Spray Cooling Basics
The need for providing coolant to metal removal
operations is readily accepted in machining industries. All
metal cutting applications generate heat due to metal deformation
and chip friction at the tool chip interface. Coolants allow
for this heat to be minimized or removed from the operation.
By removing the heat generated in the operation, tool life
increases and part finish is improved.
"Spray Cooling" for the purpose of this paper
shall be defined as "the delivery of a coolant in a spray
form using compressed air." This technology was discovered
and became available to metal cutting operations in the 1950's.
Previous to this "flood cooling" was the accepted way of providing
cooling and lubricating to the cutting tool. Flood cooling,
although more effective than dry machining, also has negatives
associated with its application. Dermatitis due to operators
contact with unstable coolant chemistry, workplace cleanliness,
chip processing and sump maintenance costs all could be improved
significantly in many machining applications through the use
of spray coolant. Many secondary machining applications could
be improved with the addition of spray coolant.
Spray delivery of coolant with improved synthetic
formulas can provide higher heat transfer from the tool chip
interface than typical flood applications of water soluble
coolant. With higher dilution capabilities, modern synthetic
coolants provide the necessary heat removal/tool lubrication
performance to maximize cutting tool performance. Being able
to maintain coolant dilution ratios more precisely with once
through coolant usage, insures that the best coolant mixture
is being delivered for the operation being performed. When
necessary, dilution ratios can be adjusted when either more
lubrication or more cooling performance is called for.
With the variety of metal cutting operations
that are performed every day it is important to not lose sight
of the role spray cooling can play in improving machining
applications. With modern day equipment, applications ranging
from tool room to high production can be covered. Improved
nozzle design and proper coolant pattern adjustment allow
users to maximize speeds and feeds and remove chips while
improving part finish and tool life.
Three factors determine the appropriate cooling
or lubricating requirement in metal removal operations. Material
machinability, machining process and cutting tool material
all must be considered when determining where spray cooling
is appropriate. When these factors call for high heat removal
spray cooling can provide the necessary cooling and lubricating
for the cutting tool.
When all variables, both direct and indirect
are factored in, many flood coolant applications can be converted
to spray cooling, improving the metal removal operation.
Trico Mfg. Corp. offers a wide range of coolant
delivery systems which can cover most applications. Economical
siphon type to multiple line pressurized systems offer the
user alternatives for almost all metal removal operations.
The siphon type units cover a range of applications
from light to moderate with up to six nozzle capability. The
use of multiple nozzles allows for adequate coverage when
tool sizes are large or heat generation is great. Typical
applications would be tool room, prototype areas, or smaller
machining work cells. This type of delivery unit can cover
secondary machining applications that are not equipped with
coolant capabilities. Drill presses and milling machines are
examples of machines that can be improved.
For more sophisticated applications or demanding
metal removal processes, the pump or pressure type delivery
systems are recommended. With the coolant being delivered
with positive pressure, a wide range of coolant stream definition
can be attained. Applications covered by these systems include
dedicated secondary machines, transfer lines, large capacity
tooling, through the tool and machining cells. The various
nozzle/valve combinations allow for customizing systems specific
to end user applications.