Quick answer: To print a date or lot code on the bottom of a container, you need a stretch of line where nothing supports the container from below. That's what a bottomless conveyor does: it grips containers by their sides and carries them across an open gap while a coder mounted underneath prints on the base. Add the CE-TRA-37 bottomless side belt transfer conveyor between two conveyors, or fit the CE-TRA-12FM C-frame gap transfer conveyor over your existing conveyor, mount your coder under the gap, and set the belt speed slightly faster than the machine feeding it.
Bottom coding sounds complicated until you see the setup. Here's the whole thing, step by step.
Step 1: Make room for the code
A normal conveyor supports containers on a belt, so the bottom is never visible. A bottomless conveyor holds each container between two gripper belts instead, leaving the base exposed for as long as the container is in the machine. That open space is where your coder goes.
- Stand-alone: the CE-TRA-37 sits between two conveyors on its own stand, adjustable from 37 to 43 inches floor to belt on the 37S and 35 1/2 to 42 inches on the 37B.
- Over an existing conveyor: the CE-TRA-12FM is a C-frame that fits over existing conveyors without major modifications and creates a 12-inch gap, adjustable from 26 to 44 inches floor to belt.
Step 2: Mount and trigger the coder
Your inkjet, laser or other coder mounts below the gap, aimed up at the passing container. The CE-TRA-37 lists a print head bracket among its features. Work with your coder supplier on the trigger, usually a sensor that fires the printer as each container reaches the print position, and on the throw distance from the print head to the container base.
Step 3: Set the container up so the code lands straight
Clean codes come down to the container not moving relative to the belts. From the CE-TRA-37 setup procedure:
- Level the machine so all four feet sit firmly on the floor and it doesn't rock.
- Match the floor rail height to the conveyor upstream, with no bump at the transfer point. The smoother the transition, the fewer problems downstream.
- Set belt height so the belts engage the container just above the center of its height, and keep them level and parallel to the frame.
- Check parallel with a straight edge across the two belts, and confirm the tops of the belt covers line up.
- Set the grip with the crank handle: firm enough that the container would be difficult to pull out, but not tight enough to dent the sides.
Step 4: Set the speed
Run the transfer conveyor a little faster than the machine feeding it, whether that's a bottle orientator, filler or capper. Running slightly faster opens a gap between containers instead of letting them bunch up at the entrance, and a gap is what lets your coder fire cleanly on one container at a time. Turn on the upstream machine first, set it to normal production speed, then set the transfer conveyor just above it and write the setting down for next time.
Common bottom coding problems and fixes
| Problem | Check |
|---|---|
| Codes are crooked or smeared | Belts not parallel, speeds not matched, or the container is slipping. Confirm equal resistance along the whole gap. |
| Containers bunch at the entrance | Transfer conveyor is running at or below the speed of the machine feeding it |
| Containers tip at the transition | Floor rails not level with the upstream conveyor, or a bump at the transfer point |
| Dented container sides | Gripper belts too tight; back the crank handle off until the container is firm but not deformed |
| Container spins between the belts | Belt speeds out of sync or one belt slipping; check belt tension |
Frequently asked questions
How do I print a date code on the bottom of a bottle?
You need a gap in the line where nothing supports the container from below. A bottomless side belt transfer conveyor grips the container by its sides and carries it across that gap, so a coder mounted underneath can print on the base as the container passes.
What equipment do I need for bottom coding?
Three things: a bottomless or gap transfer conveyor to expose the bottom, a coder (such as an inkjet printer) mounted below the gap, and a way to trigger the coder as each container passes. The CE-TRA-37 product page lists a print head bracket as an included feature.
Can I add bottom coding to an existing conveyor line?
Yes. The CE-TRA-37 is a stand-alone unit that sits between two conveyors on its own height-adjustable stand, and the CE-TRA-12FM C-frame model fits over existing conveyors without major modifications, creating a 12-inch gap.
Where should I put the transfer conveyor in my line?
Typically at the end of another conveyor, after the machine that fills or caps your containers. Set its belt speed a little faster than the machine feeding it so a gap opens between containers instead of letting them bunch up at the entrance.
Why do my bottom codes come out crooked or smeared?
Usually the container is moving or rotating as it passes the coder. Check that the two gripper belts are parallel and their speeds are matched, that the belts hold the container firmly enough that it's hard to pull out, and that the transfer between conveyors has no bump. The CE-TRA-37's frequency-controlled motors keep both belt speeds matched so codes stay straight and legible.
Does bottom coding work on tapered bottles?
Yes, with the right machine. The CE-TRA-37B has tilting capabilities for tapered bottles, and the CE-TRA-12FM has a tilting head, so the belts can match the angle of the container instead of gripping only at one point.
Talk to us about your line
Tell us your container size and shape, your line speed and what you need to code or inspect, and we'll tell you which transfer conveyor fits. Call 866-888-6327 (Mon–Fri, 8am–5pm CST), email sales@clevelandequipment.com, or see the CE-TRA-37 bottomless side belt transfer conveyor.