AGV Chassis Sheet Metal Fabrication

An AGV chassis is a locating fixture that happens to carry a vehicle. The drive units, caster assemblies, battery box, lift mechanism and sensor brackets all bolt to it, and their positions decide how well the vehicle tracks a line. If the mounting faces drift, the navigation stack compensates for mechanical error instead of doing its real job.

Sheet metal wins here for three practical reasons. Bends put stiffness where the load is, so a formed 3 mm panel can replace a much heavier flat plate. Cutouts for cable routing, sensor windows and motor mounts come free in the same laser pass. And revisions stay cheap: change a hole pattern in the CAD file, and the next unit ships with the new pattern, with no tooling to scrap.

Castings and billet-machined frames still have a place. A casting makes sense when you need thick bosses, complex internal ribs and volumes above a few thousand units per year, because the pattern cost spreads out. For 10 to 500 units a year, with design changes still arriving, sheet metal is the cheaper path.

The catch is that formed parts move during welding. Heat pulls a 1,200 mm rail out of flat, and the error shows up at the drive mount, not at the weld. That is why the sequence below matters as much as the cutting accuracy.

Most chassis we see are 5052 or 6061 aluminium, usually 3 mm to 6 mm. Aluminium keeps the vehicle light, which matters because every kilogram of chassis is a kilogram the drive motor has to move and the battery has to carry. 5052 bends cleanly and resists vibration cracking better than 6061, so it suits welded battery trays and covers. 6061-T6 gives more yield strength for the main frame, but it bends badly at tight radii and often has to be formed in the annealed state and aged afterwards.

Stainless 304 is the choice for wash-down AGVs in food, pharma and cold-chain sites. It costs more, weighs about three times what aluminium does for the same panel, and work-hardens during forming, so bend radii need to be generous. 316L appears where chlorides or cleaning chemicals are aggressive.

Carbon steel 1018 or A36 shows up in heavy payload tuggers and in weldments where stiffness per dollar beats weight. Powder coat or zinc plating handles corrosion. If you are weighing cost against mass, the table below is the rough order of trade-offs we work through with customers.

Check the temper as carefully as the alloy. Half-hard 5052 cracks at a tight radius where annealed 5052 will not. Ask for the mill certificate and confirm the gauge before cutting, because a 0.3 mm gauge error on a long rail changes the bend deduction.

Fiber laser cutting handles the flat patterns. Kerf on 3 mm aluminium runs around 0.1 mm, and positioning accuracy holds within ±0.05 mm, which is enough that a tab-and-slot joint closes by hand before welding. For runs above a few hundred parts, nesting several chassis panels on one sheet cuts material waste, and combining laser with turret punching lowers cost on repetitive hole patterns.

Press brake work creates the 3D shape. Bend deduction has to match the actual material, not the nominal gauge, and high-strength steels need springback compensation built into the program. Long rails are the hard part: a 1,500 mm bend with a small angular error twists the whole frame. Bending simulation before the first hit saves scrap.

Welding is where flatness usually dies. Tack in a balanced sequence, alternate sides, and let each joint cool before the next pass. For frames that must stay flat, we fixture them on a steel bed and check diagonals after cooling, not during. Laser welding on thin covers gives a smaller heat-affected zone than TIG and needs less dressing.

Machining after welding brings the critical interfaces back into tolerance. Datum faces, bearing bores and drive mounting pads are often milled after the weldment cools, so the final geometry reflects the assembled part rather than the flat pattern. That step is what separates a chassis that bolts together on the first try from one that needs shimming.

Keep the inside bend radius at least equal to the material thickness. Tighter radii on 6061-T6 or half-hard 5052 will crack, and the fix at that point is a new flat pattern. If the design needs a sharp internal corner, machine it after forming rather than forming it tighter.

Leave at least 2.5 times the thickness between a bend line and a hole edge. Less than that and the hole distorts as the metal stretches. Same rule for slots and cutouts that carry a bearing or a sensor.

Design self-locating features. Tab-and-slot joints and half-lap bends hold parts in position before welding, which removes a fixture and shortens setup. A few extra laser cuts usually cost less than the fixture they replace.

Do not put a weld across a flat sealing face, and do not run a long continuous weld down the center of a large panel unless you have a straightening plan. Stitch welds on alternating sides hold stiffness with far less distortion.

Give the fabricator the bend lines you care about. A drawing that dimensions every hole but leaves bend locations nominal will come back with the bends where the material wanted them, not where the drive mounts need them. GD&T on the two or three critical interfaces is more useful than tight tolerances everywhere.

Ask what happens between welding and shipping. A supplier that welds, checks diagonals, then machines the critical faces is set up for AGV work. One that welds and ships is not, and the problem will surface at your assembly station, not theirs.

Ask for the inspection record, not just the certificate. ISO 9001:2015 tells you a system exists. What you want to see on a chassis job is dimensional reports on the mounting interfaces, flatness readings on long rails, and material certificates matched to the heat numbers. We inspect 100% of parts before shipment and can send reports on request.

Consider whether the supplier can machine as well as form. Sheet metal alone cannot produce a bearing bore or a ground mounting pad. A shop with both processes under one roof controls the tolerance stack from the flat pattern through to the finished interface, and you avoid arguing about which supplier owns the error.

Finally, check the prototype path. Chassis designs change during commissioning, and a supplier who can turn a revised bracket in days keeps your build on schedule. Our quotation and DFM analysis come back within 12 hours, and production can start within 24 hours of approval, with no minimum order quantity.