Should Work Instructions contain Tool Change Intervals? Inserts, Drills, End Mills

[Umang Vidyarthi]

Re: Should Work Instructions contain Tool Change Intervals? Inserts, Drills, End Mill

We do cnc lathe/mill work. Is it common for work instructions to contain tool change intervals (Inserts, Drills, End Mills, etc)?

Thanks.

It is neither common nor essential for WIS to contain tool change intervals, for the simple reason that changing of tool depends upon multiple variable factors. There may be exceptions, but exceptions don't make the rule.

Umang

 

[bobdoering]

Re: Should Work Instructions contain Tool Change Intervals? Inserts, Drills, End Mill

It is neither common nor essential for WIS to contain tool change intervals, for the simple reason that changing of tool depends upon multiple variable factors. There may be exceptions, but exceptions don't make the rule.

It is common to place the tool change in the work instructions if the information is available. However, it is also true that if you really have no idea how to control your tool changes, then the work instruction will not contain the information. How common it is for people not to bother to deal with the problem is probably irrelevant.

Just because tool changes depend on many factors does not mean it is impossible - just not dead simple. The tools for evaluating tool change intervals are available for those that are interested, some of which have been mentioned in this thread.

 

[alspread]

Re: Should Work Instructions contain Tool Change Intervals? Inserts, Drills, End Mill

As I mentioned before; tool change frequency is required on some critical rotating aircraft parts. It is treated as a special process requiring multi-page tech-plans with precise parameters including machine load meters in some cases.

These requirements were instituted after an in-flight failure in the midwest that crash in either North or South Dakota taking many lives. Apparently a hole was drilled in a critical rotating part with excessive load causing the surface of the hole to work harden from the stress and generate small cracks. The hole was within all drawing tolerances and showed no obvious damage.
The part cracked and parts flew everywhere damaging many critical components. That investigation resulted in stringent machining controls for holemaking on critical rotating parts.

The word on the street is that this process will soon become a Nadcap controlled special process that will include critical machining and deburring of critical components.

 

[bobdoering]

Re: Should Work Instructions contain Tool Change Intervals? Inserts, Drills, End Mill

As I mentioned before; tool change frequency is required on some critical rotating aircraft parts. It is treated as a special process requiring multi-page tech-plans with precise parameters including machine load meters in some cases.

These requirements were instituted after an in-flight failure in the midwest that crash in either North or South Dakota taking many lives. Apparently a hole was drilled in a critical rotating part with excessive load causing the surface of the hole to work harden from the stress and generate small cracks. The hole was within all drawing tolerances and showed no obvious damage.
The part cracked and parts flew everywhere damaging many critical components. That investigation resulted in stringent machining controls for holemaking on critical rotating parts.

The word on the street is that this process will soon become a Nadcap controlled special process that will include critical machining and deburring of critical components.

It does take some extra effort to control drilling, as it really is a non-precision machining process that people still try to use for precision machining.

For precision machining (e.g. CNC turning, milling and grinding) they would still be better served with the R chart of the X hi/lo - R chart for tool change determinination. It is quite accurate at determining the effect of wear on the tool via variation in the resulting dimension, and very sensitive to loss of cutting edge via increase in roundness or parallelism - found to be a good leading indicator for tool change.

 

[dtr18c]

Re: Should Work Instructions contain Tool Change Intervals? Inserts, Drills, End Mill

It is quite accurate at determining the effect of wear on the tool via variation in the resulting dimension, and very sensitive to loss of cutting edge via increase in roundness or parallelism - found to be a good leading indicator for tool change.

Could someone elaborate on the effects of tool wear and roundness/parallelism?
I don't have a strong machining background and parallelism is something we struggle with. This leads me to think that tool wear could be causing these problems.

 

[bobdoering]

Re: Should Work Instructions contain Tool Change Intervals? Inserts, Drills, End Mill

Could someone elaborate on the effects of tool wear and roundness/parallelism?
I don't have a strong machining background and parallelism is something we struggle with. This leads me to think that tool wear could be causing these problems.

The blog on
X-hi/lo-R charting goes into a decent amount of detail on how to correctly precision control machining processes. I recommend reading through those entries for good background on that topic.