Cutting an arc in Z axis - I think

[gary_k]

I have a PRS Alpha and ArtCam Pro and I am trying to cut a groove with a .5" ball nose cutter in a piece of wood 5" wide x 74" long x 1.5" thick and I want the finished groove to be approximately .5" wide down the center in the X axis to be .750" deep on both ends and .250" in the center - any ideas how I would get this? I am very new to everything. Thanks

[Gary Campbell]

Gary...
IF I were going to do this, I would draw an arc that matched your specs in ArtCAM, toolpath it, and then edit the file to have a constant Y value, and use the arc'd Y values for the Z.

There may even be an axis swapper utility out there, but I havnt had to find it yet. I am sure that someone that really knows will chime in.
Gary

[scottcox]

That's exactly how I would do that, manually editing a 2D file, replacing the constant z values with the arc'd y values.

It's not exactly a mouse click away, but it would be very precise and quick to cut.

[scottcox]

After some thought, another way to do that is create a 3D model or profile of your path, then create a raster (along x) toolpath with a very wide stepover, then extract a single pass from the resulting file. You would have to be sure your single pass was in the correct y position before running it.

[srwtlc]

If you draw the arc and toolpath it as Gary stated, be sure to use the plain inch/mm post and not the arcs inch/mm post because you can't do CG arcs in the Z axis. It needs to be M3's

Back in the day, many hated VectorCam that came with new ShopBots, but situations like this is why I keep my copy installed. Most on the forum now have never heard of it. Trust me though, if you have never used it, you probably don't want to go there. ;-)

[Gary Campbell]

Gary...
THe raw unedited file is only 35 lines of code when using the inch postP as Scott says.

if you want to draw & toolpath it yourself my math shows me that:
your arc would be a 3.10 degee arc of a circle with a diameter of 2738.7"
You can draw this in Artcam by using an x center of 37" and I y center of -1369.6"
This puts your staring point at -.75 (+/- .005) and your top of arc at -.25 (+/-)

Here is the code...

I edited the first 2 lines and the last one to clear the bit on entry & exit (with spaces)
You will have to edit the rest by inserting your Y coordinate as I have and deleting the zeros and comma for the Z (dont forget the commas!

You can then run this file in a 2d offset to the acual location of your arc start

J3,0.000000,Y position,0.500000

M3,0.000000,Y position,-0.745096

M3,2.304644,-0.685882,0.000000
M3,4.609426,-0.630479,0.000000
M3,6.914335,-0.578888,0.000000
M3,9.219363,-0.531109,0.000000
M3,11.524500,-0.487142,0.000000
M3,13.829736,-0.446988,0.000000
M3,16.135062,-0.410648,0.000000
M3,18.440470,-0.378121,0.000000
M3,20.745948,-0.349407,0.000000
M3,23.051488,-0.324508,0.000000
M3,25.357080,-0.303422,0.000000
M3,27.662715,-0.286151,0.000000
M3,29.968383,-0.272694,0.000000
M3,32.274075,-0.263052,0.000000
M3,34.579782,-0.257224,0.000000
M3,36.885493,-0.255211,0.000000
M3,39.191200,-0.257012,0.000000
M3,41.496893,-0.262627,0.000000
M3,43.802562,-0.272057,0.000000
M3,46.108199,-0.285302,0.000000
M3,48.413793,-0.302360,0.000000
M3,50.719335,-0.323233,0.000000
M3,53.024815,-0.347919,0.000000
M3,55.330225,-0.376419,0.000000
M3,57.635555,-0.408732,0.000000
M3,59.940795,-0.444858,0.000000
M3,62.245936,-0.484797,0.000000
M3,64.550968,-0.528549,0.000000
M3,66.855882,-0.576112,0.000000
M3,69.237341,-0.628739,0.000000
M3,71.618716,-0.685067,0.000000
M3,74.000000,-0.745096,0.000000

J3,74.000000,Y position,0.500000
J3,0.000000,0.000000,0.500000

Have fun, Gary

[tkovacs]

Gary -
From your description it's not clear if you want an arc shape or an inverted V in the Z direction.

Terry

[bill.young]

Hey guys,

In the Virtual Tools menu there's the File Toolbox [VX] that has a handful of utilities for manipulating part files. One of them is the "Flipper" that takes a flat 2d toolpath and basically stands it on edge so that either the X or Y axis becomes the Z axis.

There is some information on using it in your "C:/ProgramFiles/ShopBot/VirtualTools/Utilities/flipper" folder, but basically you would draw a side-view profile of your path and then toolpath it in PartWorks or PartWizard, selecting an endmill from the tool library that's the same size as the ballnose bit that you'll be cutting with...a 1/2" in your case.

Then run the Flipper program and it will...well...flip the file on edge so that it's 3d. It was originally created for turning profiles for the indexer but would work for this sort of application as well.

Bill

[beacon14]

Jack,

I don't think a string level is accurate enough for your purposes. Can you tell if one end of the string is moved up 1/16" by looking at the level?

Here is my suggestion to rule in or out the level of the indexer relative to the level of the gantry motion. Chuck a V bit in the router and align the tip of the bit with the center of the headstock. Then without changing the Z height, move the gantry to the tip of the tailstock. Like this:


4774

You will have one of the following two conditions. if the heights are misaligned like the left detail there is your problem. If they are exactly aligned you will have to look elsewhere for your answer.


4775

[tkovacs]

Duh - sorry I see you want an arc from the subject line...

[Gary Campbell]

Gary K...
As usual, Bill Young saved my tail again!. If you want to do this for yourself to learn, he has made it easier for you.

Draw the arc in ArtCam as per the above coordinates. This gives you an arc 74" long that starts on 0,0 and ends at 74,0, but is horizontal.

Toolpath the vector, (on vector) with a .5 endmill and 1" stepdown to insure 1 pass, using the SB inch (not arc inch) postP

Use the "Flipper" utility that Bill shows above to swap the M3 lines Y to Y & Z to Y.

Make sure that the bit has retracted prior to the Jog move lines. (as I did in the file above)

You now should have a file that cuts an arc as per your parameters with a start point of 0,0. Run this new file in 2D offset mode to reflect your actual starting point. 0,0 is the center of the bit it will cut 1/2 bit diameter longer on each end) IF this is a problem.. simply redo the math?
Gary

[Gary Campbell]

Gary K...
Edit line 4 to Y to Z & Z to Y
Gary