How would you machine this?

[tigermm]

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

I tend to use extensions to process beyond the edges of model, but I believe is 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.

Gene

Extensions.... is there somewhere I can read up about that part of path?
I'm using 40mm HDPE so I just assumed I should set it to the dimensions of my stock. Are extensions necessary?
Does the size of the stock in FC even matter really? i.e. paths will go outside the FC stock anyway as per the outside profile of my model.
Or is the stock mainly there for simulation?

So all your models are below the XY plane?
And you measure in from the edge of the stock to find X0 and Y0? (which in my case would be the circle center if I'd left the stock in the default place)

[Russ4262]

Evening Sir.

... 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? ...

No. It does not, so long as when you add the cylinder to the same Job object, its placement is correct in reference to the rest of the actual part. Jobs support multiple base models.

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

I apologize. I have been with the project for only a couple of years. I still don't think it is as intuitive to use as it could be, and it is not as well documented as it needs to be. That said, I am partially to blame since I am a contributor to the project.
My recommendation is that you continue to use the forums for assistance. There are many great users that will help other users seeking assistance. Also, I recommend comparing your settings for the 3D Surface op with those settings in ops presented to you here in this thread as a learning process - go setting by setting.

... Stepdown of 0.95 instead of 1.00, why was that? ...

The 3D Surface and Waterline operations are unique from all others because they work with meshed versions of the models - this means all faces are converted to triangles for much simpler interaction mathematically. For this reason, 3D Surface can produce some unwanted artifacts in the paths because of the triangulated curves. I had some artifacts appearing in the paths generated, so I began adjusting certain properties (settings) in an attempt to eliminate the artifacts as best possible. You wanted 1mm step downs, so 0.95 is likely to be acceptable if it removes some unwanted artifacts in paths.

... 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? ...

Same purpose as previous question - attempting to remove artifacts in paths. Honestly, this 1mm drop to -41.00 mm did not remove any artifacts; therefore, it could likely be changed back to your original -40.00 mm.

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

Great question. Sample Interval could also be labeled Sample Resolution. This value is the spacing at which the cutter (tool bit) is dropped down to the model until it makes contact at any point. The smaller the value, the more accurately the cut will follow the true curve of a path (given a proper tool bit for the curve to be cut). Reference the last attached image. The two brown curves are identical. The green Sample Interval is 10mm and the blue is 5mm. You can see the blue better fits the curve. It is very worth noting the the smaller the sample interval the greater the processing time for the operation. This is also true of step down and step over values. Decreasing them makes the computation time grow nearly exponentially. Also, you can have a nice very small tool bit and a large sample interval, and your cut will not be smooth because the large sample interval will not provide a sufficiently dense sample of the curve being cut.

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

The Multi-pass setting essentially converts the 3D Surface into a 3D Pocket. Using Multi-pass was me not paying attention!
As far as I know, the Depth Offset is used to leave stock, like a roughing pass. Use it if you need that.

... 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.

One of the quotes I remember most from my dad during my high school years is, "Son, you're never going to learn anything if you don't ask questions." I say this respectfully and as encouragement. FreeCAD is a great piece of software. We, the FC community, are both learning and improving this project together. Keep learning!


I attached an updated file version with the two faces in a single 3D Surface op based on the taper op of my earlier version, but with Single-pass and a 0.75 mm step down. The two faces have different 3D Surface settings needs and should likely be separated, but I combined them just to show the effect. That top face is mostly flat, so the step over used is likely too dense for what you are requesting. Reference the first three images.

Have a great night, Mike!
Russell

[bmsaus4ax]

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

Sorry for this late and now mostly redundant reply.
The reason for that in my file is that the first step was not included in the selections. If included it would do the step as well.
The overlap on top is part of the face is a built-in margin in the boundary settings.
Once the operation is created , if you go into the DATA TAB -> Selected Geometry Settings -> Boundary Adjustment: and set that to a figure of minus the cutter radius the path will start on the very edge of the shape.

[tigermm]

Thanks for your help guys.

Russel, that's a great explanation and very helpful, cheers.