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Technical Service Manual 67 Revision Dat e: August 2004 PROBLEM WIT H T HE ENCODER There is a problem with the encoder causing the c onveyor speed to be unstable or causing the conveyor measured s peed to be diff erent f…

Technical Service Manual 66 Revision Date: August 2004

PROBLEM WITH SPROCKET ALIGNMENT ON DRIVE/DRIVEN SHAFTS

There is a condition with the sprocket alignment on either the drive or the driven shafts causing

the conveyor speed to be unstable.

POSSIBLE CAUSES

When the sprockets on a belt conveyor are not lined up properly, the belt can sometimes jump, jerk or "pop" as it goes

around the shaft producing a jerky belt movement and can affect belt tracking. The side of a belt loop catching on the

sprocket teeth as the belt goes around the sprocket causes the “pop”. The proper way to align the belt sprockets is to

center the belt on the shafts and line up the sprockets with the belt.

1) Adjust the outer sprockets to less 1/8" from the sides of the belt.

2) Center the belt on the shafts by lining up the belt with the wear rod carriers.

3) Align every sprocket within 1/8" of the outside edge of its belt loop. This means that half of

the sprockets must be aligned on the left side of the belt and the other half on the right side of the belt.

If the oven has a rail or combination conveyor, the problem could be with the chain idler followers. (They are located

below the surface of the belt where the chains go down to/come up from the under side of the oven). The sprockets are

adjusted with precision shims to locate them in reference to the drive sprockets. Confirm that the extension arm that

holds the idlers is straight, and that the chains track correctly. Too much bend in the extension arm can cause the chain

to jump or bind.

The assemblies to check are:

1) Sprockets/idlers

2) Drive/driven shafts

3) Belt/chains

4) Idler brackets/shims

PROBLEM WITH THE ENCODER DRIVE LINKAGE

There is a problem with the encoder drive linkage causing the conveyor speed to be unstable.

POSSIBLE CAUSES

On ALL conveyors, there are a couple of pulleys and a toothed belt driving the encoder from the conveyor assembly.

If the encoder drive is loose, then check the clamps for tightness. Check the belt for proper tension (1/4" to 1/2" full

deflection when squeezed) and missing or damaged teeth. Check the pulleys for wear and tightness of the setscrews on

the shafts.

Areas to check are:

1) Encoder pulleys and belt.

2) Encoder alignment.

Technical Service Manual 67 Revision Date: August 2004

PROBLEM WITH THE ENCODER

There is a problem with the encoder causing the conveyor speed to be unstable or causing the

conveyor measured speed to be different from the displayed speed.

POSSIBLE CAUSES

The encoder is mounted next to the conveyor drive motor inside the outer sheet metal.

Check the following items for problems:

1) Encoder assembly. If it seems to be turning, check the output at the controller with a oscilloscope.

Refer to the oven schematics for pin numbers and locations.

2) Encoder data cable. Check for kinks, cuts etc, in wiring

3) Encoder drive assembly (pulley & belt or coupling).

4) Controller power supply. See schematics.

5) Encoder mounting hardware and brackets. Check alignment and tightness.

DRIVE CHAIN TENSION IS INCORRECT

The conveyor motor drive chain tension is incorrect causing the conveyor speed to be unstable.

POSSIBLE CAUSES

If tensioning of this chain is too tight, the motor will be side-loaded excessively and the motor will fail prematurely. If

tension is too loose, the conveyor could "jerk" or vary its speed.

The chain should be adjusted with approximately 1/4" of deflection in the chain when it is pressed down from above.

(This adjustment is not an easy to see or make)

Checking and adjustment of this chain can only be done from under the off-load end of the oven.

VOLTAGE TO THE ENCODER IS INCORRECT OR MISSING

The voltage to the encoder is incorrect or missing causing the conveyor speed to be unstable.

POSSIBLE CAUSES

If you suspect the voltage to the encoder, check in the following places.

1) Power supply for the controller (+5V). See schematics

2) Encoder cables/connections.

3) Encoder voltage (No voltage will cause the conveyor to stop)

3) Controller.

The controller could be over-loading the signal from the encoder. The cables could also be distorting or reducing the

encoder signal. If the power supply has failed, the encoder may not work at all. Refer to the schematics for the oven.

Technical Service Manual 68 Revision Date: August 2004

EXCESS BELT/CHAIN UNDER OVEN IS BOUNCING

The excess belt or chain under the oven is bouncing and causing a “jerky” conveyor motion.

POSSIBLE CAUSES

If the conveyor has a "jerky" motion, look under the oven at the excess belt or chain. Sometimes, the excess belt can

start to bounce underneath. A "standing wave" can be seen on the conveyor. This can be caused by the under oven

idlers and followers sticking. Clean the "bearing surfaces" of the idlers to allow a smooth rotation and linear movement.

Another possibility is that the drive sprockets are holding the conveyor belt/chain too long on the off-load, causing the

conveyor to wrap around the sprocket and then drop quickly, instead of rolling off the sprocket smoothly. This can be

caused by excessive wear between the teeth.

1 Sticky chain/belt idlers under the oven.

2 Chain/belt drive sprockets holding conveyor too long.

3 The Chain may “catch” on the Belt at the ends of the Oven.

THE CHAINS ARE DIRTY (EDGE RAIL CONVEYOR ONLY)

The chains are dirty and/or dry (edge rail conveyor system only) causing the conveyor to “jerk”

as it goes around.

POSSIBLE CAUSES

If the chains are dirty, they will not flow smoothly around the sprockets and the idlers. The links can stick and kink up

holding an angled position instead of laying flat. Clean the chain links if they appear to have an excessive amount of build

up residue. The chains may need to be removed and soaked in a cleaning solvent to completely clean them.

If they look "dry", oil the chains, however, refer to the Preventive Maintenance Manual for lubrication recommendations.

Do not over-oil the chain. Too much oil will cause smoke when the oven heats up.

Also since the opening in the rails is very small, any chain links with any dirt could get stuck in the rails and cause a

"jerky" motion of the conveyor.

RUN “CONVEYOR SPEED CALIBRATION” PROCEDURE

The conveyor is in need of calibration if the measured speed of the conveyor to be different from

the displayed speed of the conveyor.

POSSIBLE CAUSES

Perform the conveyor calibration. Refer to the Oven Operations Manual for details on this procedure.

If after calibration, the conveyor measured speed is not equal to the displayed speed, then the electrical wiring and

components should be checked, especially the encoder output.