Pallet Based vs Pallet Free Block Machine: Pallets per Shift

A pallet based vs pallet free block machine decision is usually argued as a cost question. That is half the picture. We covered pallet price and capital staging in a separate article. Here we work the numbers that actually decide the layout: how many pallets one shift needs, what those pallets do to the face of the product, and how a running line can be changed without rebuilding the plant.

1. How do the two routes form the block?

A pallet based machine fills the mould on a steel pallet. Vibration and hydraulic pressure compact the mix, then the pallet carries the green block to the curing room. The pallet is transport, mould base and curing rack at the same time.

A pallet free line drops the block straight from the mould. Two versions exist. The wet route cubes green blocks the moment they leave the machine. The static press route forms bricks under 31.5 MPa and pushes them out as finished units. No pallet travels, so there is no pallet return loop.

Cycle length is not the only difference. A pallet line has to move a loaded mould, so the frame gets wider and the machine heavier. A QST1800 weighs 34 t and needs 104 kW installed. A cuber working wet blocks sits on a smaller frame because the product leaves the machine immediately.

2. How many pallets does one shift need?

The arithmetic is small. Pallets in circulation equals moulds per hour multiplied by the hours a pallet stays outside the machine. A fully automatic cycle of 15 to 23 s gives roughly 150 to 240 moulds per hour. Take 200 as a working figure. Over an 8 hour shift the machine fills about 1,600 moulds.

Now add the hold time. If a green block stands on its pallet for 24 hours before that pallet comes back, the fleet must cover 200 x 24, about 4,800 pallet positions. Cut the hold to 12 hours and you halve the number. Curing room design, not machine price, drives pallet count.

Turnover is the second half of that sum. A pallet that comes back every 12 hours turns twice a day. A pallet that comes back every 24 hours turns once. Doubling turnover halves the fleet for the same output, and that is why the return conveyor deserves as much attention as the curing room.

3. What pallet size and thickness should you watch?

Pallet dimensions follow the mould. The QST1800 runs a 1,400 x 1,400 x 30 mm pallet. The QST8-15 runs a 980 x 860 x 22 mm pallet. The QST1200 runs 1,350 x 880 x 25 mm.

Thickness and flatness are the two numbers that matter. A plate that was 30 mm when new does not stay 30 mm. Press cycles bend it, and a bent plate tilts the mould. Block thickness then walks out of tolerance across the face, and the ends you stack are no longer square.

Watch the mixing while you are at it. Water to cement ratio sits between 0.35 and 0.45. A plate that does not sit flat lets some moulds fill deeper than others, and the difference shows on the cured face as a change in colour and surface texture.

4. How does pallet wear show up in the product?

Wear shows up first on the face of the block. A warped or nicked plate leaves a shadow line, a scuffed corner or an uneven bed. On a split face unit or a paving block that defect is visible to the buyer, and it comes back as a claim.

There is a second effect that is easier to miss. Trapped air costs about 5 percent of compressive strength for every 1 percent of voids, and plants usually add roughly 30 kg of cement per cubic metre to cover it. A pallet that does not sit flat changes fill depth, so some blocks get less compaction than the mix design assumes. You pay for that cement and still ship a weaker unit.

Strength does not come from the press anyway. It comes from hydration over the days after stripping, and hydration depends on temperature and moisture, not on machine force. A weak curing regime will undo a good forming cycle, however flat the pallets are.

5. Where does the pallet free route fit?

The wet route suits standard solid bricks, concrete blocks and Holland bricks, small units that survive being pushed while wet. Our QSMT1000 wet block cuber does that work with 39.5 kW total power. It removes the pallet fleet, the pallet return conveyor and the forklift that shuffles them.

The static press route suits a different product set. Our QS800, QS1000 and QS1500 two way static presses run at 31.5 MPa with an 18 to 22 s cycle and no pallet. The QS1500 carries 88.4 kW. Both pallet free routes trade product range for simplicity.

• Wet block cuber, 39.5 kW, for solid bricks and Holland bricks
• Two way static press, 31.5 MPa, 18 to 22 s cycle, no pallet
• Vibration and press line, pallet based, for split face and kerb units

6. Can an existing pallet based line add cuber automation?

Often yes, and in stages. The pallet return loop, the cuber and the curing arrangement can be upgraded before anyone touches the machine. A QS cuber system brings stacking down to 1 person on a line that otherwise needs 4 to 6 operators per shift.

Watch the shift pattern as well. A press that runs 4 to 6 operators per shift carries a fixed labour cost even when the cuber does the heavy lifting, so the saving lands mainly in loading and unloading. Price the upgrade against your own wage bill before you commit.

Retrofit first, machine later, is the cheaper order of operations. Fix pallet flatness and curing, measure the reject rate, then automate the handling. Buy the machine last, and only after the product mix tells you whether you need pallets at all.