Volume 6 Issue 2 March 2005
Painting Vinyl Windows and Doors...
Has the Time Come
by Michael Braenel
Consumer demand for color in the vinyl window and door industry is growing quickly. This is due, in part, to homeowners’ desire to personalize their purchase as well as the historical precedent for color, set by both the aluminum and wood window markets.
Traditional approaches to altering the look of white vinyl include pigmenting the vinyl, foil laminates and cap stock–all of which are, in most cases, supplied by the extrusion supplier. The primary drawbacks of these options are:
• They limit flexibility and range of colors available;
• They affect the fabricator’s inventory levels; and
• They can under perform a well-designed coating in long term color and gloss retention.
The convergence of the increasing demand for color and the existence of an environmentally friendly painting process (in the form of a high-performance water-based coating and associated cleaner) present the fabricator with a unique value-added business opportunity.
This article will review what a fabricator of any size might need to consider when introducing a paint program. Two key questions need to be considered. The first is whether or not to paint lineals or squares/boxes (already welded frames and sashes, unglazed without hardware added yet). The second is whether to paint in-house or use the services of a finisher (or local paint shop).
The intuitive approach of most people is to paint the lineal directly. This is because color options historically have been offered in this form by the vinyl suppliers (this includes painted products).
The main advantage of painting lineals is the potential productivity gains brought on by more efficient masking (either automated taping or masking fixtures) and through the potential of automating the coating process through in-line spraying or vacuum coating.
The disadvantages of spraying lineals include:
• Extra caution is required when processing a painted product;
• Requirement to break down and handle or ship multiple profiles;
• The need to touch up welded corners;
• Painted product can be wasted in the cutting process; and
• Adapting to new complex profiles can present challenges (both spraying and masking).
In general, unless paint volumes exceed 50 windows per shift, it is probably not worth considering this approach.
If simplified masking can be achieved, then manual spraying of the lineal can provide efficiencies without automatic spraying. The general investment and complexity associated with the maintenance and operation of automatic equipment preclude this as an option for all but the largest of fabricators. Specialized finishers are best suited for high-volume automated production. These are normally coating profiles going into the new construction window business.
The painting of squares approach is well-suited to just-in-time coating of a wide range of colors (including custom matches). The fact that units are sprayed after welding implies that there is no waste, and virtually no colored inventory to manage. The quality of finish usually is higher than processed lineal with touched-up corners.
One perceived disadvantage to painting squares is in the increased masking effort (templates can be used if standard sizes are produced). In fact, masking is a fairly repetitive, low-skilled task that is absorbed easily within the sales margin.
In an automated window fabrication line, painting squares have the potential of disrupting the production flow as the squares are removed after the corner cleaning process. They need to be reintroduced after painting and curing to complete the assembly process.
In general, the painting of squares approach is well-suited for small- and medium- fabricators. For larger volume applications, the approach also works well when combined with an automated drying system (either batch dryer or conveyorized IR/convection system).
In-House or Finisher
When considering the question of whether or not to set up an in-house paint shop or to engage the services of a local paint shop, the following need to be considered:
• Assuming the return on investment is acceptable, is there a willingness to take on a new process?
• Is there sufficient space to dedicate to a paint line?
If your answer is no to either of these questions, then your local paint shop is the way to go. Even if they are not experienced in painting vinyl specifically, they will have no problem adapting with the assistance and certification of the paint supplier. One obvious consideration is the transportation costs.
On the other hand, consider the following:
• Do you want to retain a more attractive margin for colored product within your business?
• Is your business high end and highly custom?
• Do you want to retain the control of quality control and service within your business?
If you answer yes to these questions an in-house paint shop can represent a growth opportunity.
A potential approach is to build the demand first with the services of the finisher, then progress into an in-house system, while retaining the finisher to handle the peaks in business.
Retail premiums for painted vinyl windows range from 5 cents to $1 per united inch (UI).
The total cost (coating, shipping, labor and overhead) for a fabricator to paint a typical double hung – 96 UI, is in the range of $25-$30 (the option would be priced retail at approx. $75, using 75 cents per inch ).
Cost of lineal painting charged by finishers is up to 50 cents per foot (depending on width and complexity of profile), not including shipping and handling. Sash, frame and glazing stops are charged separately.
Coating and Supplier Requirements
It is essential that high-performance water-based coatings meet the AAMA 615 test standard, provide heat gain data and be tested to the ASTM D 4803 standard. Coatings applied to grid material for installation into thermal units need to be fog-tested.
Water-based coatings are essential when considering in-house programs, since environmental trends and increasingly restrictive OSHA guidelines make solvent-based solutions impractical for a window fabricator’s environment. Furthermore, the elimination of any hazardous or flammable materials will eliminate any added expense for handling, storing and disposing of waste.
Performance advantages of water-borne coatings include superior flexibility and impact resistance leading to long-term performance without cracking even when subjected to years of thermal cycling.
Water-based coatings also provide the fabricator an opportunity to promote an environmentally friendly solution within its marketing communications literature.
The coating supplier should offer:
• A suitable warranty;
• Quick turnaround time on custom color matches;
• Training and certification process specific to vinyl windows; and
• Sales support material to help the fabricator sell color.
In general the painting process will involve three stages: preparation, spraying and drying (curing).
Cleaning and masking are the key elements to preparation.
Masking normally involves taping off sections of profile that don’t require painting, either in lineal or in a square format. Some subjectivity often exist in determining break lines. More sophisticated masking approaches have been developed for in-line systems, but tend to lack flexibility with respect to introducing new shapes.
Profiles need to be cleaned to remove any dirt and grease, and also to remove any residual lubricants from the extrusion process itself. Attention to detail at this stage is critical, since most failures occur during this step.
For the PVC itself, prepping should be as simple as using a non-hazardous industrial cleaner, generally sprayed or wiped on, and dried fully prior to the paint application.
The Spraying Process
With respect to water-based coatings, the wet film application thickness (paint volume) tends to be less than with solvent-based materials. This requires smaller nozzles and always generates higher coverage.
The recommended painting process is high volume low pressure, since it reduces overspray to a minimum due to the low spraying pressure combined with a small fan. Spraying normally is accomplished by applying multiple layers (passes) of coating, to achieve an evenly wetted look, without creating runs. Proper atomization, gun distance, pressure settings and hand speed all contribute to a good finish. If these parameters are not controlled, orange peel or dry fume can result.
Coatings can be self-leveling and often smooth out within minutes after spraying. Spraying parameters will vary during high humidity conditions.
Some type of spray booth is required. In the case of water-based coatings, the function of the booth has less to do with the removal of toxic fumes than with the extraction of the overspray. Overspray removal is important for generating a smooth finish as well as for the protection of the painter. Masks are also required.
Factors that will determine the selection of the booth are based largely on production volume and the maximum size pieces to be painted. Simple paint walls will work in environments that are not extremely dusty. Large paint volumes need closed booths potentially requiring air make up units if the hours of operation necessitate it. Within the booth, spraying can be achieved both vertically and horizontally.
Drying waterborne coatings is a simple matter of extracting water. The factors influencing the process are temperature (surface temperature), humidity and airflow.
One approach to drying is through simple air-drying. The two fundamental drawbacks are that the outside humidity will alter the drying time, and that the potential for dust particle settlement can affect the surface finish adversely. Supple-menting this simple approach with some space heaters, and ambient airflow (fans) can be very helpful. Typical drying times will range between three hours and two days depending on the conditions. It should be noted that water-based coatings could take up to two weeks to cure fully. A 70-percent cure is sufficient to complete the window fabrication process.
Infrared (IR) heaters (ideally short wave) can provide a major boost to drying times, as well as reduce their sensitivity of the weather conditions. Eight minutes of exposure, possibly while still in the spray booth, will provide the ultimate in smooth finish while giving the curing process a very healthy boost. Under these conditions, further fabrication can take place in as little as two hours.
The key limitation with this approach is that only the areas directly exposed to IR rays are dried. In automated conveyorised systems the IR is often supplemented with convection (hot air blowing over surface). This combination can bring drying times down to less than 10 minutes.
For higher volumes, a batch dryer can provide drying times in the order of 30 minutes.
A key consideration, independent of the drying approach is that surface temperatures greater than 130 degrees F are not recommended for PVC. This is not a limitation for aluminum.
If painting is performed in batches, a small painted sample from each batch should be maintained. Destructive testing in the form of a cross-hatch adhesion test will ensure the proper application. This sample will also serve as a color reference should it be required in the future.
The capital investment ranges between $5,000 (for an open spray booth, with heat supplemented air dry) to $60,000 (for a closed down draft booth with air makeup, including IR lights in an attached drying room). Adding a batch dryer to the above can add $40,000 up to $80,000 or more for a continuous drying system. The overall area required to implement the above is anywhere from 1,000-2,000 square feet of floor space.
There are many items to consider when deciding whether or not your company will introduce a paint program. Hopefully the items discussed here will help you determine if this is the right decision for your company.
Michael Braeuel serves as vice president of sales and marketing for AquaSurTech OEM in Montreal.
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