Custom gantry system or off-the-shelf industrial robot?

As the predecessor of the classic 6-axis robot, XYZ gantry systems still play an important role in automation projects. Apart from their modularity and open accessibility, there are several arguments that play in their advantage. In this article we focus on these advantages and showcase one of our gantry projects.

The off-the-shelf 6-axis industrial robot is widely used and known in the manufacturing industry. These reliable robots dominate automated welding, painting and assembly lines. It’s partially their merit that we can afford to buy our own car.

Also for very fast pick and place applications, like in the pharma, food or packaging industry, these industrial robots are widely used. It is as if there is an infinite number of applications where these off-the shelf-robotic systems are the number one solution.

The active field of operation of these classic industrial robots is defined by

• its position,
• the reach of the arms,
• and the ergonomics around it.

As a consequence, a 6-axis industrial robot has no access to the specific coordinates that correspond to its own position. Besides that, the manipulation of very large objects or very heavy payloads can become problematic.

In these situations, gantry systems can provide a better solution.

The XYZ-gantry in a nutshell

A classic use case of gantry systems is the inevitable overhead crane and a more recent phenomena: 3D printing.

Each gantry system is based on linear robot topology that can move towards programmed positions using 3 (XYZ) or 2 (XZ) axis of movement. Different than industrial robots, it can easily be adapted to the real application needs, as it is not an off-the-shelf solution.

Classic applications for gantry systems

Apart from the classic use for cartesian positioned manipulations – like in CNC machining, PCB manufacturing, assembly of medical devices… – gantry systems are also appreciated in piling/depiling applications for large and/or heavy products.

You find them as well in plasma and laser cutting applications, and other automated pick and place projects. The obvious reason is that these applications require movements in one or more cartesian planes, without the need for extra rotations.

Advantages of a gantry system over a 6-axis industrial robot

1. Flexible and scalable

XYZ systems have infinite scaling possibilities: from a miniature model to a giant installation that spans a complete production hall. In some cases only XZ is chosen, as there is complete flexibility when it comes to the number of axis.

This is not the case for off-the-shelf industrial robots: each supplier has a fixed list of types with their specific reach, payload, number of axis… There is no option outside this standard range.

2. Footprint, reach and payloads

A traditional robot is positioned on a pedestal. From this position, it can turn 360°.

A gantry system on the other hand, hangs over the application. It can reach every single coordinate in that area, without creating an obstacle for itself. This sometimes is a problem for standard robots.

Another aspect is the relation between reach and payload. Typically, a higher range results in a higher payload. For light but voluminous products, this results in an overkill for payload, making an off-the-shelf solution less price efficient than a gantry system.

On the other hand, the 6-axis robot has more freedom of movement, as it has six configurable axis. Yet, a gantry system can be equipped with an extra rotational movement on the gripper. But this comes with an additional cost.

3. Maintenance

On average, an industrial robot does not need a lot of maintenance when properly used within its specifications. Robots are designed for a long life time.

The disadvantage, however, is that in case of defect, the systems are not open and freely accessible. The repairs have to be carried out by specialized technicians, mostly employers from the robot supplier or partners. Typically service contracts are set up for preventive maintenance, interventions and revisions.

Gantry systems, on the other hand, are open systems: the selected technology such as motors, drives and other parts can be selected following the end user’s preferences. Repair and maintenance can then be executed by an inhouse team.

Case: gantry system for (de)piling floor panels

We designed and built a gantry system for a client in the flooring industry. The system (de)piles vinyl panels.

For the construction of the linear guidings we designed a robust metal structure. There are standard commercial solutions on the market, but for this application we wanted to anticipate on defects, repairs and difficult alignments.

No more alignment hassle

Our system is based on rubber coated wheels that drive over a solid steel metal frame. A rubber belt connected to a servo motor with encoder enables movement. The wheels are clamped on both sides. There is no slip because of the coated rubber surface. Position accuracy is guaranteed at all times. This principle is applied both for the X- as for the Z-axis. In a worst case scenario, only a wheel needs to be replaced and not he complete linear guiding. So there is no downtime due to alignment challenges.

The designed and approved cycle time is 8 seconds per panel, including the vacuum gripping with peeling function.

This installation is an excellent solution for unclean, heavy duty environments. And a nice example of where these systems can be used as an efficient, maintenance and budget friendly solution compared to a standard industrial robot.

Conclusion?

As a conclusion, we can state that the application defines what is the best solution: we evaluate every case thoroughly and select the best solution for the challenge. And not the other way around.