Plasma 5-Axis Bevel-Head A/B

BobCAD-CAM Software Discussions
#1

Hi all,
we had implemented bevel-head A/B kinematics for plasma cut in our CNC and I would like to create some demo toolpath with BobCAD-CAM v33.

I’ve created a Plasma multi-axis machine with Add:

  • Machine Name: Plasma-Bevel
  • Type: Plasma
  • Axes: 5 Axis HeadHead Machine
  • Set Main Chain Rotary Axis to A with limits and pivot data
  • Set Slave Rotary Axis to B with limits and pivot data
  • Added some geometries to check all fine in Machine Simulator

Ok to test the pivots vs geometries create a dummy toolpath just to run the Machine Simulator
and try to move manually axis A/B to see if all ok and it’s all OK.

Then I’ve created a multi-axis path (Wireframe) with an inclined cut to test the movements
in the Machine Simulator ad what I see is an unwanted tool/tool-holder after a cup of plasma.

In the machine operation the tool PLASMA doesn’t have any length or way to remove or set tool length to 0:

image
image1501×901 237 KB

What I mistake in this ?
Plasma_Bevel.zip (496.1 KB)

2 Likes
#2

First part DONE!

Machine in BobCAD: working but with tool length to remove or set in some way:
I’ve tried to remove Tool subparts in the machine but the system restores them.
If I remove the entire tool root obviously I can’t post-process.
This is only a simulator problem (if a problem is) don’t change the NC that is fine.

Post-Processor: almost done.
Plasma requires more options to work in the machine.
I need to study it more deeply.

G-Code: working enough for tests.
CNC Kinematics: works fine with RTCP toolpath generated by BobCAD-CAM is very fine (checked the forum rules I can’t place video here, I agree).

Usually, with plasma there are some measures that must be applied to the output NC file:

  • PIERCE HEIGHT: is the height from material where to place ON Plasma torch.
  • CUT HEIGHT: is the height to go after Plasma is activated and checked (cut height from the material).
    Now I’ve to understand how to define them in BobCAD or in post actions.

Another step will be integrate Torch touch (perhpas using probing features) or place it as default.

To check:

  • How to define a rule to not use THC with small shapes.
  • How to define a minimum delta between torch touch actions to avoid useless touches.
  • How to define a way to place OFF torch during last movements of lead-out (plasma torches usually are placed OFF last 6-8mm of lead out movement).
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#3

Hello Silverio,
There are certainly some tricks to getting multiaxis to work with a plasma machine since the Laser/Plasma/Waterjet side of the software is not setup with multiaxis in mind. Below are some notes I have made when working on a similar project earlier in the year, hopefully some of them can be of use to you as well:

When considering toolpath in the software, the laser does have a fixed length, and coordinates are posted from the end of that length. To account for this in the toolpath, I would program the toolpath with the depth set to the surface of the part (or the location of the nozzle of the cutter if there isn’t a THC). Although because the depth of cut is set to just the surface, the simulation will not be able to display cut material, but should get you the coordinates that you need in the code…

For turning the cutter on and off, the way I’ve been able to get this to work consistently is by applying the cutter off commands to the rapid blocks in the post (27, 50, & 54). For turning the cutter on, I applied the cutter on to the initial feed blocks (51, 55, & 155). Since the on/off commands are not “smart” variables it does require using the programming blocks to both indicate when it is turned on/off and check that status as well to avoid duplicate commands. But programming blocks will also give you more flexibility when it comes to customizing your cutter on/off processes, beyond what can be defined in your toolpath.

Some things to keep in mind, if you use this method, is that you would want to make sure your retract moves are rapid moves, and not feed moves, as a feed move would leave the cutter on as it is moving away from the cut surface. One way to prevent this in the multiaxis feature is under the Link tab, select the Retracts button, and set the ‘Exit Feed Distance’ to 0. Also when creating multiaxis features, make sure you are not using direct linking moves. This is because linking moves are also executed at a maximum feedrate, where the cutter would not be turned off.

I wish you great success on your 5 axis Plasma project, and please let me know if you have some questions along the way, I would be happy to help!

#4

Thanks for the info, are very apprecied.

For CUT HEIGHT, in 5-axis I have found a workaround.
BobCAD-CAM creates the NC toolpath directly on the drive curve.

In CNC I apply dynamically a tool length of CUT-HEIGHT so the plasma torch keeps
this distance from the piece surface in any 3D position. I’ve tried and works.

Now I guess to add a custom post property to define the CUT-HEIGHT value so the
user can pass it, between post-processor, to CNC using a named parameter value (eg: #<plasma.cut_height>=12.4) and I solve all in CNC.

Stay tuned :slight_smile:

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