Parts made of wood, various types of plastics, fiberglass composites and even some metal parts, such as die cast and electroplated parts, can be difficult—if not impossible—to paint using traditional coatings because they typically require high temperatures and long oven dwell times for drying. These heat sensitive parts often warp, out-gas, melt or degrade in some way at these high temperatures. Unlike traditional coatings, UV curable coatings do not require heat to dry. Instead, UV coatings are converted chemically from a liquid to a solid via a polymerization process initiated with UV energy. UV curing is a low temperature process ideally suited to heat sensitive substrates. In addition, UV curing takes only seconds, so production rates are high. UV coatings are also known for their excellent durability, scratch resistance, and environmental friendliness.
Even though UV curing has been used commercially for over thirty years (it is the standard coating method for compact disk screen printing and lacquering for example), UV coatings are still relatively new and growing. UV liquids are being used on plastic cell phone cases, PDAs and other handheld electronic devices. UV powder coatings are being used on medium density fiberboard furniture components. While there are many similarities with other types of coatings, there are also some key differences.
Similarities and Differences
One similarity is that typically, UV coatings are applied in much the same way as other coatings. A UV liquid coating may be applied via spray, dip, roller coating, etc., and UV powder coatings are electrostatically sprayed. However, because UV energy must penetrate the entire coating thickness, it becomes more important to apply a consistent thickness for complete cure. Many UV coating processes incorporate automated spray or other techniques to ensure this consistency of application. Though this may require the addition of application equipment, remember that your end product quality will be more consistent and that you will be using and wasting less coating material with an automated system.
Unlike most conventional coatings, many UV coatings – both liquid and powder - can be reclaimed. This is because the UV coatings will not begin curing until exposed to the UV energy. So as long as the paint area is maintained well and kept clean, this can be a huge savings. Another difference to consider is that UV curing is line of sight, meaning that the entire surface area being coated must be exposed to the UV energy. For very large parts or complicated three-dimensional parts UV curing may not be possible or cannot be economically justified. However, great strides have been made in recent years developing new techniques, and modeling software is even available to help optimize the number of UV systems and simulate the most efficient cure process for three-dimensional parts.
Develop a Business Plan
Of course, UV curing requires an investment in UV curing equipment, so it is prudent to develop a business plan before deciding to make this capital investment. Determine what types of products and substrates provide the best opportunity for your business. Some heat sensitive parts you might consider include medium density fiberboard furniture components, cell phone cases, handheld PDA cases, brass hardware, fully assembled motors and fiberglass watercraft bodies, to name a few. In general, there is a trend to move away from metal and glass to plastics. This is especially true in the automotive market where weight reduction is a major driver. Plastic automotive parts often require UV coatings to meet durability requirements.
Look for ways to leverage your existing position, capabilities and knowledge. Your existing customers may have heat sensitive parts they send to someone else further away. Maybe you are in an existing market where you already know the players and dynamics, but haven’t been able to coat their heat sensitive parts. Look for markets that are growing, or for lucrative niches. Look for an opportunity to coat a product following assembly. For example, fully assembled electric motors, insulated steel or aluminum doors, or hydraulic cylinders for door closers or shock absorbers are all heat sensitive parts once assembled. Saving the painting until the end reduces work in process and the chance that the coating gets damaged during assembly.
As you begin to focus in on markets that look promising, speak to prospective customers first-hand to understand their coating requirements, growth projections and competition. Contact formulators of UV liquid or powder coatings to get their perspective and insight on markets. Attend industry conferences and trade shows in the markets of interest and talk to prospective customers and suppliers. You may even be able to talk to a competitor, or someone already using UV on heat sensitive substrates.
Think about who the competition is, or will be, and how they are likely to react. Consider how you will market your new capabilities and the costs of doing so. Formalize everything into a professional business plan. More than likely, investors or banks will ask for a business plan, and it forces you to ask the right questions and provides a plan for moving forward.
Making the Investment
The capital investment required depends on the types of products you need to cure. Larger size parts will require more UV curing equipment than small parts. Many plastic parts require surface treatment, such as plasma or corona treatment, to improve adhesion of coatings. Wood parts typically require sanding and other surface preparation systems prior to coating, which also adds to equipment costs. Probably the most difficult to assess and costly factor is how flexible the system needs to be. If the system needs to handle a wide variety of different shapes and sizes, then the material handling and curing components will require flexible setups, which typically costs more. Sometimes UV curing equipment can be retrofitted onto existing thermal oven lines, greatly reducing the capital expense.
Equipment suppliers (i.e. UV curing, pretreatment, application, and material handling equipment, or a finishing line integrator) can provide estimates of the equipment investment needed. The equipment suppliers should also be able to provide information on energy and maintenance costs for their equipment. Keep in mind that because the conveyor in a UV line is shorter and not subjected to high temperatures, it may last longer and cost less to replace.
When obtaining cost estimates from coatings formulators, you may be surprised how expensive UV curable coatings seem. UV curable coatings are almost always more expensive on a cost per unit volume basis because their raw material components are more costly. But keep in mind that since they typically have little or no solvents or water in them, nothing is lost to evaporation. Instead of comparing coating cost per pound, it makes more sense to compare the cost to coat a given surface area or a specific part on the basis of finished (dry) film thickness. Don’t assume you will have the same hazardous waste disposal or VOC abatement costs that you may be familiar with for solvent based coating. These costs are often reduced or eliminated with UV coatings.
Finishers are often surprised at how little labor is required to operate a UV coating line. Don’t just assume that labor will equal that of a thermal drying line. Labor costs are often less due to reduced clean up, rework, and part cool down time. UV curable coatings do not dry or set-up like thermally cured coatings can, clogging up spray guns and other application equipment. Many UV finishers find that compared to a thermal system, their UV system has less scrap and rework because contaminants simply don’t have time to get on the part between application and complete cure of the coating. Finally, because parts are cool following the cure, they can typically be off loaded and packaged soon after. So a given unit of labor is able to off load and package more parts per hour than is typical with a thermal high temperature system.
It’s important to do your homework first to determine if UV coating capabilities may be a way to expand your finishing business to heat sensitive substrates. Calculate your return on investment based on estimated market revenues, the capital investment needed and operational costs. It can be helpful to consider up-side and down-side scenarios. Also, consider options for reducing your risk, such as a phased entry approach. For example, start with smaller parts that require less UV curing equipment and material handling, thus lowering the capital outlay, with the ability to expand the finishing system as business builds. Another option might be to partner with a coater in another region of the country who is ready to expand to your area. Or maybe there’s a customer that wants to outsource their finishing because they don’t want to deal with the environmental aspects of painting, but has a finishing line that you could retrofit. Consider operating this line in their plant for them, but with an eye for future growth and expansion. Decide what makes the most sense for your business, complete your business plan, and if appropriate, move forward.