Curb Stones and Paving Blocks Demand in Syria: Moulds, Press Force and Mix

Curb stones and paving blocks demand in Syria is a production question before it is a sales question: both products are judged on the mould that forms them and the mix that fills it. A kerb stone is a tall narrow section charged in one pass and stripped straight upward. A paving block is flat and wide, and its face layer carries the colour a buyer sees first. Same frame, same pallet, different failure points.

Four figures hold the workshop. A QST6-15 runs a 980 × 680 × 20 mm pallet on a 15 to 23 second forming cycle with 68 kN of excitation force and 25 MPa of rated pressure, while the largest servo frame carries 280 kN and 31.5 MPa on a 1,400 × 1,400 × 30 mm pallet.

Why does a kerb stone fight the mould differently from a paving block?

A kerb stone sits in a deep narrow pocket, and filling that pocket is the first difficulty. The feed box crosses once and must drop enough mix to fill the whole height in a single pass, because a second pass lays a joint line across a tall section and the stone breaks along it later. The arch-breaking distributor pushes material down the full depth instead of letting it heap at the mouth. A starved pocket leaves a short corner, and no curing fixes that.

Stripping is the second difficulty. The mould lifts while the pallet is still vibrating, and the amplitude has to hold until the mould clears the top edge. Drop it early and the top arris drags and tears. A flat paver clears in a fraction of that travel, so running kerbs and pavers on one frame needs a longer strip and a slower lift.

How do press force and vibration frequency have to be matched?

Vibration fluidises the mix so it runs into every corner of the pocket; the press then closes on it and gives the green product enough strength to travel on its pallet. In the QST range vibration sits at 3,800 to 4,500 times per minute, and excitation force steps from 68 kN on a QST6-15 through 95 kN on a QST8-15 to 150 kN, 220 kN and 280 kN above that.

The balance is narrow. Too little vibration and the pockets fill short, so corners arrive already rounded. Too much and the coarse aggregate sinks while the fine fraction and the pigment rise, leaving a paver with a rich face and a weak body. A frame is fluidised for part of a 15 to 23 second cycle and the press holds the rest. A pallet-free wet line runs at 21 MPa, a 13 to 18 second cycle and 3,200 to 4,600 vibrations per minute.

How is the coloured face layer placed over the base mix?

A two-layer product is charged twice from one feed box: face mix first, then base mix, and the press closes on both together so they bond before the block leaves the mould. The face mix carries washed fine sand, cement and pigment; the base mix carries coarser aggregate and most of the volume. Depth is set by the face plate inside the mould, not by the operator, and it has to stay even across a moulding area reaching 1,150 × 1,100 mm on a pallet-free press and 1,440 × 850 mm on the largest static press.

Vibration is usually cut for the face charge so pigment stays at the surface instead of sinking into the base. Where the product must imitate natural stone, a high-pressure wet mix filtration press with vacuum assistance forms kerbs and pavers in one charge and strips them automatically. Its mix is cement, washed sand, stone powder, granite edge scraps and manufactured sand, fed wet with no pre-drying.

What keeps a mould edge square after a million strokes?

The mould is the tool that wears first. A production mould is cut from wear-resistant alloy steel, machined to micron level on CNC equipment and put through a hardening cycle, with a special high-temperature heat treatment on the smaller frames. What matters for pavers is the arris: once the working edge of the core rounds over, every block leaves with a soft corner in the same place.

The guiding assembly and the positioning mechanism keep the core concentric inside the frame; when the core shifts, one wall of the block comes out thicker than the other and the thin side chips under the clamp.

How many pieces does one mould route return in a shift?

Everything follows cavities per mould multiplied by strokes per shift. One mould set on a QST6-15 covers four products: a 390 × 190 × 190 mm hollow block at 6 pieces per mould and 8,640 to 11,520 per 8-hour shift, a 240 × 115 × 90 mm porous brick at 15 pieces and 21,600 to 28,800, a 240 × 115 × 51 mm standard brick at 32 to 36 pieces and 46,080 to 61,440, and a 200 × 100 × 60 mm coloured tile at 21 to 24 pieces and 27,360 to 34,560.

Eight hours hold 28,800 seconds, so a 15 to 23 second cycle returns roughly 1,250 to 1,920 strokes, and each stroke gives up the contents of one mould. A press carrying 40 pieces of 200 × 100 × 60 mm across a 1,440 × 850 mm area returns 40 units a stroke. A pallet-free line reaches up to 135,000 bricks of 240 × 115 × 50 mm in an 8-hour shift.

How do you cure, cube and pack without chipping an edge?

Green product is soft for the first hours, so handling must lift a whole layer and never a single block. Layer-separated curing keeps it simple: each layer rests on its own pallet through the curing area, so nothing is stacked green on green and no face is crushed under the layer above. A wet-brick line does the same on metal frames, every slab layer held apart while transfer vehicles move them.

When the pack goes out, strap tension is set on the touch screen between 200 and 2,500 N, with about 15 to 18 seconds per strap, and PET strap comes in 12, 16 and 19 mm widths. Keep edge boards at the four corners so the strap bears on the board and not on the block, and keep the finished stack on level ground.

• QS-1200A cuber: 15 to 18 seconds per layer, about 3,800 pallets per shift, stacking height up to 1,400 mm.
• QS-1000G-A cuber: 16 to 18 seconds per layer, stacking height 1,300 mm, and nothing thinner than 50 mm in the clamp.
• QS-1000Y mobile cuber: up to 20 layers of solid brick or 11 layers of hollow block in one pass.
• Forklift clamp: 500 to 800 standard bricks or 40 hollow blocks per bite, 10 layers of solid brick.
• Wrapper: five-sided sealed pack, packing height 680 to 1,150 mm, strap tension 200 to 2,500 N.

Which three settings decide the first pallet off the machine?

Three settings decide what the first pallet looks like: the mould route with its cavity count, the mix design with its face and base proportions, and the vibration and press timing that fluidise and compact each charge. Check corner integrity, face layer depth at four points and the height of the top, middle and bottom pieces before a shift is released. Send your product sizes, pallet size and shift target, and we return a mould route and starting settings.