How Not to Cure Powder on MDF

Over the past 20 years, the concept of powder coating wood-based products has proved irresistible. Especially powder coating medium-density fiberboard (MDF), as it has the potential to have a massive impact on the furniture industry. Mike Chapman of WolfRayet has been the leading innovator in the industry for over 30 years. The founder of Vulcan Catalytic Systems, he is now the Chief Strategic Officer at WolfRayet. This Q&A article will correct some misconceptions and advises on how to get involved in this lucrative industry.

Q: What is the most common mistake that is made?

A: Quite often, metal powder coaters think they can throw some MDF onto their line and expect success. But wood products do not do well when subjected to temperatures above 300°F.

Early adopters would pre-heat for 15 minutes, flocking on the powder, followed by 10 minutes cure. This can cause the structural strength of the MDF to become degraded. This 25-year-old approach is considered outdated. While a handful of coaters still use this method, no new systems have been built for many years.

Q: Is all MDF the same?

A: Absolutely not. MDF varies in construction and quality. There are two properties to consider when choosing MDF for powder coating. Firstly, the density of the MDF should be 50 lbs. per cubic ft. or more. Secondly, the internal bond strength should be greater than 175 psi. When these two properties are achieved or exceeded, MDF (sometimes called HDF), can be successfully powder coated.

Q: Can I still powder coat lower-quality MDF?

A: Yes. It is still possible to use MDF with lower values depending on the end use. It will require extensive edge preparation and a two-coat process to achieve the desired functional or aesthetic look for the surface. 

Using the quoted HDF values reduces the amount of sanded edge preparation. A well-prepared HDF part can be single-coated. A coating of 3-4 mils can produce a micro-texture or smooth, low gloss finish.

Q: What about the powder? Are there differences?

A: Powder formulated for coating metal has a high cure temperature. This will not work effectively for heat-sensitive substrates. By the time cross-linking starts, the MDF will start to degrade. Modern “low bake” powders are the answer as they require a curing temperature of only 265°F for four minutes of long wave Infrared.

Q: Can I use my existing convection oven?

A: Honestly, not effectively. If you are serious about producing high-quality powder coated MDF, this is not an option. Long wave gas catalytic infrared is really the most effective solution. A period of only 1-2 minutes pre-heat is required. This pre-heat increases the conductivity of the board, ensuring good transfer efficiency. Final dwell time to achieve a cure is only 5-6 minutes.

Q: It would seem powder coating MDF could be lucrative. How do I get started?

A: This is a great question and one where WolfRayet is working hard to produce the answers. I have been involved in building MDF systems worldwide for over 20 years. With WolfRayet, we have developed systems that incorporate all my experience. The range of systems covers all levels of required involvement. From the entry-level system (Galaxy Ultra Lyte) to the high-output Galaxy Series systems, we have solutions that make coating these heat-sensitive substrates easy and efficient. You may be a cabinet shop needing to coat a kitchen’s worth of doors and draw fronts each day. Or a large OEM requiring hundreds of parts per hour with automatic powder application. Whatever your situation, there is now a solution.

Q: What about existing powder coaters? Is there a way I can get into this industry?

A: It is difficult for existing metal coaters to successfully coat MDF or wood products with their existing equipment. The rule of thumb is MDF cannot be coated and cured on a metal line. However, interestingly, metal can be processed on a well-designed MDF line. We have designed a system that is dual-purpose where the coater can hand coat and cure both metal and MDF. This system has a pre-heat section that can double up as a dry-off oven if necessary. The system has a small footprint of 60' x 35' and can produce 2-3 kitchen sets per day. So, existing metal custom coaters can have an MDF coating system while having a system that can coat smaller metal parts.

Q: Why is now a good time for existing powder coating shops to invest in this technology?

A: There is untapped demand for powder coated MDF. We are frequently asked: “Where can we go to now to get this powder coating service?” In the relentless drive to reduce material and manufacturing costs, there is now a convergence of low bake powders and our approach, WolfRayet, is working hard to facilitate metal shops to enter this market. We’re also working with cabinet shops that want to buy a starter system to get them going, even if it is a powder primer followed by a liquid top coat. There is a lot of potential!