Understanding Drawdown Ratio (DDR) Scale

What Do 1:1 and 50:1 DDR Mean?

DDR (**Drawdown Ratio**) is a scale that represents the reduction in cross-sectional area of extruded material from the die exit to the final product.

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DDR Scale and Meaning

- DDR = 1:1 → The cross-section of the material remains the same after exiting the die. No stretching occurs.
- DDR = 2:1 → The material is reduced to half of its original cross-section.
- DDR = 10:1 → The material is drawn down to one-tenth of its original cross-section.
- DDR = 50:1 → The material is significantly stretched and reduced to 1/50th of its original size.

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How is DDR Calculated?
DDR is determined using cross-sectional areas or diameters.

Using Cross-Sectional Area:
DDR = (Die Exit Cross-Section) / (Final Product Cross-Section)

Using Diameters:
DDR = (D_d² - D_t²) / (d_cw² - d_bw²)
Where:
- D_d → Die exit diameter
- D_t → Guide tube diameter
- d_cw → Wire and insulation diameter
- d_bw → Conductor (wire) diameter

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DDR Scale and Application

DDR Range	Description
1:1 – 3:1	Minimal drawdown, suitable for thick-walled products.
3:1 – 10:1	Moderate drawdown, standard for many plastic extrusion applications.
10:1 – 50:1	High drawdown, used for lightweight, thin-walled products.
50:1+	Extreme drawdown, requires precise control to prevent material failure.

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Conclusion
- DDR = 1:1 → No reduction in size.
- DDR = 50:1 → Highly stretched and thinned material.
- The ideal DDR depends on the material type, extrusion speed, and final product requirements.