Every exhibit manager knows the scene. It is ten at night on move-in day, the hall closes at midnight, and a panel that “almost” engages its frame is being persuaded with whatever tool is in reach. The booth opens on time — it always opens on time — but the field-modified part never sits quite right again, and it travels that way to every show that follows. Here is the reframe that prevents the scene: fit-up failures on the show floor are tolerance failures that happened months earlier, at the drawing stage. By move-in, the outcome was already decided.
The standard that decides it
The Acrylic Fabrication Tolerances standard publishes typical dimensional variation per process: laser-cut components at approximately ±1/32 to ±1/64 inch, CNC-routed components at approximately ±1/32 inch, saw-cut components and fabricated assemblies at approximately ±1/16 to ±1/8 inch, thermoformed components at approximately ±3% to ±5% of the formed dimension. For exhibit work, that table is an assembly-planning document. A drawing that references the right range per feature — and routes genuinely critical fits to the processes that hold them — produces parts that assemble the same way in every city, with the same hand pressure, in the same order. That repeatability is the entire product: an exhibit is a kit that must go together dozens of times, by different crews, under the worst time pressure in the industry.
Where exhibit fit-up concentrates
Not every dimension on an exhibit drawing deserves tolerance attention, and knowing where fit-up actually lives is what keeps drawings honest:
- Module-to-module joints — where one fabricated unit meets the next, every show, in whatever order the crew unpacks them.
- Panel-to-frame engagement — acrylic and fabricated components meeting the modular system’s extrusions, where the extrusion manufacturer’s dimensions set the requirement and the panel must meet them.
- Repeated-mating connections — anything assembled and disassembled each show. A fit that works once but galls, binds, or loosens by show five is a tolerance problem wearing a durability costume.
These earn explicit callouts. Decorative outer dimensions do not — a reveal nobody measures and nothing mates with can live happily in its process band, and tightening it anyway is a pure cost factor purchased by habit.
Stack-up: how small variances become a big one
Across a 20-foot run of connected components, per-joint variance accumulates — that is tolerance stack-up, and in exhibits it is geography: five joints each sitting at the loose end of an acceptable band add up to an end panel that lands noticeably off its mark. The countermeasures are design moves, not tighter parts:
- Slotted mounts at intervals, so accumulated variance is absorbed where it was planned to be absorbed rather than discovered at the last connection.
- Designed gaps — intentional reveals between modules that make variance invisible, instead of flush joints that make a sixteenth of an inch look like a mistake.
- A reference-datum assembly order written into the instructions: build from a fixed point outward, so variance accumulates toward the free end where the slotted mount is waiting — not from both ends toward a middle that has to be forced.
The receiving check that prevents the midnight knife
The cheapest insurance in exhibit fabrication is verifying critical mating dimensions twice: at the shop, and again before crating. A fit-up problem found at the dock costs a day — the part goes back on the machine, the crate ships complete. The same problem found at move-in costs the show: there is no machine in the hall, so the utility knife stands in for it, and the booth carries the scar to every show after. The pre-crate check is also where the assembly instructions earn their keep — a dry fit at the shop against the written assembly order proves both the parts and the paper. For exhibits on hard show dates, pair this discipline with the scheduling conversation: assembly-ready parts are only valuable if they ship when the show needs them, and only Reserved Production ties fabrication to a guaranteed manufacturing completion date. Bring the booth drawings and the show calendar together — fit-up is decided at the drawing stage, so that is where to decide it.
