How to Calculate Block Factory Production Cost

How to calculate block factory production cost is one chain, from the press cycle to the block on the pallet. Turn cycle time into cycles per hour, cut it for the stops your shift really takes, multiply by the pieces one mould carries, and you have blocks per shift. Every cost line then divides into that number.

Most buyers start from the machine price and work backwards, and that order produces a number nobody can check. Work forwards instead. The cycle sets the output, the output sets the material draw, and the local selling price decides whether the machine earns its place.

How many blocks does a 20 second cycle produce in a shift?

Take a machine with a 15 to 23 second forming cycle and plan on 20 seconds. One hour holds 3,600 seconds, so 3,600 divided by 20 gives 180 press cycles in an hour. Over an 8 hour shift that is 1,440 cycles, the theoretical figure a quotation likes.

Now cut it. No press runs 8 hours. If mould cleaning, a mix change and two short stops cost 60 minutes, you run 7 hours, and 180 multiplied by 7 gives 1,260 cycles. The 180 cycles between the clean figure and the real one are what a shift actually costs you.

Pieces per mould varies more than buyers expect. On QST6-15 the mould for a 390 by 190 by 190 mm hollow block carries 6 pieces, so 1,260 cycles give 7,560 blocks a shift. The same sheet quotes 8,640 to 11,520 blocks per 8 hours for that block, which is the same arithmetic with no stops at all.

The piece count decides the comparison between models. The hydraulic presses run the same 390 by 190 by 190 mm hollow block at 5, 10 or 12 pieces per mould, and a 240 by 115 by 51 mm standard brick at 28, 45 or 87. Two machines with one cycle time can differ twofold in output.

The material lines, and the one that dominates

Cement, aggregate, sand, water and admixture are costed per block, not per tonne, because the block is what you sell. Weigh one block and split that mass with your mix proportions. The dimensions give the volume: 390 by 190 by 190 mm encloses 0.0141 cubic metres, so a dose in kilograms per cubic metre becomes kilograms per block.

Cement dominates in most plants that ask this question, and the reason is physical. One block carries kilograms of cement, while the electrical line carries a fraction of a kilowatt hour. Aggregate and sand are heavier but cheaper per tonne, so they sit second. Water and admixture stay small until the dose is wrong.

The machine side of this line is the mould cavity. A 25 MPa rated pressure and a 68 kN vibration force pack the mix into a fixed volume, so adding cement above the mix design raises your cost without raising the price.

How do you price the hours, the people and the wear?

Electrical energy comes from installed capacity and running hours. QST6-15 lists 34.4 kW for the machine and 3.0 kW for the stacker, so 37.4 kW installed. Read the average draw with a clamp meter, because a press does not pull rated power all cycle. At 60 percent of installed over 7 hours the shift uses 157 kWh, and 157 divided by 7,560 blocks is about 0.02 kWh per block.

Direct labour is counted per shift and divided by the blocks. Fully automatic lines in this range are specified at 3 to 4 persons for the whole production task, the closed-loop line at 3 to 6. At 4 persons and 7,560 blocks, one person carries 1,890 blocks. A crew of 8 doubles that line, and no machine setting repays it.

Mould and pallet wear follow cycles, not hours. A mould set gives its full piece count every cycle, so mould cost per block is the mould price divided by its cycle life, then by the pieces per mould. In one shift 1,260 pallets pass through on a 980 by 680 by 20 mm board.

Overhead is floor, forklift, curing and the office, and the curing floor comes from the sheet. A cuber stack holds 18 hollow blocks per layer up to 1,400 mm, so seven layers of a 190 mm block give 126 blocks, and 7,560 blocks need 60 stacks standing at once.

Add the lines, then check the total against your invoices

Put every line in one column, all per block: cement, aggregate and sand, water and admixture, energy, labour, mould and pallet wear, overhead. Add them and the cost per block is finished.

The first check is the invoice. Cost per block multiplied by last month's blocks must land near what you paid for cement, power and wages. If the model sits 10 percent under the invoices, a line is missing, and it is usually handling or rejects.

The second is yield. Count the chipped blocks at the cubing station over one shift. They carry the full material and energy cost and return nothing, so cost per saleable block is cost per produced block divided by yield.

Does the gap to the local selling price pay for the machine?

Take the price your market pays for the same block and subtract your cost per block. That is the margin on one unit. Multiply by 7,560 blocks for the margin on a shift, then by the shifts you can sell, and you have the yearly figure the machine must repay.

Two adjustments keep it honest. Sellable shifts are fewer than running shifts, because stock in the yard is not revenue. And full PLC control is quoted at 15 percent lower labour cost, with electro-hydraulic integration at 20 percent higher production efficiency.

Which figures should you bring from your own plant?

The chain is only as good as its inputs, and six come from you. A supplier can give you the cycle, the pieces per mould and the installed kW. He cannot give you your tariff, your mix or your price.

• Cycle time and pieces per mould for the exact block you will sell, read from the sheet of the model you are buying, not a similar machine.
• Running minutes per shift. Start from 480 minutes in an 8 hour shift and subtract the stops you logged, not the ones you hope for.
• Cement, aggregate and admixture doses in kilograms per cubic metre, with the volume of one block beside them.
• Installed kW of machine plus stacker, your tariff per kWh, and the average draw a clamp meter reads over a full shift.
• Crew size and the shift wage you actually pay, plus the mould price and cycle life in writing.
• The price your market pays for that block, and the shifts a month you can genuinely sell.