mass finishing technical8 - Metal and Composite Finishing Equipment

Transcription

MASS FINISHING TECHNICAL INFORMATION
MASS FINISHING
Mass finishing is a process that automates the mechanical and chemical finishing of
non-fixtured complex shaped parts.
Mass finishing utilizes many types of energy generating equipment, abrasive medias
and compounds that transmits the energy from the equipment thru the media to the
parts being processed. The machinery energies the media to move in a random or
precise flow around, into, and thru the parts being finished.
The process can be wet or dry and will run a multitude of parts and processes at a time.
Mass finishing can obtain repeatable results with a low cost per part.
Process capabilities of Mass Finishing
Mechanical
Deburring and edge radiousing
Surface refinement
Surface roughing
Pre paint adhesion
Peening
Stress relieving
Removal of tooling marks
Factors that affect the mass finishing are:
1. Equipment
2. Media
3. Compounds
1. MASS FINISHING EQUIPMENT
Visual
Uniform finishing
Blending
Brighting
Cleaning
Satin Finishing
Matte finishing
Pre plate and anodize finishing
There are a number of choices when selecting equipment for mass finishing. There can
be a lot of overlap where various machines will accomplish the same finishing process
results. Other factors to look at when choosing the right equipment will be: labor
available to assist equipment processes, time available for finishing process within the
cell or production cycle, capital, the part being processed, and other processes that can
be incorporated (part unloading, washing, rinsing, drying, inhibiting,etc) into the
equipment to reduce labor.
Equipment available in the mass finishing industries.
A. Vibratory machines
B. High energy systems
C. Specialty mass finishing systems
A. VIBRATORY EQUIPMENT
The energy that vibratory systems generate is derived from a 1200 to 3500 rpm electric
motor rotating a eccentric weighted shaft. The shaft is attached horizontal to a tub
vibratory machine or vertically to a bowl vibratory machine.
The weighted rotating shaft generates a vibrating action that is transferred to the
machine. The vibratory machines action vibrates the abrasive media (which is contained
within the urethane lined u shaped channel of the machine) impacting the parts being
processed within the media.
Energy level
Media action
Applications
low to moderate
Vibrating punching rolling action
measured in millimeters of amplitude
ranging from 1 to 8 mm, with 3-6 mm
the normal operating range.
general deburring and finishing of
machined parts, stampings, castings
weldments and composite surface prep.
Tub Vibratory equipment
Tub vibratory systems are comprised of a rectangular u shaped tub. The tubs can have
various channel diameters and channel lengths. The tub is mounted and suspended on
springs attached to the base of the machine. The motor and rotating shaft is located
within the base. The shaft is attached to the bottom of the tub and run by a v-belt drive
from the motor attached to the base.
Advantages
Disadvantages
Long part processing
Manual part unloading
Easily divided, for running
large parts that cant touch
or different medias at one time
Small flat parts stick to the
tub side walls.
Smaller systems inexpensive
and portable
Parts migrate to the drive end
of the tub decreasing media to
part ratio.
Large systems can be built for
continuous automation
Bowl Vibratory Equipment
Bowl vibratory machines are comprised of a donut shaped u
channel tub. The bowl can have various channel sizes and
overall diameters. The bowl is held suspended by springs that are
attached to a round base. The eccentric shaft is mounted
vertically thru the center column of the bowl. The motor can be in
the base running the shaft by a v-belt drive or in some machines
the motor is built around the shaft mounted within the center
column.
Advantages
!
Disadvantages
Internal part unloading and
media separation
Restrictive on very long parts
Less part to part damage
Mid level and up on capital investment
Secondary operations such as
media classification, part rinse,
cleaning and drying
Can be built for batch or continuous automation
B. HIGH ENERGY MACHINES
Centrifugal high energy is a controlled centrifugal rotation of a disc or barrel creating an
acceleration and de acceleration and a compressive flowing media action. The
centrifugal finishing processes 7-20 times the energy of vibratory machines. The
centrifugal high energy is not only is faster, but it also produces superior finishes than
the media punching action of the vibratory machines.
Energy levels
high to very high- up to 20 times the energy of vibratory machines
Media action
Controlled centrifugal flowing compressive action
Applications
Super finishing, Deburr of small parts, good for flat part separation
while processing, Drives small media into small areas with energy.
Centrifugal Disc Machines
The centrifugal disc(CD) utilizes the energy of a 100 to 200 rpm
rotating disc at the bottom of a bowl container. The rotating disc
accelerates the media to a stationary side wall which de
accelerates it and then gets re accelerated back and down to the
center of the disc. The continued media acceleration and de
acceleration flow produces energy 7-15 times that of a vibratory
machine. The CD machine is one of the few hight energy
processes that can be automated.
Advantages
Disadvantages
High energy
Higher capital investment
Easily automated
Ring and rotor wear life costs
approximately $1.00 per operating
Flow thru water system
for reline costs
Quick time cycles for cellular
manufacturing
Run wet or dry
Large and heavy parts process numbers
low because of part on part damage.
Centrifugal Barrel Machines
The centrifugal barrel (CB) equipment looks and operates like a
ferris wheel with a cover. The energy is produced by a 100 to
240 rpm rotating turret with (generally 2-4 hexagon or octagon
barrels) built within the turret that counter rotates at various
rpmʼs . The action of these fully enclosed high speed rotating
barrels produce a compressive sliding grinding action. The CB
produces the highest mechanical mass finishing process at up to
20 times the energy of vibratory finishing.
Advantages
High energy
Disadvantages
Very time consuming to load
and unload barrels.
Can run dividers in barrels
to keep parts from damaging
Cannot be automated
Very short time cycles
Batch processing only
Run wet or dry
Part radiusing up to .030
C. SPECIALTY HIGH ENERGY EQUIPMENT
Magnetic Finishing equipment
The energy from magnetic equipment is derived from
rapid rotating magnets built under the tub container
holding the parts and media. The changing polarity of
the magnets run at very high speeds drive the magnetic
stainless media within the tub to a very aggressive
spinning action.
Energy level
Very high
Media action High speed spinning of stainless pin and various shaped medias
Applications
Removes burrs from tiny holes, slots, knurled parts, and hard to get
thread burrs. Works on non ferrous parts. Highly magnetic steel parts
do not work because they move with the magnets.
Chemical Finishing
The chemical finishing process(CF) produces a high rate of
material removal and super surface refinement (down to 2 RA)
by oxidizing the surface of Ferrous ( iron based ) materials,
some non ferrous processes also work. The chemical
( occolic acid, citric acid, or phosphates) continuously
activates the process parts surface allowing a very heavy
ceramic media (120 to 140 lbs per cu ft) to remove the material at much higher rates.
The usually non abrasive media acts as the chemical carrier as well as the surface
scrubbing agent.
The process produces a refined, bright finish with minimum edge radiusing. The CF
process is generally used with bowl vibratory equipment but can be run in tubs
vibrators, centrifugal disc and drag machines. All systems must use a very accurate
compound delivery system. The low PH process chemical must be adjusted to normal
discharge rates before flowing to sewer.The burnishing or brightening secondary
compound(higher PH) step can be flowed into the same sediment tank as the process
compound(lower PH) neutralizing for proper disposal.
Energy level
Very high material removal
Media action
Vibratory or flowing action basically carrying the compound and
scrubbing the oxidized surface allowing for continuous re-oxidizing.
Application
Refining gears, finishing hand tools, gun parts that require very little
radiusing. Surface refinement and brighting within the same system.
The advantages are low initial capital requirement for high energy.
Best results for iron based alloys.
Spindle and Drag machines
The energy of the spindle equipment is generated by a
stationary or rotating bowl of wet or dry media with a
number of stationary or moving and rotating spindles
that holds the parts into the media. The drag machines
use the spindles to move or drag the process parts thru
a dense non moving media within a tub. The dense non
moving media creates a very high metal removal rate.
The slight vibration of media reduces the machine
horsepower require and introduces new media to the
cut area.
The spindle and drag machines can run larger parts that are held or fixtured for a high
metal removal, super burr removal or high luster finishing. Chemical finishing has been
introduced with these systems to improve them futher.
Energy levels
Very high
Media action
Spinning by the part with spindle machines and densely laying in the
tub for drag machines. Both utilize spindles or work holding devices.
Turbines and propellers for high metal removal, high capital outlay.
Application
Low Energy Systems
Barrels
The barrel equipments energy is produced by a
rotating hexagon or octagon shaped barrel where
its design lifts the media and parts loaded within.
The flat sides of the barrel lifts the media and
process parts up for the slide down.The finishing
action is taking place only on the downward slide.
The operating rpm range of the barrels are from 15 to 30 with 17 to 20 being the most
productive. Increases in rpm reduces the thickness of the downward slide. Media and
part levels of 50% will create the longest slide.
Barrel finishing in americaʼs industrial manufacturing sector started well before 1915.
Vibratory machines replaced most barrel applications because it was quicker, more
effective in internal areas of the process parts as well as easier to load and unload.
Barrel finishing has its limited applications today and is highly used in jewelry
production.
Energy
Very low
Media action
Sliding action only taking place on the downward movement .
Application
Processing of small flat parts keeping them from sticking together
while wet. Delicate finishing, very high luster capabilities. Some
medias can start out cutting and end up finishing as they wear in
barrel systems. Very time consuming to load and unload.
2. MEDIAS FOR INDUSTRIAL MASS FINISHING
The media transmits the energy generated by the mass finishing equipment to the parts
being processed..Medias are capable of finishing in various ways.They can cut fast,
remove burrs, edge radius, and rough up a surface for paint adhesion. Medias can also
refine and smooth surfaces to low RMS finishes, burnish and clean.
The systems energy moves the media in various ways. The media is one of the most
noticeable elements to mass finishing but equipment energy and compounds are also
very important.
The industrial preformed medias are identified by there bonding agents (Ceramics and
Plastics).
Consider the following when choosing a media for a process
A. Media Type
B. Media Shape
C. Media Size
D. Media hardness
A. MEDIA TYPE
There are basic media types used in industrial mass
finishing, identified by their bonding agents.
Ceramics
Plastics
Specialty medias
Ceramic Medias are produced by mixing an abrasive ( commonly aluminum oxide,
bauxite, silicon carbide, or quartz) with a ceramic matrix in a green(wet) state.
The matrix (the consistency of damp clay) is extruded thru various shaped dies and
then wire cut into small pieces. The green preformed media pieces are then fired at high
temperatures thru a continuous or batch kiln for up to 24 hrs with precise heat up and
cool down cycles. The harden ceramic pieces are then post tumbled to remove flash
and packaged for shipment.
The different kiln firing temp control the medias hardness. Faster cut medias are
designed to be softer allowing new cutting elements to be exposed. Polishing medias
with no abrasives are designed to be harder to burnish the parts to be brighten. There
are all cuts and hardnesses in between, so generally the slower the cut the harder the
media.
The media clay matrix and abrasives also determine the finishing and cutting
capabilities.
The weight per cubic foot of ceramic media is approximately 85 lbs, with smaller sizes
(1/4 “ and below) weighing approx 15% more. There is a light weight ceramic using light
weight quartz as an abrasive with a high porosity ceramic matrix that weighs 55 lbs per
cubic foot. There is also a high density ceramic media that is fired at higher temps to
make them tougher and fracture resistance that weights up to 140 lbs per cubic foot.
Ceramic medias hardness range between 45-65 rockwell. The ceramic medias abrasive
grit sizes range between 80 grit (165 micron) and 220 grit (63 micron) with some dust
collector fines down to 400 grit ( microns)
PROCESS CAPABILITIES OF CERAMIC MEDIAS
Advantages
Disadvantages
Burnishing (brightening)
materials
Can cause damage to softer
Heaviest burr removal and edge radiusing
of any mass finishing media
Some formulations can chip, causing
Media lodging in small holes.
Many formulations available
Further surface refinement below 12 ra
requires high energy equipment or a
secondary plastic media process.
High strength-long wearability
Cleanest running media
Low density used for delicate parts
High density used for faster cut and less chipping
Produces a brighter scratchy matte finish
Good for surface roughening for coating adhesion
Chemically inert, Biodegradable, sewage dischargeable
with sediment removal recommended .
Quickly removes polish lines
Media attrition rates between .002 and .010 of total mass per hour
Plastic Medias are produced by mixing an abrasive( primarily
a quartz, aluminum oxide, or silicon carbide) with a polyester
or synthic based resin fluid with a catalyst added to harden the
matrix. The matrix fluid is pored into multiple molds built into a
tray and sent thru a heated curing process to harden. The
media hardens quickly and then is tumbled to remove flash
and packaged for shipment. Plastics are light weight, approximately 60 lbs per cubic
foot for polyester and 50 lbs per cubic foot for synthetic. There is a high density plastic
utilizing heavy zirconium sand abrasive that weighs approximately 100 lbs per cubic
foot, this is used when fast cut but better finishes are required with a one step process.
Plastic medias are much softer that ceramic medias. The bonding agent for polyester
plastic are approximately 45 rockwell and the hardness on synthetic media are o
brinnell, the softest of all preformed medias.
PROCESS CAPABILITIES OF PLASTIC MEDIAS ARE:
Produces surface refinement to 4 RA
Cuts light weight burrs without rolling them over
Softer and lighter that ceramic media
Good for processing delicate parts or softer materials
Produces a soft grainy matte finish
Media attrition (wear)rates between .0013 to .002 per cubic foot per hour.
SYNTHETIC PLASTIC
Advantages
VS
Disadvantages
POLYESTER PLASTIC
Advantages
Bio degradable
Softest of all preforms
Non bio degradable
oil based - poly
wears quickly
Runs cleanest of plastics
Brighter finish
Sediment settles quickly
for waste treatment
Disadvantages
higher wear rates
High sediment
sticking to parts
requiring cleaning
Sediment has same
specific gravity as
water not allowing
Avail in high density
good sedimentation
Random Medias can be man made such as the sintered
ceramics for burnishing and the aluminum oxide nuggets
for fast cutting.These medias are screened for size but are
random in shape allowing processing in many areas of the
parts. Radom medias can also include sand and river rock.
There is some fast cutting and finishing applications of
the man made random medias,however, not much for
natural materials in industrial finishing.
Dry Process Media used most commonly are crushed and
sized corn cob for part drying. Corn cob, walnut shells and
wood pegs are also used for brighting with impregnated
rouges and polishing pastes. Dry preformed plastic and
composite medias have recently been developed and are run
with dust collectors to remove the dust. Many mass finishing
processes cannot allow the parts to get wet, this and high
luster are two main applications of dry media. Running dry
medias presents a challenge without the water cushioning
the parts or cleaning the mass.
Steel Media is a steel or stainless product that is cold formed
from wire, heat treated and then polished. Steel media are
available in many shapes, they have precise measurements
and wear very slowly with service life up to 10,000 hrs. The
steel media weighs approximately 300 lbs per cubic foot, so
machines have to be built especially to handle the weight.
The applications for steel are burnishing, cleaning, peening for strength, and light
deburring without media lodging in the part. Steel media processing has been
extensively used in industrial finishing and deburring applications.
MEDIA SHAPE
The medias shape is designed and picked to reach into areas of the parts being
processed that require work, while keeping out of other areas( holes, slots, etc.) to
prevent the media from lodging within the parts.
The various shapes also have process significance. Flat sided medias ( tri angles,tri
stars, and the ends of cones and cylindrical wedges) generate longer surface contact
time on edges for deburring and radiusing. Round medias ( balls, cylinders, cones)
generate a single point contact concentrating energy in one small point ( like a ball peen
hammer)producing more work in that area. Round media shapes are are used in
burnishing or part brightening. Sharp pointed media shapes can reach into difficult
areas but are also prone to chipping causing media chips lodging in small holes or slots.
Common preformed media shapes and there uses
Ceramic
Plastic
Ceramic
Plastic
Tri Angles avail in straight cut and 22 degree
angle cut. The angles provide greater
penetration into remote areas while the flats
have longer contact time on edges for
deburring and radiusing. Standard and most
popular shape for deburring. Its available in
ceramics and
Plastics medias.
Tri Stars are avail in 22 degree angle cut,
designed with reaching in a bit more remote
areas such as holes and slots than tri angles
but also keeping the flats for longer contact
time for deburring and radiusing. Its available
in ceramics and Plastic media.
Ceramic
Cylinders are avail in 22,45 and 60 degree angle cuts.
The cylinder is designed to improve finishes with the round single
point contact shape. The angles of cylinders are used to reach into
tight areas. The cylinder rolls well in mass finishing and is a good
choice for surface improvement in high energy centrifugal discs and
barrels. The cylinder is one of the first choices for part burnishing
and brightening. Its only available in ceramic media
Ceramic
Plastic
Cylindrical Wedge are used on a wide variety
of parts. They have a cylindrical surface that
mates well with concave surfaces. It also has
two flat surfaces that perform well on convex
surfaces, flat surfaces and edges. CW
combines the strong points of triangles and
cylinders to penetrate corners, slots and angles
The CW rolls well in machines, minimizes many
lodging problems and is a good shape for non chipping. Its available in ceramics and
plastic medias
Ceramic
Plastic
Cones have flats for deburring and round
areas for single point contact excellent for
finishing. Cones roll good in mass finishing and
is a good choice for parts without holes.
Cones finish slots well. Cones are one of the
first choices for surface refinement.
Its available in ceramics and plastic medias
Plastic
Tetrahedron (tets) have points to reach difficult areas and flats for
deburring, radiousing and extended surface contact. This is a good
choice for mixing with tri angles for exterior surfacing with hard to
reach areas. This shape is prone to some chipping of sharp points. It
is available in ceramics and plastic medias.
Plastic
Pyramids uses the many angles of flats to finish flat areas and
slots. Pyramids minimizes media lodging in holes. It finishes
fast because of its shape and because it creates a lot of voids
within the mass. Available only in plastic media
Plastic
Wedges is a uniquely designed shaped media that eliminates
many media lodging problems. While its configuration will
reach hard to finish inside corners, slots, and angles. This is
one of the only media shape that sharpens as it wears. A good
choice for complex machined parts. Only available in plastic
media
Ceramic
Ellipse are used for surface refinement of hard to reach areas.
Adaptable to many applications. Improves surfaces with
extended media life. Used on finishing multi shaped turbine
blades, heat sinks and slotted areas. Only available in ceramic
Media
C. MEDIA SIZE
Media size is an important factor in the selection of media for mass finishing.
Larger media generates higher energy because of the mass of each piece(like a larger
hammer delivers more energy to a nail) and the increased energy created by the voids
within the mass that it creates . Larger media cuts and finishes faster with higher wear
rates. Larger media suspends and supports larger parts.
Smaller medias hold more water/compound which assists in cushioning the part
creating less part on part damage. Smaller media have a gentler impact on the part
which results in longer process time cycles, better finishes, and less media wear.
Media sizing is also a factor with automated part unloading equipment utilizing
mechanical screening of media/part separation. Generally medias have to be a different
size (larger or smaller) than the part to utilize standard screening mechanical
separation.
The majority of mass finishing is accomplished with media sizes ranging between 1/4
inches to 2 inch. Burnishing medias ( brighting and cleaning) utilize smaller medias
ranging from 1/16” to 3/8” for best results. Smaller media under 3/8” cost more because
there is more labor and pieces per lb in its production, and media is sold by the lb.
D. Media Hardness
Media hardness is determined by the bonding agent. Ceramics are harder than plastics.
Ceramic media bondings will run between 45 to 65 rockwell hardness. Faster cutting
ceramic media are bonded softer and designed to wear faster exposing new cutting
abrasives elements. Medium cut medias are bonded harder than fast cut media.The
burnishing or brighting(porcelain) medias with no abrasive added are bonded the
hardest
and have extremely long wear rates. Ceramic bonding strength and hardness is
controlled mainly by the firing temp and dwell times within the kilns that harden them.
Plastic media bondings (synthetic or polyester) will run between o brinell (very soft) for
synthetic and 25-45 rockwell for polyester.
Harder medias can damage softer materials being processed. Harder formulations can
chip easier than softer medias becoming a problem lodging in small areas of the parts
and in sewage discharge.
3. COMPOUNDS
Soap compounds are very important to the mass finishing process. Compounds are
more often the success or failure of many processes. The mass finishing industry have
developed hundreds of compound formulations that accomplish
amazing results in many processes. Compounds developed
for mass finishing are concentrated and are generally mixed 1
to 2 oz. per gallon of water. Flow rates of compound/water
mixture run 1 to 2 gallons per cubic foot of the mass per hour
for vibratory systems and 7 to 15 per cubic foot of mass per
hour in high energy centrifugal disc systems. Small dense
media masses and clean running ceramic medias require less
soap/water flow than plastic medias.
Soap compounds accomplish the following
Cleaning the contaminations from the process parts and the media of; media sediment,
oils, dirt, oxidation, rust, and descaling, is the compounds function. The compound
holds the dirt in suspension allowing contaminates to be removed from the parts surface
and carried out of the system, just like the soap in a households cloth washing machine.
Maintaining the systems cleanliness keeps the finishing process stable and repeatable .
Inhibiting for rust and corrosion of parts while they are processed wet and keeping
them inhibited post process is very important. Its essential that mass finishing process
compounds have inhibitors in them. Maximum rust and corrosion inhibiting shelf life
after a mass finishing process is obtained by a secondary post process inhibiter spray
or dip.
Burnishing (Brighenting) of parts for or even brightening during deburring and surface
refinement applications is primarily a compound function. Each alloy of metals; alum,
brass, copper, steel, stainless or titanium etc) may require different surfactants that
bring up its maximum luster potential.
Lubricates and cushions the media and parts extending media and machine lining life
while eliminating part on part and media damage. Soap decreases media costs and
reduces process time.
Special applications such as heat treat or mill scale removal, accelerators for surface
refinement , and non keelator formulations for waste treatment systems.
Review of mass finishing process selection
The steps in selecting a mass finishing process is to determine:
1.The parts ( type, material, size)
2. The finish requirements of the part ( deburr, radius, surface finish, burnish, clean
Rinse, inhibit, dry, etc.)
3. The production rates of the part and flow thru the plant.
4. Labor available for the system
5. Capital available for the system.
6. What the part is costing currently to finish
7. Determine or eliminate various possible equipment required.
8. Send a number of parts to a finishing lab (usually the equipment manufacture your
considering) and have them finish the parts to recommend equipment and medias to
prove the process and production rates.
9, Then determine the equipment and then the finishing process costs.
DETERMINING MASS FINISHING PROCESS COSTS
A. How many parts per cubic foot can the system process
B. Media and compounds cost
C. Cost per part
A. How many Parts per cubic foot is determined by a measurement of volume and
an estamate of media to part ratio. Take the cubic inch of the parts and multiply it
times the media to part ratio and divide into cubic inches in a foot = parts per cubic
foot
1728
______________________________
= Number of parts per cubic foot
( parts L” x W” x H” ) x (media/parts ratio)
Media to part ratio is determined by the parts size, shape and weight. The media
protects the parts from damaging one another. Heavier,larger, sharp cornered parts are
more prone to part on part damage requiring more media to protect them which
increases the media to part ratio.
Below are estimates of required media to part ratio for various parts for mass finishing.
Increased media to part ratio increases protection but decreases parts per cubic foot.
Stampings, parts less than 9 cu/in
Parts requiring self unload
Castings with non critical surfaces
Machined parts
Parts requiring super surface refinement
Longer parts to keep from jack strawing
Larger parts with critical surfaces
Larger parts with sharp protrusions
Delicate parts that may tangle and damage
3:1 media to part ratio
3:1
“
4:1
4:1
“
5:1
“
5:1
6:1
7:1
8:1
Parts that cant touch will need compartmentizing
Example: Calculation of Parts per cubic with a 3:1 media to part ratio
Part is a small machined part that needs self unload
Media/part ratio estimate 3:1
Part size 3” x 4” x 2” = 24” total cu/in of the part
x 4 (3:1 Media/parts ratio) = 96 divided into 1728 = 18 parts per cubic foot
Example: Size machine required
Take the parts per cubic foot, parts production rate, process time cycle, parts production
flow, and you can determine the size of the equipment required.
at 18 parts per cubic foot if you need to produce 1800 parts per 10 hour shift at a 1 hour
process time you would need a 10 cu foot size finishing system.
B.Media and compound costs in mass finishing
MEDIA COSTS PER PART
Machines cu/ft x media weight per cu/ft x medias attrition rate per hour x % of hour
time cycle x cost of media per lb.( sold by the lb) divided by no of parts per cu/ft.
EXAMPLE 1 cu foot machine - Media weight 85 lbs cu/ft - attrition rate of .001 - 1
hour process time cycle - $1 per lb media cost - 10 parts per cu/ft.
EXAMPLE MEDIA COST PER PART 1 cu/ft machine size x media weighs 85 lbs per
cu/ft x hourly media attrition rate of .001 x 1 (hour) time cycle x $ 1.00 lb media
cost , divided by 10 parts running per cu/ft =
1 x 85 x .001 x 1 x $1
________________ =
10
MEDIA COST PER PART
COMPOUND COST PER PART
Machines cu/ft x .oz of compound used per cu/ft per hour x % of hour time cycle x $
cost per .oz - divided by number of parts per cu/ft
EXAMPLE 1 cu ft machine - 1 oz compound per cu/ft - 1 hour process time - $ 7 gal
or .06 .oz ( gallon price divided by 128 oz per gallon) - 10 parts
EXAMPLE COMPOUND COST PER PART 1 cu/ft machine size x 1 oz. compound
per cu/ft per hour x 1(hour) time cycle x .07 per .oz compound cost - divided by 10
parts running per cu/ft =
1 x 1 x 1 x $ .07
___________ = COMPOUND COST PER
10
PART
Media costing continued:
Information required for media costs:
Mass finishing media weight and hourly attrition (wear) rates per cubic foot
Media Type
Ceramic-polish
Ceramic med cut
Ceramic fast cut
Ceramic super fast
Ceramic high den.
Polyester plastic
Polyester high den
Synthetic plastic
Microbrite
Steel & Stainless
Weight Vibratory hourly attrition - High energy hourly attrition
cu/ft
Rates %
Rates %
85 lbs
85 lbs
85 lbs
85 lbs
120 lbs
65 lbs
100 lbs
50 lbs
110lbs
300 lbs
.0001
.005
.0075
.01
.01
.013
.015
.018
.0001
.0001
.0003
.015
.0225
.03
.03
.040
.045
.055
.0003
.0003
note: smaller medias 3/8” and under in size weigh approximately 15% more and
have 25% less attrition wear rates than stated above.
C. Total Mass Finishing Cost per part
MASS FINISHING COST PER PART WORKSHEET
HOURLY EQUIPMENT PAYBACK COST
Equipment investment______ divided by numbers of amortized years_______
divided by hours per year________
=
TOTAL EQUIPMENT HOURLY PAYBACK _________
______________________________________________________________________
HOURLY PROCESS COST
Equipment power cost_______ H.P. X .746 X .08 cents per KW =
_________
Media cost_____ lbs per load X____ *hourly attrition rate X ____Price/lb
_________
Compound cost_______.oz per hour X ______ cost per oz. =
_________
(Price per gallon divided by 128 = cost per .oz)
TOTAL HOURLY PROCESS COST
_________
______________________________________________________________________
PROCESS COST PER CYCLE
Total hourly process cost__________ + Equipments hourly payback X
% of hours per load___________ =
_________
Hourly labor rate________ X ________ % of hour of labor per load =
_________
TOTAL PROCESS CYCLE COST
_________
______________________________________________________________________
COST PER PART
_____Total Process cycle cost, divided by_____no of parts per cycle =
TOTAL COST PER PART
OVERVIEW OF MASS FINISHING EQUIPMENT AND MEDIAS
_________
Equipment
Vibratory
MEDIA
Ceramic media
Tub vibratory
Polish-Burnishing
Bowl vibratory
Medium cut
High Energy
Fast cut
Centrifugal disc
Light weight
Centrifugal barrel
High density
Magnetic spin finishing
Plastic media
Chemical high energy
Polyester
Spindle equipment
Synthetic
Drag machines
Random media
Alum oxide
Dry process media
Corn cob
Walnut shells
Wood pegs
Steel and Stainless

mass finishing technical8 - Metal and Composite Finishing Equipment

Transcription

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