Factors to consider when purchasing a robot
Director of Robotics at Husky Injection Molding Systems15/06/2003
Robotization
The race
The weight of the piece
More important than the payload is the couple, the tendency of a force to produce a torque and rotation on one axis, and function both the payload and the distance to the focal point of the hand grip of the robot. To make sure that a robot can manipulate a piece, should compare the applied torque, the of the piece and the hand grip, with the couple that the robot can hold.
How are benefits assessed? The benefits of a robot many times are presented in terms of speed peaks. But this information is not complete, not to be of exposing the accelerations. For example, Figure 1 shows the speeds of two robots, one with a peak speed of 4 m/s (above) and the other with 3 m/s (below). One could conclude that the fastest robot is one that has a higher peak speed. However, both robots can travel the same distance of 2800 mm at the same time, a second. This is possible because the robot with lower tip speed has a higher (45 m/s2) acceleration to the other (13.3 m/s2). It is more useful to know the time required for a robot to explore a specific distance, information which should provide it the manufacturer.
Ease of management and reliability
As for reliability, it is interesting to do with digital components such as a controller based on PC Digital drives with servo motors. As in any other team can always have a bug, for what should be fixed in the guarantee, which vary widely. To the value of a guarantee, it is important to look at the list of items subject to wear that are excluded from coverage. Taking into account the differences between the guarantees, a three-year-old not always has to be better than a one.
Robots are subject to the General provisions of the industry in regards to security and, in the case of robots to injectors, also affects the rules concerning this kind of machines.
It should be informed also of this type of issues, in particular those relating to jobs, the installation of limiting mechanical, elements of security in the area of the vertical drop, and others.
The price, of course, is one of the decisive factors that often determine the purchase, but it is very important to take into account its financial impact on a general system. For example, must be taken into account the savings that can be obtained by reducing the downtime or increasing the cycle time.
For example, in a factory with 6,000 hours of production, a 1 per cent reduction in downtime of the robot in a fuel transfer of 1,800 tons, can provide a savings of up to 8,800 euros per year, while that an improvement in 0.5 seconds in the cycle in a cycle of 10 seconds and 200 machine tons can make annual savings of 12,300 euros.
In certain applications without doubt worth the purchase of a robot for top performance.
Finally it is important to note that the robot is a part of a whole line of injection: their performance, reliability, safety and cost play an important role in the system as a whole. Therefore, the robot is chosen must respond to the objectives set for the entire system.