Choose the packing method from how often the bottle or case changes, not from a brochure throughput figure. Hand packing suits samples, start-up runs and mixed orders; a semi-automatic unit suits a bottle family that repeats across several orders a year; an automatic case packer only earns its tooling when one bottle and case combination runs at high repeat volume. Whichever you pick, most breakage is created at the transfer into the case, so drop height, divider fit and squeeze load belong in the packing specification alongside the method.
Three methods and the batch pattern each one suits
Hand, semi-automatic and automatic packing are separate operating models, and each breaks down in its own way when pushed outside its range. The threshold between them is not a bottle count. It is how many times a set of tooling gets used before the bottle or the case changes again.
| Method | Batch pattern that justifies it | Breakage risk | Tooling and changeover | Relation to line speed | Typical use |
|---|---|---|---|---|---|
| Hand packing at a bench | Any quantity, down to a single mixed case; the only workable option below pilot scale | Highest and hardest to repeat, since drop height and squeeze shift with the operator and the hour | A bench and dividers; nothing to change over | The operator is the ceiling, so the filler is slowed or buffered | Samples, start-up runs, wide bottle ranges, odd shapes packed under contract |
| Semi-automatic unit | One bottle family repeating over several orders a year | Moderate; descent height and squeeze are machine settings, feeding rhythm is still human | Case holder, lane guides and a bottle head; a swap followed by re-setting | Adaptable; can be buffered against surges and re-timed between products | Export lines with a few bottle shapes and steady order patterns |
| Automatic case packer | One bottle and case combination at high repeat volume | Lowest and most even, as long as the machine works within its design envelope | Dedicated head, lane pitch and case tooling; the longest changeover, needing planned downtime | Engineered to the filler rate; the slower of the two sets the line | Single-product lines, contract filling of one bottle family, high-volume export programmes |
Hand packing is expensive in labour, and its real value is flexibility: any shape, any case style, any mix, with no tooling. What it lacks is repeatability. The same person places bottles at a different angle late in a shift than early in it, and the drop varies with fatigue and with how crowded the accumulating table is.
A semi-automatic unit holds and indexes the case and commonly lowers a row of bottles at a controlled height, while an operator feeds the lane and drops in dividers. Controlled descent removes most of the drop-height problem and turns squeeze load into a setting. Output then depends on how steadily the operator feeds the unit, which is why lines with a frequently changing bottle range tend to end up here.
An automatic machine takes the person out of the transfer. Bottles come from the filler in lanes, are grouped, picked by a head as a row or a whole case, and lowered on a programmed motion profile, so every cycle has the same descent curve and the same squeeze pressure. The price of that consistency is rigidity: the machine is built around a bottle envelope, a case footprint and a lane pitch, and anything outside them means new tooling and rebuilt lane guides.
Where glass gets damaged between conveyor and case
A bottle can pass an impact test at the mould and still reach the customer cracked, because the damage is often done in the two metres between the conveyor end and the inside of the case. Four mechanisms cover most of it, and each needs a different correction.
- Single-point impact. A bottle let go by the gripper, or falling the last inch of a chute, lands on one spot of the base or heel and all the energy goes there.
- Bottle-to-bottle contact in the drop. One bottle's shoulder hits another's side wall. The resulting chip may only show once the bottle is filled and pressurised.
- Lateral squeeze. The machine presses the bottles together to seat them with more contact load than the side wall tolerates.
- Case-edge impact. A loaded case is pushed, tilted or dropped onto a pallet and the shock reaches the bottles through the box wall, not through a divider.
Only the last of these is a carton matter. The other three belong to the packing station, which explains why changing the method frequently cuts breakage more than tightening the bottle specification does.
Drop height, cushioning and cell clearance to specify
Drop height
Drop height is the most useful figure in a packing specification and the one most often missing. Impact energy rises with the square of impact velocity, and velocity with the square root of drop height, so halving the drop roughly halves the energy. The effect on chipping is usually greater still, because a shorter fall gives the bottle less time to rotate before it touches down.
The figure to write down is the distance from the lowest point of the bottle to the surface it will rest on, at the instant of release, with the case seated in its holder. That is not the same as the height of the head above the case rim whenever the head descends into the case before letting go. A tape measure against the machine frame is accurate enough. Record it as a maximum, not a nominal value.
Cushioning
Cushioning only works where the bottle touches something, and there are three such places. The case base takes the vertical impact of the first bottles in, so a bottom pad or moulded base insert goes there. The divider governs side contact by fixing the gap between neighbours. The space between the outermost bottle and the case wall is where a case-edge blow usually gets through.
A loose pack is not a gentler pack. A bottle with room to move can rotate and hit the one beside it with nothing in between.
Cell clearance
Clearance is the point the bottle supplier, the carton supplier and the packing station dispute most. A cell cut exactly to the bottle diameter forces a squeeze on every cycle. A cell that is too roomy lets bottles rattle in transit and costs the case stacking stiffness. What works is a small controlled clearance, with the divider fingers doing the retaining instead of friction between bottles. If a divider will not fit, review the divider before widening the case.
Dividers, pads and collars, and the load each one carries
Inserts are the first thing cut when a buyer trims packing cost, so it pays to know what each one does. Taking out the wrong one puts its load back into the glass.
| Insert | Function | When it is enough, and when it is not |
|---|---|---|
| Full-depth corrugated partition (egg-crate or cell divider) | Prevents bottle-to-bottle contact, adds vertical stiffness so glass and board share the load above, and holds the bottles in a fixed grid for a predictable pallet footprint | Needed for tall, narrow bottles with a high centre of gravity. Removing it alters stack performance as well as protection |
| Part-depth divider, ending below the shoulder | Separates the bodies and leaves the necks free; lighter and cheaper | Often adequate for stout, wide-bodied, short-necked bottles. On tall narrow ones the necks lean together, causing scuffing and shoulder chips near the top of the case |
| Top pad | Spreads the load from the case above and keeps the closure out of direct contact | Part of the standard export pack |
| Collar around the bottle cluster | Tightens the group so it moves as one body inside the case | Used where the cluster would otherwise shift |
| U-board on case corners | Shields the board from pallet straps and corner knocks | Protects the case, not the bottles |
A properly specified glass export pack is a small system of bottom pad, cell divider, top pad and case. Because each part has its own load path, a lighter pack is not automatically the cheaper one once the stacking claim has been tested again.
Case styles and the packing methods they allow
Fixing the case style without checking the packing method, or the reverse, usually produces a compromise at the packing station. Most glass export packs fall into three families.
- Regular slotted case, closed by tape or hot melt. Its flat, square, open top lets a packing head descend cleanly, and it forgives the dimensional drift that board moisture causes. It is the default for automatic and semi-automatic packing.
- Die-cut case with a locking or tuck-in base and hinged lid, often with die-cut partitions inside. It grips the cluster tightly and is favoured for presentation packs, but the erected case is not a true rectangular volume and its inner geometry depends on how the base was locked. It is normally packed by hand or on a machine fitted with a dedicated erecting and holding fixture.
- Tray with lid, or a shallow case with a separate cover. Common for wide jars and short bottles that sit stably in a shallow grid. The short descent suits a pick-and-place head, but a tray has less vertical stiffness than a full-depth case and needs a solid pallet pattern beneath it.
Where a retail customer has already dictated the case style, the method is chosen from what that style permits, leaving drop height and divider design as the adjustable variables. The board grade, closure and print of the box itself are covered separately in our carton construction and closure specification, and the two should be reviewed together whenever a new bottle is introduced, since a bottle change nearly always changes the correct pack.
Matching packer rate and lane pitch to the filler
Three rates describe a packer, and the brochure prints only the first. Nominal cycle rate is what the machine does uninterrupted. Effective rate is what remains after case supply, divider placement and discharge are accounted for. Recovery behaviour, meaning the time the filler needs to regain speed after any packer stop, is what decides whether the line as a whole keeps running.
The filler is the costly part of the line, so the normal design runs the packer a little faster and puts an accumulation table between filler discharge and packing head. A packer sized exactly to the filler has no margin and stops the filler at every divider jam; one sized far above it carries tooling it never uses. Specify the packer's effective rate above the filler rate, then size the accumulation for how long the packer realistically stops, not for the ideal case.
Lane pitch is the other dimension to match. Filler discharge and packer infeed must agree on bottle spacing in travel and on how a lane splits when a partial row forms. A mismatch does not cost speed. It shows up as a transfer guide shoving bottles sideways at pick-up, which breaks glass. If a newly commissioned line breaks bottles only at the packer infeed, check lane pitch and guide rail alignment first.
What a changeover involves and what must be proven again
Changeover is the reason a high-volume automatic line can be the wrong choice for a buyer with many bottle shapes. Counting minutes in the abstract is less useful than listing what physically changes and what has to be re-verified afterwards.
| Item | Physical change | Re-verification | Effect on output |
|---|---|---|---|
| Pick-up head | Gripper cups and neck or body clamps exchanged for the new diameter and neck finish | Grip force for the new bottle weight; finish free of scuffing | Line is down until the swap is done and a test row has run |
| Lane guides and pitch | Rails shifted or replaced to suit the new body diameter | No sideways pressure in travel, no infeed jams | The longest single job, covering the full infeed length |
| Case holder and tooling | Jaws or change plate matched to the new case footprint | Case sits square and stays put as the head descends | Moderate; the pallet pattern downstream changes too |
| Divider placement | Magazine or hand-drop station re-set for another divider format | Divider seats fully and does not pinch the shoulder | A frequent cause of rejected cases at start-up |
| Descent profile and drop height | Motion programme, cushioning and squeeze setting for the new bottle | Drop height measured on the first bottles, breakage checked on the first case | Quick, but must precede full speed |
| Discharge and palletising | Case orientation, taper and layer pattern re-programmed | Pallet footprint and stack height checked against the carton specification | Felt downstream, not in the packer cycle |
Turn this into a changeover matrix: for every bottle-and-case combination you plan to run, note which items change and which stay. Prepared before a machine is ordered, the matrix generally shows whether an automatic packer is the right choice without waiting for the first live changeover.
Pallet pattern, stacking and container loading
The packing method sets how much load the case must carry later. In a hand-packed case without a full divider the bottles bear the load almost directly, while a full-depth divider splits it between glass and board. In a stack of ten cases, whichever load path is in place is multiplied by ten, so settle this before fixing the pallet pattern.
- Derive the pallet pattern from the case as built, not as drawn. Board and moisture leave a case slightly off its nominal size.
- Orient cases so pallet overhang is zero or negative. An overhanging corner gets crushed by the strap, and the bottles sit in that corner.
- Treat corner boards and a top cap as part of the method. They keep strap load off the case wall.
A stacking claim has to be proven on the configuration actually packed, by a compression or vertical load test, and proven again when the pack changes. Our page on running a vertical load test on a packed case explains the test logic and how to read a load-deflection result.
With the pallet built, container loading becomes arithmetic: pallets per 20GP or 40HQ, floor-loaded or single-stacked, total volume and weight, port terms. That calculation is in the container loading and CBM guide. The inputs come from here, namely the pallet pattern and the stack height the packed case is qualified for. Buyers who pick a container load first and a packing method second usually end up revisiting the method. If you are weighing packed cases against bare bottles on a bulk pallet, see shipping glass containers in bulk.
Cost components and how the trade term shifts the risk
Packing charges are quoted per project, and quotations often cover only part of the picture. Four components make up the real cost:
- direct material, meaning case, divider, pads and tape;
- capital recovery on the equipment, a per-unit figure that depends wholly on how many units pass over the machine;
- labour, which includes rework, repacking rejected cases and inspection time on damage claims as well as line operators;
- loss. A bottle broken at the packing station is paid for once; one broken at destination is paid for in product and again in the customer relationship.
The trade term determines who is exposed to that loss. Under EXW the buyer collects at the plant and bears transit risk from the loading dock. Under FOB the seller's risk runs to the ship, so the pack has to survive inland haulage and port handling. Under CIF the seller arranges carriage and insurance, and under DDP the seller holds the risk through to the destination warehouse. The further the seller's risk reaches, the stronger the buyer's case for demanding a tested pack and not merely a described one.
Ask also for one-off and recurring costs to be shown apart. Machine tooling, divider tooling and the first qualification run happen once; case, divider, labour and breakage recur. A method that looks costly on the first quotation is often the cheaper one per unit by the second order.
Tracing a breakage spike at the packing station
Classify the damage before adjusting anything, and sort it by position in the case, not by bottle type. Damage clustered at one corner of the case indicates handling or palletising. Damage scattered through the middle indicates the packing drop, divider fit or squeeze load. From there, work through the causes below, listed from most to least frequent.
- Dividers not fully seated. A finger standing proud means the bottle lands on it instead of in the cell, then chips at the base or leans onto its neighbour. Lift a packed case after a run and confirm each divider sits flush with the rim before the top pad goes on.
- Drifted drop height. Cushions compress, rods wear, and over months the release point creeps up. This is a maintenance issue; measure actual release height on a schedule against the specification figure.
- Case supply variation. An erected case a few millimetres out of square stops the divider dropping and the bottles aligning, so the head forces them in. The fix lies with the case supplier, and it is found by measuring a sample of erected cases across a shift, not one case.
- Lane pressure at the infeed. Bottles under accumulated back-pressure are loaded before the head arrives, and the head adds more. Cutting accumulation or fitting a pressure-relief section often clears shoulder chips that were being blamed on the case.
- Glass temperature and surface condition. A cold or damp bottle behaves differently at the surface, and condensation between bottles in a cell can raise contact pressure at the shoulder. In an unheated warehouse, a complaint that follows the winter season is the clue.
Frequently asked questions about case packing glass bottles
How do I choose between a semi-automatic and an automatic case packer?
Before comparing rates, count the bottle-shape or case-size changes expected in a year. More than a few favours a semi-automatic unit, whose tooling set is small and changeover matrix short. Long, uninterrupted campaigns of one bottle in one case favour an automatic machine.
Which drop height goes into the packing specification?
The maximum distance between the bottle's lowest point and its resting surface at release, with the case seated. Take it from the machine, not from a drawing, and re-measure periodically, because wear moves the release point even when the programme is untouched.
Is a part-depth divider enough?
That depends on bottle proportions, not product value. Stout bottles often run safely with one, provided the board gives the case enough vertical stiffness by itself. Tall narrow bottles need full depth. Test the real configuration instead of generalising.
Can a die-cut presentation case run on an automatic packer?
Generally not on a general-purpose machine, because a standard head has no true rectangular volume to register against. The options are a machine with a dedicated erecting and holding fixture, or hand packing.
Why would breakage occur at the packer infeed but not at the filler?
The bottle is rarely at fault. Look at lane pitch and guide rails: a rail set slightly narrow pushes bottles sideways at transfer, and back-pressure pre-loads them. Reducing accumulation and realigning the guides typically removes this type of chip.
What should be separated on a packing quotation?
Three lines: direct material (case, divider, pads), one-off tooling (heads, change plates, qualification run) and a unit rate covering labour, equipment recovery and expected loss. A single packing charge conceals whether cost is driven by volume or by tooling, which is what decides the cheaper method at your annual volume.
Does the packing method affect the stacking claim?
Yes. The claim applies only to the configuration tested, so it cannot be carried over from an earlier pack that used a different divider.
When should packing be reviewed if the bottle is changing?
At the moment the new bottle is specified. Diameter, height, centre of gravity and often neck finish all move, and with them the divider cell, drop-height setting, grip points and pallet pattern. Reviewing then avoids a second round of tooling after the bottle is already in production.