Zacobria Pte. Ltd. 47 Tannery Lane, #06-04

Singapore 347794.

Phone: +65 68844002    Email:   info@zacobria.com

6-axis flexible robots.

A 6-axis robot is typically based on 6 rotating motors (meaning that the motors turn around by nature). A 6-axis robot therefore should not be compared with an X-Y-Z linear robot which is based on linear drives – such linear drives are very accurate in going straight and making linear moves. For example, in order for a linear-drive robot to make a straight line, just one axis is necessary to move actively, and the line will be very straight.
Specialised robots.

A brief note about specialised robots. When considering a very special task that requires a particular “skill”, a specialised robot is typically necessary. For example in the case of very precise cutting where a 3-axis X-Y-Z robot or laser cutter is the machine of choice, or in the case of very precise cutting and milling with micro-meter accuracy where a CNC or milling lathe is the machine of choice, or in the case of highly specialised welding according to sophisticated patterns where a special welding robot is the machine of choice.
Some of these specialised robots use linear drives (linear motors), meaning that the motor is moving in a straight line instead of turning around. A linear drive is therefore very good at going straight very accurately.
Flexible 6-axis robots.
A 6-axis robot is a fantastic piece of equipment, and with its 6 axes of freedom it can move around in the space within its reach, within an accuracy repeatability of typically 0.1 mm (also called 100 micron).
 Where a 6 axis robot out perform the linear robot in motion is when there are moves that requires turns and twists and also where going straight in a combination is necessary.
Zacobria offers this excellent combination of a very flexible 6-axis universal robot from Universal-Robots that is very easy to programme and a wide range of choices for tools and grippers, as well as assistance in your project of implementing automation and 6-axis robots.
A 6-axis robot outperforms a linear robot in motion where there are moves that require turns and twists, and also where going straight in a combination is necessary.
An important factor to notice is the rigidity of a 6-axis robot. The rigidity is desirable to achieve the very high accuracy and repeatability of 0.1 mm.
This means that both when in use and when not in use, a 6-axis robot is very rigid in order to perform with high accuracy.
A 6-axis robot consequently has a very solid and rigid structure and does not behave flimsily – because flimsy means losing the accuracy – so a 6-axis robot is rigid and strong.
A 6-axis robot can thus go to virtually any position in its reachable space, and many waypoints (positions) involving twists and turns can be programmed, so it might seem as if a robot can perform any task during such moves from point to point.
This is where one of the first learning experiences occurs: The difference in “movements” and “tasks” becomes obvious, design considerations begin to surface, and a 6-axis robot can handle many industrial tasks. It is important to learn that a 6-axis robot is “an arm”, so detailed attention to “the hand” (robot tool) that is mounted on the robot is important in order to perform the task in the best way possible. Such a hand or tool can typically be a gripper, vacuum pads, or fixture to hold another tool that is custom-made according to the shape of the items to be handled.
Universal robots from Universal-Robots are very easy to programme due to their innovative teaching mode.

Move the robot by hand to teach it the position where it needs to go.

The programme logic, like controlling inputs and outputs and making logical decisions, is done by selecting an object from the touch screen. Therefore, it is not necessary to know traditional line programming in order to programme universal robots from Universal-Robots.
Example of robot gripper based on air chuck, with two sets of fingers for inside grip pushing outwards (e.g. in cylinder) and outside grip pushing inwards (e.g. holding a pipe).
Air chuck gripper customised with fingers.
Get to know the terms used in the world of industrial robots:
Robot Repeatability:
Typically, a 6-axis robot is programmed by setting waypoints, also called positions – this is a basic fact that is important to realise when using 6-axis robots. A typical task for a 6-axis robot being a "Pick and Place" scenario, that is, the robot picks an object at one location and places it in another location, there are mainly only 2 positions, namely the picking position and the place position, that are very important. What the robot does in between is not very important (assuming that there are no obstructions in between, otherwise the programmer must ensure that there are waypoints in between that the robot has to go through in order to get around the obstruction); here the main task is to pick from and place at these fixed locations – and this is what is called Repeatability, which is typically 0.1 mm at both the Picking location and the Placing location. Such a movement is often called “Operational task”.
Robot accuracy:
With the introduction of many new and innovative 6-axis robots that are very flexible, many new ideas for implementing a robot become much more feasible and are much easier to realise.
As descried above for a Pick and Place scenario, it is very easy to get the robot to perform very well.
Other and substantially different tasks for which it is desirable to apply robots are tasks where specific patterns have to be followed – not only at the starting and end points, but also along the way in connection with cutting, welding, gluing, and painting etc. This means that each and every 6-axis robot position becomes important as regards movement. Such a movement is often called a “Process task”.
The accuracy of the robot now becomes important, and this is not to be confused with repeatability – these are two different parameters.
Realise the difference between the Robot Arm and Robot Hand (Gripper).

 A 6-axis robot is also called a “robot arm” because it really is an arm, not a hand.
To successfully implement a robot system it is important to first consider the tasks to be performed, then choose the hand, and finally choose the robot. It is very tempting to think that a 6-axis robot can do any tasks because of the great flexibility of its moves, and because it is relatively easy to program.

A 6-axis robot is a fantastic machine and if you combine it with a good choice of hand (which is often called a gripper when talking about machines), there is every chance of achieving a good result when the robot is set to perform a wide range of tasks.
You should consider the most important feature of the task: Is it a steady hand? Or a heavy payload ability? A soft or rigid posture? A simple or complex manipulation of objects? Or any use of tools? – And most importantly: Is it an Operational task, or is it a Process task?

A very fine solution is a combination of a good arm and a good hand (gripper). The 6-axis robot arm can move around in the reachable space and take the object or tool to a position where the job is to take place.
Choose the tool or hand that is best able to do the job because – after the safe use of equipment – this is by far the most important part of the project. Then choose a robot that can manipulate the object or tool to where it is needed.
Robot Arm with the gripper.
Robot Hand

(Gripper).
Typical tasks for a 6-axis robot in the two categories.

Operational task:
These are the most common areas where a 6-axis robot can be implemented, and also the areas that are most easily programmable.

Pick and Place (Point to Point) where Repeatability is important. This is the easiest type of task for a 6-axis robot and the type of task that you can program most quickly.

Machine tending    (CNC – Injection Moulding Machine)

Packing.    Packing items or Picking items.
Operation
Task

Tending

CNC - machine
Process Tasks.

Performing a job like cutting, welding, grinding, or painting etc. where accuracy is important.
This requires more accuracy, more waypoints, and more programming.

These tasks are becoming more and more frequent and with still better software functions for patterns, it is an area in rapid growth.
The tasks are mentioned to show how easy it is to implement them. Non-contact tasks are the easiest tasks to implement because they do not require super-high accuracy.
Semi-contact is a situation where there is actually no physical contact between the robot tool and the object (for example, applying glue or silicone is a semi-contact situation because of the viscosity of the fluid; there is no physical contact between the robot tool and the object, but the silicone or the glue is actually in contact with both objects). In such cases there is still no need for super-high accuracy, although it should be better than required for painting jobs.

For situations where there is a physical contact between the tool and the workpiece, it is important to consider the rigid nature of the contact. For example in the case of grinding where it might be necessary to implement a spring force to absorb the contact, meaning that in such cases, contact is also of a flexible nature.
Where solid contact is concerned, it is important to consider the accuracy and be aware of the rigid contact between the tool and the workpiece, which might “fight” against each other if they are out of alignment, so accuracy is important in such cases.

Painting  No contact between Robot and object
Blasting  No contact between Robot and object
Gluing  Semi-contact between Robot and object
Cutting  Semi-contact between Robot and object
Grinding  Contact between Robot and object
Welding  Contact between Robot and object
Drawing  Contact between Robot and object
Assembling  Contact between Robot and object
Remote command for path offline (time to calculate path)
Remote command for path online (virtually no time to calculate path)
As regards the last two situations where commands for the movements are sent from a remote system to the robot, e.g. from another host, it is important to consider how much time you have got to make the path. The sooner the desired route to take is known the better because then a better path calculation can be made.
Painting Task
The emergence of these flexible and easy-to-use 6-axis robots is a big advantage to Singapore and a way to increase productivity and justify production in Singapore because the time to market is shorter when products are produced near the market.

Also, by implementing a 6-axis robot you can increase the availability of productive working hours because parameters of the work setting need not be changed so often – which all takes time and has to be managed.

This means reduced costs because you can run an economically sound production in Singapore compared to the cost of setting up production elsewhere in the world, which would require more administrative work and management of product logistics.
Collaboration mode:

The Universal-Robots are equipped with a force-sensing mechanism that detects unexpected obstructions, and are tested according to international standards.
This means that Universal-Robots will stop if they meet a force of no more than 150 Newton. Consequently, the robot can work in collaboration with its surroundings when a normal risk assessment of the workplace has been conducted.
“For the first time, our IMM machine is working to capacity over much longer periods of time, so now we can utilise resources for other tasks”.
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Author:
By Zacobria Lars Skovsgaard
Accredited Universal-Robots support Centre.