How would you machine this?

[tigermm]

Hi all,

I'm trying to cut the 2 internal features of this part (Clone.face22 the large tapered hole, and Clone.face25 the 2mm recess next to it)

I've tried everything I can think of (and read about) to get these to cut nicely with a 6mm ball end mill and had no luck.

Face25 I'd like to have parallel paths 1mm apart, but can only get them 3mm apart as per the paths in my project file.

Face 22 I'd like to follow the tapered contour in 1mm Z increments, but not waste time cutting out the entire center of the circle (using 40 paths!), only as much as I need for clearance. At one point I had another circular body in the middle (150 dia) and told 3Dsurface to avoid the last 3 faces which were the faces I selected on the cylinder, but it still wanted to run my poor endmill through 40mm of solid material!
I also tried 3Dpocket but read that it ignores ball shaped endmill so shouldn't be used, plus it ignored my center cylinder too.
Waterline just gives me 1 loop around the top as the whole path

HELP!

Cheers,
Mike.



OS: Windows 10 Version 2009
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.24276 (Git)
Build type: Release
Branch: releases/FreeCAD-0-19
Hash: a88db11e0a908f6e38f92bfc5187b13ebe470438
Python version: 3.8.6+
Qt version: 5.15.1
Coin version: 4.0.1
OCC version: 7.5.0
Locale: English/New Zealand (en_NZ)

[bmsaus4ax]

Hi all,

Face 22 I'd like to follow the tapered contour in 1mm Z increments, but not waste time cutting out the entire center of the circle (using 40 paths!), only as much as I need for clearance. At one point I had another circular body in the middle (150 dia) and told 3Dsurface to avoid the last 3 faces which were the faces I selected on the cylinder, but it still wanted to run my poor endmill through 40mm of solid material!

Cheers,
Mike.

The attached file may be something like what you describe.
This is a model using copy of the SubtracitveLoft001, a 150mm circular body in the middle, and a thin cube under both to provide a floor for the "pocket", combined as a Fusion ( union in part WB )
Operation is 3D Surface
Selected faces, taper, bottom of void, wall of centre plug, and top of plug.
Step down of 1mm and Avoid Last X Face '1' ( top of plug )
.
Had to turn off Operation to get the file small enough to post.
.
EDITED: Afterthought - taper the plug wall as well so ball endmill shank will not rub to full depth.
.
OS: Ubuntu 20.04.2 LTS (ubuntu:GNOME/ubuntu)
Word size of FreeCAD: 64-bit
Version: 0.20.25288 (Git) AppImage
Build type: Release
Branch: master
Hash: bbb557aab6129efd9486d6df19f06c2976fdb7e5
Python version: 3.9.6
Qt version: 5.12.9
Coin version: 4.0.0
OCC version: 7.5.2
Locale: English/Australia (en_AU)

[Shalmeneser]

BTW, you can simplify your first body.
* the fewer dimensions, the best.
* do the cut with PartDesign_Groove

[GeneFC]

Face25 I'd like to have parallel paths 1mm apart, but can only get them 3mm apart as per the paths in my project file.

Change the Step over percent so that the tool overlaps for subsequent passes. Probably something like 25%. I would also use "Offset" instead of "Spiral", but that is your choice.

Face 22 I'd like to follow the tapered contour in 1mm Z increments

I would use "Profile" and select only Face 22. You may need to carefully check the start and final depths.

I could not select Face 22 when the stock was sitting at zero distance from the top of the object. When I moved the stock up then I could select Face 22. Perhaps a bug. I never use the stock for anything, and I leave it set at the default 1 mm, so I have not seen this before.

I don't think you need any "3D" operations.

Gene

[Russ4262]

Another solution using 3D Surface is provided. Although, I think the solution provided by Bmsaus4ax has less air milling upon initial glance. As with his file, mine has the two 3D Surface ops de-activated for file size reasons.

Thanks for posting the file. It helps identify more shortcomings in 3D Surface that could be improved. I also found a bug of sorts in 3D Surface while working on solution for your issue. Thanks!

Russell

OS: Windows 10 Version 2009
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.24291 (Git)
Build type: Release
Branch: releases/FreeCAD-0-19
Hash: 7b5e18a0759de778b74d3a5c17eba9cb815035ac
Python version: 3.8.6+
Qt version: 5.15.2
Coin version: 4.0.1
OCC version: 7.5.0
Locale: English/United States (en_US)

[tigermm]

Change the Step over percent so that the tool overlaps for subsequent passes. Probably something like 25%. I would also use "Offset" instead of "Spiral", but that is your choice.

I did change the stepover but always ended up with only 2 paths no matter what value I used. Granted they were closer together though.

I would use "Profile" and select only Face 22. You may need to carefully check the start and final depths.

I could not select Face 22 when the stock was sitting at zero distance from the top of the object. When I moved the stock up then I could select Face 22. Perhaps a bug. I never use the stock for anything, and I leave it set at the default 1 mm, so I have not seen this before.

I don't think you need any "3D" operations.

Gene

I thought profile was only for 2D machining? From memory it told me that Profile could not be used for that face (could be wrong, I tried a lot of different things)

And yes, I had to select Face 22 first as FreeCAD kept switching the stock back to visible and blocking further selection (BUG?)

Interesting that you never use stock, how do you specify your 0,0 point for operations?

[tigermm]

The attached file may be something like what you describe.
This is a model using copy of the SubtracitveLoft001, a 150mm circular body in the middle, and a thin cube under both to provide a floor for the "pocket", combined as a Fusion ( union in part WB )
Operation is 3D Surface
Selected faces, taper, bottom of void, wall of centre plug, and top of plug.
Step down of 1mm and Avoid Last X Face '1' ( top of plug )
.
Had to turn off Operation to get the file small enough to post.
.
EDITED: Afterthought - taper the plug wall as well so ball endmill shank will not rub to full depth.

Thanks, thats definitely along the lines of what I'm after.

I noticed though that the toolpath for the top recess doesn't go all the way out (It leaves about 4mm uncut) is that the same on your system?

notfullcut.jpg (326.32 KiB) Viewed 1343 times

[tigermm]

Another solution using 3D Surface is provided. Although, I think the solution provided by Bmsaus4ax has less air milling upon initial glance. As with his file, mine has the two 3D Surface ops de-activated for file size reasons.

Thanks for posting the file. It helps identify more shortcomings in 3D Surface that could be improved. I also found a bug of sorts in 3D Surface while working on solution for your issue. Thanks!

Russell

That's exactly what I was hoping for Russel, thank you!
I'll add the cylinder in the middle and profile it first to give clearance for the taper cut. Does this need to be part of the same body, or will a second body suffice?

Now my question is..... how did you get that when none of your parameters look much different to what I tried?

Just for my learning:
Stepdown of 0.95 instead of 1.00, why was that?

Final depth of 41, is that so there is less left to trim off due to using a ballnose mill? Or to stop it trying to machine the whole bottom of the pocket?

What exactly does the Sample interval do? (from the wiki: Set the Sample Interval used for the OCL scan)

I see you've used Multipass but not used a depth offset, do they not need to both be specified?

Sorry for so many questions but I'd love to understand the way to do this in future rather than asking someone else to help me every time.
Cheers,
Mike.

[GeneFC]

Interesting that you never use stock, how do you specify your 0,0 point for operations?

That comment probably needs to be explained a bit.

All of my models include the stock in the path operations. It is built in, and it does not cause any problems.

What I meant is that I almost never change the defaults in an attempt to represent the actual chunk of metal I plan to use when machining the model. I often don't even know since almost everything I do is "one off" and I grab whatever is available in my supply at the time.

The stock is used internally to set various path actions, such as starting and finishing depths. I *always* check those items to make sure I am getting what I want.

I tend to use extensions to process beyond the edges of model, but I believe in some cases expanding the stock works as well.

Setting the zero position is independent of the stock. I usually position my model so that Z=0 is at the top of the final shape. If the actual physical stock is taller for some reason then I need to take care not to crash into the excess stock when starting to machine.

I suspect others use the stock in a different manner. Fine, whatever suits you. But that does not dictate where the Z=0 must be.

The surprise to me in this case was that I could not select the cylindrical face when the stock was sitting right at the top surface of the model. I had not seen that behavior previously. When I moved the stock everything was fine.

Gene

[tigermm]

BTW, you can simplify your first body.
* the fewer dimensions, the best.
* do the cut with PartDesign_Groove

- I had real issues trying to get the sketch fully constrained, so just ended up adding dimensions till it worked. Not ideal I agree but I was frustrated.
- That's a nice way to do it, will remember that in future.

Cheers.