Branching vs Coathanger Technologies in PVC Pipe Extrusion

Why die-head technology matters

In PVC pipe extrusion, it’s not enough to simply melt and push material through a die. The way the melt is distributed and compressed inside the die-head determines:

• Wall thickness uniformity around the circumference
• Weld line strength and overall pipe integrity
• Layer distribution in multi-layer pipes
• Material usage and the level of overweight
• Process stability when formulations or viscosity change

Choosing between a traditional coathanger-type die-head and a branching die-head directly affects all of these factors, and therefore production cost and pipe performance. 

What is coathanger technology?

In a conventional coathanger die-head, the molten PVC enters the die through a central inlet and is spread out through a tapered manifold that resembles an inverted coathanger. The manifold is designed to balance pressure and velocity before the melt is formed into the final shape.

In a conventional coathanger die head, hot PVC enters through the middle and spreads out into a channel shaped like an upside-down coathanger. This channel is designed to keep the flow before the melt is formed into the final shape.

This technology is widely used in the plastics industry, especially for flat products like films, sheets, and coatings. For circular pipes, however, this design can lead to:

• Flow paths of different lengths around the circumference
• Local variations in wall thickness and layer distribution
• Higher material consumption due to “safety” overweight
• Sensitivity to changes in melt viscosity or formulation

What is branching technology?

Rollepaal’s branching technology is specifically developed for the production of circular PVC pipes. Instead of distributing the melt from a single manifold, the flow is split into multiple symmetrical, short, round channels (branches) that feed the complete circumference.

Key design principles:

• Symmetrical branching: all flow paths have equal lengths, keeping layer thickness consistent around the pipe.
• Short, round channels prevent stagnation, reduce the risk of clogging, and make cleaning easy. 
• No restrictor gap needed: there is no requirement for a melt-flow restrictor with varying gap lengths around the circumference, so the die is largely independent of changes in melt viscosity. 
• Modular design: the same RMD die-head platform can be configured with single- or double-compression tooling and supports quick tool change.

In short, branching technology offers a modern, performance-driven alternative to traditional coat-hanger die-heads, delivering measurable savings and higher product reliability. The result is a die-head optimized for both multi-layer and solid-wall PVC pipes, enabling stable processing and significant material reduction. In many cases, weight savings of up to 10% can be achieved, delivering a return on investment in less than half a year. Below are the three key reasons to switch to branching: a clear technical and financial advantage.

1. Weight reduction

• Branching provides much more uniform wall thickness, eliminating the need for excessive over-weight.

• In real production, branching typically results in 3–4% material savings on solid-wall and multilayer PVC pipes.

• This reduction alone often leads to an ROI of less than 1.5 years, depending on pipe range, output, and material costs.  For larger diameters or high-volume production, the payback is even faster.

2. Even distribution of layers

Because branching uses symmetrical flow channels of equal length, every layer (inner, core, outer) follows the same path. This ensures:

• • Stable skin-core ratios, even with viscosity or formulation changes

  • Higher quality in foam-core and recycled-core structures

  • Less scrap caused by layer shifting or inconsistent distribution

3. Superior weld quality

Branching vs coathanger:

Where branching technology makes the biggest impact

Branching technology delivers the most value when you are:

• Producing pressure pipes that must meet stringent dimensional and performance standards
• Switching to multi-layer pipes with recycled core and high-quality virgin skins
• Working with foam core structures to reduce weight and material cost
• Running multiple formulations (K-values, stabilizers, recyclate blends) on the same line
• Looking to minimize changeover and cleaning time and maximize uptime

In these situations, traditional coathanger die-heads quickly reach their limits, while branching technology continues to deliver stable quality and predictable output.