Robotics and Automation Cell Casters: How to Choose the Right One

A robotic assembly cell spends almost all of its working life sitting still. The arm cycles, the fixtures hold, the base frame carries the load without moving an inch. The casters matter for the hour the cell is moved and the hour it is re-established at its new position. Choose for arriving level, not for rolling.

Arriving level requires the right load rating, the right mount for the frame, and a re-leveling procedure that accounts for what real floors do when a loaded machine crosses them. For applications where the environment demands different wheel properties, see our guide to casters for cleanroom and semiconductor equipment.

Where CarryMaster casters sit in automation environments

CarryMaster leveling casters are positioned by the manufacturer as industrial leveling casters suited to stationary machinery, including robotic and automation cells. That positioning covers the load range, the mount types, and the wheel materials in this catalog. It does not extend to performance claims about the machines those cells run. The casters carry the cell to its position and hold it there. What the cell does once it is level is outside the scope of any caster specification.

The range runs from 110 lbs per caster to 3,307 lbs per caster. Every model uses PA6 nylon except the AC-1800F, which uses MC nylon. All models are available through the CarryMaster leveling caster range.

How to calculate the load rating you actually need

Four casters never share a load evenly on a real shop floor. Surfaces have high spots, low spots, and gradients that shift weight to two or three contact points the moment you push the cell. Sizing to four equal shares gives you a margin that does not exist in practice. For a full explanation of the underlying method, see how to calculate caster load capacity.

The two-step sizing method

Step 1: per-caster load with safety factor

Divide the total cell weight by three. Multiply the result by a safety factor of at least 1.5. The product is the minimum load rating required per caster.

Step 2: manufacturer four-caster cross-check

Every CarryMaster leveling caster carries two ratings: a single-caster load capacity and a four-caster system rating. The four-caster figure must exceed the total cell weight. Both checks must pass. A model that clears Step 1 but fails Step 2 is not a valid choice.

Worked example: 3,000 lb robotic assembly cell

A welded-base robotic assembly cell, 3,000 lbs, four mounting points.

Step 1:

• 3,000 ÷ 3 = 1,000 lbs per caster (uneven-floor baseline)

• 1,000 × 1.5 = 1,500 lbs required per caster (minimum with safety factor)

Step 2:

• Chosen model must have a four-caster rating above 3,000 lbs

Model	Load/ea	4-Caster rating	Step 1 pass?	Step 2 pass?
AC-1000S / AC-1000F	1,764 lbs	3,527 lbs	Yes	Yes
AC-600S / AC-600F	1,103 lbs	2,205 lbs	No	No

The AC-600S fails Step 1 because 1,103 lbs is below the 1,500 lb requirement. It also fails Step 2 because its 2,205 lb four-caster rating does not clear the 3,000 lb cell weight. The AC-1000S passes both checks and is the correct choice for a stem-mount frame. The AC-1000F is the flange-mount equivalent.

Where the safety factor comes from

The 1.5 minimum accounts for three real conditions: dynamic shock load when the cell crosses a floor joint or ramp transition, uneven weight distribution from asymmetric tooling or cable management, and the fact that a welded base frame distributes load differently than a bolted one. Cells with heavy tooling mounted above the centerline, or with cable trays concentrated on one side, should use a higher factor. When in doubt, round up to the next model in the range.

The full cleared model range

All load figures are from the product page body, cross-confirmed against manufacturer cut sheets.

Model	Mount	Load/ea	4-Caster rating	Wheel
AC-50F / AC-50S	Flange / Stem	110 lbs	220 lbs	PA6 nylon
ACP-200F / ACP-200S	Flange / Stem	441 lbs	882 lbs	PA6 nylon
ACT-400F / ACT-400S	Flange / Stem	441 lbs	882 lbs	PA6 nylon twin
APLC-200F	Flange only	441 lbs	882 lbs	PA6 nylon
AC-300F / AC-300S	Flange / Stem	551 lbs	1,102 lbs	PA6 nylon
ACT-800F / ACT-800S	Flange / Stem	882 lbs	1,764 lbs	PA6 nylon twin
AC-600F / AC-600S	Flange / Stem	1,103 lbs	2,205 lbs	PA6 nylon
APLC-700F	Flange only	1,543 lbs	3,086 lbs	PA6 nylon
AC-1000F / AC-1000S	Flange / Stem	1,764 lbs	3,527 lbs	PA6 nylon
AC-1300F / AC-1300S	Flange / Stem	2,205 lbs	4,409 lbs	PA6 nylon
ALCT-1000F	Flange only	2,205 lbs	4,409 lbs	PA6 nylon twin
ALC-1000FB	Flange only	2,205 lbs	4,409 lbs	PA6 nylon
AC-1800F	Flange only	3,307 lbs	6,614 lbs	MC nylon

The heaviest single caster in the range is the AC-1800F at 3,307 lbs per caster. If the calculation produces a required per-caster rating above that figure, the cell is outside this product line's range.

Re-leveling a cell after you move it

A cell that arrives at its destination out of level is not ready for production. Re-establishing level is a procedure, not a casual adjustment. For a broader look at what drives the selection decision before you get to this step, see how to choose a leveling caster.

Shop floors are not flat. The destination may be higher on one side, lower in the middle, or sloped enough that two casters on the low side carry substantially more load than the other two. The cell will tell you all of this during re-leveling, but only if you follow the procedure in the right order.

The re-leveling sequence

1. Position the cell at its destination. Do not begin leveling while the cell is still moving or being steered. Once it is in position, leave it there. Adjusting position after leveling begins resets the work.

2. Back all four leveling feet off to their highest position. Retract all four feet so the cell rides on the wheels. This gives a clean baseline and prevents one partially extended foot from introducing a false reference.

3. Identify the high corner. Use a level on the cell's reference surface, not on the floor. The floor is the variable. The cell's reference surface, typically the top plate or the arm mounting surface, is what needs to be level. Use the corner already at the correct height as your fixed reference.

4. Extend the foot at the high corner first. Thread the foot down until it firmly contacts the floor. Do not apply full clamping load yet. Make all subsequent adjustments relative to this corner.

5. Adjust the remaining three feet in sequence. Work from the high corner diagonally to the low corner, then to the two remaining corners. Extend each foot until the level reads correctly on the reference surface. Check the level in two axes at each step. A foot that looks correct in one axis may introduce error in the other.

6. Apply final clamping load to all four feet in sequence. Once all four feet are in contact and the cell reads level in both axes, apply full clamping torque to each foot. Recheck the level after tightening. Tightening one foot can shift the others slightly on an uneven floor.

7. Recheck after the load has settled. Concrete floors have micro-variation that only becomes apparent under sustained load. A cell that reads level immediately after clamping may shift slightly once the load settles. A second check before production resumes catches this.

Why the sequence matters

The most common re-leveling error is adjusting all four feet simultaneously, estimating by eye, and tightening in whatever order is convenient. That approach works on a perfectly flat floor. On a real shop floor with meaningful variation across the cell footprint, it produces a cell that is close to level but not level, and close is not a production standard for a robotic assembly cell.

The second most common error is leveling to the floor rather than to the cell's reference surface. The floor is the variable. Leveling to it produces a cell that is parallel to an uneven surface, which is not the same as level.

Budget more time than you expect the first time. Teams that have moved the same cell to the same destination repeatedly can work faster because they know which corner is low and by how much. Until you have that knowledge, treat re-leveling as a full step in the move, not an afterthought.

The governing principle: The casters carry the cell to the destination. The re-leveling procedure carries the cell back into production. Both are part of the same move. Neither is optional.

Wheel material on a shop floor that gets swept, not scrubbed

Every leveling model in the CarryMaster range uses PA6 nylon except the AC-1800F, which uses MC nylon. PA6 nylon is a hard wheel. It rolls well on smooth concrete and does not mark finished floors under normal conditions. It does not provide cushioning on rough or uneven surfaces. For a comparison of how nylon behaves relative to other wheel materials across different floor types, see nylon and polyurethane wheel materials compared.

The leveling range has no soft-wheel option. If the travel path includes a surface that requires a softer wheel, the caster selection cannot solve that constraint. Survey the travel path before the move and address surface conditions directly: clear debris, cover floor joints if needed, and use a transition plate at any threshold that would transfer a shock load to the caster. The safety factor in the load calculation absorbs some of this, but it is not a substitute for a clear path.

The AC-1800F's MC nylon wheel suits heavier loads and offers better wear characteristics on rough concrete. Neither wheel material requires floor preparation beyond what a standard swept concrete floor provides.

Stem mount or flange mount: which fits your frame

The mount type is a frame question, not a preference. Confirm it before the frame goes to weld. Stem mount is available on AC, ACP, and ACT series only. APLC, ALC, ALCT, and AC-1800F are flange only. No stem option is available above 2,205 lbs per caster. If the two-step sizing method produces a required rating above that figure and the frame is designed for stem, the frame design needs to change, not the caster selection. For a full comparison of how each mount attaches and which frame geometries each suits, see choosing between stem and flange mounting.

What a caster spec sheet cannot tell you about a moving cell

A spec sheet gives you load capacity, wheel material, mount type, and unit weight. Those numbers are necessary. They are not sufficient.

Floor condition along the travel path. A leveling caster is rated for static load and for rolling on a flat, clean surface. The rating does not account for floor joints, drain grates, paint overspray, or weld spatter. Any of those conditions transfers a shock load to the caster that is not reflected in the rated capacity. Survey the travel path and clear it before the move.

Load shift during transit. When you push a cell, the load distribution changes. Acceleration and deceleration shift weight forward and back. A turn shifts weight to the outside casters. The static four-caster rating assumes the load is stationary and centered. A cell with a high center of gravity, or with tooling that extends beyond the base footprint, can shift more load to two casters than the four-caster rating accounts for.

The leveling range after the move. Every CarryMaster leveling caster has a leveling adjustment range built into the foot. That range is finite. If the destination floor slopes enough that one corner of the cell needs to be raised substantially more than the others, the adjustment range may not be sufficient without shimming. Survey the destination floor before the move, not after.

The question the spec sheet does not answer: what happens once the cell is stationary. Buyers researching this topic will encounter references to products that retract the wheel after positioning or provide a separate jacking mechanism. Those products are not part of this catalog. If your application requires them, we source them from a different product line.

What the cell does once it is level. A caster selection does not govern what the cell does once it is level. The spec sheet for a leveling caster covers the move and the re-establishment. The cell's own design determines what happens inside it after that, not the casters underneath it. Any claim connecting caster selection to machine performance is outside the scope of this catalog.

The honest framing: A caster selection is complete when both load checks pass and the mount fits the frame. Everything after that is a site preparation and move execution question.

Pre-move checklist

Run this before every cell move. For cells that do not require leveling casters, see the non-leveling caster range.

Load and selection

• Total cell weight confirmed, including tooling and mounted components

• Per-caster load calculated: total weight ÷ 3 × safety factor (minimum 1.5)

• Selected model passes Step 1: per-caster rating exceeds calculated requirement

• Selected model passes Step 2: four-caster rating exceeds total cell weight

• Mount type confirmed against frame design before fabrication

Travel path and destination

• Full travel path walked, debris and weld spatter cleared

• Floor joints, drain grates, and thresholds identified and addressed

• Destination floor surveyed; which corner will be low is documented

Re-leveling at destination

• All four feet backed off before leveling begins

• High corner identified using a level on the cell reference surface, not the floor

• Feet adjusted in sequence: high corner first, diagonal low corner second

• Level checked in two axes at each step

• Final clamping torque applied in sequence; level rechecked after tightening

• Second check completed after the load has settled

If you have a cell weight, a mounting-point count, a frame mount type, and any notes on the travel path or destination floor, contact the Zambus team for a model recommendation. Call (973) 777-4922 or use the contact form at zambus.com.

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Frequently asked questions

Can a cell stay on its casters permanently, or should it come off them once it is positioned?

The leveling feet are designed to carry the static load indefinitely once the cell is positioned and leveled. The casters remain in place; the feet transfer the load to the floor and hold the cell level. You do not need to remove the casters after positioning. The design assumes the cell will stay on the casters for the duration of its time at that location, and the feet handle the sustained load.

What happens to a nylon wheel that sits loaded and stationary under a cell for a year?

PA6 nylon can develop a flat spot on the contact surface when loaded and stationary for an extended period. The flat spot affects rolling behavior the next time the cell is moved. It does not affect the cell's stability while stationary, because the leveling feet carry the load, not the wheels. Before the next move, inspect the wheels. Replace any wheel with a significant flat spot before pushing the cell across the floor.

If a cell frame has six mounting points instead of four, how does that change the calculation?

Use the same method but substitute the actual mounting-point count where appropriate. Divide the total cell weight by three regardless of how many mounting points the frame has, because the divide-by-three baseline accounts for uneven load distribution on a real floor, not for the number of casters. Apply the 1.5 safety factor to that result to get the minimum per-caster rating. Then confirm that the chosen model's four-caster system rating, as published by the manufacturer, exceeds the total cell weight. The four-caster rating is a manufacturer system figure; for configurations with more than four casters, ask the supplier for the equivalent system rating.

Does adding a brake change the load rating of the caster?

The load ratings published in the CarryMaster catalog are for the leveling caster as a unit. If a brake option is available for a specific model, ask the supplier whether the published load rating applies with the brake fitted or whether a separate rating applies. Do not assume the published figure carries over without confirmation.

How much adjustment range should be specified when the floor flatness across the new location is unknown?

The catalog does not publish the adjustment range for a specific model; request it directly from the supplier. Survey the destination floor before specifying, because a floor with significant slope across the cell footprint may require more adjustment range than a nominally flat floor. Ask the supplier for the adjustment range of the selected model when you inquire, and confirm it is sufficient for the worst-case floor condition you expect to encounter.

Can the caster be adjusted once the cell is fenced and the services are connected?

Access to the leveling feet after installation depends on the cell's guarding layout and service routing. If the cell's base perimeter will be enclosed by fencing or cable trays after commissioning, confirm that each foot remains accessible before finalizing the installation. Re-leveling after a floor settlement event is easier if you planned access from the outset.

What thread or bolt pattern information does a supplier need before quoting?

For stem-mount models, provide the stem diameter and thread specification your frame is designed to receive. For flange-mount models, provide the bolt pattern dimensions and the bolt size. CarryMaster flange models ship with bolts and nuts, but the frame must be drilled to match. Providing the frame drawing or the mounting-point dimensions at the time of inquiry avoids a second round of communication before the order is placed.

Are the same casters used under the cell and under the carts that service it?

Not necessarily. A robotic assembly cell is a stationary machine that is moved infrequently. Select the casters under it for load capacity and leveling range. Carts that service the cell move continuously, carry different loads, and may operate on different floor surfaces. The selection criteria overlap but are not identical. Specify each application separately.

What should be specified when a cell will be relocated repeatedly rather than once?

Repeated relocation increases wear on the wheels and the leveling mechanism. When contacting the supplier, specify the expected number of moves per year, and ask whether the selected model is rated for that duty cycle. Also document the re-leveling procedure and the destination floor conditions each time the cell is moved, so that the team performing subsequent moves has a reference for which corner runs low and by how much.

What documentation should be requested when a commissioning procedure calls for a leveling tolerance?

Ask the cell manufacturer or integrator for the leveling tolerance required at the arm mounting surface, expressed in the unit and axis they use for commissioning. Then ask the caster supplier whether the selected model's leveling adjustment mechanism can achieve and hold that tolerance on the floor type at the destination. The caster supplier can confirm the leveling foot's adjustment resolution; the cell manufacturer owns the tolerance specification. Neither party can answer both questions, so both conversations are necessary before commissioning begins.