Volume 36, Number 2, February 2001

Fenestration Focus


Today's Special
Maximizing Standard Insulating Glass Production

by Tim Harris

In the early-and mid 1980's, windows of special shapes and sizes were were somewhat the exception to the rule. Since the demand was low and it normally did not disrupt production or shipment orders, most window manufacturers could run these types of insulating glass units at their convenience. Today, however, a high percentage of homes sold include specials—a special, in this article will be defined as any insulating glass unit (IG) that does not have four 90-degree corners. This would include IG units with a radius side, those with only three sides or those with more than four sides. Some companies will include picture and patio units into this category in an effort to better optimize the main line rectangles

The increase in demand for specials creates a challenge to the IG manufacturer as to how to best optimize the insulating glass production line efficiencies. Our company can help you manufacture your insulating glass specials in a productive, cost-effective and high-quality manner. The concept of using flexible insulating glass spacer systems (FISS) for specials to support main line productions has been used successfully for more than 15 years.

By removing specials from your main line production and incorporating FISS into your specials production, I believe that you will see a significant increase in units per man hour (UPMH). To calculate UPMH, reference the formula below. We have done several studies comparing FISS with conventional systems and have found a significant increase in UPMH and a decrease in special IG unit cost when converting specials production to FISS.

Formula UPMH: total number of units produced in a given time divided by the total number of man-hours it takes to produce these units.
Let’s take a look at the various areas, which may be affected by this change, and see how it impacts each process.

1. Inventory:

In today’s competitive market place excessive or numerous parts add to increased inventory cost. When using conventional metal spacer bar systems you could have four or more separate parts in inventory (excluding glass). With FISS you may only need one part (excluding glass). You will undoubtedly gain valuable floor space.

2. Frame preparation:
Conventional spacer bar systems will entail cutting the bars to length, bending bars if necessary, drilling holes in the spacer bar for muntin end pin location, desiccant filling, corner key insertion and frame assembly. You need to assure proper sizing of the bar to glass to accommodate an acceptable moisture vapor path (MVP) and to ensure a consistent sightline. With FISS you will only need to apply the material to the glass with a hand tool or by hand, which gives you correct inset, sightline and MVP.

3. Muntin pattern insertion:
Conventional spacer bar systems will insert the pre-fabricated muntin pattern into the spacer frame and insert the end pins into the holes in the spacer bar. This assembly is then set onto the one lite and then the second lite is placed on top. With FISS you insert the muntin pattern into the lite with the FISS applied and affix the muntin to the FISS with the appropriate hardware. You then complete the unit by placing the second lite on top.

4. Sealing the IGU:
Conventional units can be sealed using either hand-gunning or auto-gunning equipment. Depending on the sealant used, you may or may not be able to use these units immediately. With FISS there are specific recommendations for each on how to seal the units. Most FISS can be used immediately after being sealed. One area, which needs to be addressed, is that of sight line appearance/differences. Most of the FISS colors closely match existing spacer systems or desiccated matrix. Certainly when you lay the two IG systems side-by-side there is a visual difference. Due to the location in homes of specials, the difference in appearance between the FISS and conventional bar system is usually only noticeable to the IG manufacturer. Most specials are located above another window unit or above entryways, both locations make the sightline less noticeable than eye level windows. This makes it difficult to observe the subtle appearance differences between the two IG system sightlines. You may find yourself improving UPMH, improving quality and reducing IG unit cost.

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