Why Purchase A 4 Axis SCARA When You Only Need 3 Axes?

The WEISS intelligent 3 axis system surpasses traditional 4 axis SCARA robotic performance.


WEISS 3 axis system vs. 4 axis SCARATraditional, tried-and-true SCARA systems remain a very popular solution for palletizing and tray packing applications. However, their typical design configuration features four axes consisting of two rotary axes and one lifting swivel unit, which is generally not needed for most palletizing applications. The bottom line is, there’s no need to invest in 4 axes for this type of automation application.

In terms of figures, a SCARA costs on average around the same, per axis, as a WEISS 3 axis solution. By eliminating the 4th axis, since only a 3-axis system is required, you are able to achieve significant savings. Additionally, the work envelope of the SCARA is difficult and costly to guard. The WEISS 3 axis system offers a compact envelope, thereby allowing for a more cost effective safety solution – providing you with additional savings.

Ultimately, 4 axis SCARA robots typically have one axis too many for a lot of applications, can be costly, especially when considering the additional safety concerns regarding the work envelope and they take too long to program. A simpler and more economical alternative like a WEISS 3 axis intelligent system is the more appropriate choice for these types of automation applications.


The major advantage of a WEISS 3 axis system is that you only pay for what you need. Thus, procurement costs for the three axes are significantly lower when compared with a 4 axis SCARA.

The key to this intelligent handling solution relies on standard components that have been proven in thousands of applications and can be combined to create perfectly matched sub-systems. For this specific palletizing example, WEISS selected a type HN 100 linear motor axis as the basic axis.

Permanently connected to the basic axis is the HP series direct-drive pick & place module, which forms the 2nd and 3rd axis. Unlike a 4 axis SCARA robot, the strokes of the axes can be precisely matched to the dimensions of the tray.

WEISS 3 axis system vs. 4 axis SCARA comparison
WEISS 3 axis system vs. 4 axis SCARA Tray Comparison


Vital efficiency advantages in the assembly process also come to the forefront when comparing the work process of the two concepts.

The operating range of a SCARA robot is limited to a semi-circle in front of it−however, the standardized DIN pallet is always rectangular. This means the SCARA robot is often seen with only three pallets, which just fit into its working range. This semicircular arrangement then makes it extremely difficult to achieve linear “advancing” of the pallets within a fully automated assembly process − as is the norm in modern, flowing conveyor belt production processes.

Furthermore, once pallets of different sizes come into play, the system has severe difficulties. A square pallet simply does not fit in with a curved robot action radius. As a result, manual intervention is often the only option which may include: relocating, rearranging, or completely exchanging the pallets.

Comparison of SCARA with 3 axis combination from WEISS


When comparing the assembly and removal process, the difference between the two systems becomes even clearer as both stations are often positioned close together. In the SCARA scenario, there is usually only one response to this−using one robot for assembly and one for removal.

Given the sophisticated combination of various handling and axis units, the WEISS automated process is considerably more flexible. For example, two pick & place units can be positioned on a basic axis with a length of up to four meters and can work independently of each other. Instead of eight axes, only six are required. The customer effectively pays for six axes (basic axis with two carriages and two pick & place units) and utilizes the rail of the basic axis twofold − making cost advantages compared to the eight SCARA axes even more significant.

Costly 8 axis SCARA vs 5 axis WEISS solution

For processes where time is not a factor, the second pick & place module is not even needed. The remaining module on the long basic axis takes care of both assembly and removal.


The design principle of a SCARA robot requires the use of different gears−whereas the handling solution from WEISS operates completely without gears, which is made possible by linear drives. This “gearless” design makes the handling system significantly more precise than the 4 axis SCARA robot – which offers positioning with an accuracy of up to 0.01 mm, whereas the conventional SCARA can only manage 0.05 mm or more.

Eventually with age, the imprecision increases further due to wear on the gears. Of course, the smaller the parts, the more significant this becomes. Greater precision notably pays off even for parts with an edge length of under 100 mm. The time-consuming processes required by the SCARA robot for its image processing system and position correction are no longer necessary.

In terms of productivity, the axis combination is in another league as the drives are screwed on directly, giving the overall system its enormous rigidity. This allows for faster acceleration and shorter cycle times.


The WEISS 3 axis system provides a myriad of combinations that are more economical than 4 axis SCARA robots for a multitude of handling tasks.

While ideal for palletizing and tray packing applications, the 3 axis system can also be leveraged for a wide range of associated applications including: automotive, medical, inspection, and electronics. In fact, the system is currently being used for the inspection of circuits in the production of electronic cigarettes.

Importantly, end-users can leverage the WEISS Application Software (WAS) to enable simple and intuitive commissioning of the system’s most important parameters. This makes life easier for smaller and medium-sized plant engineering companies in particular. In contrast, the programming process for the software of a SCARA robot is still a major barrier for these firms.

Finally, the axis combinations are not only easy to commission, the demounted individual modules can also be used in other automation processes at a later stage. This may take some time to pay off, but significant dividends are ultimately achieved.

Note: Whereas this example utilizes the WEISS HP140 pick & place module, the WEISS HP70 direct drive pick & place module also can be leveraged as an option to achieve specified end user requirements for desired results.