Block Sizes Used in Iraq: How the Mould Layout Sets Output per Shift

Block sizes used in Iraq are not picked from a catalogue. They begin as a wall thickness on a drawing: the structural or partition duty sets the block width and height, that width sets the cavity behind the face shell, and the cavity grid sets how many pieces leave the machine on every stroke. Run that chain in order and a mould order becomes predictable. Run it backwards from a stock list and the mould forms the wrong block for the wall.

Wall thickness first, then the block, then the cavity

A buyer rarely needs a size for its own sake. He needs a wall that carries a load, or one that divides a room, and the thickness that duty requires is the real input. Give us that number with the drawing: face shell, web thickness, core count, end profile and build height all follow from it.

A buyer rarely needs a size for its own sake. He needs a wall that carries a load, or one that divides a room, and the thickness that duty requires is the only real input. Give us that number with the drawing: face shell thickness, web thickness, core count, end profile and build height all follow from it. Each of those decisions moves the cavity.

That is why the block drawing comes before the mould drawing. A wall thickness turns into a block, the block into a cavity, and the cavity count is what the plant pays for in every cycle.

How many cavities fit on a 1,400 x 1,400 mm pallet?

The 34 t machine in our range runs a 1,400 x 1,400 x 30 mm pallet, and the 20 t machine a 1,350 x 1,150 x 30 mm pallet. Those are outer dimensions. The area that can carry cavities is smaller: the mould frame needs a land around the block field, the feed box needs clearance at the edges, and the rollers need a clamp band on the pallet.

Inside that reduced area the count is arithmetic. Divide the usable length by the block length plus the steel between cavities, round down, and repeat across the width. Whatever remains is dead area, which is why a modest difference in pallet width can cost a whole column.

The count belongs to the machine, not the block. The same 390 x 190 x 190 mm hollow block is listed at 5 pieces per mould on one press, 10 on a second and 12 on a third, and the 200 x 100 x 60 mm paver at 16, 24, 32 and 40 across four press sizes. Pieces per pallet without a model has no single answer.

Height works on the same arithmetic from the other side. A taller block needs a deeper cavity, so each stroke takes more concrete, the feed runs longer and the vibration window stretches. The cycle drifts toward the 25 second end of the range, and each extra second is multiplied across the shift.

From pieces per cycle to shift output

Output is the product of three numbers: pieces per stroke, strokes per hour, and effective hours. The first comes from the cavity grid. The second comes from the cycle, 15 to 25 seconds on the large machines and 15 to 23 seconds on the smaller pallet, minus pallet exchange, feed box return, mixer recharge and stacker handoff. The third is the shift clock minus the same stops.

Nameplate figures sit at the top of that chain, not in the middle. The largest machine in our range is rated up to 220,000 standard bricks in an 8 hour shift, and that belongs to a 240 x 115 x 51 mm standard brick on a full pallet. Put a heavier block on the same pallet and the piece count falls.

Sheet numbers on a smaller machine show the chain at work. The QST6-15 lists 6 hollow blocks of 390 x 190 x 190 mm per mould and 8,640 to 11,520 pieces in 8 hours, and on the same frame 32 to 36 standard bricks per mould and 46,080 to 61,440 pieces.

So when a buyer asks what a size will produce, the answer needs four inputs: the block drawing, the machine and pallet model, the cycle the plant can hold, and the hours it runs.

What changes when you switch block size?

A new size means a new mould body, and on a machine of this size the swap is measured in hours: unclamp the old body, lift it out, land the new one, align it to the pallet, torque it down. Then the machine is re-set, because a new cavity grid changes what the vibration and the press work against.

Vibration is set inside a 3,800 to 4,500 per minute band, with 280 kN behind it on the 34 t machine and 220 kN on the 20 t machine. A deep narrow cavity needs a different amplitude from a shallow paver cavity, or the mix bridges at the corners. Pressure stays at 31.5 MPa on both, but the closing point moves with block height.

Then comes the first batch. Until the settings settle, blocks come out with the wrong height, rounded corners or a torn face, and those pallets are scrap. Count the changeover in hours and the first pallets as loss, and run long campaigns instead of swapping for every order.

Why blocks from one mould mate and blocks from two do not

A mould cut on a CNC machine holds its cavity positions to a tight tolerance, so every block from that cavity repeats. The variation that matters runs between cavities and between moulds: steel wear, vibration stronger at the centre of the face than at the ends, and pressure that is not even across the pallet.

Two blocks a fraction of a millimetre apart in height will not stack flat. Build a wall from pallets of two batches and the course steps, the mortar bed thickens to hide it, and the joint shows on the face. The plant pays for that twice, in mortar and in labour.

Keep one mould's output together through curing and dispatch, measure green height on a fixed interval and write the reading down. Wear shows as a change in dimension, not as a crack, so a tape finds it first.

What to send before a mould is cut

We cut to the drawing you send, not to an assumed local size. The mould drawing follows the block drawing, and the block drawing follows the wall.

• The block drawing, or the wall thickness and its duty, with the tolerance you accept on width and height.
• The hollow pattern: number of cores, web thickness, and whether the ends need tongue and groove or a chamfer.
• The machine model and pallet size, so the cavity grid is calculated on the real forming area.
• The cycle you run and the hours the plant really works, so output is quoted on your shift.
• The aggregate and mix you use, because green strength decides how hard the machine can vibrate without tearing the face.

Send those five items and the answer comes back as a cavity count, a cycle, and a shift figure you can check against the plant you run.