Reduce manufacturing costs with advanced foam dispensing process
The challenges of curved and customised lines
Adapting to new and disruptive trends in window manufacturing and sealing requires an increasingly less labour-intensive process. The trend that is now in vogue is the use of smaller diameter window shapes (half circles, full circles, ovals and even omega signs). While these are attractive, they can be difficult to produce.
A key part of the window manufacturing process is linear bending, hollow extruded plastic tubes that serve as the inner frame of a finished window. Linears hold the glass in place so that the outer frame can be secured to the inner linear frame.
The traditional, labor-intensive process required heating the hollow lineals in a kiln for a number of minutes. The operator removes the parts from the furnace and inserts a preheated flexible rubber wedge that matches the track opening for the specific linear cavity. Linear parts can have multiple hollow tracks and a snake is inserted into each. These rubber snakes are actually made of a precision machined material that can cost up to 12,000 per set. Their lifespan is usually not very long, as they are continually going through a heating and cooling process that weakens them.
The lines are then placed on a heated metal table where operators use pins inserted into the table for support as they slowly bend the line into the desired shape. The manual system results in gaps in the seal and the plastic liner can warp if not bent correctly. This twisting ruins the product and creates waste, because the linear will not properly seal the glass. It also results in wasted time, effort and heating costs. The labor-intensive process is not only costly, it is also quite time-consuming.
U.S. Manufacturer Seeks Better Solution for Producing Custom Linears
A major window manufacturer was using this time-consuming manual method to bend linear elements for custom windows. They were looking for a way to improve the process because the excessively slow production cycle could not meet the company's need to increase production to meet market demand.
This manufacturer approached a local distributor to find a different way to fill the beads, and the distributor presented the challenge to Graco, which develops modular and configurable systems for polyurethane processing.
Graco began by examining the material that formed the foam filler. The window manufacturer had been working closely with a polyurethane foam manufacturer who recommended a formula that would blend well, process easily at a reasonable cost and offer adequate density to provide support when bending without adding significant weight. The material's formula was specifically designed to react and cure over a period of time, rising and filling the linear from bottom to top, going from liquid to solid.
Graco worked with the foam manufacturer to further refine the appropriate medium for this process, including collaboration to obtain chemicals with satisfactory density, mixability and processability.
Success Required Rigorous Material Testing
Graco' s Advanced Fluid Solutions (AFS) team conducted research and testing at Graco's Ohio laboratory facility. They adjusted the additives in the base polyol, changing the ratio to achieve the desired density for the finished foam. They also tested a variety of guns to determine the best gun for the process. The AFS team continued to work with the foam manufacturer to adjust the material several more times until they finally arrived at a successful formulation.
Based on the new formulation, Graco configured the system. They recommended the use of a hydraulic fixed ratio (HFR) system, in which two materials are mixed under a high-pressure impact, forcing them to become a single liquid. After the liquid is injected with a specialized gun, it begins to react in a matter of 8 to 10 seconds, first creaming, then gelling and finally turning into solid foam.
The equipment selected includes the Graco HFR™ (heated) metering system, equipped with a Fusion® air purge gun and pour nozzle adapter, which provides high-pressure impact mixing and dispensing. Two separate liquids are pumped and mixed at the time of injection into the patented gun and injected into the linear cavities. The foam density formulation allows the linear to be completely filled, providing excellent support during folding without adding significant weight.
Improved Capabilities and Reduced Production Time
Graco took the system to several window manufacturing facilities for production testing, where it was used to inject foam into linear lines for bending in simulated production tests. The result showed that manufacturers were able to bend the linear lines into smaller, more concise radius curves. The foam-filled linear lines have no voids or gaps in the cavities, giving them excellent internal support of the line during bending.
In addition, while the original window manufacturer began the project looking for a better way to bend the linear lines, they obtained a solution that reduces production time by 50 percent and provides a very significant waste reduction.
The process has now been adopted by several other window manufacturers around the world.