View Full Version : Can I use the VI command to cut a Arch in z-plane?

05-27-2009, 08:32 AM
Hello all, I'm a rookie here and I need to cut a arch in the z-plane. I've written a program to cut the shape by iterating arches, but to make them smooth I need to make the steps very small. This will take a long time, have the bit proceed very slowly and potentially cause the plastic that I'll be cutting to melt.

It seems that I can swap the x and z axes and then program CA to cut in the z-plane. Is this a reasonable idea?

Additionally, will it be possible to zero the z-axis, swap the axes and then transfer that zero to the x-axis?

Any thoughts will be very appreciated and I apologize if I've missed this info in another thread.


05-27-2009, 11:53 AM
The software to make this happen would not be all that expensive compared to all the time you will have involved and possibly messing up your machine. If you describe how big of curve you need someone can reccomend which software. If it is not to wide of a z curve the partworks program should do a ramped flute that may work for you.

05-27-2009, 12:20 PM
Thanks for the note. For the current project, iI need a series of curves (a transition from 1/4 of a circle to a flat surface) with the deepest curve being about 4 inches wide and a little over an inch deep. The shallowest is about 7 inches wide.

If it helps with the software selection, I'm looking to be able to precisely define the parameters, not just make an approximate shape.

Thanks again!

05-27-2009, 12:38 PM
Are you proposing to literally physically swap the x and z axis cables? I would not do that.
I think there was a application on the shopbot site that would swap two axis in the sbp file.


05-27-2009, 12:57 PM

I was not planning on swapping cables but rather using the VI command in the control software to change the Driver Channel for the two axes. (See page 35 of the command reference.)

I do like the idea of using a software solution rather than mucking with those settings.


05-27-2009, 01:29 PM
I have v carve pro which is supposed to be the same as the normal partworks that comes with the program. It will do ramped flutes, which can be made in any shape. I wonder if that would help you. Try this link and see if the fluting section on the bottom does enough for your purpose. http://www.vectric.com/support/VCarvePro/V5/tutorials_index.htm

05-27-2009, 01:41 PM
What design software are you using?
I think you could get aspire to do this.


Gary Campbell
05-27-2009, 05:16 PM
There are a few different ways to do these, most of them not difficult, but none the less, require some time and learning. Here is my favorite:

Place your vectors in V Carve or Pwks in the Y direction and so that the Y position is where you want it and the X position is the same as you wish for the Z. Toolpath on Vector at a .001 depth. Then use the "Flipper" program to swap the X for the Z and you should be good to go. You will have to manually add your lead ins and outs. IF it makes a difference, you could move the vector +.001 in the X direction to eliminate a depth error.

You could also use a spreadsheet to do the same. And, as you mention above the VI can be used. Make sure the X & Z are both zeroed and at the 0 position prior to the swap.


05-27-2009, 09:09 PM
Somebody please correct me if I'm wrong, but I think that if the VI command is used to do this, AND the unit values of the two axes are NOT the came (because either the pinion teeth counts or the motor gearbox gear ratios may be different), then the VU command must also be used to swap the unit values.

Gary Campbell
05-27-2009, 09:32 PM
Right on.. you must swap the Unit values at the same time, if different.

05-28-2009, 12:46 PM
Thanks to all for their comments!

I've programmed the toolpath successfully in the .sbp format, but in the wrong plane. I did it with the code because the curves need to have very specific dimensions and I have limited CAD experience (but plenty of programming experience). I think I can use VI and VU to swap if I can't figure out an alternative. (Big thanks to Harold for pointing out the needed VU command.)

I will try using the Flipper to swap a single arch and then modify the .sbp to allow it to cut the different arches along the length.

Thanks again for assistance. I'll give this a try and report back.

By the way, is there any reason that the Shopbot does not have this capability? I remember when I did this last time in G-code it was pretty straight-forward. I defined the start and stop point of the arch in 3-D, the radius of the arc and whether it when the long way or the short way...


05-28-2009, 01:53 PM
Mike if you have programming experience you can program a Z profile that includes compensation for the shape of the bit. I have done that many times and gotten great results.

The fundamental equations you need are:

X^2 + Z^2 = R^2

for a cirle centered at "0,0", so add offsets to move the cut to where you want it.

A simple tool width fix is to subtract the tool radius when cutting "uphill" and add it when going "downhill".

More sophistication is easy to add once you get the idea of how to cut vertical arches and circles.. arches can be ellipses, circles, or bezier cut in the X-Z direction. The shopbot is much more flexible than the toolpath software. When you can write your own you can have anything you want.

Good luck-


05-28-2009, 02:34 PM
I haven't run SB code on my SB for sometime but according to shopbottools.com/manufacturing.htm
"ShopBots run from industry-standard G-code or from ShopBot PartFile code"
That being the case run a g-code file just use a G18 to switch to the XZ plane or G19 for the YZ plane

05-28-2009, 04:28 PM
Due to the fact that ShopBots can't do an arc in the Z axis without making the arc be small M3 segments, I don't think that a G-code arc in the Z axis (G2 or G3) will convert and work.

If you have an old copy of VectorCam (came with ShopBots back in the day), you can draw the design, break or interpolate the Z arcs and then generate the code. No flipping or changing axis needed. Approaches and departs included.

I keep my copy of Vector installed just for these purposes.

05-28-2009, 11:50 PM
"Due to the fact that ShopBots can't do an arc in the Z axis without making the arc be small M3 segments"

Scott, correct me if wrong but it wouldn't know its in Z. if you ran the g-code as a normal 2d arc in the Y direction then edit the code and put in a g18 then the arc in Y would become an arc in z, whatever the y output reads would be carried out in z.

funny you should mention Vector, I still have a copy here that came with my bot, even though I stopped using it in about 2002, 2003 and had never upgraded it I had just received an upgrade notice from Fred Smith last week.

05-29-2009, 10:29 AM
True Gary, in theory. As long as the G-code for the Y arc was posted as G1's only (inch post and not an arc_inch post), but the G-code to .sbp converter doesn't recognize a G18/G19, so the axis can't be swapped that way.

If you're running Mach3, then your good to go.

Yeah, I got the same Vector upgrade notice. Since the Vectric products came out, I'm forgetting how to use it. ;-)