A caster can match a bolt pattern and still be wrong for the fabricated cart base. Its plate may bear on an uneven pad, a nut may be inaccessible after assembly, or the brake pedal may meet a sheet-metal skirt as the wheel swivels. These are interface problems, not merely hole-location problems.
For an OEM buying medical cart metalwork, release the caster model and the complete mounting envelope before freezing the base drawing. This article focuses on the metal interface. It does not provide a caster rating, stability calculation or approval for a finished medical cart.
Start with the actual selected caster
Obtain the manufacturer’s controlled drawing for the selected mounting style and variant. Include the top plate, hole sizes or slots, overall height, swivel envelope, brake arrangement and installation requirements relevant to the design.
Do not substitute the nominal wheel diameter for the complete envelope. Two casters with the same wheel diameter can have different plate geometry, swivel offsets and brake access. A product-family illustration is not necessarily the drawing for the selected SKU.
Blickle’s bracket guide notes the importance of contact between the top plate and the mounting surface. Translate the selected manufacturer’s requirements into your base design rather than assuming that four bolts will pull any pad into an acceptable condition.
Separate the contact face from the locating features
Identify which face supports the caster and which features locate the pattern. Dimension the mounting interface from a stable frame datum, not from a flexible cosmetic skirt. If the pad is welded, define the inspection condition after the weld and any subsequent finishing operations.
A four-point base can be sensitive to the relationship between its mounting faces. The responsible designer should decide how pad position, orientation and frame twist will be evaluated. Do not invent one universal flatness tolerance for every cart size or construction.
Describe whether the frame is supported freely or on an agreed fixture during inspection. A check that forces a flexible frame flat can hide a different free-state condition. The inspection setup should match the drawing intent.
| Interface item | Input to release | Review question |
|---|---|---|
| Supporting pad | Defined contact face and finished state | Does the caster plate seat as intended? |
| Hole pattern | Selected caster drawing and datum scheme | Are slots, washers and installation direction coordinated? |
| Frame connection | Drawing-defined reinforcement and joints | Where do the designer’s loads enter the base? |
| Moving envelope | Swivel and brake geometry | Is clearance retained through the permitted motion? |
Check the sweep with the surrounding parts present
Review the full caster motion with skirts, corner guards, lower shelves, cable clips and fasteners represented. Check more than the wheel tread: the fork, brake pedal and projecting bolt ends can be the limiting features.
If the design intentionally restricts orientation, that restriction must be an engineered and documented feature. A collision with a sheet-metal return is not an acceptable substitute for a defined stop.
Allow access for the approved installation and maintenance tools. A nut hidden inside a sealed base can turn a routine replacement into disassembly of the cart. Decide whether the chosen captive hardware or access opening is appropriate before the fabrication drawing is released.
Keep load selection with the complete design
The caster catalog rating is not the rating of the welded pad, the complete cart or a particular operating condition. Blickle distinguishes dynamic and static load capacity and explains that application conditions affect selection.
Ask the OEM design team to supply the relevant operating and transport load cases. Payload location, uneven support, floor obstacles, braking and attachments can affect the review. A sheet-metal supplier can quote the specified pad, reinforcement and joint; it should not infer a universal safe payload from an image.
The monitor-mount reinforcement guide addresses another input to the base: loads introduced above the frame. Both interfaces belong in the same complete-cart assessment.
Agree the first-piece check before the batch
A practical review can use the selected caster or an approved mating reference to check pattern fit, seating, tool access and interference. State exactly what that check demonstrates. A fit check with an unloaded caster is not a mobility, fatigue or stability test.
Record any approved shim, washer, spacer or fastener requirement in the released assembly. If production relies on an undocumented adjustment made during the first-piece review, later batches may not reproduce the accepted interface.
For quotation, provide the caster reference, base and reinforcement drawings, joint requirements, finished inspection condition, hardware ownership and requested records. Resolving these items early gives the fabricator an interface it can make and check, while leaving complete-cart performance with the responsible equipment team.
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