Block Making Machine in Yemen: Start From the Power Supply

A block making machine in Yemen should be selected after the power question is answered, not before it. The press is the easy part to buy and the hard part to keep running, and a machine only earns money on the days it finishes a full shift without a stop. So the first question on site is not which model is fastest, but how many kilowatts the site can hold steady for eight hours, and what happens to the rhythm when that supply drops. Buyers who answer this first usually end up with a smaller machine that runs every day.

1. The power check comes before the model

A block machine line is a chain of motors, and the chain is longer than most buyers expect. A single semi automatic press with a vibration table sits in the 5.5 to 45 kW band. Add a batching and mixing plant, a pallet feeder, a conveyor, an air compressor and a cuber, and the connected load climbs past 60 kW. Each station is useful, but none of them makes a block on its own. If the supply cannot carry the whole chain at once, the extra stations become idle capital that still needs maintenance.

There is a second reason to start here. The press draws its current in bursts. The hydraulic pump motor and the vibration motors run at full load for a few seconds, then rest, and the cycle repeats every 12 to 25 seconds per mould. A supply that looks comfortable on paper can trip on these repeated peaks, and a trip means a half compacted mould emptied by hand.

2. Three power routes and genset sizing

Route one is a supply you can hold for a whole shift. Then a fully automatic line with pallet feeding and stacking is the right choice, because automation pays back through labour and cycle consistency. Route two is a supply that drops for part of the day, and here a semi automatic press fed by a diesel generator is the practical answer. The generator must be sized on starting current, not on running power. A 15 kW press can pull two or three times its rated current for the one or two seconds the motor accelerates.

As a working rule, keep the continuous load of the generator at or below 70 percent of its rating, and check the largest motor that starts directly. Inrush is the number that decides the set, and it is written on the motor plate, not in the brochure. Route three is the smallest option: a semi automatic or hand fed machine in the 5.5 to 11 kW range, one shift a day. It costs the least and runs on one small set, which is often the right first step.

3. Block sizes the market actually buys

Most demand in a market built around private houses comes as short runs of a few standard shapes, not one shape at high volume. A 400 × 200 × 200 mm hollow block for walls and a smaller solid unit for columns, lintels and filling are the first two that come up, with 390 × 190 × 190 mm appearing where a supplier already runs that mould. Wall thickness usually sits at 100 mm, 150 mm or 200 mm, sold as 4 inch, 6 inch and 9 inch.

The number that decides whether a mixed order is profitable is mould change time. A mould with quick clamps and locating pins can be swapped in 30 to 60 minutes by two workers. A mould bolted down that needs the tamper head reset can take half a shift. If most of your orders are small and mixed, buy the quick change system and budget for two or three mould sets from the start rather than one.

4. Cement is the largest single cost item

Cement is normally 6 to 12 percent of the mix by weight and the most expensive input per tonne, which is why operators try to cut it. That is the wrong lever. Below about 6 percent cement by weight a dry cast hollow block loses strength quickly and starts failing in handling and stacking. The water to cement ratio is just as sensitive: under 0.40 the mix is too stiff to fill the mould and the block comes out with voids, above 0.55 the block sags when it leaves the pallet.

Real savings come from grading and compaction. Correct aggregate grading, with a sand fraction around 35 to 45 percent of the total aggregate, packs the solid volume better, so less cement paste has to fill the gaps. Compaction does the rest: 20 to 40 kN of pressing force with vibration at 3,500 to 4,800 rpm on a properly filled mould reaches a higher density than a rich mix compacted badly.

5. Keep the spare parts ordinary and available

A machine that has to run for years on a site far from any industrial area must be built from parts a local workshop can replace. Prefer a simple structure with mechanical mould clamping, a standard hydraulic circuit and industrial electrical components that carry a common rating and are sold by more than one supplier. A proprietary control board turns every breakdown into a shipping event.

Buy an early stock of the parts that wear: one extra mould set for your main block size, two vibration motors, a full set of hydraulic seals, and limit switches for the pallet and mould positions. These are small items, and they decide whether a two hour repair stays a two hour repair. Ask the supplier for the vibration motor rating in kW and seal part numbers you can also buy locally.

6. Stage the investment and protect cash flow

Spend the first money on the machine, the moulds, the pallets and a curing area. Leave out the cuber, the pallet return system and the automatic batching plant in the first year. Those systems add 15 to 25 percent to the line cost and they only pay back once the plant already runs two shifts at full output. In a typical first year budget the machine accounts for 40 to 55 percent, pallets 8 to 12 percent, curing and handling 10 to 15 percent, and foundation and shed 8 to 15 percent.

Monthly net margin equals blocks sold per month multiplied by the margin per block, and payback in months equals total investment divided by that monthly net margin. At 400 blocks per hour over a 10 hour shift with a single mould, the theoretical output is about 4,000 blocks a day. Take the real figure from your own cycle time, subtract rejects and unsold stock, and use the margin after cement, aggregate, labour and power.

7. What we need to quote a machine

Send these numbers with your enquiry and we can match a machine class to your site instead of sending a wide range.

• Block sizes and thickness you sell most, with drawings if you have them
• Power you can hold for a full shift in kW, and the generator rating if one is used
• Number of mould sets for the first order and the changeover time you expect
• Pallet size you prefer, for example 900 × 550 mm or 1,400 × 1,400 mm
• Shift length and working days per month
• Cement grade and the aggregate sizes available near the site