Need advice on creating sbp for spherical divots

[jbolyard]

Hello - New to the forum. Thanks in advance to those willing to help.

I have a small project (picture attached) - I want to make multiple of them (4) out of a single board.

My problem is that I think I should be able to use a ball mill or round nose router bit and get the ShopBot to make those spherical divots in quick fashion. Something like plunge in center and spiral out, plunge and spiral, repeat as many times as needed based on the step size I choose. The divots are 0.375" deep with radius 0.7" - about diameter 1.25" at the surface.

Right now - I only have Vectric and Cut 3d software. Since this is actually 3D (not 2.5) - I'm trying to use Cut 3d. All I can do so far is create a HUGE cutting path which surfaces the entire part including cutting the divots. Not what I want - I only want to cut the divots and then change bits to cut the outline (that part I can do).

Any help? Other software that I should try (but I can't spend a lot on software for just this little project).


Thanks for any assistance!
Jay Bolyard

[John David]

I believe you can draw a circle around the perimeter of what you want to machine and whendoing the tool paths you need to highlight those circles. The toolpaths will be created inside those boundries.
Hope that helps
jd

[adrianm]

John, that only works for Aspire not for Cut3D.

Jay, you could do it with the fluting toolpath in PartWorks. Might not be as fast as you would like though or you could use a large ballnose with a VCarve toolpath.

[jbolyard]

Thanks for the ideas so far.

I have a 1/2" roundnose router bit which I wanted to use for this.

I'm not very familiar with fluting paths - I thought they just followed a single line at a depth. How would I use that here? Wouldn't I need a 1.4" custom diameter roundnose bit (ouch - cost) and just plunge?

I didn't expect this would be a difficult task - guess I'm asking too much here. :confused:
Jay

[gc3]

http://www.deskproto.com/download/trialversion.htm

[adrianm]

Thanks for the ideas so far.

I have a 1/2" roundnose router bit which I wanted to use for this.

I'm not very familiar with fluting paths - I thought they just followed a single line at a depth. How would I use that here? Wouldn't I need a 1.4" custom diameter roundnose bit (ouch - cost) and just plunge?

I didn't expect this would be a difficult task - guess I'm asking too much here. :confused:
Jay
There are quite a few examples of how to do it on the Vectric forum. I'm on my mobile at the moment which is a bit tricky to paste links with but if you search for fluting over there you'll get loads of examples on how to do it. You only need standard ballnose bits to do it.

[dana_swift]

Jay there are many "free" solutions to your problem.

// The manual method

{
If you are comfortable with programming, you can hand-write a SBP file to cut a dimple to your specifications with a ball nose bit.

Then you can set up a master file and call the dimple cutter as a subroutine at each of the locations you want your dimples.

If you want to try this method, I can write more info.
}

// Using PW3D

{
Download a copy of Sculptris (its free). Draw a dimple to meet your needs.
Save the file as type "OBJ". Import into PW3D.
Toolpath the dimple
In PW import the PW3D file and place it each place you want a dimple on your workpiece.
}

There are more methods of course, but one of these two should get you to your destination with no further expense other than your time.

D

[jbolyard]

Jay there are many "free" solutions to your problem.

// The manual method
[INDENT]{
If you are comfortable with programming, you can hand-write a SBP file to cut a dimple to your specifications with a ball nose bit.

Then you can set up a master file and call the dimple cutter as a subroutine at each of the locations you want your dimples.

If you want to try this method, I can write more info.
}
D

I haven't manually programmed for the shopbot - but I have done so with G-code for other machines - so this may be the best option. A list of X-Y coordinate sets for all the dimples and a subroutine. Where I need (I thought) the computers help is to create the path that'll do the dimple. If you can give me a good idea on how to start I'll try it!

I also need a link to the language reference for a shopbot - I don't have original manuals - I'm using this machine at a TechShop facility.

I do have this as a part in 3D (CATIA) ... can be turned into an stl, igs, stp etc - not a 3Ddxf though unfortunately.

Thanks,
Jay

[adrianm]

Here's an example of a fluting toolpath to do it. You probably would want more spokes for a smoother finish but it shows you the technique. You can also do it with spirals.

[steve_g]

Jay

You can actually V-carve with a ball nose bit... However you can only go to a depth of 1/2 the diameter of the ball. To go a full .375 you will need a .75 ball nose. if a true sphere is not necessary just pocket the circle with the 1/2" ball to .375 depth.

SG

"Right now - I only have Vectric and Cut 3d software"

not sure which software you are calling "Vectric"

[jbolyard]

Jay

You can actually V-carve with a ball nose bit... However you can only go to a depth of 1/2 the diameter of the ball. To go a full .375 you will need a .75 ball nose. if a true sphere is not necessary just pocket the circle with the 1/2" ball to .375 depth.

SG

"Right now - I only have Vectric and Cut 3d software"

not sure which software you are calling "Vectric"

Sorry about the software name - I meant VCarvePro and Cut 3D - both by Vectric.

When you say V-Carve - do you mean starting with the surface circles and creating a v-carve toolpath to a depth of 0.375 using a 0.75" diameter round nose? Will that give me a spherical divot with radius 0.75"? I do not want a flat bottom.

Thanks,
Jay

[steve_g]

Jay...

My attached drawing shows your options as I see them, other than creating a 3D file I think you were trying to avoid...

V-carved with a .75 ball will give you a flat on the bottom... V carved with a 1.25 bit gives you a .6125 deep dimple, and other than a 3D file, to meet your specifications will require a 1.41 bit to get a arc 1.25 diameter and .375 deep.

SG

[jbolyard]

Here's an example of a fluting toolpath to do it. You probably would want more spokes for a smoother finish but it shows you the technique. You can also do it with spirals.

Thank you! I took a look at your example - and also read/watched a few fluting tutorials. This plus the suggestion of a spiral... and voila!

I believe I've achieved what I was looking for.

A spiral vector created in Corel Draw - imported into VCarvePro via dxf - fluted with a 1/2" round nose. Change start point to outside instead of inside. Continuous/smooth flute.

I had to keep playing with the diameter of the spiral to end up with the correct diameter at the surface of the part - but I got it.

Here's the Vcarve file - predicted to execute in 33 seconds for each divot - that'll do nicely. I just need to test it now. Anyone see flaws in what I did?

Thanks to all for the help ---

I still have some programming questions about Master and subroutines though. Can they nest two deep? Is each call of a sub-subroutine still setting a new temporary 0,0 location?

[steve_g]

Jay...

exactly where I was going when I got called away for a family birthday party... The only difference I see was that I edited my spiral outer spiral to start on top of itself.

SG