Difference Between Drawdown Ratio (DDR) and Draw Ratio Balance (DRB)

In the extrusion process, Drawdown Ratio (DDR) and Draw Ratio Balance (DRB) are two key concepts that determine how the material is shaped. However, they serve different purposes.

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1. Drawdown Ratio (DDR)
- Definition: DDR is the ratio of the cross-sectional area of the material at the die exit to the cross-sectional area of the final product.
- Formula:
DDR = (D_d² - D_t²) / (d_cw² - d_bw²)
or simplified:
DDR = (Die exit cross-section) / (Final product cross-section)
- Meaning:
  - If DDR = 1:1, the material remains unchanged after exiting the die.
  - If DDR = 10:1 or 50:1, the material is significantly stretched and reduced in thickness.
  - A very high DDR can cause material breakage.

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2. Draw Ratio Balance (DRB)
- Definition: DRB is the ratio of two drawdown ratios, ensuring that both the inner and outer surfaces of the extruded material are drawn evenly.
- Formula:
DRB = (D_D / d_cw) / (D_T / d_bw)
Where:
- D_D → Die cylinder diameter
- D_T → Guide tube (mandrel) diameter
- d_cw → Wire and insulation diameter
- d_bw → Conductor (wire) diameter
- Meaning:
  - DRB = 1 → The inner and outer surfaces are evenly drawn (ideal condition).
  - DRB < 0.9 → Material is under-drawn, causing concentricity issues.
  - DRB > 1.1 → Material is over-drawn, increasing the risk of tearing.
- Ideal DRB Range:
  - FEP and PFA: 0.9 – 1.15
  - ETFE: 1.04 – 1.07 (requires more precise control)

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Comparison: DDR vs. DRB

Feature	DDR (Drawdown Ratio)	DRB (Draw Ratio Balance)
Definition	Measures overall material reduction	Ensures even drawing of inner and outer surfaces
Purpose	Determines final product size reduction	Checks uniform stretching of material
Formula	DDR = (D_d² - D_t²) / (d_cw² - d_bw²)	DRB = (D_D / d_cw) / (D_T / d_bw)
Ideal Value	Varies by material (e.g., 1.5:1 – 100:1)	Should be close to 1 (0.9 – 1.15 recommended)
Low Value	Minimal stretching, thick product	Inner and outer layers are drawn unevenly
High Value	Thin material, risk of tearing	Outer layer overstretched, risk of tearing
Application	Measures general extrusion reduction	Controls insulation and tube concentricity

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Summary: DDR vs. DRB
✅ DDR measures how much the material is reduced in size. 
✅ DRB checks whether the inner and outer surfaces are drawn evenly. 
🔹 A high DDR means the material is significantly stretched. 
🔹 A DRB too high or too low means the inner and outer layers are drawn unevenly. 

Difference Between Drawdown Ratio (DDR) and Draw Ratio Balance (DRB)

In the extrusion process, Drawdown Ratio (DDR) and Draw Ratio Balance (DRB) are two key concepts that determine how the material is shaped. However, they serve different purposes.

---

1. Drawdown Ratio (DDR)
- Definition: DDR is the ratio of the cross-sectional area of the material at the die exit to the cross-sectional area of the final product.
- Formula:
DDR = (D_d² - D_t²) / (d_cw² - d_bw²)
or simplified:
DDR = (Die exit cross-section) / (Final product cross-section)
- Meaning:
  - If DDR = 1:1, the material remains unchanged after exiting the die.
  - If DDR = 10:1 or 50:1, the material is significantly stretched and reduced in thickness.
  - A very high DDR can cause material breakage.

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2. Draw Ratio Balance (DRB)
- Definition: DRB is the ratio of two drawdown ratios, ensuring that both the inner and outer surfaces of the extruded material are drawn evenly.
- Formula:
DRB = (D_D / d_cw) / (D_T / d_bw)
Where:
- D_D → Die cylinder diameter
- D_T → Guide tube (mandrel) diameter
- d_cw → Wire and insulation diameter
- d_bw → Conductor (wire) diameter
- Meaning:
  - DRB = 1 → The inner and outer surfaces are evenly drawn (ideal condition).
  - DRB < 0.9 → Material is under-drawn, causing concentricity issues.
  - DRB > 1.1 → Material is over-drawn, increasing the risk of tearing.
- Ideal DRB Range:
  - FEP and PFA: 0.9 – 1.15
  - ETFE: 1.04 – 1.07 (requires more precise control)

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Comparison: DDR vs. DRB

[table border=1]

Feature	DDR (Drawdown Ratio)	DRB (Draw Ratio Balance)
Definition	Measures overall material reduction	Ensures even drawing of inner and outer surfaces
Purpose	Determines final product size reduction	Checks uniform stretching of material
Formula	DDR = (D_d² - D_t²) / (d_cw² - d_bw²)	DRB = (D_D / d_cw) / (D_T / d_bw)
Ideal Value	Varies by material (e.g., 1.5:1 – 100:1)	Should be close to 1 (0.9 – 1.15 recommended)
Low Value	Minimal stretching, thick product	Inner and outer layers are drawn unevenly
High Value	Thin material, risk of tearing	Outer layer overstretched, risk of tearing
Application	Measures general extrusion reduction	Controls insulation and tube concentricity

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Summary: DDR vs. DRB
✅ DDR measures how much the material is reduced in size. 
✅ DRB checks whether the inner and outer surfaces are drawn evenly. 
🔹 A high DDR means the material is significantly stretched. 
🔹 A DRB too high or too low means the inner and outer layers are drawn unevenly.