Marshalltown SP684 SURFACE SHARK Surface Planer - Manual (Page 13)

SP684 SuRFACE ShARK SuRFACE PLANER PAGE 13
The planing process is directly controlled by these
conditions:
1) The use of a suitable mechanism (flail) of sufficient
strength and hardness to impact the work surface and
remove material while delivering an acceptable service
life.
2) Sufficient static weight supporting the flails which
allow them to effectively penetrate the work surface
and remove material.
3) Adequate horsepower capable of propelling the
rotating flails against the work surface to deliver
acceptable productivity rates.
Since no two materials are exactly alike, no two work
surface materials can be penetrated and removed by
the exact same method. The nature of the planing
process, along with operator experience, skill and
common sense, would suggest that efficient and
productive material removal is a matter of trial and error.
Combinations of flail type, condition, configuration,
spacing along the width of the flail drum and feed
rate are direct factors that will determine the overall
success of the job application.
FLAIL DESIGN AND APPLICATION
While individual flail design and configuration may
vary, basic operational characteristics are identical:
impact a work surface material and remove a
percentage of the material. This common operational
characteristic has led to the development of two basic
flail configurations:
1) high carbon, heat treated, alloy steel designed for
direct contact and removal of the surface material. The
high carbon content of the flail material also helps to
improve service life
2) high carbon, heat treated, alloy steel with tungsten
carbide inserts brazed into the flail body. The tungsten
carbide inserts are intended to directly contact the work
surface and remove material. The inserts effectively
resist wear and usually deliver a substantially longer
service life than the plain, heat treated steel types. The
flail body is designed to serve as a matrix or support for
the tungsten carbide inserts, hence the requirement for
heat treatment. The heat treatment process also aids
the flail body in resisting wear.
Several Factors Directly Affect the Selection of a
Flail Design for a Specific Job Application:
1) The type and amount of material to be removed from
the work surface. Materials of higher yield and tensile
strengths along with the actual volume of material to
be removed will generally be the first factors under
consideration.
2) Purchase costs versus service life. The original
purchase cost of plain, heat treated steel flails must
be compared against the substantially higher costs
of tungsten carbide insert flails. In turn, these costs
must be compared to anticipated service life. All flails,
whether of high speed steel or tungsten carbide insert
design, will eventually wear to the point of requiring
replacement. The amount of unproductive time spent
to replace worn flails on a job can be substantially
greater than the actual replacement cost of many flails.
It then becomes a balance between purchase cost,
productivity, service life and labor cost.
3) Surface finish and texture. The finest grained surface
finish available from the planing process is comparable
to a “swept or broomed” like finish. FIGuRE 1. If a
smooth, flat finish is desired, the planing process must
be followed with a grinding or polishing type process.
Many job requirements may call for large amounts of
material to be removed, but followed with additional
specifications requiring a finer surface finish or texture.
Many times these jobs dictate the use of an aggressive
flail configuration because of productivity and cost
considerations. Less aggressive flail configurations
can then be utilized for the final finishing sequence.
Generally speaking, the more aggressive the flail
configuration, the more coarse the resulting finish and
texture.
FIGuRE 1