Great question came in the other day.

“Since the computers control the machines, why do we need to have physics in our graduation curriculum?”

I won’t tell you the State Board of Education that was looking at removing Physics from the  high school curriculum.

Apparently they don’t see a need for a  person entering the Precision Machining workplace  to know any physics.

Who needs physics to push a button?
Who needs physics to push a button?

If they don’t understand the forces around them, how can they keep from getting hurt?

Here’s what I shared with them.

Since everything is computer controlled– that’s the new MAGIC, right?- why would any high school graduate going into the workplace these days need to know any physics?  I’m guessing that, “so they can understand how the electricity that powers his machine the computer, and the lights,”  isn’t a good enough answer.
1)Power and Work: All machines are horsepower rated. This determines what jobs they can perform. Materials are machined based on horsepower per cubic inch  of removal per minute.  By the State Board’s reasoning, “Since the clock takes care of the minutes, are we okay to just not know any of this?”
2) Mechanics: This is our craft! We need leverage, thread pitch, gear ratios, belts and pulleys. We calculate the surface feet per minute of rotating tools or workpieces,  given the RPM and diameter. Even the computer needs this info. Cams, clutches, springs, motors, friction and frictional losses- these are physics. Bearings,  force, stress, strain- these are applicable to understanding the machining task regardless of machine control type. Compressed air- expansion, horsepower required, volume, fluid flow…
3) Heat: Heat is the enemy in machining operations. Why not learn a little bit about this? Savvy shops today are using infrared thermography to detect bearing wear in equipment. Some kinds of tool failure are  caused by heat. Understanding insulation, conduction, thermal expansion and contraction are key if the parts will be in spec after they have cooled down  post machining.
4) Sound: Decibel measurement is important as applied to occupational exposure. Harmonics come into play on tools and workpieces as oscillation- chatter. Water hammer in plumbed systems and fluid power applications.
5) Light and optics: Non-contact gaging using lasers, optical projectors for quality control; optical flats for high precision measurements rely on counting interference bands…  We use portable spectrometers for product sorting.  Someone in the shop will need to have an understanding of spectrums, wavelengths, and emissions  if they are to be more than an idiot operated go/no  go gage.
6) Magnetism: Magnetism can cause surface finish problems if chips cling to work. There are several types of magnetic tests performed in our shops and those of our suppliers. They use eddy currents, permeability,  gauss, oersteds, saturation, coercivity. We employ  magnetism for proximity detection of parts, magnetic workholding , and for testing. It goes with out saying that it is magnetism in the electric motors that drives our machines.
What do you think about this topic? Do the people showing up looking for work have what it takes to understand your process? Or are they merely able to do what they are told?

When machining  carbon and alloy steels, Crater Wear is the normal tool failure mode.  Overheating is an unpredictable failure mode.  It can be one of two failure modes, Thermal Checking ( or Cracking- my first boss called it “Crazing” ) or Deformation. Usually, when an irate customer ran into overheating issues, the tool they sent back to me had deformed to the point that it looked like it had been made out of lava.
The lack of predictability of failure by overheating  creates issues for the shop beyond the obvious. Parts produced immediately prior to failure are suspect and must be validated prior to release, to avoid sending rejectable product to customers. Overheating can thus be a “delivery problem” in your customer’s eyes.
Here are 5 tips to get out of Overheating  Tool Failure Mode and back to normal predictable Crater Wear Tool Failure Mode when machining steel:

  1. Improve lubrication coolant delivery or formulation. Sometimes adding an extra coolant line to the position will eliminate the problem. Confirming your coolant is up to spec should be done before electing to buy a new “super duper formulation.” First things first!
  2. Use  a harder grade of carbide with more Ti (Titanium)
  3. Increase the Feed Rate (IPR) inches per rev
  4. Reduce the Speed (SFM)
  5. Consider Ceramic or Cermet Tooling. Note- these are not  really appropriate for low carbon (less than 0.20% C) steels. Low carbon steels  become gummy and stringy at speeds typically used  for ceramic tools.

These tips will address your  overheating problem by reducing the friction, surface adhesion, and  improving removal of heat, (improved coolant, delivery); improving the tool’s ability to withstand cutting conditions, and reducing the heat inputs by decreasing speed and increasing feed.
For more great information on this subject look at this lesson from Fox Valley Technical College.