TL;DR
Conveyor jams are usually caused by a warped PCB, a worn chain link, or a drive sprocket particle buildup. Stop the machine, cool the zone, and remove the board before inspection.
What you might see
- conveyor stop alarm during production
- PCB stalled inside the oven tunnel
- drive motor current spike on conveyor alarm
- audible scraping or clicking from conveyor
Likely causes
Excessively warped PCB catching on conveyor rail or mesh
Worn or broken conveyor chain link dragging on the guide rail
Solder or flux residue buildup on drive sprocket reducing traction
Conveyor edge guide set too narrow for the board width
Required tools
- High-temperature gloves
- Oven access panel wrench
- High-temperature-safe solvent
- Conveyor chain inspection tool
- Replacement chain link set
Safety first
- The oven interior is at reflow temperature when a jam occurs. Do not reach inside until the tunnel temperature drops below 60 degrees C.
- Flux residue and cleaning solvents are flammable. Ensure the oven is powered off and cool before applying solvent to any interior surface.
Procedure
- 1
Stop the machine immediately and select the conveyor stop mode on the controller. Do not attempt to force the conveyor by cycling power.
- 2
Allow the oven tunnel to cool below 60 degrees C before reaching inside. Use the oven temperature display to confirm.
- 3
Open the side access panels and carefully remove the jammed PCB. Check the board for solder shorts or excessive warpage.
- 4
Inspect the conveyor chain in the jammed section for broken or binding links. Replace the chain section if a broken link is found.[1]
- 5
Clean the drive sprockets and chain with a high-temperature-safe solvent to remove flux and solder residue.[1]
- 6
Verify the conveyor edge rail width against the PCB width specification. Adjust the rail width so there is at least 1 mm clearance on each side.
- 7
Manually advance the conveyor one full cycle while the oven is cool to check for binding.
- 8
Resume production and monitor the conveyor current draw for the first 10 boards.
Sources
Heller Industries Heller 1900 / 1936 MK7 Reflow / Wave Solder Oven general technical documentation, Heller Industries
Heller Industries reflow oven general conveyor maintenance procedures (general)
More guides for Heller Industries Heller 1900 / 1936 MK7
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Solder balls are usually caused by a ramp rate too high, moisture in the PCB, or solder paste slump from printing to reflow delay. Check the preheat profile and board storage first.
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