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.