There are many robot types and models that vary following multiple parameters. Here are some essential parameters to define a robot type:
- the number of axes: the majority of industrial robots have 3 to 7 axes.
- the function and flexibility of the robot: this usually determines the number of axes. Ex: 4 axes will be sufficient for palletization.
- the working environnement: the environnement rather determines the mechanical protection of the robot. Ex: A robot performing plasma welding must be protected against splashing. A robot performing food or pharmaceutical handling must be easily cleanable and resistant to aggressive products.
- the robot’s admissible load.
- the range (or radius of action) of the robot.
- speed: this could determine the type of robot (SCARA or Anthropomorph) or possibly the number of robots needed.
- robot mounting position: floor, wall, inclined, ceiling.
- the integration of particular technologies such as: painting, welding, force sensors, vision, …
What’s an industrial robot?
If you read this article and don’t know what’s an industrial robot, I suggest you start with this article.
Different families of robots
There are several families of robots that each have their own domain. You will only find a sample in this article. The number of existing models on the market is huge and can not be summarized here.
Cartesian robots (linear robots)
XYZ table: This type of robot usually has 3 or 4 axes (the fourth axis is used to rotate around the Z axis). It consists of an assembly of linear axes with generally 2 axes for the X, one axis for the Y and one axis for the Z. It is very interesting in terms of its cost and possible dimensions. It will be much less flexible than an anthropomorphic robot (an arm).
- Advantages :
- Cost: The material cost is interesting but you must also count the cost of design and development before making the comparison with an already assembled robot.
- Reduced footprint: The footprint will not be much larger than the useful working area.
- Scaling: The size of an XYZ table can be very small (eg a small 3D printer) but also very large (eg automated overhead crane).
- Speed: The maximum speeds are not always as good as with other types of robot. Speeds are lower on larger models.
- Manufacture of a quality structure: The mechanical structure supporting the axes must be rigid, massive et very flat.
- Little flexible: It will be difficult in the future to imagine other uses than the original one.
- Limited orientations: a table has 3 to 4 axes and can be extended to 5 and 6 axes but the cost will be less competitive compared to an anthropomorphic robot.
The SCARA robot
This robot type is almost always mounted with 4 axes and is used in small applications. It is composed of 2 rotary axes on a flat assembly and 2 rotary axes assembled on a screw. It is possible to make linear displacements in the XYZ axes and allow a rotation around the axis Z (RZ). The linear displacements in the XY axes are realized by the movement of the axes 1 and 2 (rotary axes assembled in plateau) and the displacements along Z and around Z (RZ) are made by the axes 3 and 4 (rotary axes assembled on a screw). It is usually faster than an XYZ table and requires a very small footprint. Its price is also often an advantage. It works only linearly, no rotation around the axis of X and Y plans is possible! It is very convenient for transfers from one machine to another or simple handling operations.
- Advantages :
- Very interesting price.
- Low footprint (some versions have a wall mount and therefore no footprint).
- High speed for many models.
- Rotation possible only around the Z axis (RZ).
- The assembly relative to the work plan must be perfectly coplanaire because there is no possibility of correcting the planes X and Y.
The DELTA robot or spider
It is equipped with 3 to 6 axes. It is often found in 4 axes. It is specially designed for very fast applications. It is widely used in the field of packaging (pick & place) in the food and pharmaceutical industry.
- Advantages :
- Speed! These robots are the fastest.
- Cleanability of the lower parts that are close to or in contact with the products.
- Cylindrical action volume accessible at all points.
- Requires a rather heavy and expensive structure.
- The action volume usually has a relatively low height (Z).
- In the 3 and 4-axis versions, the assembly with respect to the work plane must be perfectly coplanaire because there is no possibility of correcting the X and Y planes. There are also delta 5 and 6 axis robots which allow rotations around all axes.
- The embedded load is usually quite low (on fast versions).
The anthropomorphic robot
This robot looks like the human arm and is the most flexible because it performs rotational movements around all XYZ planes (in its 6-axis version). It is very much in the form of 6 assembled axes but it is also available in 4 axes (often for palletization), in 5 axes and in 7 axes. Many different sizes and loads can be found in the ranges of major manufacturers. The range of action can range from 0.3m to more than 4m and the load can go from 0.5kg to more than 1200kg. This robot is widely used in the fields of welding, painting, complex object handling, automotive, …
- Advantages :
- Very flexible.
- Low footprint and ease of integration.
- Can also be wall, incline or ceiling mounted.
- Many models are available in the ranges of major manufacturers.
- Rigidity and absolute accuracy are not the best.
- In some configurations and some movements, the robot may encounter singularity problems (this appears when 2 axes are perfectly coaxial).
- In the 4-axis versions, the assembly in relation to the work plan
must be perfectly coplanaire because there is no possibility to correct
the X and Y planes.
- Advantages :
I’m Thibaud Norberg, a passionned robotics engineer, born in Belgium in 1981. My wife, my son and I live in Maredsous (Belgium) which is well known for his Abbey, cheese and, last but not least, his beer.
I’ve been working in robotics since 2003 in 2 companies which are called “integrators” in our domain.