A field service engineer in Hamburg keeps his kit in the back of a van that starts at 6:40 every morning and does not stop until the last call. In February he sent us a photograph of a blow-moulded case with a cracked latch and a torque wrench rattling loose inside. The wrench still calibrated fine. The foam pocket had gone soft after two winters of being sat on, walked over and stacked under spools of cable.
Load, drop, repeat
Tool cases get specified by what they carry: an 18 V drill with two batteries, a 1/4 inch socket set, a multimeter, a 6 inch adjustable wrench and the leads. That is roughly 4 to 6 kg in a box people still expect to lift with one hand. We build the shells from EVA sheet in the 0.20-0.25 g/cm3 band and check them at 1.0-1.5 m, six faces, three drops per face, which is the routine buyers recognise from ISTA 2A and the drop section of ASTM D4169. Our EVA case program runs the same checks for palletised freight under ISTA 3A, because the damage mode at pallet level is completely different from a single carton.
The foam is the actual product
Ask anyone on the line what fails first and the answer is never the shell. It is the cavity layout. Cut a pocket 2 mm too loose and the tool rattles; cut it too tight and the technician digs it out with two fingers, which is how foam tears. We lay cavities out from the physical tools rather than spec drawings, and the first article always goes back to the customer to be loaded and unloaded twenty times before sign-off. Die-cut EVA foam holds its edges far better than pick-and-pluck grid foam under heavy hand tools, and egg-crate foam in the lid stops the contents scuffing each other on the way to site.
- Wall build: single-layer EVA for light hand tools, EVA laminated to 600D Oxford cloth when the case gets dragged across concrete
- Closure: YKK #5 or #8 coil zipper with a covered garage, or an aluminium frame with two latches for instrument sets over 8 kg
- Extras: webbing handle sized for the loaded weight, rubber feet, document sleeve in the lid, clear window for a calibration label
Cases in our EVA tool case line start at 500 pieces, with tier pricing at 500, 1000 and 3000. Samples are on the bench in about three days when the tool set is already in the workshop; a new cavity layout means a new foam die and a week more. Tooling cost is usually recovered somewhere around 3,000 units. Send the tool list through the customization page or straight to lucy@lianpingbag.com. The Hamburg kit is being re-cut with a deeper pocket for the torque wrench, and the first article goes back to him next week.