Total Lubricants USA Technical Training Series: Metalworking Coolants

1
Total Lubricants USATechnical Training
SeriesMetalworking Coolants
2
Coolants

• Water-containing fluids designed to
• provide lubrication between tool and workpiece
• remove heat from surfaces
• flush away debris created during machining
• Coolants are used in place of cutting oils
  because
• heat removal is about 2-3 times faster than oil
• much thinner in composition which allows faster
  machining with closer tolerances
• produce less misting than similar viscosity oils
• typically are easier to dispose of

3
Coolant Use

• Coolants are used to perform many different
  metalworking tasks including
• turning
• boring
• drilling
• sawing
• honing
• milling
• grinding
• broaching
• gear hobbing, etc.

4
Metalworking Fluid Selection

• Selection of a particular MWF depends on the
• type of machine and operation
• type of metal and speed of cut
• machine lubrication requirements
• MWFs must provide effective rust corrosion
  protection for the tool, workpiece, and machine
• MWFs consist of 4 basic types
• straight oils
• emulsifiable (soluble) oils
• synthetic fluids
• semi-synthetic fluids

5
Types of Metalworking Fluids
6
Emulsifiable Oils

• Known in the industry as Soluble Oils
• Consist of about 75 - 90 oil
• Usually formulated with naphthenic oils
• Common additives include sulfur, chlorine, fats
• Form oil-in-water emulsions
• Provide good tool life, anti-weld properties, and
  rust corrosion properties
• Typically provide the best lubricating properties

7
Synthetic Coolants

• Contain large quantities of water but no oil
• Form a clear or translucent solution when mixed
  with water
• Have a higher pH than emulsifiable type oils
• Provide benefits such as increased workpiece
  visibility, good wetting properties, stability,
  tramp oil rejection, and little rancidity
• Formulated with rust corrosion inhibitors,
  extreme pressure enhancers, biocides,
  surfactants, anti-foam agents, more

8
Semi-Synthetic Coolants

• Formulated much like a synthetic fluid but
  contain from 5 to 25 oil
• Designed to combine the best features of both
  emulsifiable oils and synthetic fluids
• Offer better lubricity than synthetic fluids and
  better visibility tramp oil rejection than
  emulsifiable oils
• Provide a good finish on most non-ferrous metals
  and recommended where other fluids are not
  practical

9
Coolant Performance

• Successful performance of any coolant depends
  primarily on proper
• storage of the concentrate (neat coolant)
• preparation of coolant dilutions for the initial
  charge and for daily makeup
• maintenance of coolant dilutions including the
  use of good housekeeping techniques and
• routine condition monitoring by a laboratory to
  detect and correct discrepancies before problems
  arise

10
Proper Storage

• Storage methods are important to the success of
  the finished product
• Improper handling can render a coolant useless or
  may lead to premature solution failure
• Coolant concentrate should be stored inside
  between 50o and 100oF outside storage should be
  avoided
• Concentrate must be protected from moisture

11
Coolant Make-Up Water

• Make-up water must be of suitable quality
• The pH water hardness along with chlorides,
  sulfate, and iron content must be considered
• Hard water can split emulsions and form scum
• Chlorides can split emulsions and create rust
• Sulfates may promote microorganism growth
• Hard water discourages foam soft water provides
  the best emulsion stability

12
Coolant Dilutions

• Coolant should be added at the point of maximum
  agitation
• Coolant mixtures should be prepared using
  dedicated mixing equipment and containers
• To initially charge a system, it is necessary to
  know the sump capacity of a machine or system

13
Maintenance of Coolant

• Coolant maintenance is absolutely essential to
  ensure consistent quality of manufactured parts
• Daily checks are needed since coolant dilutions
  are constantly changing through carry-off on
  parts, water evaporation, oil leaks, etc.
• Individual operators have the best ability to
  detect potential problems and maintain coolant
  solutions by performing simple daily checks

14
Maintenance of Coolant

• Daily checks by operators should include
• verifying coolant concentration
• noting abnormal conditions such as excess tramp
  oil, solids, and/or foam, abnormal appearance or
  odor, etc.
• Routine lab testing is performed by Total
  Lubricants to ensure satisfactory fluid
  performance
• If a problem is detected from lab testing,
  corrective actions are implemented to ensure
  uninterrupted service from the coolant
• Water vaporization from machine sumps usually
  makes it necessary to add makeup coolant at a
  reduced concentration level

15
Coolant Concentration

• Concentration is the single most important factor
  to coolant success
• concentration must be maintained as consistently
  as possible within an established range
• rich concentrations may cause an increase in skin
  irritation, produce excessive foaming, reduce the
  coolants ability to remove heat, increase
  costs
• lean concentrations can destroy tool life, create
  rust and corrosion problems, promote growth of
  microorganisms, and lead to rapid fluid failure

16
Concentration by Refractometer

• A fast and easy method for checking coolant
  concentration is with a handheld refractometer.
• A refractometer is an optical instrument that
  reads the amount of total solids by passing light
  through a sample of coolant.
• Synthetic coolants produce the sharpest line on a
  refractometer soluble oils are often difficult
  to read accurately
• Tramp oil or chemical contaminants may cause
  inaccurate readings

17
Routine Lab Testing

• Coolant condition monitoring tests include
• concentration
• total alkalinity
• total oil content (soluble/semi-synthetic)
• pH
• microbe activity (aerobic/anaerobic bacteria
  fungi)
• solids
• tramp oil
• cation levels (Ca, Mg, Na, Fe, Al)
• conductivity
• rust prevention properties

18
pH

• pH expresses the hydrogen ion concentration in a
  solution
• pH scale ranges from 0-14 0-6.9 is acid 7.0 is
  neutral and, 7.1-14 is alkaline
• pH is measured with pH paper or electronic meter
• A high pH (8.5) promotes good protection from
  corrosion and microorganisms
• A low pH is best for non-ferrous metals and is
  kinder to an operators skin.

19
Control of Microorganisms

• Coolants provide an excellent environment for the
  growth and reproduction of microorganisms
• Common microorganisms consist of bacteria and
  fungi (yeast and molds)
• Microorganisms digest helpful ingredients and
  produce foul odors
• Microorganism content is determined by growing
  cultures from coolant samples
• Biocides may be added to fluid to combat growth

20
Foam

• Some foam is good since it cleans machine
  surfaces and promotes good wetting properties
• Excessive foam, however, is a safety hazard and
  may cause pump cavitation
• Foaming is dependent on coolant concentration,
  water hardness, type of coolant, agitation, and
  severity of the operation
• Foam may be effectively controlled with anti-foam
  agents

21
Tramp Oil

• A layer which floats on the surface consists of
  split-out oil, carry-over oil, and/or process
  oils
• Tramp oil causes incorrect refractometer
  readings, severe loading of grinding wheels, and
  a reduction in heat removal capacity and wetting
  ability
• Failure to control tramp oil often leads to an
  increase in the growth of microorganisms
• Effective control can usually be obtained by
  using oil skimmers and felt-covered wipers

22
Solid Contaminants

• Solids are formed during the machining process
  and consist of fines, shavings, and dirt
• Solids which are not effectively removed can
  scratch surfaces and interfere with close
  tolerances
• Solids provide additional breeding ground for
  microorganisms and promote operator dermatitis
• Most solid contaminants can be reduced or
  eliminated through the use of magnetic skimmers,
  filters, and chip separator devices

23
Operator Procedures

• Prior to the beginning of the shift throughout
  the work day
• observe the holding tank to detect any
  significant changes in tramp oil levels, dirt, or
  fungal growth (slime)
• slime-type growth on walls should be reported as
  soon as observed so that an anti-fungal treatment
  can be added (line clogging can quickly become a
  problem)
• dirty sumps should be changed out as soon as
  production maintenance schedules permit
• operators will obtain a feel for the general
  operating condition of their machine through
  daily inspections

24
Dermatitis

• Dermatitis is an irritation or inflammation to
  the skin
• Coolants contain surfactants and wetting agents
  (soaps) which tend to dry skin
• Alkaline cleaners, degreasers, solvents, and
  abrasive cleaners further irritate the skin
• Common industrial irritants include kerosene,
  chlorinated solvents, acidic solutions, and
  metals including chromates, zinc, cadmium,
  mercury

25
Dermatitis

• Factors external to the work environment which
  may cause dermatitis include
• poison ivy, poison oak, ragweed, and sumac
• white pine, Frazier fir, teak trees
• lemons, oranges, onions
• penicillin, sulfa-drugs, anti-histamines
• dyes, bleaches, deodorants, nail polishes
• wool, silk, nylon, leather, fur
• detergents, polishes, waxes

26
Dermatitis

• Synthetic coolants tend to dry out skin the most
• Dermatitis, by definition, is not caused by
  bacteria although bacteria may aggravate an
  existing case of dermatitis
• Factors such as age, type of skin, previous
  exposure, duration of contact determine an
  individuals susceptibility level to dermatitis
• Proper fluid maintenance and operator hygiene are
  key factors in preventing or reducing dermatitis