This repository contains the modules in RAPID generated by RobotStudio. In these modules, you will find the code used to define different paths to draw the letters AEC with the robot ABB IRB140. For this reason, it was necessary to use a marker as the end effector and to design the marker holder.
- Maria Alejandra Arias Frontanilla
- Camilo Andres Vera Ruiz
- Edwin Alfredo Higuera Bustos
(That's why AEC :) )
The first thing to keep in mind to properly design the tool is the robot documentation. The tool must have an specific fixing method, in the case of the ABB-IRB140 the documentation as showed bellow, makes clear that four m6 screws must be used.
The robot tool holder has 9mm of depth, so we will use 20mm screws, using 7mm inside the tool holder and 13mm inside the tool.
We use Fusion 360 to design the tool, it consist of 5 parts, the case, the cap, the guide, the spring and the marker.
The marker is taken from a free GRABCAD model avaible here.
The spring comes from a 3d printer that had an improvement in the bed springs.
The other 3 parts have been model from scratch, the images bellow show an isometric view of each part and the last one shows the full assembly.
The 3 parts were made with an ender 3 v2 3d printer, with PLA using a 0.4 mm nozzle, 0.56 mm of extruction width, 4 wall layers for bring more strength to the part, and 30% infill.
The cover has 4 prism to give it structural integrity. The guide moves inside the case through 4 slots making the spring movement to give the marker tolerance with the table at drawing, the guide fits inside the marker in the same way that the marker cover fits in the marker while using it, and the cap fits in the case in a similar way as bottle caps
The images bellow show the manufactured parts with each individual assembly, including the guide with the spring, the guide with the marker, the 3 in the same assembly and the full assembly with the five parts.
Well, once we have designed the tool, we proceed to mount it on the robot and see that it fits correctly.
To carry out the calibration process of the built tool, it is first necessary to create an empty tooldata object located on the robot's flank, to which values are assigned automatically, using a four-point and one-axis technique, which consists of performing four approaches with the tool to a point in space which is indicated by a guide like the one shown in the figure.
These approaches are made with different orientations, and at the end a last approach will be made from the z axis.
When computing the obtained values, a tooldata is returned that will allow us to manipulate the tool in an appropriate way.
Ok, now for comparison purposes we import the CAD model of the tool into RobotStudio, for this we import our geometry as a .SAT file.
After verifying that the geometry will be imported correctly, we proceed to create the TCP coordinate base of the new tool, in this case the coordinate base is called Frame_1.
Frame_1 is then placed at the tip of the tool and constrained to be normal to the contact surface.
This point only remains for us to convert our mesh into a virtual tool that can be used from RobotStudio, for this we go to the modeling section, Create tool where the following dialog boxes will appear.
The first of the pop-up windows asks us for a name for the tool, its mass as well as the center of mass, fortunately for us RobotStudio provides the necessary resources to associate the latter automatically.
As for the mass of the tool, it was obtained by conventional means.
The second popup only asks us to assign a frame, at this point we clearly mark Frame_1
Now proceed to place the tool on the side of the robot, leaving it ready to start working.
Here you can see our assembled tool.
Ok! We already have the tool in RobotStudio. Let's begin to create the necessary things to draw our AEC. What do we need? We need to create a Workobject.
In order to use the same path, which will allow the robot to draw our AEC, with a different plane orientation or position, we need to create a workobject.
A workobject defines a different coordinate system. In our case, we will attach that workobject to a rectangular surface as shown in the image below.
As you can see, the workobject creates a different coordinate system. If we move the surface, everything that is defined in that workobject will move as well. That's exactly the behaviour that we are looking for. If it seems a little bit confusing, don't worry. We will see it later with more detail.
Workobject ready. Now what? We need to create the targets that will belong to the path. Ok... Targets... Sure. What's that? Targets are points with a determined position and orientation that will reach the robot with its TCP. In our case, those targets will be defined in the workobject that we just created. Those targets will have a position in x and y of the workobject's coordinate system. The image below shows all the targets that we need and their respective names.
Those names can be found in the variables declaration in the source code. Here you can see how all those targets belong to the workobject called Tablero.
The last target is called Up. This one is used to lift the marker in order to begin another trace.
We created also another target called Home to set the pose of the robot in a beginning position.
Ok! We are getting closer. We have our targets and now we will create the paths. Paths allow us to indicate the way we want the TCP to go from one target to another one. In our case, we created four different paths: Path A, Path E and Path C to draw the letters A, E and C and the Path Lines to draw the lines of the letters A and E.
There are many ways how we can go from one target to another. In this lab, there were three main movements:
- MoveJ: With this movement the TCP goes from one target to another with a free movement of the joints. That means that it won't (most of the times) follow a line between targets.
- MoveL: With this movement the TCP goes from one target to another following a line.
- MoveC: With these movement the TCP goes from one target to another following an arc.
For the letter A we wanted a MoveJ to the target Home and from target Home to target Up. The other movements needed to be linear.
The same occurs with Path E, C and lines. All this can be found in both files .mod in RAPID. (Both files have the same paths since they are attached to a workobject).
In order to move the TCP from one target to another, it was necessary to set the zone. This one is a parameter that allow us to determine how close we want the TCP to be of the target to consider that it has already achieved the desired position. In our case, that parameter was set to fine. With that value, we assured that the TCP reached exactly the target that we specified.
Other parameter that is really important is the speed of the movement. In our case, it was set to v400, that means, 400 mm/s.
After having all the paths ready, we created a main routine that called all those paths. The main routine is the entry point and it is the one that will be executed by default in RAPID.
After doing this, we can synchronize everything that we created in the workspace of the robot in RAPID. This process is shown in the image below.
After doing this, we can check in the Module, which was automatically created, the main function with all the paths.
PROC main()
Path_A;
Path_E;
Path_C;
Path_Lines;
ENDPROC
We can now check if everything works properly by simulating.
In the image below, it can be seen the TCP trace following all the paths that we created.
Ok. It works! Interesting. What if now we want to change the position and orientation the surface where our letters are written. Do we need to create all the targets and paths again? :O ... Tha answer is no. We don't have to :D. We just need to move or rotate the workobject the way we want to and synchornize again and that's it! That's the magic of the workobjects. Since all the targets are attached to the workobject, when moving the workobject, we also update the position of the targets and the paths.
In our case, we moved the workobject to the cuadrant +x, -y and changed the orientation of the surface 30 degrees. We synchornized and it worked. The result can be seen in the image below.
Nowadays, tools like Robotstudio are great to check the possible behaviour of the routine. But! There's no comparison to see it for real. It's far more exciting and also complicated. In Robotstudio we had surfaces that were totally plane. That was definetely not the case in the actual laboratory. Anywar, after changing some height parameters and trying, we finally got it :D
You can see the robot drawing the letters in a horizontal plane in this video: Horizontal plane drawing. And the one with a different position and orientation in this video: Inclined plane drawing.
Setting up all the components to create the path for the TCP was a realtively easy task. After knowing how the software works, it was easy to check and try again if necessary with the help of simulations. However, real life tends to be quite different. It is really important to take into account all the obstacles that may appear in the way when checking the behaviour in a real environment. These kind of things occur not only in an academic space but also in the industry.
The tool spring played a fundamental role in the lab due to the board uneveness, it could be seen as a trivial thing in the academic world using a marker, but in a real world industrial application, the spring or a equivalent system could be fundamental for the proper behavior of the tool.