2 McKee formula introduction
Type 0201 corrugated cartons (ie, conventional slotted containers RSCs) are the simplest and most commonly used shipping containers. The corrugated direction of this type of carton is usually parallel to the stacking force from top to bottom. The compressive strength of RSCs can be estimated by the McKee formula if the perimeter of the box is known, the edge pressure test value of the cardboard, the bending resistance of the cardboard, the ratio of the length to the width of the carton, and other factors:
In the formula: BCT is the compressive strength theoretical value (N) of the 0201 container; ECT is the edge pressure (cm) of the cardboard; Dx is the bending stiffness (N/cm) of the cardboard manufacturing direction; Dy the lateral bending stiffness of the cardboard (N /cm);BP is the perimeter of the box (cm).
By replacing the bending stiffness with the cardboard thickness, the McKee simplified formula with accuracy close to the original formula (1) but easy to use in terms of testing and calculation is obtained:
In the formula: BC is the cardboard thickness (cm).
If the value of the compressive strength required for the box is returned to equation (2), the board's edge pressure value (ECT) can be calculated and the appropriate board structure can be determined.
3 Calculate the edge pressure value from the ring pressure value
When inputting a new cardboard structure and using the ring pressure method as the calculation method, the TOPS Pro software obtains the edge pressure value (ECT) from the ring pressure value (RCF) by the following formula.
1) For three-layer corrugated cardboard:
A=(Rough Paper 1 RCF)+(Paper 2RCF)+(Paper RCF)×(Watt Retardation Factor)
2) For five-layer corrugated paper:
A=(Paper 1 RCF)+(Paper 2 RCF)+(Paper 3 RCF)+(Paper 1 RCF)×(Corrugated tension factor 1)+(Bond 2RCF)×(Corrugating factor 2) )
If the total mass per 92.9m2 (1 000ft2) paper is ≤ 38.6 kg (85 lbs), then: ECT = (A/6) × 0.8 + 12, otherwise, ECT = (A/6) × 1.27-6
4 Analysis of compressive strength of TOPS Pro carton based on McKee formula
The characteristics of the carton container in circulation are greatly affected by the environmental conditions it experiences. Some of these conditions, such as stacking time, relative humidity, etc., are difficult to change; others, such as tray packaging patterns, tray size, tray assembly gaps, and rough handling, can be determined by assembly.
In order to obtain carton properties, TOPS Pro uses a McKee formula to calculate compressive strength values ​​taking into account a range of structural factors and environmental factors.
Taking into account the structural factors of the carton, the correction value of the carton compressive strength is calculated as follows:
Where: TBCT is TOPS Pro carton compressive strength correction (N); SF is a form factor. It is related to the size of the box relative to the height; LWRF is the aspect ratio factor; HFF is the horizontal fluctuating factor. If non-vertical flutes are not selected, the value is 1. Otherwise, it is 0.9; PP is a printing factor. Related to the type of printing and the amount of printing.
Taking into account the environmental factor, the actual compressive strength of the carton is calculated as follows:
In the formula: BP is the actual compressive strength of TOPS Pro carton (N); FGF is the gap closure factor; HF is the humidity factor; STF is the stacking time factor; PSF is the tray interval factor; IF is the interlocking palletizing factor; OF is the excess tray factor and PS is the product support force (N).
(to be continued)
Type 0201 corrugated cartons (ie, conventional slotted containers RSCs) are the simplest and most commonly used shipping containers. The corrugated direction of this type of carton is usually parallel to the stacking force from top to bottom. The compressive strength of RSCs can be estimated by the McKee formula if the perimeter of the box is known, the edge pressure test value of the cardboard, the bending resistance of the cardboard, the ratio of the length to the width of the carton, and other factors:
In the formula: BCT is the compressive strength theoretical value (N) of the 0201 container; ECT is the edge pressure (cm) of the cardboard; Dx is the bending stiffness (N/cm) of the cardboard manufacturing direction; Dy the lateral bending stiffness of the cardboard (N /cm);BP is the perimeter of the box (cm).
By replacing the bending stiffness with the cardboard thickness, the McKee simplified formula with accuracy close to the original formula (1) but easy to use in terms of testing and calculation is obtained:
In the formula: BC is the cardboard thickness (cm).
If the value of the compressive strength required for the box is returned to equation (2), the board's edge pressure value (ECT) can be calculated and the appropriate board structure can be determined.
3 Calculate the edge pressure value from the ring pressure value
When inputting a new cardboard structure and using the ring pressure method as the calculation method, the TOPS Pro software obtains the edge pressure value (ECT) from the ring pressure value (RCF) by the following formula.
1) For three-layer corrugated cardboard:
A=(Rough Paper 1 RCF)+(Paper 2RCF)+(Paper RCF)×(Watt Retardation Factor)
2) For five-layer corrugated paper:
A=(Paper 1 RCF)+(Paper 2 RCF)+(Paper 3 RCF)+(Paper 1 RCF)×(Corrugated tension factor 1)+(Bond 2RCF)×(Corrugating factor 2) )
If the total mass per 92.9m2 (1 000ft2) paper is ≤ 38.6 kg (85 lbs), then: ECT = (A/6) × 0.8 + 12, otherwise, ECT = (A/6) × 1.27-6
4 Analysis of compressive strength of TOPS Pro carton based on McKee formula
The characteristics of the carton container in circulation are greatly affected by the environmental conditions it experiences. Some of these conditions, such as stacking time, relative humidity, etc., are difficult to change; others, such as tray packaging patterns, tray size, tray assembly gaps, and rough handling, can be determined by assembly.
In order to obtain carton properties, TOPS Pro uses a McKee formula to calculate compressive strength values ​​taking into account a range of structural factors and environmental factors.
Taking into account the structural factors of the carton, the correction value of the carton compressive strength is calculated as follows:
Where: TBCT is TOPS Pro carton compressive strength correction (N); SF is a form factor. It is related to the size of the box relative to the height; LWRF is the aspect ratio factor; HFF is the horizontal fluctuating factor. If non-vertical flutes are not selected, the value is 1. Otherwise, it is 0.9; PP is a printing factor. Related to the type of printing and the amount of printing.
Taking into account the environmental factor, the actual compressive strength of the carton is calculated as follows:
In the formula: BP is the actual compressive strength of TOPS Pro carton (N); FGF is the gap closure factor; HF is the humidity factor; STF is the stacking time factor; PSF is the tray interval factor; IF is the interlocking palletizing factor; OF is the excess tray factor and PS is the product support force (N).
(to be continued)
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