Design of Cassava Chips Machine

Design of Cassava Chips Machine - This machine is used for slicing cassava with a certain thickness as needed. Sliced cassava is a feedstock or raw material from cassava chips. This machine uses some cutting blade mounted an angle on the blade holder (disc). Slicing process occurs when the spinning blades and cassava move straight towards the knife. Slicing process produces cassava piece shape with a thickness that can be adjusted through the depth of the blade. A more complete description and specifications of this machine can be seen in a previous article titled Cassava Chips Machine by Planer Cutting System.

Read more: Description of Cassava Chips Machine

In this article I will explain how to design of cassava chips machine. Design process begins by calculating the power requirement for cassava cutting process. The power will be a reference in choosing an electric motor. Having chosen the type of electric motor, the next process is to calculate the strength of the machine parts according the machine construction. In this post, the calculation of the strength and dimensions of the machine parts are limited only to the calculation of cutting blade strength.

Power requirement for cassava cutting process 

The electric motor is a power supply to drive the entire system dynamic of cassava chips machine. Advantages of electric motors compared to other types of resources for electrical energy easily available and practical for small-capacity machine. Selection of the electric motor based on the calculation of the cutting load.

The cutting process occurs when the cutting force is greater than the cutting load requirement. Cutting load derived from the cassava ruptures strength. Cassava ruptures strength is ability of cassava to withstand the cutting forces provided by the cutting blades. The greater ruptures strength of cassava, the cutting load will be even greater. So that the force required by the cutting blade becomes larger in order to cut the cassava.

Besides cassava ruptures strength, there are other factors that affect of the cutting load such as the cassava diameter and number of cutting blades. So that the cutting load of cassava can be calculated with the following formula:

Note:

F = Cassava cutting load (Kg)

σ = Cassava ruptures strength (mN/mm2)

i = Blade number

d = Cassava diameter (mm)

g = Gravity (m/s2)

The total forces requirement in the cutting process consists of cutting forces and frictional forces. The cutting forces which received cassava force of blade movement during cutting process. The frictional force is the force that inhibits the movement of the blade when the cutting process due to the thrust of cassava to feed. Friction is occurs between cassava with blades spinning disc.

Cutting force is influenced by the angle blade and the cutting load. Angle blade will also affect the sharpness of blade, the sharp cutting blades will cut the smaller force is needed, but the life time blade becomes lower. Therefore, it is necessary to design the right angle of blade so that the required cutting force as small as possible with a higher life time.

Based on many references of the blade, blade angle ideal range is 20 degree. If the cutting load already known on the previous formula, then the blade cutting forces can be calculated with the formula;

Note:

F_C = Blade Cutting Force (Kg)

F = Cutting Load (Kg)

α = Blade Angle (20 degree)

Frictional force caused by the thrust that form the normal force perpendicular to the friction area of cassava. The driving force comes from pressure given to cassava in order to move towards a spinning cutter blade. On cassava chips machine, the pressure cassava assigned manually by hand, so the pressure tend to be constant. The pressure must not be less than the blade axial force, because it will cause unstable slice thickness. The pressure must not be greater than the cassava ruptures strength, because it will cause a rupture.

If the coefficient of kinetic friction between the cassava with a disc blade is µ, the friction forces that occur are:

Note:

F_F = Friction force (Kg)

P = Cassava driving force (Kg)

µ = coefficient of kinetic friction

The total force requirement to the cassava cutting process is a tangential force consisting of a cutting forces and friction forces, formulated as follows:

Note:

F_T = Total force requirement (Kg)

F_C = Blade Cutting Force (Kg)

F_F = Friction force (Kg)

Having in mind the total force required for the cutting process of cassava, the force requirement can be converted into units of power because the force is the tangential force generated from the electric motor rotation. In general, the power requirement for the cutting process of cassava chips machine can be calculated using the formula:

Note:

P = Power Requirement (Kw)

T = Torque (kgmm)

n = Blade speed (rpm)

The torque on the blades can be calculated using the formula:

Note:

T = Torque (kgmm)

F_T = Total force requirement (Kg)

R = Radius of blade position (mm)

Design of the cutting blade strength

The cutting blade strength of the cassava chips machine is located at the tip of blade, so that the blade tip must always be sharp in order to retain the ability to cut cassava well. Cutting ability will decrease if the blade tip experiencing torpor due to frictional forces and cutting forces. Bluntness caused the blade tip isn’t able to withstand the frictional forces and cutting forces. So that the blade does not experience the bluntness, the tip of blade should be made radius.

Frictional forces and the cutting forces are working continuously on the cutting blade will cause the stress at the blade tip. Cutting blade strength is the ability of cutting blades to withstand the stress so as not to cause wear and tear. Cutting blade has a good strength if the allowed stress for the blade material is greater than the maximum stress. The maximum stress of cutting blades can be calculated using the formula:

Note:

σ = Maximum stress (Kg/mm2)

F_C = Blade Cutting Force (Kg)

F_F = Friction force (Kg)

A = Area of the blade tip (mm2)

Area of the blade tip can be calculated using the formula:

A=2.r.l

Note:

A = Area of the blade tip (mm2)

r = Radius of the blade tip (mm)

l = Length of the blade tip (mm)

Cutting blades on the disc is clamped by the clamp fastened with two screws. Disc and clamp gets a load in the direction of the x-axis and y-axis of the cutting forces and frictional forces. The load was detained by two bolts. Force on the x-axis direction resulting tensile force on the bolt. Force on the x-axis direction is equal to the normal force of blade.

F_x = N

Force on the y-axis direction resulting in shear forces on the bolt. Force on the y-axis direction of the same with a blade cutting forces and frictional forces together.

F_y = F_C + F_F

Once known force on the x-axis direction and forces on the y-axis direction, then we can calculate the strength of bolt which binds cutter knife.

That is a description about the Design of Cassava Chips Machine. If you find misconceptions in this post, please provide the correction in the comment box. If you want to know more details about cassava chips machine can be seen in a previous article titled Cassava Chips Machine by Planer Cutting System.

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Design of Paper Shredder Machine

Design of Paper Shredder Machine - This machine is used to crush pieces of paper, especially A4 paper HVS document type, maximum paper weight of 80 gms and a maximum of 10 sheets per cycle. This machine uses a knife crusher is a kind of zigzag blades capable of cutting the longitudinal and transverse directions simultaneously. A more complete description of this machine can be seen in a previous article entitled paper shredder machine by zigzag cutting system and more detail of specification can be seen in an article specification of paper shredder machine. (Read more: description of paper shredder machine) (Read more: Specification of paper shredder machine)

In this article I will explain how to design of the paper shredder machine. The design process begins by calculating the power required for the cutting process. The power will be a reference in choosing the electric motor. After determining the electric motor, the following design process is the calculation of machine parts according to the concept and construction design. Base on description of the paper shredding machine, we can determine what parts of machine must be calculate dimension and strength.  Therefore, part design of paper shredder machine is spur gear transmission, helical gear transmission and main shaft.

Shredder Blade Calculation

The cutting process will occur if cutting forces on each shredder blade exceeds the tear strength of the paper. Cutting forces required on each shredder blade are:

Note:
Fi    = Cutting Force per Blade (Kg)
KS   = Tear Strength of Paper (mN)
S     = Max Paper Load (Sheet)
g     = Gravity (m/s2)

Tear strength of paper can be seen in the paper specification for HVS document type of paper.

The cutting force required to crush a paper is influenced by the number of blade and the number of blade cutting edge. So the cutting forces for vertical and horizontal direction can be formulated as follows:

Note:
F1   = Cutting Force for Vertical Direction (Kg)
F2   = Cutting Force for Horizontal Direction (Kg)
Fi    = Cutting Force per Blade (Kg)
i      = Number of Blade
k     = Number of Blade Cutting Edge

Power Requirement for Paper Shredder Design

The power required to crush a paper is influenced by torque and speed of blade. Power Requirement for cutting process can be calculated by formula:

Note:
P   =  Power Requirement (Kw)
T    =  Torque (kgmm)
n    = Blade speed (rpm)

Torque in the blade occurs due to cutting force in the vertical cutting direction (F1) and the the horizontal cutting direction (F2), so the total torque in the blade can be calculated by formula,

Note:
T     =   Torque (Kgmm)
F1   =   Cutting Force for Vertical Direction (Kg)
F2   =   Cutting Force for Horizontal Direction (Kg)
R1   =   Radius of blade on F1 point (mm)
R2   =   Radius of blade on F2 point (mm)

Machine Part Calculation for Paper Shredder Design

Based on the machine construction is described in the article paper shredder machine, there are some critical part must be calculated its dimensions and strength. The machine parts are main shaft, spur gear and helical gear.

Main Shaft Design

Main shaft is the supporting shaft for shredder blade. On the shaft, there is a cutting force on each shredder blade whose value according to the results of previous calculations (cutting force for each blade = Fi). The cutting forces will cause the bending load on the shaft. Main shaft also receives a torque that is distributed by the gear transmission. Therefore the main shaft receives a bending load and torque loads simultaneously. Main shaft calculation as it can use the existing formula in the article torque and bending load of shaft together. (Read more: shaft design)

Spur Gear Design

Paper shredder machine uses two pairs spur gear. The first of spur gear is used as a gear drive for the shredder blade. The spur gear serves to make the shredder blade right and left rotating at the same speed but in opposite directions.  The second of spur gear is used as gear reducer which serves to reduce a rotation by gear ratio is 1/8. Its ratio is too high, so spur gear transmission system is divided into two parts, namely the first stage spur gear by gear ratio is 1/4 and the second stage spur gear by gear ratio is 1/4. Spur gear calculation for determined spur gear dimension and strength can use the existing formula in the article calculation of spur gear dimension and strength with reference to the power requirement and the speed of standard motors. (Read more: spur gear design)

Helical Gear Design

Paper shredder machine uses a helical gear as a gear reducer of the electric motor. Helical gears have the ability to withstand the radial and axial force so it is good if connected directly to the high speed motor. This machine is fitted helical gear using a ratio of 1/5. Helical gear calculation for determined helical gear dimension and strength can use the existing formula in the article calculation of helical gear dimension and strength with reference to the power requirement and the speed of standard motors. (Read more: helical gear design)

That is a description about the Design of Paper Shredder Machine. If you find misconceptions in this post, please provide the correction in the comment box.

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Heat Treatment Furnace Design

Heat Treatment Furnace Design - Heat treatment furnace is a type of furnace that is used to provide a heat treatment at a work piece such as normalizing, tempering, annealing, hardening, hot forming, stress relieving, etc. The heat required for the heat treatment process varies depending on the type of material and heat treatment processes that need. In general, heat treatment furnace has a temperature between 400 to 1200‘C.

Generally, the design of the heat treatment furnace includes the calculation of power requirement, wall furnace design, heater design, determined of thermocouple and thermocontrol, design of boogie system and door system. But in this post is only described about estimated energy and power requirement.

If you want to design a heat treatment furnace, you must be know about user requirement are:

• Maximum Temperature, the temperature is very influential in the design of furnace because it will be based on calculation of power requirement, heater design, wall furnace design, and determined of thermocouple and thermo control.
• Work piece material and heat treatment process, if the maximum temperature unknown, you can see the charts or the tables of material temperature. An example of a table for the material temperature in VCN-150, VCL-140 and EMS-45 (standard Bohler) is displayed below.

• Furnace capacity includes the volume of the furnace chamber and the weight of material to be processed. As well as the temperature, furnace capacity will also be based on calculation of power requirement and wall furnace design.
• Heating time target and the available power. Time and electric power have a relationship of mutual influence. The goal faster heating time, it takes more power, and otherwise.

Estimated energy requirement for the heat treatment furnace

If the data is known, you can calculate the energy needed to heat the furnace. At the time of furnace work, the heater element will heat the air in the furnace chamber. The hot air will be absorbed by the furnace walls and work piece in the furnace chamber. Therefore, the total energy required to heat the furnace is:

Note:
Q_R   = Energy Requirement (Joule)

Q_m   = Energy for Work piece Heating (Joule)

Q_a   = Energy for Air Heating (Joule)

Q_w   = Energy for Heat Storage (Joule)

The energy to heat the workpiece is calculated on the basis of the heat capacity that can be received by the workpiece on a specific temperature change. Each material has a different specific heat capacity. Here is a table of the specific heat capacity of certain specified materials.

If the initial temperature of workpiece is T1 and heated to a temperature T2, the energy required for heating the workpiece can be calculated by the following equation:

Note:
Q_m   = Energy for work piece heating (Joule)

m     = Mass of work piece (kg)

c_m    = Specific heat capacity of work piece (Joule/kg ^oC)

T₁    = Initial temperature (^oC)

T₂    = Final temperature (^oC)

Energy for air heating is the energy used to heat the air in the furnace chamber. If the initial air temperature is T1 and heated to a temperature T2, the energy required for heating air can be calculated by the following equation:

Note:
Q_a   = Energy for air heating (Joule)

V_a    = Air volume (m³)

C_a   = Air heat capacity is 1200 Joule/m^{3 o}C

T₁    = Initial temperature (^oC)

T₂    = Final temperature (^oC)

Heat storage is heated air that is absorbed by the furnace wall. The furnace wall function is resist the heat in the chamber. Therefore, the furnace wall is made of a material having a thermal conductivity which is very low such as firebrick, insulating bricks, ceramic fiber, calcium silicate and rockwool. Although able to withstanding the heat, the furnace wall can still absorb heat depending on the material heat capacity used for the furnace wall. Then, the value of the heat capacity of the furnace wall for some materials indicated.

Energy required to replace the heat absorbed by the furnace wall is by the following equation:

Note:
Q_w   = Energy for heat storage (Joule)

V_w   = Volume of wall furnace (m³)

C_w   = Heat capacity of wall material (Joule/m^{3 o}C)

T₁    = Initial temperature (^oC)

T₂    = Final temperature (^oC)

If ‘L’ is the furnace length, ‘W’ is the furnace width and ‘H’ is the furnace height, so volume of the furnace wall is:

 

Estimated power requirement for the heat treatment furnace

The power required to heating process in the furnace chamber for on the time is by following equation:

Note:
P_R     = Power requirement (Watt)

Q_R     = Energy requirement (joule)

t         = Time heating (sec)

Determining the electric power to be greater than the power requirement or divided by the efficiency of the furnace so that the heat generated on time. Furnace efficiency is regarding the heat loss that occurs in the furnace chamber.

That is a description about Heat Treatment Furnace Design on the topic of energy and power requirement estimated. Other topics related to Heat Treatment Furnace Design  will be described in other post like the wall furnace design, heater design, determined of thermocouple and thermocontrol, design of boogie system and door system.

Furnace calculation formula and table are reference to the handbook of Heat Transfer by Holman and Technical Bulletin by Applied research services.

If you find misconceptions in the furnace calculation, please provide the correction in the comment box.

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Belt Conveyor Design: Capacity, Power Required and Pulley Size

Belt Conveyor Design: Capacity, Power Required and Pulley Size - Conveyor used to move material from one location to another as needed. Belt conveyor is of a type which uses a belt as a support material which is driven by motor and other components of the conveyor. Belt conveyor can be used to carry unit load and bulk load in an upright position or inclination angle.

Several parameters are used in the calculation of the conveyor belt that the capacity, power requirement and pulley size.

Belt conveyor capacity in upright position

Belt conveyor capacity is the amount of material transported tons per hour (tph). The conveyor capacity in upright position may be formulated as follows:

Note:
Q = Conveyor Capacity (tph)
A = Cross-sectional area (m2)
v = Belt velocity (m/min)
γ = Material density (Ton/m3)

Cross-sectional area is belt area which formed by tension bracket and angle of surcharge. Value of cross-sectional area is affected by angle of through, belt width and angle of surcharge, as indicated in the following table.

Belt conveyor capacity in angle inclines position

Note:
k = Inclination Reduction Rate

Value of Inclination Reduction Rate is indicated in the following table.

Power requirements for belt conveyor

Power required to drives the belt that transports the transfer material. Power requirement (P) calculated according to the effective force belt (Fe) with the following formula:

Note:
P = Power Requirement (Watt)
Fe = Effective Force (N)
v = Velocity (m/s)

Effective Force is calculated by multiplying the weight of components on the conveyor (material, conveyor belt and drum pulley) with the gravity and coefficient of friction with the following formula:

Note:
Fe = Effective Force (N)
µR = Coefficient of friction
g = gravity (m/s)
M = Material weight (kg)
Mb = Belt weight (kg)
Mr = Drum pulley weight (kg)

The coefficient of friction depends on the type of the support belt and pulleys are used as shown in the following figure.

Material weight (M) is calculated based on the volume of the multiplication with the density of the material or to the following formula:

Note:
M = Material weight (kg)
A = Cross-section area (m2)
L = Conveyor Length (m)
γ = Material density (kg/m3)

Determined of pulley size for belt conveyor

Pulley size is closely related to the speed of the conveyor. In the design of pulley, the minimum diameter of pulley can be calculated by the formula:

Note:
Dm = Minimum diameter of pulley (mm)
F = Maximum Force (N)
C2 = Correction factor 2
B = Belt Width (mm)
ß = Pulley angle (degrees)

The value of correction factor 2 as a function of the pulley as in the following table.

Maximum force (F1) is a multiplication factor between the effective forces (Fu) with a correction factor pulley 1 to the following formula:

Note:
F = Maximum Force (N)
Fe = Effective force (N)
C1 = Correction factor 1

The value of correction factor 1 as a function of the pulley as in the following table.

That is a description about Belt Conveyor Design: Capacity, Power Required and Pulley Size. If you find misconceptions in the belt conveyor formula, please provide the correction in the comment box.

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Dust Collector Design: Air Flow, Static Pressure and Power Fan

Dust Collector Design: Air Flow, Static Pressure and Power Fan - Dust collector is a dust suction or smoke causing air pollution from industrial processes such as melting material, welding, screening the flour, material falling from conveyor to another conveyor and several other processes important applications. In the dust collector, a dirty air filter will separate dust and air. Dust will enter the shelter, while the air out of the plant so that it can cope with air pollution. (If you want to know more about definitions, functions, principles and any types of dust collector, read more: What is a dust collector)

Dust collector can clean the air of many sources of dust and smoke, by performing right calculations will be known air flow needed to suck the dust. In this article I will explain how to design of dust collector system, especially on the calculation of static pressure and air flow required so that can know the power fan of dust collector. As for the other part calculation, I will describe in the next article.

Calculation of Air Flow for Dust Collector Design

Air flow is the volume of air necessary for sucking the dust in the suction area. We must decide a suction area before calculate the air flow. Suction area is the spherical zone which can reach air suction. The outer end of the ball is an area with a minimum speed of the air to suck the dust. Over the suction zone, the greater the volume of air flow necessary. We must put a suction area in place that has the greatest potential for dust presence. If the source of the dust is in a remote part of the intake would be more effective if we divide it into several sections.

Air flow in the suction area can be calculated by the formula:

Note:

Q_i      = Air Flow of Suction Area (m3/hour) 

V_min   = Air Speed Minimum m/s) 

A       = Wide of Suction Area (m2)

d        = Diameter of Suction Area (m)

Value of the air speed least for sucking the dust is depending on the type of dust, the dust density and size of dust particles.

If the dust collector is used to suck the dust at a certain point in the suction zone, the air flow of the dust collector is the sum of the air flow in each suction area.

Note:

Q_t   = Total air flow of Dust collector 

Q₁   = Air Flow in first area

Q₂   = Air Flow in second area

etc.

Calculation of Static Pressure for Dust Collector Design

Static pressure is a loss due to the air flow pressure pickup area to exit the dust collector system. The pressure loss can occur in the suction, pipe duct, elbow and cyclone. Calculation of static pressure refers to duct size.
If the duct is used in the form of a tube, the diameter of ducting pipe can be determined by the formula:

Note:

d     = Ducting pipe diameter (m)

Q_i    = Air Flow of Suction Area (m3/hour) 

v     = Air Speed in the duct (m/s)

Duct in the adjacent suction area must be combined in order to be more effective, as indicated below:

Size of conduit ducts 1 and 2 are calculated using the above formula with sufficient air flow of each suction area. Regarding the size of the tubes 3 is calculated by the formula:

Duct size to the inlet of the dust collector is calculated by the formula:

Static pressure of the dust collector is a number of static pressure at any point of the possible loss of pressure calculated with the following formula:

Static pressure in the suction area or free entrance

Static pressure in the straight duct

Static pressure in the elbow duct

Static pressure in the cyclone, its value determined is 800 Pa.

Note:

ΔP = Static Pressure (Pa)

v     = Air velocity (m/s)

λ     = Duct friction

l      = Pipe length (m)

d     = Pipe diameter (m)

γ     = Air density (kg/m2)

g     = Gravity (m/s2)

Calculation of Power Fan for Dust Collector Design

Calculation of power fan can use the following formula:

Note:

P     = Power Fan (kW)

Q    = Total Air Flow of Dust collector 

ΔP  = Static pressure (Pa)

η     = Motor efficiency

If a fan using a standard factory specifications, then you only need to give the data of air flow and static pressure for fan supplier and they will decide its fan.

That is a description about the Dust Collector Design: Air Flow, Static Pressure and Power Fan. If you find misconceptions in this post, please give correction in the comment box.

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