A stringer pallet assembly machine builds pallets from continuous beams (stringers) and deck boards by nailing the top deck, flipping the pallet and nailing the bottom deck, usually with automatic feeding and stacking. Leading automatic systems are quoted at 2,000 to 2,400 or more pallets per 8-hour shift, compared with a few hundred per shift on semi-automatic tables.
What the machine has to do
A stringer pallet, such as the North American 48 × 40 in (1219 × 1016 mm) pallet, has two or three long stringers running the full length and boards nailed across them (see stringer vs block pallets and the GMA 48x40 pallet). Because all geometry is regular, the build is easy to mechanize: stringers go down in parallel, boards cross them, nails fix them.
An assembly system must therefore position stringers at the right spacing, place deck boards at the right gaps and overhangs, drive nails at the correct locations, and then repeat for the second deck. Accuracy matters because each board has a specified spacing that affects load distribution and forklift entry.
Typical line layout
Automatic stringer lines vary by maker, but most follow this sequence.
- Stringer infeed. Stringers are loaded from a magazine, hopper or by an operator. Notched stringers for partial four-way entry are produced beforehand (see stringer notchers and chamfering machines).
- Lead board and deck board feeders. Boards drop from magazines or are placed by workers at a feeding station. Lead (edge) boards are often fed separately so that they land with the correct overhang.
- First-deck nailing station. Multiple nailing heads fire simultaneously or in sequence.
- Flip unit. The half-built pallet is rotated 180° so the second deck can be added.
- Second-deck feeding and nailing. The same process as the first deck.
- Exit conveyor and stacker. A stacker counts and piles finished pallets, ready for the forklift (see pallet stackers and destackers).
Capacity and cycle time
Trade reviews of US-built machines give a feel for the range:
| Class | Operators | Quoted output |
|---|---|---|
| Semi-automatic nailer with collated nails | 1 | About 300–400 pallets per 8 hours |
| Mid-range automatic with bulk nails | 2–3 | About 2,000+ pallets per 8 hours |
| High-end automatic line | 2–4 | About 2,400+ pallets per 8 hours |
These numbers are manufacturers' claims reported by Pallet Enterprise magazine; actual results depend on board quality, nail supply, pallet design and downtime. Warped or poorly cut boards reduce throughput through jams and rejects, so raw material quality should be part of any capacity plan.
A cycle time of 20 to 30 seconds per pallet is cited for some semi-automatic machines, which translates into a theoretical 960–1,440 pallets in an 8-hour shift, but real shifts include breaks, nail refills and changeovers.
Components worth inspecting
- Nailing heads. Count the heads, the nail drive method (pneumatic or hydraulic) and the nail spacing adjustment. Nail systems are either bulk-fed or collated, as explained in pallet nailing machines.
- Board feeders. Magazines should handle boards of varying thickness and slight warp. Vacuum or push feeders have different tolerances.
- Pallet size changeover. Some lines adjust by handwheel or motor within minutes, others need tool changes. Check how many sizes the plant runs per week.
- Hydraulic press. A press seats boards and nails before the pallet leaves the line, which improves rigidity.
- Controls. Modern PLC controls store recipes for each pallet design; fault diagnostics shorten stops.
- Safety guarding. Light curtains, interlocked doors and emergency stops are required for compliance; see safety in pallet plants.
Who builds them
North America has a long tradition of automatic stringer pallet equipment, with names such as Viking, Bronco, CAPE, GBN and Rayco appearing in trade reviews. European and Asian suppliers also offer lines, including used units of Spanish and other European origin that circulate on the second-hand market. For a buyer outside North America, check that the machine's nail type, pallet size range and electrical standard (voltage and frequency) match local conditions.
Choosing and integrating a line
- Define the product mix. If most output is one or two sizes of stringer pallet, an automatic line fits well. For many sizes, semi-automatic is safer.
- Match upstream capacity. An automatic line consuming 2,000 pallets per shift needs thousands of boards and stringers ready each shift, which affects multi-rip saws and cut-off capacity.
- Plan the material flow. Space for stringer storage, board stacks and finished pallets decides whether forklifts block each other; see pallet factory layout.
- Budget for spares. Nailing heads, feed tubes and sensors are wear items.
- Plan treatment. Pallets destined for export need heat treatment after assembly.
Frequently asked questions
What is the difference between a stringer pallet machine and a block pallet machine?
A stringer machine nails boards to continuous full-length beams, whereas a block pallet line first builds with blocks and stringer boards, which needs additional stations. The geometries differ, so the machines are not interchangeable.
How many operators does an automatic stringer line need?
Published figures describe lines run by about two to four people, covering board loading, quality checks and stacker handling. Staffing depends on the degree of automation and how boards are fed.
Can a stringer line make heat-treated pallets?
The line builds the pallet, and heat treatment is a separate step in a kiln after assembly, or lumber is treated before assembly. Pallets must then be marked in line with ISPM 15.
Which wood suits automatic nailing?
Straight, dimensionally consistent boards with controlled moisture content work best. Very wet or twisted boards cause splitting and feeding problems.
Sources
- Pallet Nailing Machine Review — Pallet Enterprise
- Pallet assembling system (US patent 3,968,560) — Justia Patents
- PalletPro130XP coil nailer specifications — Senco
- STAKMA Offers Innovative, Automated, Robotic Pallet Nailing Solutions — Pallet Enterprise