Blow Up Ratio Calculator

Select Calculation Method:

Use Bubble Diameter Use Layflat Width

Bubble Diameter (

D_{b}

Layflat Width (

W

Die Diameter (

D_{d}

1. What is the Blow Up Ratio Calculator?

Definition: The Blow Up Ratio (BUR) Calculator determines the ratio of the bubble diameter (or final tube diameter) to the die diameter in blown film extrusion, a key parameter in plastic film manufacturing. BUR indicates the increase in the bubble diameter over the die diameter, affecting the thickness of the melt after blowing.

Purpose: Used by manufacturers in film extrusion to optimize film thickness, strength, and clarity, ensuring consistent quality in products like packaging and industrial films.

2. How Does the Calculator Work?

The calculator uses the following formulas, as shown in the image above:

$BUR = \frac{D_{b}}{D_{d}}$

$BUR = \frac{0.637 \times W}{D_{d}}$

Where:

$D_{b}$ : Bubble diameter (or final tube diameter, in mm, cm, or inches);
$W$ : Layflat width (in mm, cm, or inches);
$D_{d}$ : Die diameter (in mm, cm, or inches);
$BUR$ : Blow Up Ratio (dimensionless).

Since it’s difficult to use calipers on the bubble to measure its thickness directly, the layflat width formula provides a more practical approach.

Steps:

Select the calculation method: Use Bubble Diameter or Use Layflat Width.
If using bubble diameter, enter the bubble diameter ( $D_{b}$ ) and die diameter ( $D_{d}$ ), and select their units. The calculator converts to millimeters and computes $BUR = \frac{D_{b}}{D_{d}}$ .
If using layflat width, enter the layflat width ( $W$ ) and die diameter ( $D_{d}$ ), and select their units. The calculator converts to millimeters and computes $BUR = \frac{0.637 \times W}{D_{d}}$ .
Results are formatted (scientific notation for values < 0.001, otherwise 4 decimal places) and displayed for BUR, bubble diameter, layflat width, and die diameter.

3. Importance of Blow Up Ratio

The Blow Up Ratio is critical for:

Film Thickness: Higher BUR reduces film thickness, affecting strength and durability.
Mechanical Properties: Influences tensile strength and clarity through biaxial orientation.
Production Efficiency: Helps optimize material usage and minimize waste in extrusion processes.

4. Using the Calculator

Example 1: Calculate BUR using a bubble diameter of 300 mm and a die diameter of 150 mm:

Bubble Diameter ( $D_{b}$ ): 300 mm;
Die Diameter ( $D_{d}$ ): 150 mm;
BUR: $\frac{300}{150} = 2.0000$ .

Example 2: Calculate BUR using a layflat width of 471.2 mm and a die diameter of 150 mm:

Layflat Width ( $W$ ): 471.2 mm;
Die Diameter ( $D_{d}$ ): 150 mm;
BUR: $\frac{0.637 \times 471.2}{150} = \frac{300.1544}{150} \approx 2.0010$ .

5. Frequently Asked Questions (FAQ)

Q: How accurate is the Blow Up Ratio calculation?
A: The calculation is mathematically precise using the formulas $BUR = \frac{D_{b}}{D_{d}}$ or $BUR = \frac{0.637 \times W}{D_{d}}$ . Rounding errors may occur due to formatting to 4 decimal places or scientific notation for small values.

Q: Why can’t I enter negative values for diameters or width?
A: Diameters and widths must be positive as they represent physical measurements of the bubble, die, or film.

Q: Why use layflat width instead of bubble diameter?
A: Measuring the bubble diameter directly with calipers is challenging due to its shape and flexibility, so layflat width provides a more practical measurement for calculating BUR.