[speedofsound]

Please bear with me, as this noob is making the jump from 2.5D to 3D milling.

For my question, let's use a very simple part, say an ellipse measuring 2 x 1 x .25 (thickness).

In V21, I can draw this part, and generate the toolpath.

In a few tests, I tried both a planar and a spiral toolpath. No problems there, the mill is cutting the part as I'd anticipated - with one exception:

How can I rough the part? I do not see any way to incrementally step the Z depth down. I know in the CAM window, the U/D button is normally used when I make 2.5D parts. It doesn't appear to have any affect on the 3D toolpath.

Must I make a separate toolpath/generate code for each incremental depth of cut? Or is there a simple feature I'm missing?

Any help would be appreciated, as always.

thanks,

Alan

[moldmker]

On CAM side, make sure your 3D button is on.

Set your U/D window with Roughing Enabled and define an increment.
Disregard the Tool Cutting Depth, with 3D turned on it isn't used.

After creating your 3D path with Planar or other method, use CutAuto to create the code. This should show the toolpath being roughed down in steps.

Note that the stepped down toolpath is only shown temporarily. Sometimes it's handy to have the actual roughing passes for future reference.
To do this, highlight the code just created and select Edit > Geometry from NC and this will backplot the code into the CAD window. You may want to put it on a separate layer to blank it.

Good luck,
moldmker

[speedofsound]

On CAM side, make sure your 3D button is on.

Set your U/D window with Roughing Enabled and define an increment.
Disregard the Tool Cutting Depth, with 3D turned on it isn't used.

After creating your 3D path with Planar or other method, use CutAuto to create the code. This should show the toolpath being roughed down in steps.

Note that the stepped down toolpath is only shown temporarily. Sometimes it's handy to have the actual roughing passes for future reference.
To do this, highlight the code just created and select Edit > Geometry from NC and this will backplot the code into the CAD window. You may want to put it on a separate layer to blank it.

Good luck,
moldmker

Thank you for your time; your information is very helpful.

I had discovered the 3D button on the CAM side, after getting several 2D toolpaths from my 3D surface. Clicking it was a "Doh!" moment indeed. Also have been using machine "auto" once I generate the code. This seems to work properly.

I will experiment with the U/D settings, perhaps I did not have a value entered correctly. My test programs would simply plunge to full depth (.235 in this case) and begin milling. I'd like to make this part in 2 lighter passes, finish passes aren't required.

[HMB3000]

I will experiment with the U/D settings, perhaps I did not have a value entered correctly. My test programs would simply plunge to full depth (.235 in this case) and begin milling. I'd like to make this part in 2 lighter passes, finish passes aren't required.

In the lower part of the u/d dialog box you need to check the auto-ruogh box and put in a value for depth of cut.
If you just want say a .005 finish pass and the 3d contour allows you can just offset the tool for finish pass. I use 2 H value all the time for the same tool

[speedofsound]

In the lower part of the u/d dialog box you need to check the auto-ruogh box and put in a value for depth of cut.
If you just want say a .005 finish pass and the 3d contour allows you can just offset the tool for finish pass. I use 2 H value all the time for the same tool

Thanks for the tips.

I regularly use the u/d button for 2.5D milling, and am familiar with with the auto-roughing portion of the window. My issue is the program seems to ignore my input in the u/d window.

Basically, my real project is milling a 4" diameter "disc" out of 1/4" ABS plastic sheet on a small benchtop CNC. This disc must have a 5 degree draft on the vertical wall. I'll do a small production run of these parts, and I"ll probably just use an off-the-shelf tapered endmill, but wanted the 3D practice (very novice user here). Given the small size of my Taig, I'd prefer to feed it a little quicker in two .125" passes (1/8" ball). For production, my larger Milltronics VMC will be used, so rigidity seems essentially moot for this material.

I'll edit with a quick drawing, if anyone is open to some toolpath strategy suggestions/tips.

Thanks again!

*edit*



screenshot of this part I'm working on. My process has been to draw the profile, clean it up, apply planar surface, extrude surface to desired height, generate toolpath.

Would making a negative (for a casting experiment) of this basically be a tapered pocket operation? I'd imagine it would just need to be mill "inverted" for the correct approach to milling the draft angle. Just thinking out loud...

[moldmker]

I'll add this:

I always set my UCS Z zero at the top of my solid.
Never had a problem with roughing not working correctly.

moldmker

[speedofsound]

I'll add this:

I always set my UCS Z zero at the top of my solid.
Never had a problem with roughing not working correctly.

moldmker

Later this afternoon, after your first reply, I tried this with success.

Will check the roughing tomorrow, and I'll bet it works fine.

Notice in my quick drawing above, Z zero is at the bottom of the part. I'll bet the root of the quirks I experienced are here.

Thanks again for your help.

[Sam A]

I'll add this:

I always set my UCS Z zero at the top of my solid.
Never had a problem with roughing not working correctly.

moldmker

I to am just starting to do 3D with CNC and BCC 21. Why set the Z zero at the top of the solid?

Sam

[moldmker]

This rule isn't set in stone by any means.

If the Z zero is at the top of part, then any Z moves that are into the part would be negative. Makes it easier to proof-read the G-code.

Also, if your rapid plane is defined at Z .100", there are no worries of hitting the part with any of the cycles.

Also, a lot of the commands require the Z top of the part to be input. If it's always at 0 there are no worries, otherwise you will need to verify and enter the the height for each part.

I know, I know...the router guys like to have Z zero set at the table height. If you're always cutting the same thickness parts that's fine. But if you start setting up oddball jobs, it may bite you.

moldmker

[tjones]

My rule is this.

If I set zero at top of part then my Z must always go further to cut the part (or crash).

If I set Z at the bottom of the part then I can crash at any place.

[HMB3000]

Z Zero at the top of the part work fine untill you get into some 4 or 5 axis moves. Then you could have both postive and negative values for Z moves.

[tjones]

True.

Hopefully that will be a concern in V23.:rainfro: