (Look at certs for current vs. previous deliveries.)
What inserts are you using? (I've seen even some big name-brand ones have inconsistent quality.)

You are right to question workpiece rigidity, tool holder condition, tool center height and any other variable, but be sure to verify one at a time. If you don't, and the problem goes away, you won't know for sure what was wrong.