Short answer: Underlay provides the foundation and density controls how closely the visible stitches are placed. They are separate settings, but they need to work together for the fabric, thread, stitch type and design size.

Underlay and Density Solve Different Problems

Underlay is sewn before the visible top stitching. It can stabilize the material, support edges and create a base for the top stitches. Density controls spacing in the visible satin or fill stitching. A design can have good density and poor underlay, or good underlay and excessive density.

Why More Stitches Do Not Automatically Fix Coverage

If embroidery looks weak, adding density may seem like the obvious solution. But the real problem may be fabric movement, missing support, stitch direction or the wrong construction for the object. Adding more stitches can make the garment stiff or increase puckering without fixing the original cause.

Fabric Changes Both Settings

Stretch fabric may need a controlled foundation and lighter top stitching. Stable material may need less support. Textured material may need a base that helps keep top stitches from sinking. This is why universal settings do not produce universal results.

Thread and Size Matter

Fine thread, standard thread, very small lettering and large filled areas occupy different amounts of physical space. The digitizer needs to consider the actual application rather than copying the same density and underlay from one design to another.

Learn Each Subject in More Detail

Embroidery Underlay

Learn center walk, edge support and why foundation stitching should match the garment and object.

Read the Underlay Guide

Stitch Density

Learn how stitch spacing changes coverage, stiffness and machine time.

Read the Density Guide

Also Review Pull Compensation

Underlay and density cannot be separated completely from compensation. Thread tension and fabric movement can change the final width and alignment of embroidered objects. Pull compensation helps the digitizer account for that change.

Continue Through Digitizing Fundamentals

Use this overview as the connection point between underlay, density, compensation, stitch direction and production quality.

Browse Digitizing Fundamentals

Sources and Further Reading

Technical statements on this page are supported by public manufacturer documentation where appropriate. The software is listed for educational and comparison purposes only. The order does not indicate that one program is better than another, since each software platform is designed for different users, workflows, and embroidery production needs.

MELCO DesignShop 12 Features and Education Videos Public Melco education covering stitch types, density, underlay, pull compensation, digitizing, grouping and sequencing.
MELCO Auto Density Public Melco explanation of density adjustment based on column width.
MELCO Performance Wear Embroidery Overview Public production guidance showing how fabric, backing, density and underlay interact.

Embroidery Underlay and Density Guide