Custom coaters.. What kind of oven?!

[Guest]

There seems to be a lot of custom coaters in here and I'm curious to hear what others are using for curing. I have a feeling that I will soon outgrow my current oven and I'm looking for ideas or solutions.

So what are you doing for curing? Kitchen range? Custom oven? Huge walk-in oven? Whatever it is, how do you like it? What would you do differently?

Post pictures if possible and just for shits and giggles (and some motivation)... For those of you have that have been around for a while... What kind of oven did you start with?

Thanks once again!

[Guest]

Re: Custom coaters.. What kind of oven?!

I am using a double house oven in half of a two car garage. My whole place would fit into HarleyDads oven .

[Guest]

Re: Custom coaters.. What kind of oven?!

^^^ That looks VERY familiar! LOL... Even the blasting cabinet :P

I had mine setup the same way... except I moved the blasting cabinet further away from the oven and placed a steel shelve between them... The cabinet didn't have the best seal and I didn't want any glass dust contaminating the oven.

I also didn't feel like bending down anymore so I built a stand that raises the oven 16" off the floor. I will have to take some pictures when I get out of here...

[Guest]

Re: Custom coaters.. What kind of oven?!

Harleydad... I'm asking for pictures of ovens... not garages! LOL.

That's awesome dude.... Someday... someday...

[JNZFinishing]

Re: Custom coaters.. What kind of oven?!

Daaaaamn!

[Guest]

Re: Custom coaters.. What kind of oven?!

Oven Venting Considerations

NFPA 86 specifies oven ventilation requirements for fire protection. NFPA 86 should be reviewed in its entirety.
Some of the NFPA 86 recommendations (air intake basis at 70 degrees f) and other considerations are as follows:

• One ft3/min for every 5700 btu/hr oven capacity rating for removal of byproducts of combustion of natural gas, plus
• 2.2 ft3/min for every pound of powder through the oven for removal of potential volatile compounds, which may be generated in the powder curing operation.
• The workplace environment should be monitored to ensure that the combination of bake oven venting and room air turnover is sufficient to meet Permissible Exposure Limits (PEL) and other exposure limits for regulated substances which may be outlined on the powder MSDS.

[Guest]

Re: Custom coaters.. What kind of oven?!

A convection oven has five major components.
• Oven enclosure (shell)
• Heater unit
• Supply air system
• Recirculated air system
• Exhaust air system
Oven Enclosure (shell) contains the environment necessary for the curing process, including a support structure; insulated panels (enclosure); and product openings/air seals.
The oven support system should be designed to carry the enclosure weight and the product conveying system. Structural steel must be connected with slotted hole connections to allow for expansion.
Insulated Panels (enclosure) contains the heat of the process. Panels 30 to 33 inches wide with fiber insulation (one inch of four-lb density insulation for every 100F) sandwiched between aluminized metal skins are used. The assembled panels are tongue-and-groove for easy installation. The outer skins are connected with formed metal channels. These channels form a through-metal condition, allowing significant heat loss at the joint. This panel joint can become too hot to touch, so the channel is slotted to reduce the area available for heat migration. This technique reduces joint temperature to less than 100F in a 450F oven, without losing the structural integrity of the channel.
Corners present another problem with panel construction. At the edges of the oven, panels do not fit tightly together and leakage occurs. Void areas are filled with loose insulation and the areas are jacketed with sheet metal flashing. This is not sufficient to stop the escape of cure products that condense and stain oven walls. Continuous gaskets must be used to create a proper seal along horizontal seams.
Personnel access must be provided. The door and hardware must seal the opening without using a positive latching device. Any panic hardware with positive latching features must allow the door to be opened from the inside. Locate access doors so that an exit is never more than 25 ft away. Oven doors with windows are easier to locate.
A great source of oven problems is enclosure openings where products enter and exit. These openings are designed using minimal clearance for the ware. Bottom entry/exit designs make use of the natural sealing features of hot air and present no real problems. Openings in the sides of ovens require mechanical air seals to contain the environment.
To seal an opening, it is best to draw hot air from the oven and force it back into the opening. For this to work, a significant velocity must be developed at the center of the opening. Additionally, the oven must run negative relative to the production environment. These two requirements draw factory air into the oven. This pressurization is relieved by exhausting the enclosure, resulting in a considerable source of heat loss.
An alternative to traditional construction methods is an oven module. When the design allows for shipping, 20-ft-long completely assembled sections of the oven can be fabricated. This construction includes all-welded interiors that eliminate areas for dirt to collect; steel buried in the panels to reduce interior surface area; fewer joints with through metal for less heat loss; and speed and ease of assembly at the customer's factory. Despite the many positive features, these ovens are rarely practical because of their configuration.
Heater units. The second system at work in an oven is the heater unit. The heater generates the energy for curing and begins the distribution of energy.
To properly size heater equipment, a detailed heat load must be calculated. Energy losses for the ware load, conveyor load, enclosure and exhaust requirements must be considered. These losses are used for selecting the sizes and corresponding electrical devices necessary for energy control.
The heat load calculation also provides information for selecting an oven supply fan. The heat required to maintain good oven temperature is delivered by heating the supply air to no more than 100F above the oven operating temperature and distributing this air to the oven. The fan volume must be expanded for the elevated temperatures. The supply fan should turn over the oven volume about two times a minute. Because the fan is a constant volume device, the fan motor is sized for cold starts to avoid overloading. This provides an oven temperature profile better than plus or minus 10F throughout the enclosure.
Many heater units have filtration systems to continuously clean the oven environment. Filter efficiency varies with the application, but the types modified for the elevated temperatures used to filter final makeup are most effective. Filters require much lower velocities than in normal heater units. When filters are used, heater unit size must be increased. Oven filters continuously clean the air and, as a result, load very slowly. It is not necessary to pre-filter high efficiency filters.
Sometimes the products of combustion are not compatible with the coating. In these cases, indirect-fired heater units are an option. These use air-to-air heat exchangers and may require one third more energy to operate.
Supply Air System. Another problem occurring when the products of the cure and combustion combine and come in contact with a direct flame is the production of NOx. When this becomes a problem, it is overcome by introducing large amounts of fresh air into the heater. This lowers the temperature of the flame-heated air to a point where NOx is not produced. This, like the indirect oven, is applied at a significant cost of energy.
As the heater unit discharges the supply air, it is directed into the oven supply system. The purpose of the supply system is to deliver and distribute the energy developed in the heater unit. The rectangular supply duct is constructed of aluminized metal. For proper operation, velocities in the duct should not exceed 2,500 fpm. This assures good laminar flow and good temperature control. Supply ducts should be along all walls and between every other conveyor run to eliminate cold spots.
Recirculated air systems.The recirculating system returns oven air to the heater unit so that energy is continually added to the oven. This is accomplished using the duct with the supply fan to create a negative pressure condition within the enclosure. The oven air naturally migrates to the areas of low pressure, where it is captured in the duct system and returned to the heater.
Recirculating duct is fabricated in much the same manner as the supply duct. The duct is designed for slightly lower velocities. The velocity in the duct is held at 2,000 fpm and openings are 20-25 pct greater than the supply.
It is poor design to use the recirculating duct to provide control over the oven environment. The influence of suction pressure is negligible, even at short distances from the source. While air naturally moves to the areas of lower pressure, this movement cannot be easily controlled. It is better to place a small amount of recirculation in the hottest part of the oven and let the supply air do the work. This assures that the design requirements will be maintained.
Exhaust air system. Every oven must be exhausted. Exhausts create a negative environment so that air seals operate properly and remove VOCs and other cure products from the oven. Additionally, the exhaust purges the oven prior to start-up. The requirement for purge is to change the enclosure atmosphere four times in approximately 20 min prior to ignition.
The main job of the exhaust is to maintain a safe environment. A good rule of thumb is to exhaust 10,000 cu ft of air (expanded for elevated temperatures) for every gal of solvent driven off in the oven. This assures the oven atmosphere will be maintained below the lower explosion limit of the solvent with a safety factor of four.
Exhaust also eliminates smoke build-up. Smoke is produced when curing some electrocoatings and powders. The exhaust requirement here is best recommended by the coating supplier.
The flexibility of convection curing keeps it popular with today's finishers, despite pressures to increase quality and reduce the space required for paint shops. A properly designed and installed convection oven requires little attention relative to pretreatment and application processes. It runs effectively with simple controls. It can be combined with other curing methods.

[Guest]

Re: Custom coaters.. What kind of oven?!

Well I guess your post was under 60,000 characters King. LOL

[banditpowdercoat]

Re: Custom coaters.. What kind of oven?!

I dunno if I meet NFPA But it's an elec oven, 10" thick walls, Steel stud configuration, with galvanized roofing fro siding

http://banditpowdercoat.com/Powdergallery/nfpicturepro/albums/userpics/10002/normal_Oven%20012.jpg

http://banditpowdercoat.com/Powdergallery/nfpicturepro/albums/userpics/10002/zoe3%20011.jpg

[Guest]

Re: Custom coaters.. What kind of oven?!

All I saw was Stud and had to go back and remember the topic

[Guest]

Re: Custom coaters.. What kind of oven?!

There are a few used ovens for sale on ebay and we also have a topic on how to build your own

[wiseguyz]

Re: Custom coaters.. What kind of oven?!

All I saw was Stud and had to go back and remember the topic

Spoken like a true Stud-ette!

[Guest]

Re: Custom coaters.. What kind of oven?!

I still use the orig electric house oven that i started with then I have my homebuilt 4X4X6 for the large stuff and batch runs.

[Guest]

Re: Custom coaters.. What kind of oven?!

I still use the orig electric house oven that i started with then I have my homebuilt 4X4X6 for the large stuff and batch runs.

That's more than likely where I will end up very soon... Any pictures of your homebuilt oven? I would really like to take a look at it.

[Guest]

Re: Custom coaters.. What kind of oven?!

The best course of action - minimize your cost as much as possible without sacrificing safety of quality. I put alot of information about ovens to plant the seeds knowing that our Guys can figure out a way to incorporate these idea's into their shops