[Ultraviolet]

Hi,
I am building a fabric cutter, and I need the the 4th axis to turn the rotary blade tangent to the line it is cutting. I tried setting the machine for 5 axis head/head configuration and modified the post processor, but no luck. It would not produce the g-code for the 5th axis (my 4th axis).

Here is my configuration:
1. I own Madcam 5.0 4X. I am not sure that I would need madcam 5X, so I down loaded the trial version on another computer to test the 5th axis functions.
2. I set the machine to be a 5 axis head/head machine, similar to what was explained in http://www.cnczone.com/forums/madcam/211984-cnc.html . In this post, it uses a table-head machine, I tried both the table-head machine and the head-head machine. I would think that I would use the head-head machine since the icon of this machine shows that the head can be rotated. In the icon, it is labeled "C". This is the axis I want to control, not the "A" axis of the head-head machine.
3. I made a test profile that is rectangle with one end a semi-circle. Looks like a Popsicle, but without the stick. Theses are just curves on top of a plane surface, not a solid.
4. Set up the machine for a 5 axis head-head machine and set the advance settings to:
Rotational axis 1 direction (1,0,0), angle vector (0,0,1) min. angle 0, max angle 120.
Rotational axis 2 direction (0,0,1) angle vector (0,-1,0) min angle -360, max angle 350 origin (0,0,0)

5. Here's where I start to go astray. I first tried 4-axis profiling with the forth axis set to indexed 0 degrees ( I tried all angles). The cutter was lying flat on the plane, not perpendicular.
6. Next I tried 5-axis profiling in indexed mode using the trial version of madcam 5x. I was able to chose top for the direction of the index, and the tool was in the correct direction. This function is not available in the Madcam 4X version. Two problems: First,it did not produce g-code to the a or b axis using the mach-3-metric-5-axis PP. Second, the 5-axis tool icon is not activated tor the Madcam 4X version. Do I need the 5X version of of MadCam? Can the Madcam 4x work the 5th axis of the head-head machine?

Summary:
1. Need help setting up the 4 axis to be tangential to the profile curve
2. Do I use the 4X / 5X profiling function or the 4 / 5 -axis cut along a line function to create the tool paths?
3. Help making sure that my PP is set up correctly. I used the mach-3-metric-5-axis as a template
2. Can this be done with Madcam 4X or do I need Madcam 5X?

Thanks,
Ultraviolet

[Gregore]

i have no idea if madcam could do this or not , But I wonder if the post processor could be tweaked to do this or even coded into the controller
.

Also could you not set the cutter up on a bearing so the cutter tip trails the bearing axis ( like shopping cart wheels ) and thus the cutting edge will always face into the line of cut . The only issue with this is the greater the trail the less accurate the tip follows the intended path

[Ultraviolet]

i have no idea if madcam could do this or not , But I wonder if the post processor could be tweaked to do this or even coded into the controller
.

Also could you not set the cutter up on a bearing so the cutter tip trails the bearing axis ( like shopping cart wheels ) and thus the cutting edge will always face into the line of cut . The only issue with this is the greater the trail the less accurate the tip follows the intended path

Gregore,
Yes, you point out some very good options that should work. Here is my plan of attack depending on success.

1. Try to have MadCam generate g-code for the 4th axis.
2. Prototype a rotary drag knife as you suggested. No 4th axis is needed.
3. Investigate if my controller do the calculation. I am using USBCNC controller. I notice the the Mach3 controller can do tangential, but I don't want to change controllers at this point.
4. Modify the g-code by hand or script to calculate the 4th axis as you suggested
5. Use a scissors and cut the fabric by hand. - LOL

[Gregore]

Does your control use C code ? If so I would think that writing code to have the cutter always turn to face the cut direction would be rather easy compared to some of the stuff I have seen people write c code for .

I myself am just starting out and barely understand any of it yet .

[Ultraviolet]

Does your control use C code ? If so I would think that writing code to have the cutter always turn to face the cut direction would be rather easy compared to some of the stuff I have seen people write c code for .

I myself am just starting out and barely understand any of it yet .

My controller is CNC USB.Unfortunately, the controller uses embedded firmware. Both the firmware and application code is not open source. There is no way for me to edit it.

[svenakela]

My controller is CNC USB.Unfortunately, the controller uses embedded firmware. Both the firmware and application code is not open source. There is no way for me to edit it.

So how is the programming for this thingy? Can you give an example of a program for a cut?

[Zorbit]

Some quick thoughts.

A drag knife will need the tool path changing, you can't just follow the outline of your intended shape or it will cut off the corners. You will need some tool overshoot for sharp direction changes. Software for cutting vinyl signs often has this built in.

Re: using Madcam and a 5 axis machine - how about using the "surface normal" function ? Perhaps you could mount your rotary blade on a mandrel, define the appropriate size and tool shape ( ball end ?), and Madcam would drive it around your shape. I can see there would still be a problem on internal corners.

[svenakela]

Some quick thoughts.

A drag knife will need the tool path changing, you can't just follow the outline of your intended shape or it will cut off the corners. You will need some tool overshoot for sharp direction changes. Software for cutting vinyl signs often has this built in.

Re: using Madcam and a 5 axis machine - how about using the "surface normal" function ? Perhaps you could mount your rotary blade on a mandrel, define the appropriate size and tool shape ( ball end ?), and Madcam would drive it around your shape. I can see there would still be a problem on internal corners.

I am pretty sure his machine is not a drag knife, he wants a spindle orienting the knife all the time. I.e. the spindle is another servo/stepper that needs a fourth direction.

[svenakela]

Like these two:

[svenakela]

Like these two:

[Ultraviolet]

I am pretty sure his machine is not a drag knife, he wants a spindle orienting the knife all the time. I.e. the spindle is another servo/stepper that needs a fourth direction.

Yes, this is what I am trying to accomplish.
My questions is: Can MADCAM produce the gcode to do this and what version of MADCAM do I need? 4X or 5X?
It seems that it might be possible because you could configure the machine to be a 5 axis machine head-head machine and use the 5th axis to rotate the spindle and ignore the 4th axis. Thus, technically I would just need a 4 axis machine, However, when I do this, no gcode for the 4th and 5th axis is produced. If MADCAM cannot do this, then I will move to the fallback plans:
1. Different controller - Mach3
2. Drag knife
3. Edit the g-code manually
4. Write a script to edit g-code

Thanks