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Setting up Tangential Knife-Questions
« on: April 10, 2012, 06:04:41 PM »
I have finally gotten to the point where I am testing the Hardware that I have been building for a Tangential Knife set up.
There are some posts on the forum about it, but I haven't seen my particular problem worked out yet.  Hopefully somebody has some suggestions for things that I can try.... I have been racking my brain trying to solve this.
I am using some software that I wrote which will take regular 3 axis gcode and add in the fourth axis--  Axis A.  I know that Mach3 has a feature for this, but I would like greater control if it is possible.
The problem is that with every new motion called for axis A, the other X, Y, and Z motions slow to a crawl.
I have attached the gcode that I have been using for a test.
Any advice is welcome.
Thanks to everybody for a great forum.... I have learned a lot from reading the diverse topics covered.

Sincerely, Andy :)
Re: Setting up Tangential Knife-Questions
« Reply #1 on: April 10, 2012, 06:07:49 PM »
Here some code that I am using for testing.  It is far from an efficient means of directing a particular motion, but regardless of this fact, I am hoping to get things to move faster.
Re: Setting up Tangential Knife-Questions
« Reply #2 on: April 10, 2012, 06:09:23 PM »
Having trouble attaching multiple attachments... having to reply to my own post :)
Re: Setting up Tangential Knife-Questions
« Reply #3 on: April 10, 2012, 06:46:08 PM »
Hi Andy
I,m building a large tangential controlled plotter cutter 6M by 2M and using the Z for bringing down my Knife cutter. I have setup a pneumatic cylinder and use the Z direction pin as the actuator. So far it seems to be working, am still tuning it now.

You could try to turn on Tangential control in Settings Click on it.
Also activate the Z is 2.5D on the config page.

Hope it helps

I'm using Cambam as the G code generator and use the engrave style.


Re: Setting up Tangential Knife-Questions
« Reply #4 on: April 11, 2012, 04:34:58 PM »
Thanks for the quick response.  Glad to hear you are having success on your end. 

I have two different directions that I can go with my Tangential setup.

Method 1.
Use the Tangential Feature in Mach3 and create my g-code as with an Engraving option in RhinoCAM.
This seems to be the most straight forward approach, however I am having some difficulties with this method right now. The Mill moves in a very jerky motion. It may be do to using G01... but I haven't been able to sort this yet.

Method 2. (My Preferred method if I can get it to work)
Use custom software to predetermine the A axis numbers needed for a given curve. This part I have actually done already and it seems to give me good numbers for a given set of curves.
This is basically similar to what Mach3 is doing on the Fly as Method 1 happens. I am also having difficulties with getting Mach3 to respond well to this Gcode too. When I run the attached g-code, The machine does what it should, just Very Very slowly.  I turn up the Feed override and it seems to go a bit faster, but no where near a useable speed.  Mach3 says is is going 30 ipm, but it seems more like 3-4 ipm.
My guess is that my problems are coming from G01 moves... where mach3 is trying to get the A axis to reach its coordinate at the same moment as X and Y are reached for each line.
Of course I would like this to happen in this manner, but I asking too much... where is the bottleneck in terms of speed if this is the case.  I have the Stepper which drives A tuned to a high acceleration and Velocity.
Look ahead is 200.
My XmL for Method 2 is attached.
Thanks for any ideas that anybody has.  I have been pulling my hair out with this one.

Re: Setting up Tangential Knife-Questions
« Reply #5 on: April 11, 2012, 04:36:00 PM »
Here is the Gcode for Method 2... :)