Teach offset and load determination

Hi,

Teach Offset:

First of all, it is not mandatory but for Robot to take into account the positional accuracy while working on the positioning command it is better to do Mastering with Teach Offset with the TOOL. If the tool is standard and you are not changing it frequently then the mastering with Teach Offset is easy to be done. If you have different tools then it would be good if you can do mastering with Teach Offset with each of your tool and save the Data.

Load Determination:

There are two you can determine the load of a particular tool you are using:

1). KUKA.LoadDetermination: It is a paid software from KUKA depending on the KSS version. After installation, it will allow you to follow step by step procedures to determine the load of your tool. You can do this test with empty gripper or loaded gripper. Usually, it is done on empty tool as in material handling industry one may have different types of products to be handled and it becomes practically impossible to do this test for each type of product.

2). Theoritical Calculations: You can calculate the load (Mass, Moment of Inertia, etc) of your tool theoretically with some mathematical tricks.

Now, if you have the load values of the empty tool then for, the parts usually do a theoretical calculation and simply add the mass and inertia to that particular tool. Like in your program you can set:

$TOOL=TOOL_DATA[Your Particular tool]
$Load=LOAD_DATA[Your Particular tool]+Calculated value.

For, example you have TOOL[1] as an empty gripper. So, you can do mastering with Teach Offset with empty gripper and whenever you have parts then calculate the load values in your program for that particular part and then assign these values to your working tool (let say TOOL[10]) like:

$TOOL=TOOL_DATA[10]
LOAD_DATA[10]=LOAD_DATA[1]+Calculated values of particular part.

This was one way of approach. The second way is to do mastering with Teach Offset of your gripper+part but this case would be more convenient if your have less number of tool and parts.

Quote from Casius

Inside the programs, for motion PTP or LIN, do I have to specify when is the tool with part and when the gripper is empty?

Just before your inline form of motion, you can assign the load of that tool like I mentioned above for empty or occupied gripper.

Quote from Casius

Extra:
Collision box, false or true, is not active for inline when the points are declared in config. That means the collision can't be monitorized?

Yes, you have to configure the collision detection.

Thanks

Hi Casius,

Unfortunately, I personally never used Collision Detection so I may not be so helpful in that case. But you can find a description about Collision Detection in System Integrator Manual. It is a separate topic under the chapter "Configuration".

About the mastering, the first mastering values of the axes are always saved in RDC until there is any hardware change or the first mastering is carried out again. First Mastering is always done without load on the robot, I mean empty flange. The best way is to un-master the robot as soon as it arrives in the facility and carry out first mastering before further commissioning the robot. Mastering with Teach Offset will give you an error in mastering position of axes from the first mastering and it will save the offset values for the respective tool. It will infact help in the repeatability of the robot.

And the robot will always take into account the offset of respective tool while positioning. It also depends on your application, as sometimes we do not care the robot to be so accurate in positioning then we may opt for other types of mastering. Please go through mastering manual or System Integrator manuals, it explains what I mentioned here.

Thanks

Quote from Casius

I have some questions please.
It's mandatory to teach offset with load correction? First mastering is done.

I do see question mark after second sentence but I don't see question. First mastering is done without tools (just robot). If your application does not require great accuracy, that is sufficient (there is no some secret "police" going after people that did not use offsets). If your application does require best possible accuracy then you need to use mastering with offset for every tool.

Quote from Casius

For load data determination.
Do I have to make it with part and without the part in gripper?

The gripper has 4-5 kg.
The part has 1.4 kg.
The robot is KR 10 R900 Sixx, load 10kg.

you only specify static mass, nothing else. load has more parameters (mass distribution matters).
since gripper is heavier than part, you could enter average data (say 5.3kg) so robot will be always a little off (0.7kg over or under is some 13% or so).
the best way is to use two tools and different loads (for example tool1 is gripper empty, tool2 is gripper with load).

Quote from Casius

Inside the programs, for motion PTP or LIN, do I have to specify when is the tool with part and when the gripper is empty?

yes

Quote from Casius

Extra:
Collision box, false or true, is not active for inline when the points are declared in config. That means the collision can't be monitorized?

Correct.... read documentation: collision detection does not work for any global positions. that includes all home positions (all six are global).
Nothing stops you from replacing 'PTP HOME' with 'PTP MyOwnHome' and have it declared in local program.

I'll add one caveat to this: for a robot with the Absoulte Accuracy option (Position-Accurate Robot), performing the with-load Mastering for each tool (with accurate Load Data already determined) is necessary in order to obtain the benefits of Absolute Accuracy. Failing to perform the proper sequence of No-Load Mastering, Load Determination, and With-Load Mastering will result in a robot that is no more accurate (and possibly less) than an ordinary robot of the same model.