Most case erector purchases that go wrong do not go wrong because the machine was defective. They go wrong because the specification was incomplete in a way that nobody noticed until the machine was installed and running. The blank was an unusual construction. The peak rate was calculated from annual volume rather than from the busiest hour. The downstream machine could not keep up. Each of these is a specification error, and each is avoidable with an hour of work before the enquiry is sent.

This is that hour of work, in nine steps. Each step gives the decision, the figure to establish, and the mistake that step is most likely to produce.

Step 1: Establish the case construction and the board grade

The first question is not how fast the machine needs to run. It is what is being formed. Case constructions that look similar on a drawing behave very differently in a machine.

RSC (0201) is the standard slotted shipping case and the construction most erectors are designed around. It is formed by folding four bottom flaps and sealing them.

Half-slotted (0203) removes one set of flaps and is common for produce and for products that are loaded before closing. It is easier to form but has a weaker bottom.

Die-cut and crash-lock bottoms require tooling that a standard RSC machine does not carry. These are covered by a different machine class, and the tooling requirements are set out separately in the lock-bottom, crash-lock and self-locking comparison.

Two-piece and three-piece constructions with a separate body and lid are outside the RSC flow and require a dedicated forming sequence.

Board grade then sets the machine’s adjustment envelope. You need four numbers, not one: liner weight in g/m², caliper in mm, ring crush in kN/m, and the expected moisture range at the machine. A blank at 1.4 mm with good liners forms well; a blank at 1.9 mm made from heavily recycled liner with low ring crush does not, and it feels stiffer in the hand while failing. Where the board is lightweight or recycled, the settings discipline in the thin and low-grade board guidance applies.

The mistake at this step: sending the enquiry with a case size and a photo, and no construction name, no board grade and no caliper. This is the single most common cause of a wrong quotation.

Step 2: Define the full size range, not the current range

Establish the minimum and maximum length, width and height across everything the machine might plausibly run over its service life — not just the formats running today.

A working reference range for a general-purpose machine is L 200 to 600 mm, W 150 to 400 mm, H 100 to 400 mm. Machines exist above and below that, but the envelope drives the magazine size, the fold rail travel, the mandrel dimensions and the discharge height, and none of those are economically expandable afterwards.

The mistake at this step: specifying the current range and assuming later formats will fit. A machine bought for 400 × 300 × 250 mm cannot be economically expanded to 600 × 400 × 400 mm; that is a different machine. Growth in case size is one of the most expensive assumptions in packaging equipment.

Step 3: Calculate the required case rate from the peak, not the average

This step is where most under-specification originates.

Take the busiest hour of the busiest shift, divide by 60 to get cases per minute, and then add a margin of about 15 per cent for recovery and catch-up after a stop. Do not divide annual volume by annual hours; that produces an average rate the line never actually runs at, and it produces a machine that is too slow on exactly the days it matters.

An example makes the point. A plant shipping 2 million cases per year across 4,000 operating hours averages 500 cases per hour, which is 8.3 CPM and suggests a semi-automatic machine. But if the line runs five days a week on two shifts with a morning peak, the busiest hour may be 1,800 cases, which is 30 CPM and requires a fully automatic machine. Average rate and peak rate lead to different machines.

The mistake at this step: quoting capacity from annual tonnage. Annual figures describe the business; hourly figures describe the machine.

Step 4: Apply the efficiency discount

A machine rated at 40 CPM does not deliver 40 CPM across a shift. Real output sits at 75 to 85 per cent of rated speed once changeovers, minor stops, board variation, operator intervention and downstream interruptions are counted.

For planning purposes, treat a 40 CPM machine as delivering 30 to 34 CPM effective. If the peak requirement is 32 CPM, a 40 CPM machine is the correct size and a 35 CPM machine is not, even though the rated figures look adequate.

The mistake at this step: comparing a required rate against a rated rate. The comparison only means something when both are expressed on the same basis. The fuller treatment of this discount, including its effect on whole-line throughput, is in the case erector productivity analysis.

Step 5: Choose the bottom sealing method

Four methods are in common use and they have different cost structures and speed ceilings.

Hot-melt glue is the default for high-volume work above roughly 25 CPM. Consumable cost per case is low, bond strength across the fibres is high, and the method tolerates recycled board reasonably. It requires a glue system with temperature control, nozzle maintenance and adhesive storage discipline. The cost comparison against tape, with figures per case and break-even volumes, is set out in full in the hot-melt versus tape sealing analysis.

Tape has the lowest equipment cost and the lowest maintenance requirement. Material cost per case is higher and rises with board dust, recycled content and humidity. It suits lower volumes, multi-format operations and plants that want to avoid adhesive handling entirely.

Cold glue and starch set by absorption rather than cooling and suit highly absorbent recycled board and food-contact applications where a starch-based adhesive is preferred. Compression time is longer.

Self-locking and crash-lock bottoms use no consumable at all, which removes adhesive cost, nozzle maintenance and temperature control from the operating load. They require specific tooling and specific blank quality, and the conditions are covered in the lock-bottom and crash-lock requirements material.

The mistake at this step: choosing glue or tape on consumable cost alone. The binding constraint is often speed ceiling, board grade tolerance or maintenance capability rather than cost per case.

Step 6: Establish the changeover frequency and format count

Count the changeovers per shift and the total number of formats in the product range. These two numbers determine whether recipe memory and tool-free adjustment are worth paying for.

Up to about two formats running continuously, a machine with hand adjustment is adequate. From three to fifteen formats with occasional changes, tool-free handwheel adjustment is sufficient. Above fifteen formats, or above two changeovers per shift, recipe memory with servo positioning starts to pay, because changeover time at that frequency is the dominant loss. The economics of reducing changeover, including the SMED treatment of the problem, are analysed in the changeover optimisation material.

The mistake at this step: buying recipe memory to fix a changeover problem that is actually a documentation problem. Recipes do not help if the machine has no recorded baseline to put into them.

Step 7: Confirm the floor, headroom and services

Four physical facts must be established before the machine can be correctly specified.

Footprint. A single-head machine at 35 CPM occupies roughly 6 square metres; a compact machine can deliver 30 CPM in under 4. Confirm the available area including access for maintenance on all sides, not just the machine’s own footprint.

Clear height. Allow for service access above the forming station. Below about 2.4 metres free height, access becomes a safety problem.

Infeed and discharge direction. Confirm which way the blanks are loaded and which way the formed cases leave, and confirm the discharge height matches the downstream conveyor.

Utilities. Establish the available compressed air pressure and volume, and the electrical supply. A machine specified against a compressed air system that is already at capacity will underperform, and the fault will look like a machine problem.

The mistake at this step: specifying from a catalogue footprint and discovering at installation that the maintenance access side faces a wall.

Step 8: Set the automation level and the operating headcount

Semi-automatic, 8 to 12 CPM: one to two operators, with the operator loading blanks and managing discharge. Suits low volumes, highly seasonal work and very large or irregular cases.

Automatic, 25 to 40 CPM: around 0.3 to 0.5 operators for the erecting function, since the role becomes supervision shared across the line. Suits most production work above roughly 200,000 cases per year.

Fully automatic with servo and recipe memory, 35 to 45 CPM: the operating role is supervision and changeover. Suits high-volume, multi-format work.

The labour comparison between semi-automatic and fully automatic machines, with a worked cost model and the volume threshold where the answer changes, is set out in the semi-automatic versus fully automatic analysis.

The mistake at this step: buying automation to reduce headcount and then discovering the constraint was elsewhere on the line. Automating the erector raises line output only if the erector was the constraint.

Step 9: Compile the enquiry sheet

One page, twelve items. A supplier with all twelve can quote accurately on the first pass. A supplier missing three will either ask, or guess.

The mistake at this step: sending the sheet without the peak rate and without the board grade. Those two omissions cause more re-quotations than the other ten items combined.

The four typical profiles, decided

Small single-format plant, under 150,000 cases per year. A compact semi-automatic or small automatic machine, tape or glue by consumable economics, hand adjustment. Recipe memory and servo positioning are not worth paying for at this volume.

Contract packer, 50 or more formats. Automatic with tool-free adjustment and recipe memory, and a formal changeover procedure. The machine matters less than the changeover discipline around it.

Food and beverage line, 60 to 90 CPM. High-speed automatic, glue sealing, specification driven by the filler rate rather than by case volume. Efficiency discount matters enormously here because the line cannot be buffered.

E-commerce sortation centre. Automatic with the peak rate as the sizing figure and a realistic view of peak duration. Where the peak runs for weeks, the machine is the answer; where it runs for days, temporary capacity is frequently cheaper.

The framework produces a specification, not a machine. Send the completed twelve-item sheet, together with your peak case rate, size range, board grade and shift pattern, to [email protected] or contact us on WhatsApp at +86 13681839278. We will confirm the machine class that fits, the effective rate at your case size after the efficiency discount, the sealing method that matches your board and volume, and the utility and footprint requirements, so the quotation you receive is the one you can actually install.