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.
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)
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 |
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.
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)
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 |
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.