A tube rack can fit between the same fingers as a microplate and still need a different gripping setup. The rack may put its load higher above the contact, leave gaps where the fingers expect a continuous wall, or block the withdrawal path with projecting tubes. Before keeping the tool, we would compare how each item is supported from pickup through release.
The decision is whether the existing fingers and fixtures remain usable, need a local change, or should be replaced for the new configuration. Opening width is one input; contact geometry, loaded condition and the receiving nest determine whether that choice works through the whole handoff.
Compare the interfaces, not only the outer size
Place the plate and rack drawings on the same reference basis: where each item rests in the source fixture, where the fingers touch it and where it seats at the destination. A rack can have open regions, a removable insert or feet below its main body. Tubes and caps can project beyond that body. A plate may be located by its skirt or a carrier, while its lid occupies a surface that was previously available for gripping.
The ANSI/SLAS microplate standards separate footprint, height and flange geometry. For this review, the actual part drawing, tolerances and representative samples matter: a similar footprint does not make a rack’s side wall or support features equivalent to those of a plate.
Consider a hypothetical rack with the same nominal footprint as the released plate, but with tubes concentrated toward one side. Its mass distribution can shift the load relative to the grip, while the extra height changes the clearance envelope. An empty rack trial would miss both conditions. We would define the permitted loading patterns with your team, then assess the tooling and motion for those conditions rather than carry over the plate’s limits.
There are several possible outcomes. The same fingers may remain suitable if their contact and support still work. Replaceable fingers or a different nest may solve a local geometry mismatch while retaining the gripper body. A common carrier can give both items a shared external interface, but it adds mass and height and needs its own retention, seating and station-access checks. Those tradeoffs should be resolved before treating common tooling as a cost saving.
Trace each change through the handoff
At pickup, the fingers need access to the intended contact without squeezing a tube, catching a label or gripping only a removable insert. A contact near an unsupported opening can deform a rack differently from a continuous plate wall. Longer fingers may clear the source nest, but they also change the load applied to the gripper jaws. The selected gripper’s force, finger-length and load limits need to be checked at the proposed contact position, not just at its catalogue opening width.
During transfer, the loaded mass, its position relative to the grip, orientation and acceleration or deceleration affect retention and tooling loads. Friction gripping depends on the contact conditions; support beneath an item changes the load path but needs access underneath it. Increasing the gripping force alone may damage the rack without resolving an unsuitable contact. The review should connect the chosen support method to the required movement and the component limits.
At the receiving station, taller tubes can clear the entrance yet obstruct the opening fingers or their exit. Follow the full approach, seating, release and withdrawal path. If the rack can enter backwards, a locating feature or an agreed orientation check may be needed. A finger-position signal reports the finger position; by itself it does not establish that every tube is retained or that the rack is seated on the intended datum.
LabCarry reviews the agreed gripper, fixtures, platform movements and interface indications against these inputs. Your team defines the laboratory process, permitted labware loading and application restrictions, and decides how its scheduler uses the returned states. For the new setup, distinguish the evidence for item identity, grip, seating and release instead of treating one unchanged signal as proof of the entire transfer.
Plate-to-rack change comparison
| Interface item | Released plate setup | Proposed tube-rack setup | Review action |
|---|---|---|---|
| Item identity | Supplier, part and revision | Supplier, part and revision | Define permitted variants |
| Loaded condition | Mass, lid/carrier and load distribution | Mass, tubes/inserts and load distribution | Identify representative test states |
| Reference geometry | Datum and locating features | Datum and locating features | Update finger and station references |
| Permitted contact | Approved surfaces | Approved surfaces | Confirm material and process restrictions |
| Restricted zones | Labels, lid, seals or optical areas | Tubes, caps, labels or open regions | Set clearance limits |
| Gripper setup | Tool, fingers, opening and mounting reference | Proposed tool, fingers, opening and reference | Decide reusable and changed elements |
| Source fixture | Support and pickup access | Support and pickup access | Check interference and extraction |
| Receiving station | Opening, seating and release space | Opening, seating and release space | Check placement and withdrawal |
| Travel orientation | Released posture and constraints | Required posture and constraints | Review retention and clearance |
| Sensing and states | Object, grip and release evidence | Required evidence for the new item | Revise interface mapping if needed |
| Acceptance | Released tests and configuration | Proposed tests and configuration | Record repeat, new and not-applicable checks |
Record the difference before accepting another labware variant
When a new rack, plate, lid, insert or carrier enters the project, begin with the released configuration and record only what has changed. Keep an unknown field open instead of treating a missing tolerance as a match. The record should end with one of three decisions: retain the released setup, change the affected tooling or fixture, or hold the variant until the missing input is available.
Use the released and proposed part drawings together with representative samples. Put both configurations on the same datum basis, then trace each difference into contact, support, loaded condition, station access, sensing and acceptance. A shared nominal footprint does not close those questions; the earlier interface comparison explains why the actual contact and support geometry still control the hardware decision.
| Field to copy | Project entry |
|---|---|
| Record and baseline | Difference ID: ___; released item, part and revision: ___; reference drawing: ___ |
| Proposed variant | Supplier, part and revision: ___; lid, insert or carrier: ___; sample ID: ___ |
| Changed geometry | Feature and datum: ___; baseline dimension/tolerance: ___; proposed dimension/tolerance: ___; evidence: ___ |
| Contact and load | Permitted or restricted contact: ___; loaded mass and distribution: ___; source of each value: ___ |
| Affected handoff | Pickup access: ___; retention: ___; receiving fit: ___; withdrawal: ___; sensing: ___ |
| Review decision | Retain / modify / hold: ___; reason and affected setup revision: ___ |
| Verification to close | Requirement and limit: ___; method and sample conditions: ___; test ID: ___; result/evidence: ___ |
| Release | Open items: ___; decision owner: ___; approved variant and restrictions: ___; date: ___ |
Example: a label moves into the finger contact
Consider an illustrative rack that keeps the same nominal envelope but moves a label across the released finger contact. The difference record identifies the affected surface and the drawing revision. Your team first defines whether contact on that label is permitted. We can then review whether the finger location, contact conditions or sensing arrangement needs to change.
If contact is prohibited, the released contact position cannot carry over unchanged. If it is permitted, the label may still alter friction, compliance or the signal returned by the setup, so the record needs a representative verification condition before release. A rack fitting the station nest does not by itself close the gripper-interface decision.
Release the new configuration explicitly
Record whether the tool is retained, modified or replaced, and which fingers, fixtures, item revisions and platform configuration that decision covers. Keep the earlier plate results attached to that plate setup. The rack review should identify which checks can be retained with a reason and which require fresh evidence under its own loaded conditions.
Use the labware and gripper interface record to collect the two configurations. Where the plate has a lid, the covered-microplate gripping review explains the distinction between holding the plate body and holding its cover. Link the agreed repeat checks to the hardware FAT record, with the build and revision retained in the quality and traceability record.
For a mobile manipulator platform review, send us the plate and rack part references, loaded conditions and views of the pickup and receiving nests. We can then discuss whether the change belongs in the fingers, fixtures, carrier or platform interface before committing to a common tool.