Payload and grippers: how to assess a Cartesian robot

The load starts from the moved set

Product weight is only one of the inputs used to select a Cartesian robot. The tool and other moving components also load the axes. Load retention, offset from the tool and the motion path complete the assessment.

Imagine two boxes with the same mass: one rigid and closed, the other flexible and with contents that move. The first can maintain its shape during setting; the second can deform and change the load distribution. The same mass does not mean the same handling condition.

Gather product dimensions and variations, identify where picking may occur, and record how the part arrives at the machine. It is worth including the less favorable conditions that are part of normal production, not just an ideal sample.

Example: product mass and tool mass

Consider, just to organize the information, a 12 kg product and a 6 kg tool. If both follow the same axis, the moved mass of this set is 12 + 6 = 18 kg, before considering other associated moving elements. This survey does not alone define the required nominal capacity: it is necessary to check the manufacturer's specification reference point and the movement conditions.

If the product is displaced in relation to the fixing point, the load distribution also matters. Therefore, two tools with the same mass can generate different requests. Take a drawing with the fixing and handle positions, in addition to the list of masses, for evaluation.

Compare grip shapes

These classifications can be combined: a mechanical tool can be driven by compressed air or by an engine. What defines the choice is the complete task, from initial contact to release at the destination.

For suction cups, the theoretical force depends on the pressure difference and the effective area. Friction, surface and product stiffness influence actual behavior. A Schmalz documentation highlights the need to consider these conditions and carry out testing. An isolated catalog value does not characterize the entire application.

Position and movement change assessment

In addition to lifting the product, the tool needs to guide it and stop in the expected position. A handle far from the center of mass and a trajectory with changes in direction require assessment of the efforts and stability of the assembly.

Analysis example: a box can be lifted without difficulty in a stationary test and lose stability during transfer. Validation needs to reproduce the predicted grip, path, orientation and release for the operation.

Turning the tool is also part of lifting. In the palletizing with X, Y, Z and rotation, the orientation of the box allows you to compose the layers. The selection of drive and movements depends on the arrangement and available space.

Configure the robot and integrate the cell

In the CR-NX line, axis travel, grippers and programming are defined for the application. The cell also includes product arrival, support fixtures, line interfaces and access conditions. These responsibilities must be stated in the proposal.

The palletizing Carioli system considers the displacement between the gripping point and the product when calculating the deposit, within the conditions foreseen for the tool and the process. This compensation does not increase load capacity and does not replace stability checking.

Prepare an assessment with samples

Provide engineering with a list of product families and the conditions that must be met:

• Minimum and maximum mass and dimensions of each family.
• Photos of the packaging and regions available for contact.
• Variations in position and orientation upon arrival.
• Brand restrictions, deformation or contact with the product.
• Travel path, required rotation and delivery conditions.
• Acceptance criteria for picking up, transport and release.

A useful assay records the condition tested and what was observed. The conclusion must indicate which products and movements it applies to. This helps to compare configurations and avoid treating an isolated demonstration as validation of the entire production.