An AGV chassis weld fixture should protect the relationships that make the vehicle assemble and roll correctly. Holding the outside perimeter square is rarely enough. Wheel-module interfaces, axle relationships, battery and controller bays, sensor mounts and top-module points can all depend on a common mechanical reference system.
The fixture therefore starts with the released AGV chassis design, not with an empty table and a collection of clamps. The OEM defines payload, drive geometry, wheel arrangement, sensor and battery interfaces, structural requirements and vehicle-level acceptance. The fabricator translates the released mechanical scope into cutting, forming, welding and inspection controls.
For robot and AGV chassis fabrication, the most useful RFQ explains which interfaces are critical, how the chassis is supported in operation and whether final inspection is free-state or installation-simulating.
Choose datums from vehicle function
Begin by mapping how the completed chassis is located in the vehicle and during downstream assembly. Wheel or drive-module pads often matter more than a cosmetic cover edge. A battery tray may tolerate more positional variation than a steering or sensor interface. The drawing should make that hierarchy measurable.
A practical datum structure may use a primary plane formed by released wheel-module, leveling or assembly pads. A secondary feature establishes the longitudinal direction, while a tertiary feature fixes the remaining lateral position. The exact scheme depends on the vehicle architecture and belongs to the responsible mechanical designer.
Keep these interface groups separate during planning:
- Wheel, caster and drive-module mounting relationships.
- Battery, controller and power-module support points.
- LiDAR, camera and safety-scanner datums.
- Top-module, conveyor or payload interfaces.
- Service covers, guards and cosmetic panels.
- Charging, towing or site-specific mechanical interfaces.
If every hole receives the same general tolerance, the fixture team cannot tell which relationships deserve hard locators, which need in-process checks and which can follow normal formed-part variation.
Constrain the chassis without over-locating it
The fixture should locate the assembly with the minimum controlled contacts needed to reproduce the released datum system. Extra stops can create a false sense of control while forcing component variation into stress, gaps or local bow.
Primary supports should be separated enough to stabilize the frame and placed under structurally appropriate regions. Secondary and tertiary locators should control direction without trapping normal tube, plate or formed-sheet variation. Round and relieved locators, adjustable supports or replaceable pads can be appropriate when their function and setting method are released.
Avoid locating precision interfaces from unstable cut edges or weld seams when the drawing provides better references. If critical pads will be machined after welding, provide tooling pickups or rough datum features that survive the weld stage and support the later machining setup.
Fixture stiffness matters, but a heavy base is not automatically a correct base. The tooling designer must account for chassis weight, clamp forces, welding position, released process loads and floor support. A fixture that twists on uneven feet can transfer its own geometry into the chassis.
Make clamp sequence part of the process plan
Clamps seat components against locators; they should not be used to reshape an out-of-condition component until the holes appear aligned. Direction, order and force all affect the result.
Load the main structural members first and confirm contact at primary references. Add cross-members and brackets in a sequence that preserves access and avoids trapping stack-up. Apply clamps toward nearby supports so thin rails or panels are not suspended between forces.
| Clamp stage | Purpose | Common failure to watch |
|---|---|---|
| Seat main rails | Establish the primary structure on released supports | Rail rocks because debris or bow prevents contact |
| Set longitudinal reference | Align the chassis direction | Clamp drags the frame sideways instead of seating it |
| Add cross-members | Establish width and module interfaces | Accumulated cut-length variation is forced into a gap |
| Secure local brackets | Hold drive, battery and sensor details | Small clamp rotates or bows a precision bracket |
| Tack confirmation | Verify contacts before heat accumulates | A locator becomes inaccessible after early tacks |
| Weld-stage release | Allow the approved sequence or repositioning | Clamps open too early and the assembly walks |
Document the sequence with fixture identifiers. During prove-out, observe the chassis as every clamp closes. Transfer marks, feeler checks or suitable measurement methods can show whether the component reaches the intended locator or is merely held nearby.
Do not accept “clamp until it fits” as a fixture instruction. If a component needs a controlled preload or forming action, the drawing and process plan should define that condition, its limit and the final free-state acceptance.
Plan tacks and welds around distortion risk
Welding introduces local expansion and contraction. Long side rails, asymmetric brackets and dense weld clusters can pull the chassis out of plane even when the fixture begins accurately. The route should balance heat, maintain access and avoid locking large residual stresses into the frame.
Review tack location, tack size, joint gaps, weld direction, alternating sequence and cooling stages with the released welding requirements. The correct route depends on material, thickness, joint design, process and chassis geometry; there is no universal pattern that guarantees a flat AGV frame.
Some locators may need to remain engaged through a stage; others may need released clearance after tacking to avoid binding as the weldment contracts. Define those actions deliberately. If the finished chassis has to be pried from the fixture, investigate the datum, relief and sequence rather than making forceful unloading a normal step.
DRAmetal’s welding service scope is drawing- and RFQ-defined. Welding procedure, qualification, inspection and any external process requirements must be stated when they apply.
Inspect both the fixture and the chassis
A fixture can be dimensionally stable while the product moves because of component variation or welding. A chassis can also pass one final check while a locator is drifting toward a maintenance problem. Track the two systems independently.
Establish base and locator checkpoints that are accessible without a complete teardown. Verify them after installation, collision, repair or another released trigger. For the product, identify CTQs that reveal wheel support, axle, module and sensor relationships.
State when a measurement is taken: before welding, after tacking, in the fixture, after unclamping, after machining or after finish. Coating, installed hardware and gasket stacks can change local interface conditions, so the supply condition should match the acceptance plan.
The robotics frame FAI and datum checklist helps teams define supports, datum simulators, equipment and report fields. For wheel-specific planning, the existing AGV wheel-alignment article can complement the fixture design, but the released vehicle drawing remains authoritative.
Validate free-state and restrained conditions deliberately
Fixture inspection shows geometry under restraint. The AGV may operate without that restraint, so important chassis relationships may also need free-state evaluation. Conversely, some interfaces are meaningful only when installed against released supports.
The OEM should define which condition predicts assembly and vehicle behavior. A free-state setup still needs controlled support points and orientation. A restrained setup needs released locators, clamp or fastener sequence and a clear limit on what restraint is allowed to correct.
During first article, compare stages where useful. A large difference between restrained and free-state results may reveal residual stress, uneven support or an assembly sensitivity that deserves engineering review. DRAmetal does not infer vehicle stability, navigation accuracy or payload performance from chassis dimensions alone.
Release a production-ready fixture package
Before repeat production, collect the following:
- Released chassis model, drawings, BOM and weld map.
- Functional datum map for wheel, drive, battery, sensor and payload interfaces.
- Fixture drawing, locator map and replaceable-wear details.
- Component loading, seating and clamp sequence.
- Tack, welding, cooling and unloading stages.
- In-process hold points and final product CTQs.
- Free-state or restrained inspection definition.
- Fixture checkpoint and maintenance plan.
- Configuration and revision-control method.
- Approved nonconformance and deviation route.
Related customer project: AGV Chassis: Wheel Alignment and Battery Access.
Send the right inputs with the RFQ
Provide 3D models, 2D drawings, datum scheme, wheel and drive interfaces, load requirements, material and finish, weld symbols, machining stages, inspection state, records, variants and quantities. If the fixture itself is part of the supply scope, release its ownership, acceptance and maintenance requirements separately.
The robotics industry hub connects AGV chassis work to related frames, brackets and mechanical kits. DRAmetal can manufacture and inspect the released chassis and drawing-defined tooling components. The OEM or integrator owns structure, dynamics, motion control, battery and sensor validation, machine safety and final vehicle acceptance. With those boundaries established, send the AGV chassis package for RFQ review.
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