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Companies have many choices when it comes to conveying methods to move a load through an oven. Factors to consider when selecting a conveying system include the product configuration, weight, oven temperature and desired process flow. A system typically is more cost-effective when using a conventional means of material handling.

As a guide to discuss with your supplier, here are 10 common ways to convey product through an oven, along with their pros, cons and limitations.


2 PH 0222 Wisconsin Oven Chain Edge Mesh Belt Conveyor

Chain-edge-driven mesh belts have cross structures interwoven into the underside of the belt. They also are connected to drive chains on the belt edges. Photos credit: Wisconsin Oven Corp. (Click on the image to enlarge.)


Positive-Drive Mesh-Belt Conveyors

A versatile conveying choice, positive-drive mesh belts (flat wire, precision mesh, flat-flex, compact grid, etc.) are driven by sprockets spaced across the width of the belt. Teeth on the sprockets engage the openings in the belt so the system drives and tracks consistently and accurately. The sprockets provide both positive belt engagement and tracking, and they create a reliable means of conveyance across a wide temperature range.

Attachments are available for flat-wire belts. For reduced belt wear, the belts ride on either rollers or a herringbone-style slide bed to support the product and belt.

Because the belt-drive sprockets engage with the belt, there is a limit to how small the openings in the belt can be. As a result, positive-drive mesh-belt conveyors are not able to convey tiny parts such as screws, rivets or pins. These small parts must be loaded into trays that are conveyed on the belt.

Positive-drive mesh belts are probably the most common conveyor style used in industrial ovens. They are best suited for conveying light-to-medium loads at temperatures up to approximately 1,200°F (649°C).


3 PH 0222 Wisconsin Oven Friction Driven Mesh Belt Conveyor

Friction-driven mesh belts are a low-cost belt option that offer an array of mesh options to suit many needs. Photos credit: Wisconsin Oven Corp. (Click on the image to enlarge.)


Friction-Driven Mesh-Belt Conveyors

These conveyors rely on friction between the belt and the drive drum to move the conveyor. Because they rely on friction, friction-driven conveyors require a belt-tensioning system. In addition, a belt-guiding system is necessary to prevent the belt from going off track and causing shutdowns due to improper system alignment or the belt stretching unevenly over time. For reduced belt wear, the belts ride on either rollers or a herringbone-style slide bed to support the product and belt.

An array of mesh options are available for friction-driven mesh belts to suit many needs. These belts can handle tiny parts such as eyeglass screws or rivets to medium parts such as nuts and bolts or chain-side plates. Retaining mechanisms such as turned-up edges or shingle plates can be added to keep parts from falling off the belt when loading from a part chute or vibratory feeder.

Friction-driven mesh belts are best suited for conveying light-to-medium loads up to approximately 1,250°F (677°C).


4 PH 0222 Wisconsin Oven Positive Driven Mesh Belt

Positive-drive mesh belts are driven by sprockets, spaced across the width of the belt, to provide both positive belt engagement and tracking. Photos credit: Wisconsin Oven Corp. (Click on the image to enlarge.)


Chain-Edge-Driven Mesh-Belt Conveyors

Chain-edge-driven mesh belts offer an array of mesh options similar to friction-driven belts. These conveying systems have cross structures that are interwoven into the underside of the belt and connected to drive chains on the belt edges. The chains provide positive belt engagement and belt tracking. Because belt sag increases as the belt width increases, these self-supporting belts are more limited on the width than other methods.

Chain-edge-driven mesh-belt conveyor systems do not require belt guidance or tensioning systems because the side chains are used to drive and guide the belt. Retaining edges also are available. 

Chain-edge-driven mesh belts are best suited for conveying light-to-medium loads. Because these belts weigh more than friction-driven mesh belts, they require the oven to have a higher heat input, which increases operating costs.


5 PH 0222 Wisconsin Oven Slat Conveyor with Attachments

Attachments or fixtures often are added to slat-type conveyors to hold or position the load as it passes through the oven. Photos credit: Wisconsin Oven Corp. (Click on the image to enlarge.)


Chain Conveyors

Chain conveyors are suitable for racks, baskets or larger parts that can be carried by two or more chains that are abreast. The chains ride on a structural channel or wear strips. Engineering chains with rollers typically are used at lower temperatures while drag chains without rollers are used at higher temperatures (up to approximately 1,250°F). 

Chain conveyors are best suited for conveying light-to-medium-heavy loads. Due to the low weight of chain conveyors, ovens using chain conveyors require only a small amount of additional heat input to account for the thermal mass of the conveyor.


Slat Conveyors

Slat-type conveyors are similar to chain conveyors; however, the chains are connected with slats (flat bars, rectangular tubes, channels, etc.) to allow more mixed-sized loading to occur. These conveyors can withstand a higher loading per square foot than belt conveyors. Attachments or fixtures often are added to the slats to hold or position the load.

Slat conveyors are best suited for conveying medium-to-heavy loads up to 1,250°F. Slat conveyor ovens typically require more heat input than ovens with other conveyor belts because these conveyor belts tend to weigh more.


Pusher Conveyors

Designed for indexing systems with racks or baskets and higher temperatures, a pusher conveyor has a pusher mechanism located at the front of the oven that moves the baskets or fixtures against one another through the oven. A separate extractor mechanism is required at the exit to pull the load from the oven.

For the pusher conveyor to function properly, the baskets or fixtures need smooth, flat bottoms or wheel guides to accommodate rollers located inside the oven. Side guides can be added to help keep the load from walking laterally on the conveyor if the baskets or fixtures become bent or warped. Severely warped or damaged baskets will not work with this design, however. Also, empty baskets are fixtures are required to unload the oven at the end of a shift, which can be a disadvantage if the oven is emptied frequently.

Pusher conveyors are suitable for heavy loads up to 1,250°F. Because no additional conveyor weight is continually added during operation, additional heat input is not required for the pusher conveyor system.


6 PH 0222 Wisconsin Oven Slat Conveyor with Part Fixture Holes

Slat-type conveyors are similar to chain conveyors; however, the chains are connected with slats such as flat bars, rectangular tubes or channels to allow mixed-sized loading to occur. Photos credit: Wisconsin Oven Corp. (Click on the image to enlarge.)


Pivoting Pusher-Dog Conveyors

Pusher-dog conveyors primarily are used for indexing systems with baskets or fixtures to drive their travel in a straight, linear direction. This method utilizes a hearth for the load to ride on and has a separate pushing mechanism with pivoting pusher dogs that ride on a separate support hearth. The pivoting pusher dogs push the load in the direction of travel during the push stroke and then pivot and retract under the load on the return stroke. Due to the pivoting dogs and the space necessary for the pivot to occur, space is required between loads in the direction of travel.

These ovens typically have several pusher-drive systems to allow varying index distances. In this way, the loads can be further apart on the ends of the oven for the doors to close and closer together through the majority of the oven.

This style is suitable for heavy loads up to 1,250°F. Because no additional conveyor weight is heated during operation, additional heat input is not required for the conveyor system.


Powered-Roller Conveyors

Powered-roller conveyors primarily are used with baskets and fixtures as well as for long, flat products. The baskets or fixtures must have smooth, flat bottoms for the conveyor to function properly. Baskets or fixtures that are warped or bent require additional guides to help keep the loads from walking laterally on the conveyor. Severely warped or damaged baskets will not work with this design.

This conveying method is a little more costly than other methods due to the labor required. The roller-drive components often are mounted on the oven exterior, with holes and seals in the walls for higher temperature ovens.

This style is suitable for heavy loads up to 1,250°F. Because no additional conveyor weight is heated during operation, additional heat input is not required for the conveyor system.


Overhead-Trolley Conveyors

Overhead-trolley conveyors offer a means of passing parts through an oven and to other locations throughout the facility. With vertically hung parts, they optimize otherwise wasted overhead vertical space. The conveyor can utilize straight runs as well as curved and sloped sections to convey parts to the desired work area or zone. Tracks are available in round, enclosed or I-beam designs. Power-and-free systems allow the product to stop at strategic locations for ease of operator handling while the conveyor continues to travel. The conveyor tracks are held by a structure attached to the ceiling or from a structure mounted to the floor. Part hangers typically hang from the conveyor chains so the operator may hang product.

Typically, overhead-trolley conveyors are used for curing applications or other processes below 500°F (260°C). Higher temperatures can be achieved by mounting the conveyor outside of the oven and providing a slot with seals in the oven roof, through which the part hangers are suspended.

Because there is typically a small amount of conveyor weight being continually added during operation, minimal additional heat input is required.


7 PH 0222 Wisconsin Oven Chain-on-Edge Conveyor

Chain-on-edge (or inverted-trolley) conveyors consist of a single strand of chain, turned on its side, with tracks to allow the chain to serpentine through the oven and throughout the facility. Photos credit: Wisconsin Oven Corp. (Click on the image to enlarge.)


Chain-on-Edge Conveyors

Chain-on-edge conveyors — also called inverted-trolley conveyors — consist of a single strand of chain, turned on its side, with tracks to allow the chain to serpentine through the oven and the facility. The tracks for overhead trolleys can be placed upside down and serve to guide the chain. Part fixtures are attached to the chain and supported with tracks to carry the parts. If needed, the part fixtures can be designed to rotate. The oven floor will have a slot for the conveyor posts to penetrate, with the parts carried on top of the posts and the bottom of the posts attached to the chain, which remains below the oven, outside of the heat.

Chain-on-edge conveyors often are used for curing applications and can be used for other applications up to 1,250°F because the conveyor is outside the heat. Because there is little conveyor weight being continually heated, a small amount of additional heat input is required during normal operation.


Indexing-Car Conveyors

Just like the Big Ten Conference, which has more than 10 schools in the conference, any list of oven conveying systems cannot stop at 10 either.

One additional conveyance method is the indexing-car style system. It consists of load cars with an attachment that engages with a chain-drive system mounted to the floor. The attachment chain can be mounted either above the floor level or in a pit. Installing it in a pit reduces trip hazards and can protect the chain from the heat. These types of systems offer the ability to maintain the use of the load car throughout the facility without having to transfer the load from one container to another.

The temperature rating for these systems is limited to the temperature rating of the load cars. Indexing-car conveyors are best suited for conveying medium-to-heavy loads. Ovens using this conveyor style typically require more heat input than others because the load cars tend to be on the heavy side and they have to be heated along with the parts being conveyed.

Although these common conveyors provide cost-effective designs to consider, there are others such as carousel, Ferris wheel or web conveyors as well. Working with an experienced conveyor oven manufacturer can help you optimize your oven conveying system for your application. Be prepared to discuss your application in-depth to identify which option best suits your needs.