AGV Chassis Design Guide: Frame, Welds & Tolerances

An AGV chassis is more than a base plate with wheels. It sets drive-wheel geometry, battery location, sensor alignment, ground clearance, guarding and service access. If the chassis twists during welding or stacks too many tight dimensions from the wrong datum, software cannot fully compensate for the mechanical error.

This guide explains how to design a fabricated AGV or AMR chassis for repeat production and practical assembly.

Define the architecture from interfaces

Start with the systems that must fit and remain aligned:

• Drive wheels, casters and suspension modules.
• Battery pack, retention and removal path.
• Motor controllers and power distribution.
• Safety scanners, lidar, cameras and bumpers.
• Payload deck, lift module or conveyor.
• Charging contacts and docking features.
• Covers, doors and service panels.

Create interface control dimensions around these systems before detailing every bracket. The chassis should support module changes without forcing a complete structural redesign.

Sheet metal monocoque, tube frame or hybrid

Architecture	Advantage	Limitation
Formed sheet monocoque	Low part count, good packaging and scalable laser/bend production	Bend sequence and local stiffness need careful DFM
Welded tube frame	High structural efficiency and easy concept changes	More weld fixtures, distortion and secondary brackets
Hybrid sheet/tube	Strong frame with integrated panels and mounting features	More process interfaces and BOM complexity
Machined base plate	Precise local interfaces	High weight, material cost and machining time

Many production AGVs use a hybrid structure: a welded or formed primary frame with laser-cut brackets, battery trays and removable covers. Select architecture around load, annual volume and configuration range.

Load cases to define

Do not size the chassis only for static payload. Include:

• Maximum payload and center of gravity.
• Acceleration, braking and emergency stop.
• Threshold or floor-joint impact.
• One-wheel or three-point support condition.
• Forklift or crane handling.
• Transport tie-down and vibration.
• Lift-module reaction forces.
• Battery and drive-module concentrated loads.

State allowable deflection at sensor, drive and payload interfaces. Structural survival and alignment are different acceptance criteria.

Protect wheel and drive geometry

Tracking depends on the relationship between drive wheels, casters and chassis datums. Control:

• Drive-axis parallelism or angle.
• Mounting-face flatness.
• Distance between drive modules.
• Caster height and preload interfaces.
• Ground clearance at full rated load.
• Wheel access for service.

Use machined pads, controlled formed surfaces or post-weld machining only where the alignment budget requires them. Machining every interface after welding adds cost and may hide a frame design that is too sensitive to distortion.

Datum strategy

A practical datum scheme might use:

• Datum A: primary supported base plane or defined mounting pads.
• Datum B: longitudinal vehicle centerline or drive reference.
• Datum C: transverse locating face or axle reference.

Locate safety sensors, docking contacts and payload modules from functional datums rather than from cosmetic outer covers. Covers can float within normal fabrication tolerance while critical systems remain aligned.

Our GD&T basics for sheet metal explains how to separate feature control from general dimensions.

Design welded frames for repeatability

Welding introduces shrinkage and angular distortion. Reduce sensitivity through design:

• Use tabs, slots and interlocking bends for self-location.
• Balance welds around the neutral structure.
• Avoid excessive weld length where intermittent welds meet structural needs.
• Keep critical mounting faces away from heavy weld concentrations.
• Provide fixture access and inspection points.
• Sequence subassemblies so distortion can be corrected early.

Specify weld size and continuity by load requirement. “Weld all around” on every bracket increases heat, labor and distortion. For methods, see our welding distortion control guide and weldment design guide.

Battery integration

The battery is often the heaviest single module. Review:

• Load path into the frame.
• Slide, lift or drop-out service route.
• Mechanical retention under impact.
• Electrical isolation and grounding strategy.
• Cooling or ventilation.
• Drainage and contamination protection.
• Connector access and strain relief.
• Tolerance for pack swelling or supplier variation where applicable.

Do not make a removable battery dependent on flexible covers for structural retention. Use controlled chassis features and a serviceable locking method.

Sensor and bumper mounting

Safety scanners and lidar need stable orientation and unobstructed fields of view. Thin external skins may vibrate or move after minor impact.

Mount critical sensors to the primary structure or a stiff controlled bracket. Add:

• Adjustment range for calibration.
• Positive location after adjustment.
• Protection from direct collision.
• Cable routing with bend-radius control.
• Access without removing major payload modules.

Bumpers and contact strips should transfer load to defined frame points rather than deforming cosmetic panels unpredictably.

Stiffness without unnecessary mass

AGVs benefit from low chassis mass, but simply reducing thickness can create noise, sensor movement and weld distortion. Use geometry first:

• Closed or boxed sections.
• Return flanges on broad panels.
• Ribs and beads away from wheel interfaces.
• Local doublers under concentrated loads.
• Crossmembers placed along the load path.
• Strategic aluminum covers over a steel primary frame.

The sheet metal lightweighting guide covers ribs, flanges and part consolidation.

Serviceability and assembly

Design around the maintenance sequence:

• Can the battery, drive wheel and controller be removed independently?
• Are fasteners visible and tool-accessible?
• Do covers use captive hardware?
• Can technicians reach connectors without sharp-edge exposure?
• Are left/right parts clearly identified?
• Can harnesses be installed before the chassis closes?

Reducing assembly time also reduces production variation. A chassis that requires technicians to force modules into alignment needs a datum or tolerance redesign.

Finish and corrosion

Indoor AGVs often use powder-coated steel frames with zinc-plated or stainless hardware. Warehouses with condensation, food processing, cold storage or outdoor transitions need a stronger corrosion plan.

Define:

• Material and pretreatment.
• Powder type, thickness and color.
• Masked grounding and precision interfaces.
• Protection inside closed sections.
• Dissimilar-metal isolation.
• Drainage and washdown exposure.

Apply coating allowances to slides, wheel mounts and tight module interfaces.

Prototype validation

Measure and test the chassis as a system:

• Dimensional first article from functional datums.
• Wheel alignment and ground-clearance check.
• Static payload and deflection test.
• Twist/three-point support condition.
• Emergency-stop and threshold-load validation.
• Battery removal and service trial.
• Sensor calibration range.
• Cover fit and final assembly time.

Feed results into the drawing, weld sequence and fixture before volume production.

AGV chassis RFQ checklist

• Formed assembly model and controlled drawing set.
• Payload, center of gravity and dynamic load cases.
• Wheel, drive, sensor and docking datums.
• Material, weld and finish specifications.
• Battery and service-removal sequence.
• Critical module and harness interfaces.
• Prototype validation and inspection plan.
• Pilot quantity, annual demand and variants.

Related customer project: AGV Chassis: Wheel Alignment and Battery Access. Related resources: robot and AGV chassis · robotics fabrication capabilities · send the chassis model.