Arcs in the yz plane

[rhfurniture]

Hi,
I have a benchtop and I have attached a small router horizontally - ie spindle in line with the X axis to the existing Z axis in order to bore end holes, mortice for muntins in wide rails, dovetails and round end tennoning.
It is the last with which I am currently tusseling. Is there any way in which to use the inbuilt arc routines to move the head in an arc in the YZ plain.
Alternatively does anyone have a sub-routine to do a similar segmented arc?
My current project involves cutting a dowel spigot on the top of a door stile to form a hinge.

Regards and TIA,

R.

[gerald_d]

If your router is mounted horizontally, why don't you re-define your axes so that the classic x becomes your new z? Probably just a case of re-plugging motor cables, but I don't know the benchtop at all.

[bjenkins]

Gerald probably has the best idea if you are only using the horizontal router. If you don't want to swap your axes, then it is pretty simple to generate a set of points to get your arc. I've used Excel to write a function and generate a set of points based on a starting point. If you format your columns right, it's relatively easy to paste the coordinates into a shopbot program. Recently, I've actually taken to writing the functions in my shopbot programs. The shopbot language has enough basic programming capability to do most things. I've done carved volutes, scallops, v-carved stars with this approach. Once you have the function written it is easily reused.

[gerald_d]

PS. Remember switch off the system before moving cables.

[rhfurniture]

I have considered swapping leads, and also writing a shell that would swap X's and Z's to part files generated in part wizard etc, but as I do want to use it in both modes (not simultaneously), I think it would get tooo confusing regarding space awareness - at the moment I think of my shopbot space as autocad modelspace world coordinates, and I want to stick with it.
Following the journey home (where I do most of my thinking) I reckon I can write(with CAD) some stock segmented curves (the resolution doesn't need to be too high), and use a scaling variable for all the sizes in between. Though any other suggestions would be most welcome.

Thanks,

R.

[gerald_d]

Do we know for a fact that the ShopBot is restricted to circular arcs in only one of the three planes? This was the case some years ago, but things may have changed since, with later software and controllers. Havn't seen this discussed much and wonder if the SB guys could give us an update?

rh, you mention using PartsWizard. As I understand it, PW chops all arcs to straight segments. If this is true, then it does not matter which plane you are working in.??

[ron brown]

Yes Greald,

It is just too bad they don't use Vector....

Ron

[gerald_d]

Seriously, does PW still convert all curves to straight-line machine movements? This could explain why there has been no recent dicussion on the limitation for xy arcs - until this thread came along.

[Brady Watson]

"As I understand it, PW chops all arcs to straight segments"

No. This is a function of the post processor. If you use the 'Shopbot_arcs_inch.con' or 'Shopbot_arcs_mm.con' post it will write the code in arcs. In fact, this is the only post that I use and the cuts are a bit smoother. If running PW2, it is in the dropdown when saving the toolpath. If using PW1, just download the ArtCAM post from the support area and install it in the post folder. Then it will be available when you save your toolpath.

I'm pretty sure that the SB will do arc movement in ANY 2 planes, not just the XY.

-Brady

[beacon14]

No, there is an option to output PW in "arc" format, which uses the SB circle commands (CG) to cut arcs and circles.

[beacon14]

never mind - Brady beat me to it again!

[gerald_d]

Better watch out Ron, PartsWizard is starting to catch up to us!

[btk]

I have not used the Shopbot extensively yet (just getting started with mine, however I have done some other CNC programming), and I am a bit confused by either the questions, the responses or both.

I understand that the Built in Arc/Circle functions in Parts Wizard (or I guess in Controller also) have no problem in XY because it is simply following points along circle.
However when moving in the YZ plan, special considerations need to be made depending on the
diameter of the tool.

However RH (the original poster) has mounted his tool horizontally (i.e. perpendicular to the YZ plane) so I would figure it would be just a matter of plotting the points of a circle or arc segment
as suggested by Bud above and cutting along these points.

[Brady Watson]

BTK,
Using a ball-end mill will eliminate the projection of a square-ended mill when running in the YZ or XZ plane. This is why 3D toolpaths are run with a ballnose bit.

Try the suggestions listed above...and use a ballnose. This isn't the 1st time this question has been asked.

-Brady

[rhfurniture]

Sorted and it works a treat. (using segmented arcs)
Reading (and re-reading) the manual (which could well be a year or so behind the software) it would seem that shopbot arcs via inbuilt commands can only be specified in the XY plane. If there is any way of using them in the XZ or YZ planes through the part files, I would be most interested. A part file containing such arcs from a full 3d CAM software (which I do not have) might throw some light.

Regards,

Ralph.

[mrdovey]

rh...

You can cut arcs in the xz and yz planes, but you may need to "roll your own" commands to do the cutting. Here's a sample (cut with a 1" core box bit):


4776

...Morris