Fruit and vegetable packing is rough on packaging machinery in ways that warehouses never are. Trays run on damp concrete floors in packhouses, board absorbs moisture from wash lines and rain, temperatures swing from field heat to cold store, and the tray has to hold a net weight of produce that shifts and sweats during transport. A tray erector built for dry goods will jam here. The ZRAY fruit and vegetable tray erecting machine is engineered around those conditions.

This article covers tray formats, the corrugated specifications that survive cold chains, the machine parameters, the washdown considerations, and the maintenance schedule a packhouse should run. We focus on what keeps a tray line above 90% uptime through a full harvest season.

Tray Formats and Board Specifications

Two tray families cover most fresh produce packing:

• Open trays (fruits, vegetables, eggs) — formed and glued on four corners, open top for filling, often running through shrink or stretch wrap after filling.
• Tray and lid sets — tray plus separate lid blank, formed on the same machine with a quick changeover, used for grapes, berries, and tomatoes.

Board requirements differ from dry-goods cases:

Three properties matter more than the grade name:

• Moisture resistance: produce washing means the board will see water. Specify MR (moisture resistant) board for packhouse use, and keep blanks wrapped until feeding. Board above 12% moisture jams the magazine and weakens hot melt bonds.
• Wet-strength board for leaf greens and berries packed in ice or with high condensation — standard kraft delaminates after a day in a wet cold chain.
• Print and coating: coated (varnished) board reduces suction cup grip. If your tray has a full-coverage coating, tell us before we size the cups — we drop to a softer silicone cup or add a second pick row.

Machine Parameters for the Packhouse Line

On the washdown question: we do not build a full washdown machine for most packhouses, because a sealed machine costs more and runs hotter. We build a washdown-tolerant machine — stainless where food touches, sealed IP55 cabinets, sloped panels — and design the layout so operators can hose the floor without spraying the electrics. Tell us if you run high-pressure hosing inside the machine area; that changes the enclosure spec.

Why Hot Melt Works in a Cold Chain

Cold stores at 1–5 °C are brutal on glue. Here is how the machine is set for cold chain:

• Tray is glued before cooling. The machine forms and glues trays at packhouse temperature (15–25 °C), where hot melt bonds normally. Trays are then moved into cold storage. The glue bond set at warm temperature survives cooling; the failure mode to avoid is gluing trays that are already cold.
• Glue temperature control: the tank holds 150–170 °C with a closed-loop thermocouple. If the packhouse line sits idle overnight, the warm-up cycle reaches setpoint before the first tray runs — do not rush it. Running cold glue produces joints that pop in the cold store.
• Open time and board moisture: hot melt open time is 3–6 seconds. On damp board the bond surface wets out poorly, so joints peel in the store. Keep MR board and the bond survives stacking.

For berry and grape shippers who insist on food-grade adhesives, we offer cold glue (PVA) as an alternative. The trade-off is 60–90 seconds of curing time, which means you need space for a compression section after the erector. Warm melt stays the default for speed.

PLC Alarms Specific to the Tray Line

The packhouse will see the same alarm family as other ZRAY machines plus a few tray-specific codes:

Packhouse operators on 3-shift harvest schedules log the same alarm history by shift, and our remote diagnostics team reads it over the network to separate glue issues from mechanical wear.

Maintenance Schedule for Harvest Season

Harvest runs are 4–8 weeks of 2–3 shifts with no mercy. The schedule below assumes you want the machine to survive the whole season without a mid-harvest breakdown.

We schedule the pre-season service to land 2–3 weeks before your first harvest week, so the machine is proven before the pressure starts.

Laying Out the Packhouse Line

Three layout points our engineers check at the planning stage:

• Line sequence: blank magazine → tray erector → glue set → filling station → wrap/seal → palletize. The erector output has to match the number of filling hands or the filling station starves.
• Conveyor height: match the tray discharge height to your filling table. A 900 mm discharge height is the common standard; we set it to your table height at commissioning.
• Floor and drainage: keep the erector zone dry. A packed machine sitting in a puddle of washdown water will eventually draw moisture into the air system. Slope the floor away from the machine or add a drip tray under the air filter.

Matching Tray Output to Your Filling Station

The erector is not the bottleneck in most packhouses — the filling station is. But when the erector output is mismatched, you lose time on both sides. Here is the calculation we run at the planning stage.

Worked example: eight filling hands at 12 trays per minute each would need 96 trays/minute — that exceeds any single erector. In practice, filling hands never run at their theoretical rate on a produce line; they slow when fruit is small, wet, or graded by hand. Plan the erector against the sustained filling rate, not the theoretical one.

• If your filling station sustains 15–25 trays/min, the single-line tray erector matches it directly with no buffer.
• If filling exceeds 25 trays/min for more than 30 minutes at a time, add a buffer conveyor between the erector and the filling station instead of buying a second erector. A 5 m buffer at 25 trays/min holds roughly 120 trays — about five minutes of filling time — which absorbs the erector’s size-change and blank-reload pauses.
• Wrap station speed: if you run shrink or stretch wrap after filling, size the wrapper to the tray output too. A fast erector with a slow wrapper just moves the bottleneck downstream.

We also set the erector to run slightly above the filling rate (105–110%) on purpose. That small margin means the buffer never fully empties, and the filling hands never wait on trays — the most expensive waste in a packhouse is idle hands during a harvest week.

Where the Tray Machine Sits in the ZRAY Range

For farms and packhouses that run open trays plus lids, the Single-Piece Case Erector platform with the tray package (low-height forming, MR board kit, washdown-tolerant build) covers most operations up to 25 CPM. If your packhouse fills trays at very high volume or runs double lanes, the Double-Head High-Speed Case Former doubles the output without doubling the footprint.

Send us your tray blank, produce type, and cold chain profile. We will confirm the board and cup spec and run the FAT with your trays — email [email protected] or WhatsApp +86 13681839278, and our engineers reply within 24 working hours. Full service terms, the 45-day delivery schedule, and the FAT plan are on our contact page.