3-axis interpolation

[dale]

Does anyone know if you can ramp in the z-axis while cutting an arc? I am trying to cut a toolpath that begins with an arc and ramps down from z0 to z-.150 My cam program writes the code but when it is converted the z move is ignored.
Is there a way to manually write this part of the program and if not maybe this is something that could be considered in future versions of the software
Thanks
Dale

[birdsofplay]

What version are you using ?

This is spoz ta work in the new SB SW, I thought !

Havent tried it out yet myself.

[bruce_clark]

Bob,

I just looked at the CC command specs. There is
nothing about ramping down (3 axis interpolation),
just "plunges" which to me means only 2 axis
moves. This is sb2b10 command reference. If
this command is/has changed, I would LOVE to see
it, so I can modify the G-code converter to
include this part of the command. Don't worry,
a lot of older CNC controllers could not do this
either.

The work around is to convert the arc or circle to
short line segments (cords) with increasing depth.
Programs like Bobcad, Vector ect will let you do
this. If you are programming by hand, all I can
say is "have fun", as you will be breaking out the
old trig book and pocket calculator!

Bruce Clark
bwclark@centuryinter.net (mailto:bwclark@centuryinter.net)

[dale]

It wasn't that difficult. The software converted the arc to 10 line segments. After writing the toolpath I picked each segment to change the depth. It was very time consuming and being as lazy as I am I was looking for a quicker way.
Thanks for the input
Dale

[Ted Hall, ShopBot]

Hi Dale,

Well now that you have it all figured out ...

Try using the spiral plunge feature of [CC] (or [CP]). If you set the tool to cut say a 6 in diameter arc, from say 30 to 110 degrees, you can have it plunge say -.165in over this distance by just entering that value as the 'plunge' and then turning on the 'Spiral' feature. You may also want to leave the bit in the material at the end and can also check that option.

Note: I just noticed that the spiral does not show up correctly in Preview Mode ... you have to do this one on the tool for the moment.

[engiplas@n-link.com]

Ted, I tried this and sent you an e-mail about it, but no response. At the end of each spiral the Z axis raises up and then goes down to do the next spiral. I need to thread a hole, so the Z axis must stay down and the spiral continue. When you do the same technique with the rectangle cutting, the Z axis does not raise between the plunges.
How do I do what I need to do?

[Ted Hall, ShopBot]

Hi Don,

Sorry I missed this question in your e-mail. Here's the situation. In addition to the question asked above, your application requires multiple spirals in the plunge, as in the command: [CC] 1.0,t,1,,,-.1,5,,,3,1
Which would be the instruction to make a 1 inch diameter spiral plunge to -.5 with 5 spirals.

You are correct in that there is a little glitch that has creeped into the software so that with multiple passes there is a pull up between passes. (This is acutally the Safe-Z pull up feature which is inadvertantly being activated between passes.)

We'll get this fixed in the next release ...

In the short run, to make this plunge work the way you want, just disable the Safe-Z pull-up feature: [VC] , , ,N
Then you can spiral plunge the way you would like.

[royalce@caribe.net]

I am a new user :
When i make somthing in auto cad in 3d is possible to use this files to cut in shobot in 3d.
If is possible how

[malcolm@isle-of-bute.demon.co.uk]

I am just about to place an order for a ShopBot PR96. I really want the machine to carve half hull models of yachts. Does anyone have any experience of 3d carving on the ShopBot ? I am also looking at what 3d software to purchase?

Any help would be very much appreciated.

Many thanks.

Malcolm Johnston
Isle of Bute
Scotland

[birdsofplay]

Doing a 3D model in any cad will be challenging.


But any CAD that can do 3d should also be able to export stl files. These can be sent to a stereolithogrophay house, for a fee, and you will receive an exact part created from liquid plastic and hardened by laser. I have a demo thinwall, Chess Rook complete with an internal spiral staricase, it's all one monolithic piece and couldnt be produced in any other way.
I have seen, somewhere, a couple of programs that purport to import stl file and output g-code.
This might be cheapest as the stl -> g-code programs were ~ $1000
Seriously expensive programs like SurfCAM and
Ungraphics UGShop take 3d models and create tool paths but you'll have to evaluate the utility/cost issues. UGShop is about $16000

If your CAD can do "planar slices" of 3D models then you could make slice files and combine and cut them with the SB.

go see this site too,

http://www.sculptor.org/stereo.htm

Autocad, MicroStation, Solid Edge, Art cam et al do 3d. All these are multithousand $ packages nad require a certain amount of training to use.

If you're just starting out, well ...
this will be a wonderfull quest for you, just dont be impatient, this kinda stuff comes with a fairly protracted learning curve.

[chandler@n-link.com]

Ted,
I have been using the spiral plunging to thread holes (3"-5" dia)in a plate (1-1/2" thick) with 8TPI. I made a jig to hold a pipe and can turn the OD of the pipe to size and thread it also. This has been working very well. I graduated up to the big time and found a problem I don't understand. I tried to thread a hole,32" dia,and 14 turns around using the same program. everything starts out fine, then after 4-5 turns the Z axis stops going down for 1/3 to 1/2 a turn. when it starts moving again it will catch up to where it should be by the time it is back at the starting point of the circle. The coordinate display stops as well as the motor. I tried it several times experimenting with turning the stack on-off with no change. If I do a smaller hole it works fine again.

[Ted Hall, ShopBot]

Hi Don,

Seems to be a glitch that is related to the pull up feature (that we have disabled for your spiral plunge). I've actually been working on several other things related to that, and will also test for this problem. I haven't tested it yet, but my bet is that if you can get away with reducing the circle resolution, you will avoid the problem ... I'll let you know about the broader solution to this.

[acarias@teleline.es]

hello
I want to know if this machine can
make a ruder of the boat in from a 3d
DXF file.
i don`t know if the precission of the superficial
finish is enough with an acurate in z axis of 0.5 mm.
thanks from spain

[seaside@esva.net]

I cut shaping contours for rudders and daggerboards on my ShopBot, but they require sanding after they are assembled to remove the steps. There's a picture of a dinghy kit rudder and sailrig parts at www.seasidesmallcraft.com/contour.htm (http://www.seasidesmallcraft.com/contour.htm) to give you an idea of what they look like. The rudder in the picture is pretty simple, but I've also done some NACA foil shapes.

If you don't mind a little sanding to remove the steps, this method works fine. If however you want to cut the rudder without having any steps to sand out, I think you would have to turn the blank in an indexing lathe setup so that you were always cutting with the bottom face of the bit instead of a corner, requiring some pretty tricky geometry to figure out the toolpath and rotation angles.

Hope this helps,

Bill

[larryg]

I have used Corel Draw and Quatro Pro to produce a cutting file that will cut and arc while the Z-axis also arc's down and back up while cutting. I do it by the desired arc in Corel and converting to a 2D cutting file. I then make another arc in corel that would be the same length as the original but with the curve I want on the Z axis really on the Y axis of this file. Convert the file to a 2D cutting file and use a editor to past the Y axis points into the original file. Then use search and replace to replace all M2 with M3. Not the most straight forward way but I have gotten excelent results.