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Building a Powdercoat Oven

dercoating is an excellent coating system, superior to paint in many ways, and is now available to the hobbyist through the coating guns offered by Eastwood, Co

ings, Harbor Freight, and others. The main deterent to hobby use, though, is the fact that the coated object has to be baked at temperatures as high as 450 degrees

periods up to 25 minutes, depending on the type of powder used. For smaller objects, an old kitchen oven can be used, but when the size of the object increases b

which will fit into a kitchen oven, the equipment cost goes up at a breathtaking rate.

of my hobbies is restoring and riding old three-wheelers, four-wheelers, and motorcycles. The kitchen oven I have in my shop will barely accomodate a wheel, an

g arm would be out of the question. I decided to build a powedercoat oven to use in coating objects up to the size of an ATV or motorcycle frame. I wanted the o

ollapsible so that it could be stored away when not in use. There's not much hard info on the internet about building ovens, but I contacted a few people that had

rimented with this sort of thing, then made a few decisions of my own, and forged ahead.

oven is assembled from a series of panels which is actually 2" rigid fiberglass board wrapped in 28ga sheetmetal. Each panel is different from the others, but all h

one dimension of 36", which is the largest size that my brake will handle. All fastenings are steel pop rivets, except a few screws which hold the panels together

oven. The base is a lightweight frame built up of light gauge metal drywall studs, with burner pans filling in the open areas of the frames.

is provided by 4 salvaged kitchen oven burner elements, of about 3000 watts each This was the real uncertainty for me, whether the element would heat up the la

me quickly enough. As it turned out, the oven heats up to 450deg in about 10 minutes. Temperature control is provided by a scrounged kitchen oven thermostat w

rols a 50 amp definite purpose contactor to turn the elements on and off. The temperature floats a bit but it seems accurate enough.

total draw of the heating elements is about 12kw. My local power rate is 8.7cents/kwhr, so the oven would cost about $1.04 per hour to operate.

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me

 

Here is a front view of the oven. Inside dimensions a

wide x 36" high x 72" deep. Two of the four heating

elements are visible. The shiny bar across the bottomabout 1/2 way into the oven is actually an intermedia

support member. It might not be clear from the pictu

but the elements are recessed about 1-1/2" below the

lip of the base. A pair of rails, made from small chaniron will be laid the length of the oven and a trolley w

used to carry the coated object into the interior of the

 

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me

 

The trolley is made from 2" angle iron with 4ea fixed

casters. If I were to do it over, I would use 1-1/2" ang

that the wheels would protrude at the bottom more. Tvarious rods and pipes that protrude upward are for

supporting the items to be coated. Scroll down a little

further...

 

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me

 

and we have a picture of an ATV frame mounted on

trolley and being loaded into the oven. The railsmentioned earlier are in place and visible in this pict

 

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me

 

Here is a wheel being loaded on the trolley.

 

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A picture of the top of the oven showing the view

windows. These windows were salvaged from twoscrapped kitchen ovens. The black box on the side of

oven is the interior light, a part also taken directly fro

the kitchen ovens.

 

For a closer look at how this oven was constructed, click here to go to the Construction Page.

DISCLAIMER

This website is presented for the enjoyment of its readers only. The owner of the website is not a professional engineer or designer, nor does hepurport to offer advice or consultation on the subject of oven construction. The fabrication of heat producing equipment such as an oven is aninherently dangerous process. Installation of electrical components requires specialized knowledge of the trade and of electrical codes. Anyoneconsidering the construction of such an oven should consult the appropriate professionals for preparation of a qualified design. Under no

circumstances shall the website owner be responsible for any loss or damages, regardless of severity, that arise from the use of information

published on this website. 

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Details of Building the Powdercoat Oven

 

Before we start the actual construction details, I think discussion of a few tools is

in order. The main tool needed is a sheetmetal brake. Here is a picture of mybrake, obviously a low budget model (I actually paid $50 for it at a welding shop).

Those of you familiar with this type of brake will notice that the clamping leaf is

not stock. Apparently some previous owner had bent the original and fabricated a

homemade leaf. This type of brake is slow to use and doesn't (in my opinion)make the sharpest bends, but it is tolerable for the purpose here. Capacity is 36"

wide x 18 gauge, but I have my doubts about whether it could handle 18 gauge

steel.

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structruction Page

 

A few of the hand tools used for this project. Not shown is a drill for drilling thepop rivets holes. Other than the brake, not many specialty tools were needed. A

shear would have saved a lot of time and made squaring the panels a lot easier.

 

The first step is building the base. The base is constructed from 3-5/8" metal

drywall studs, available from building supply houses. The studs were laid on edge

and fastened with pop rivets into a frame with two bays. These two bays will haveburner pans installed in them to enclose the bottom of the oven.

Click on this picture to view a larger size.

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structruction Page

 

Each bay of the base has a burner pan as the floor. This pan provide support for

the heating elements and prevents heat from escaping from the bottom of the

oven. The two outer flanges lay on the base rails and are pop riveted for fastening.

 

This picture shows a burner pan installed in one of the bays and the heating

element being installed.

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structruction Page

 

The next step is the construction of the panels that make up the shell of the oven.The panels are made of 28 gauge galvanized sheetmetal wrapped around a core of 

2" rigid fiberglass insulation. Typical procedure was to bend a single piece of metal 4 times to form it into a rectangular box, then fill the remaining two openends with separate fillers. All seams are fastened by pop rivets. This picture shows

the brake making the third bend.

This picture shows placement of insulation in a panel. This is not the same panel

as in the previous picture. This panel overlaps the panel adjacent to it and you can

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structruction Page

 

see the overlap protruding about 1-1/2" at the bottom of the picture. This panel

actually requires three separate fillers to enclose the insulation. The drawing in thenext frame will show better how the panels are constructed.

 

Here is a drawing of the oven. Click Here to view a PDF file of this drawing.

You must have the Adobe Acrobat Reader to view this file. Visit www.adobe.com

to download the Acrobat Reader for free.

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structruction Page

 

The electrical panel shown here was fabricated from the same sheetmetal as the

rest of the oven. The two round objects on the bottom of the panel are actually

220v receptacles. Two heating elements are wired together and plug into each of these receptacles. This allows the oven to be disassembled easily for storage.

Click here for a larger view with labels. Warning: 200K file.

The schematic to the left shows how the oven is wired. The heart of the electrical

system is the contactor, which is an electromagnetic switch. Power (110v) is

routed through the ON/OFF switch and is controlled by the thermostat. Thiscircuit activates the coil of the contactor, which closes the 220v circuit that feeds

the heating elements. The thermostat causes the contactor cycle open and close to

requlate the termperature. The oven has an interior light and switch which I have

omitted here for clarity.

Click Here to veiw a PDF file of this drawing.

All text, images, and drawings are Copyright 2004 by Gary Brady

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Design Considerations

All data presented on this page has been collected from the construction and operation of the oven shown in this website. If you've built an similar oven, ple

contact me. I'd like to collect data from your experiences.

Oven design considerations are grouped into the following two general categories:

Performance:

Performance criteria are the physical aspects of the oven as they relate to how the oven will perform. The performance related criteria here are volume of th

oven, type of insulation, and heating element output.

The volume of this oven is 36 cubic feet, while total exterior surface area is 72 square feet. Each of the four elements is approximately 3000 watts for a tota

12000 watts, or 12kW. Using a 2" rigid fiberglass insulation board for the entire enclosure except the base, the oven heats to 450 deg in less than 10 minute

This actual data indicates that a heat input of 333 watts/CF of oven volume will provide an acceptable heat up time. This heat input factor would be valid on

for an oven of this approximate size. The exterior surface area will increase at a proportionately higher rate as the volume increases causing a greater heat lo

for larger ovens. An increase in insulation thickness would be warranted for larger ovens.

Utility:

Utility consideratons are those physical characteristics that define how the oven will be used. Shape, objects to be baked, size, racking of items, type of mat

used for construction, and portability are all utiility considerations.

The oven shown in this website was intended to be used for ATV frames and smaller items, so the horizontal configuration of a rectangular box, loading fro

he end, was the chosen shape. The trolley type racking device was also chosen, since it works will with frames as well as smaller items such as wheels,

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ign Page

fenders, etc. The trolley requires modification from time to time to hold different items. An overhead trolley, similar to  this one, which rides in Unistrut

mounted to the underside of the top, may be more serivceable for some items to be coated.

The type of material used for construction will probably be dictated by the capabilities and needs of the builder. Clearly, there is no one right way to build an

oven. One of my most important considerations was that the oven be portable, that is, that it could be disassembled and stored away on a shelf in the rafters of 

my shop when not in use. Professional powdercoaters would proabably want an oven that was stationery or mounted on wheels. I chose the panelized approach

for this oven. There is no structure per se; the panels are the structure and are light in weight and easy to handle. This approach is not very sturdy, however, and

in fact, the base is quite flexible unless lying flat on a smooth concrete floor. The fact that I own a sheetmetal brake was also a factor in the construction that I

chose.

 

All text, images, and drawings are Copyright 2004 by Gary Brady.

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Material List

e following spreadsheet is a list of items I purchased for the construction of the oven. A number of items were already in my scrap bin, including one kitchen ove

modeling contractor and frequently haul old appliances to the dump). Another oven was picked up (literally) from the side of the road. The thermostat ,heating ele

view windows came from these ovens. The steel for the trolley and rails had already been purchased, and was left over from a prior project.

e contactor was purchased from an air conditioning supply house,and in fact, is very similar to the contactor found in the condenser unit of many home A/C unit

tactor has a 50amp capacity with a 110v coil.

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erial List

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(Res. Amps 240-600V) - 50

L37-844 Regular price: $162.24 Sale price: $27.90 Order

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KNAUF INSULATION BOARDPrinter Friendly

DESCRIPTION

Knauf Insulation Board is a thermal and acoustical insulation product made from inorganic glass fibers

preformed into boards bonded by a thermosetting resin. It is available plain, with a factory-applied FSK

facing or PSK (metalized polypropylene-scrim-kraft) facing, or with a factory-applied all-service jacket (ASJ).

APPLICATION

Knauf Insulation Board is a versatile product for thermal and acoustical applications such as: heating and air-

conditioning ducts, power and process equipment, boiler and stack installations, metal and masonry walls,

wall and roof panel systems, curtain wall assemblies, and cavity walls.

FEATURES AND BENEFITS

Energy Conservation

●  Excellent thermal efficiency results in lower operating costs.

Low-Cost Installation

●  Lightweight, easy to handle and fabricate.

●  Fast, easy installation lowers labor costs.

Noise Reduction

●  Excellent acoustical properties effectively reduce noise.

Appearance

●  FSK, PSK and ASJ vapor-retardant facings provide a neat finished appearance.

SPECIFICATION COMPLIANCE

In U.S.:

●  ASTM C 612

- Type IA (1.6, 2.25, 3.0, 4.25, 6.0 PCF)

- Type IB (3.0, 4.25, 6.0 PCF)

●  ASTM C 795

●  ASTM C 1136 (facings)

- Type I, II, III, IV (ASJ)

- Type II, IV (FSK, PSK)

●  California Title 24

●  HH-B-100B; Type I (ASJ facing), Type II (FSK, PSK facing)

●  HH-I-558C

- Form A, Class 1 (1.6, 2.25, 3.0, 4.25, 6.0 PCF)

tp://www.knauffiberglass.com/index.cfm?fuseaction=prd.dspProdDetail&ID=12 (1 of 7)11/14/2004 8:10:21 AM

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Storage

●  Protect material from water damage or other abuse. Cartons are not designed for outside storage.

Vacuum packaged material can be stored outside if care is taken not to puncture the polybag.

Preparation

●  Apply the product on clean, dry surfaces. Metal ducts must be sealed before application. Prescore

rigid insulation board where necessary to conform to curved surfaces.

Application

GENERAL:

●  All insulation joints must be firmly butted. Insulation can be secured with adhesive, mechanical

fasteners, or banded. Minimum compression is to be used to assure firm fit and still maintain thermal

performance.

●  Vapor retarders should overlap a minimum of 2" (51 mm) at all seams and be sealed with appropriate

pressure-sensitive tape, or mastic. When applying pressure-sensitive tapes, the tape must be firmly

rubbed with a proper sealing tool to make sure the closure is secure. Follow tape manufacturer's

recommendations.

●  Fasteners shall be located a maximum of 3" (76 mm) from each edge and spaced no greater than

12" (305 mm) on center.

●  Where vapor retarder performance is necessary, all penetrations and facing damage shall be

repaired with tapes or mastic with a minimum of 2" (51 mm) overlap. Tapes should be applied using asealing tool and moving pressure.

●  Use on ducts, plenums, vessels, tanks, and equipment operating at temperatures of 450°F (232°C) o

less.

●  Tapes and mastics (dry) should have a UL 723 rating of 25 Flame Spread, 50 Smoke Developed.

DUCTS AND PLENUMS:

●  Use 3.0 pcf (48 kg/m3) insulation board in concealed areas.

●  Use 6.0 pcf (96 kg/m3) insulation board in exposed areas.

●  Insulation Board is not designed to be exposed to the airstream.

VESSELS, TANKS, AND EQUIPMENT:

●  For irregular surfaces, use 1.6 pcf (26 kg/m3) insulation board and band with minimum compression.

●  For outdoor applications, Knauf Insulation Board must be covered with appropriate jacketing, mastic,

or other vapor retarder. All exposed surfaces must be protected.

●  Apply jacketing, mastics, and other vapor retarders in accordance with manufacturer's instructions.

Caution

Fiber glass may cause temporary skin irritation. Wear long-sleeved, loose-fitting clothing, head covering,

gloves, and eye protection when handling and applying material. Wash with soap and warm water after 

handling. Wash work clothes separately and rinse washer. A disposable mask designed for nuisance type

dusts should be used where sensitivity to dust and airborne particles may cause irritation to the nose and

throat.

NOTES

The chemical and physical properties of Knauf Insulation Board represent typical average values determined

in accordance with accepted test methods. The data is subject to normal manufacturing variations. The data

is supplied as a technical service and is subject to change without notice. References to numerical flame

spread ratings are not intended to reflect hazards presented by these or any other materials under actual fire

conditions. Check with your Knauf regional office to assure information is current.

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THERMAL EFFICIENCY (ASTM C 177)

Mean Temperature1.6 PCF

k2.25 PCF

k3.0 PCF

k4.25 PCF

k6.0 PCF

k

75°F .24 .23 .23 .23 .22

100°F .25 .24 .24 .24 .23

200°F .33 .30 .29 .28 .27

300°F .42 .38 .37 .35 .34

THERMAL EFFICIENCY (SI) (ASTM C 177)

Mean Temperature

1.6 PCF

(26 kg/m3)k

2.25 PCF

(36 kg/m3)k

3.0 PCF

(48 kg/m3)k

4.25 PCF

(68 kg/m3)k

6.0 PCF

(96 kg/m3)k

24°C .035 .033 .033 .033 .032

38°C .036 .035 .035 .035 .033

93°C .048 .043 .042 .040 .039

149°C .061 .055 .053 .050 .049

SOUND ABSORPTION COEFFICIENTS, 1/3 OCTAVE BANDS(ASTM C 423, TYPE A MOUNTING)

Type Facing Thickness 125 Hz 250 Hz 500 Hz 1000 Hz 2000 Hz 4000 Hz NRC

1.6 PCF

(26 kg/m3)Plain

11/2"

(38 mm).19 .44 .86 .98 1.00 1.02 .80

1.6 PCF

(26 kg/m3)Plain

2"

(51 mm).31 .57 .96 1.04 1.03 1.03 .90

1.6 PCF(26 kg/m3) Plain 21

/2"(64 mm) .43 .82 1.12 1.07 1.04 1.03 1.00

1.6 PCF

(26 kg/m3)Plain

3"

(76 mm).47 .92 1.17 1.06 1.06 1.04 1.05

2.25 PCF

(36 kg/m3)Plain

1"

(25 mm).05 .24 .59 .86 .97 1.00 .65

2.25 PCF

(36 kg/m3)Plain

11/2"

(38 mm).17 .49 .93 1.03 1.03 .99 .85

2.25 PCF

(36 kg/m3)Plain

2"

(51 mm).26 .62 1.05 1.07 1.04 1.05 .95

2.25 PCF(36 kg/m3)

FSK 1"(25 mm)

.14 .69 .81 .99 .55 .27 .75

2.25 PCF

(36 kg/m3)FSK

2"

(51 mm).63 .76 1.11 .75 .42 .22 .75

3.0 PCF

(48 kg/m3)Plain

1"

(25 mm).08 .23 .62 .88 .96 .99 .65

3.0 PCF

(48 kg/m3)Plain

11/2"

(38 mm).09 .39 .89 1.03 1.06 1.01 .85

3.0 PCF

(48 kg/m3)Plain

2"

(51 mm).29 .65 1.11 1.13 1.06 1.03 1.00

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3.0 PCF

(48 kg/m3)Plain

3"

(76 mm).54 1.01 1.18 1.07 1.07 1.04 1.10

3.0 PCF

(48 kg/m3)Plain

4"

(102 mm).95 1.11 1.17 1.07 1.07 1.06 1.10

3.0 PCF

(48 kg/m3)FSK

1"

(25 mm).21 .63 .84 .93 .51 .22 .75

3.0 PCF

(48 kg/m3)FSK

11/2"

(38 mm).45 .60 .99 .73 .53 .27 .70

3.0 PCF(48 kg/m3)

FSK2"

(51 mm).67 .77 .93 .74 .47 .28 .75

3.0 PCF

(48 kg/m3)ASJ

1"

(25 mm).15 .71 .65 .82 .41 .16 .65

3.0 PCF

(48 kg/m3)ASJ

11/2"

(38 mm).42 .55 .91 .69 .40 .23 .65

3.0 PCF

(48 kg/m3)ASJ

2"

(51 mm).75 .71 .80 .66 .41 .24 .65

4.25 PCF

(68 kg/m3)Plain

1"

(25 mm).06 .24 .69 .99 1.05 1.02 .75

4.25 PCF(68 kg/m3)

ASJ21/2"

(64 mm).75 .63 .63 .62 .41 .25 .55

6.0 PCF

(96 kg/m3)Plain

1"

(25 mm).05 .26 .77 1.04 1.04 1.03 .80

6.0 PCF

(96 kg/m3)Plain

11/2"

(38 mm).13 .58 1.01 1.05 1.00 1.01 .90

6.0 PCF

(96 kg/m3)Plain

2"

(51 mm).32 .81 1.08 1.06 1.03 1.04 1.00

6.0 PCF

(96 kg/m3)FSK

1"

(25 mm).23 .65 .39 .48 .47 .32 .50

6.0 PCF(96 kg/m3)

FSK11/2"

(38 mm).61 .47 .78 .61 .51 .35 .60

6.0 PCF

(96 kg/m3)FSK

2"

(51 mm).77 .50 .72 .58 .53 .41 .60

6.0 PCF

(96 kg/m3)ASJ

11/2"

(38 mm).60 .46 .62 .48 .47 .31 .50

6.0 PCF

(96 kg/m3)ASJ

2"

(51 mm).77 .44 .60 .50 .41 .30 .50

FORMS AVAILABLE*

Density Thickness R-Value R-Value (SI)

1.6 PCF

(26 kg/m3)

11/2"

(38 mm)6.3 1.1

1.6 PCF

(26 kg/m3)

2"

(51 mm)8.3 1.5

1.6 PCF

(26 kg/m3)

21/2"

(64 mm)10.4 1.8

1.6 PCF

(26 kg/m3)

3"

(76 mm)12.5 2.2

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1.6 PCF

(26 kg/m3)

31/2"

(89 mm)14.6 2.6

1.6 PCF

(26 kg/m3)

4"

(102 mm)16.7 2.9

2.25 PCF

(36 kg/m3)

1"

(25 mm)4.3 .8

2.25 PCF

(36 kg/m3)

11/2"

(38 mm)6.5 1.1

2.25 PCF(36 kg/m3)

2"(51 mm)

8.7 1.5

2.25 PCF

(36 kg/m3)

21/2"

(64 mm)10.9 1.9

2.25 PCF

(36 kg/m3)

3"

(76 mm)13.0 2.3

2.25 PCF

(36 kg/m3)

31/2"

(89 mm)15.2 2.7

2.25 PCF

(36 kg/m3)

4"

(102 mm)17.4 3.1

3.0 PCF(48 kg/m3)

1"(25 mm)

4.3 .8

3.0 PCF

(48 kg/m3)

11/2"

(38 mm)6.5 1.1

3.0 PCF

(48 kg/m3)

2"

(51 mm)8.7 1.5

3.0 PCF

(48 kg/m3)

21/2"

(64 mm)10.9 1.9

3.0 PCF

(48 kg/m3)

3"

(76 mm)13.0 2.3

3.0 PCF(48 kg/m3)

31/2"(89 mm)

15.2 2.7

3.0 PCF

(48 kg/m3)

4"

(102 mm)17.4 3.1

4.25 PCF

(68 kg/m3)

1"

(25 mm)4.3 .8

4.25 PCF

(68 kg/m3)

11/2"

(38 mm)6.5 1.1

4.25 PCF

(68 kg/m3)

2"

(51 mm)8.7 1.5

4.25 PCF(68 kg/m3)

21/2"(64 mm)

10.9 1.9

6.0 PCF

(96 kg/m3)

1"

(25 mm)4.4 .8

6.0 PCF

(96 kg/m3)

11/2"

(38 mm)6.7 1.2

6.0 PCF

(96 kg/m3)

2"

(51 mm)8.9 1.6

*Available in widths of 24" (610 mm) and 48" (1219 mm)

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