The folded tray is the backbone of professional signage. That clean box shape with returned edges makes a flat panel look engineered, hides the fixings, and gives depth for lighting. With ACP, you can build trays without a press brake, using a technique the trade calls rout and return. Here is how it works and how to get it right.
What rout and return means
You rout a V-shaped groove into the back of the sheet, deep enough to remove the rear aluminium skin and the core, but leaving the front skin intact. That thin remaining face acts as a hinge. Fold along the groove and the edge returns at a crisp angle, with the painted face wrapping the corner unbroken. No seams, no press brake, no welding.
Choosing the groove angle
- 90 degree V-bit: folds a tight 90 degree corner. Standard for tray edges.
- 135 degree V-bit: gives a gentler fold for shallow angles and wrapped profiles.
- Two parallel grooves: create a rounded, softer corner where a sharp edge would look severe.
Getting the depth right
This is the whole craft. Groove too shallow and the fold fights back or cracks the core unevenly. Groove too deep and you score or cut the front skin, which shows on the finished face. The target is to leave the front skin plus a hair of core. Dial it in on offcuts, then lock the depth as a preset for each sheet thickness you stock. Consistent sheets make this easy, which is why core and skin consistency matter when you choose your panel supplier.
Assembling the tray
- Rout the outline and all V-grooves in one machine setup so everything references the same zero.
- Notch the corners where returns meet, so the folds close neatly.
- Fold by hand or against a straight edge. The corner should click into place with light, even pressure.
- Fix the corners with rivets, corner brackets or bonding tape on the inside face where nothing shows.
Why sign makers love this method
Speed and finish, mostly. A full fascia tray goes from flat sheet to folded box in minutes after routing. The painted face wraps every visible edge, so there are no raw edges to touch up. And because the material is light, one person can handle trays that would need two pairs of hands in solid metal. Compare that with the cost and setup of folding solid aluminium and the economics are not close.
Material choice for trays
For most tray work our customers use 4mm signage ACP. The extra body keeps large faces flat and makes folds feel solid. Smaller trays and interior work fold beautifully from 3mm. Both are made to fold predictably groove after groove. If you are speccing a lightbox tray, our lightbox signage page covers the details that change when LEDs go inside.
Want fold-test offcuts from current stock before committing to a batch? Ask us. We will send pieces you can groove and fold on your own machine.