Precise continuous movement for laser cutting

Quote from bokodimate

.. I tried using CNT ..

There is always a number behind CNT. The number can vary between 0 and 100, the lower the value the better the path will be. So you can try to adjust the value until the result fits your needs.

Quote from bokodimate

I tried using CNT, but then the cuts are not precise

CNT0 will produce the same motion as FINE. The difference wiil be :

FINE-> Robot stops at the target point

CNT0->Robot pass through the target point. It should fix your problem.

CNT0 will not fix this, the robot will still decelerate to 0 velocity.

What version of controller do you have? Starting with v9.30p04, there is a new option called spline motion. This will do exactly what you need it to do, but I don't know if RoboDK supports it.

Since it's from Fanuc, it is of course a paid option.

What is the distance between your points?

You could try to decrease distance between points, which should allow you to increase the CNT value. You will need to maintain a very high CNT value to get steady speed.

Could you post a picture of your tool path from RoboDK?

At what speed does your laser need to feed at? If you slow your feedrate while increasing your cnt does it reduce the undercut?

Spline motion will not be an option for you. "Due to the changes to the system and validation effort required, there are no plans to port back to earlier versions."

Quote from bokodimate

RoboDK generates the code and the points for each CAD file. Unfortunatelly, I can't decrease the distances nor set the CNT value manually for every point.

This would be a somewhat janky solution, but I've done it before: export the program as an ASCII file (.LS), and write a script (I tend to use Python) that adds CNT values and specific speeds to every point. Then import back into the robot (assuming your robot has the ASCII Upload option).

You might be able to use the corner region (CR) termination option for that era of controller. Another option would be to try out the corner distance (CD) termination option. Both are option of course.

Quote from bokodimate

RoboDK generates the code and the points for each CAD file. Unfortunatelly, I can't decrease the distances nor set the CNT value manually for every point.

You can modify the post for this, but you did state that CNT was producing poor cut quality.

    # set default CNT value (all motion until smooth value is changed)
    # CNT_VALUE = 'CNT5' # 5% smoothing (set CNT1-CNT100)
    CNT_VALUE = "FINE"    

Quote from SkyeFire

This would be a somewhat janky solution, but I've done it before: export the program as an ASCII file (.LS), and write a script (I tend to use Python) that adds CNT values and specific speeds to every point. Then import back into the robot (assuming your robot has the ASCII Upload option).

I've had to do this also.

I like to call it my Post-Post Processor. Not ideal, but if you only need to do it every so often it will get 'er done

I've never used RoboDK, but from what Nation stated, if it is possible to spit out more points, I would go for it. I would start with a point every mm and go from there.

Quote from pdl

I've never used RoboDK, but from what Nation stated, if it is possible to spit out more points, I would go for it. I would start with a point every mm and go from there.

I haven't used RDK to create paths, but from the description of the issue, I'd guess that it outputs points on the path. And you're not going to get accurate robot motion along curves that way without Spline-type motion, or (as you suggest) lots of closely-spaced points with small CNT values.

Don't have my computer at hand right now, but looking at the RoboDK documentation, looks like it is possible to adjust a parameter to generate more or less points in the path.

Laser Cutting - RoboDK Documentation

Quote

Note: In the Advanced Settings tab, you can find the Linear Tolerance that will control the number of points you will send to RoboDK. The smaller the number is, the higher the number of points and therefore the precision of the path.

Hi guys,

I'm a bit late to the show, I'm sorry. For those more active on the forum, feel free to tag me in next time.

First of all, RoboDK can create "FINE" and "CNT" motion.
From your Curve Follow Project or your Robot Machining project.
Here's where:

Are you working with a NC file from a CAM software or the points extracted from either the 3D model or imported from a CAD software?

In the first case, the point distance will be set by the CAM software. You can change the tolerance there.
If it's extracted from the 3D model imported in RoboDK, you can change the CAD Import Settings to increase or decrease the number of points. I love to have high number of points at this stage.
You can do the same with the CAD plugin by changing the "Linear tolerance" parameters.

Then you can right-click the curve in RoboDK -> "Split curve" -> "Set point spacing" to define the distance between the point of a curve section.

Another method is to go to "Tools"->"Options"->"Programs" and set a "Minimum distance between point" for your linear motion.

Hope it helps.

Jeremy

Hi there,

Let see how we can help you with this.
Can you provide your .rdk file?
Can you also provide the NC file out of Alphacam? (I think you should find it in your Temp folder just after you press "launch robot integration" from Alphacam (type %temp% in a file explorer window to reach your temp folder automatically).

Jeremy

Just sent you a PM.

I just found the problem.

Someone created a custom post-processor for this project, which is very cool. (The post-processor translate from the simulation (RoboDK Language) to the robot language (.LS in this case))

But they didn't implement the Rounding section.

We currently read this:

def setZoneData(self, zone_mm):
    """Changes the zone data approach (makes the movement more smooth)"""
    self.CNT_VALUE = 'FINE'

While we should see something like this:

def setZoneData(self, zone_mm):
    """Changes the zone data approach (makes the movement more smooth)"""
    if zone_mm <= 0:
        self.CNT_VALUE = 'FINE'
    else:
        self.CNT_VALUE = str(int(min(100,max(1,zone_mm)))) + ' %'

Using a custom post-processor is the best way to generate exactly the type of code you are looking for.
But you need to be careful to no remove feature while adding new ones, which was the case here.