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Treeline
06-11-2013, 02:52 PM
I haven't used Curve milling much, but I had a need for Milling Along Curves. A quick question for those who know: I understand all of the selections possible in the "Along Curves" dialogue box except the selection for "Raise Z for Multiple Z Cuts".

Could somebody explain exactly what that does?

I don't understand what it does since there is already a Safe Clearance selection that "should" create a safe boundary already.

Dan B
06-11-2013, 04:29 PM
This is for when you want multiple cuts. It gives you a position above the curve to start at, then you define your step-down. Check out the attached screen capture.

187800

The first path is starting 20mm above the curve.

Dan

Treeline
06-12-2013, 09:54 AM
OK, thanks, but I'm still not getting it.
It looks to me like the "Raise Z for Multiple Cuts" setting tells the tool to raise 20mm after each cut so that it can go back to the same start point for the next Z cut, and that it will do that for each of the Z cut passes. Is that right?

If so, then what's the point of having a "Safe Clearance" setting (9.525 in your example)? Is that not the height that the tool is supposed to go to between each cut/pass so that it clears the table top by that much space?

Further clarification would be much appreciated because it appears to me the two settings noted have essentially the same purpose, that is, to insure safe clearance between each of the passes to avoid crashing the table.

Dan B
06-12-2013, 11:04 AM
I agree, you're still not getting it. :D

The "Raise Z for multiple cuts" is not the same as the "safe clearance". Try doing multiple passes starting 20mm above the curve without entering a value in the "raise Z" box. You won't get multiple cuts. You need to tell madCAM how far above the curve to start doing multiple passes. It has nothing to do with the safe clearance.

Dan

Treeline
06-12-2013, 11:14 AM
Then let's agree to agree about my not getting it. ;)

The way I set up my job was to draw the lines/curves on the surface, but I figured that I would have to extend those lines/curves downward to the depth that I want them cut to.
If I understand you correctly now (which I don't guarantee that I do), the way to do it is to just draw the lines/curves on the surface, and the way you determine the depth to cut to, is by first entering the "Raise Z for multiple cuts" which I guess is the depth the cut(s) are to be made (?), and then the next entry is to enter how much you want to take in each pass.

Am I getting closer to getting it?

lukewarm
06-12-2013, 11:24 AM
If you have physical access to your machine it's very simple. Air cut without that option, then air cut with it. Watch how it works. Essentially both ways you cut to the same depth, using multiple Z levels you cut to that depth with multiple passes.

Hope you figure it out. It took me awhile to wrap my head around how CAM behaved so don't get frustrated! Just experiment with your machine though while air cutting. It really does help.

Treeline
06-12-2013, 12:13 PM
Essentially both ways you cut to the same depth, using multiple Z levels you cut to that depth with multiple passes.

Hope you figure it out. It took me awhile to wrap my head around how CAM behaved so don't get frustrated! Just experiment with your machine though while air cutting. It really does help.

Oh I'm all wrapped alright. :drowning:

Let me repeat for clarification: I do NOT have to EXTend the lines I drew on the surface downward to the depth I want the cut to be. Right?
What I do is to just draw the line on the surface, and then it's the entry in the "Raise Z for Multiple Cuts" that determines the overall depth of the cut from the line downward, and the next entry determines how much to take in each pass beginning from the line itself and working it's way down to the depth entered in the "Raise Z for Multiple Cuts" box.

For example, if I want my depth of cut to be .950", then I would enter .950 in the "Raise Z for Multiple Cuts" box.
Then to make that depth of cut in passes of .125", I would enter .125" in the next box.

What I'm having trouble with is the word in the phrase "Raise Z for Multiple Cuts". Does that mean that the number I enter (.950" in my example) determines the bottom of the cut from which the Z is raised?
That would sort of make sense if so, because that would be telling the cutter that while the depth is .950", I want the cutter to start the cut .950" higher (where the line itself is located on the surface of the object), and then make passes down to the .950" depth by .125" as per my example above.

I'm trying to understand the logic of the whole thing. I definitely understand about wrapping one's head around a lot of this stuff, and I've done so quite successfully. Still, there are some things like this that I need to try better to understand the logic behind it.

lukewarm
06-12-2013, 12:40 PM
Yeah sorry I don't want to lead you astray since I do not use MadCAM personally so I cannot comment on the exact details. It will be one or the other, and once you do a few air cuts with different settings you'll understand and get it straight in your head.

For my CAM software you can either touch off on the top of the piece or the bottom of the piece, however cut depth is always measured as ZERO being the top of the piece and the bottom of the piece being denoted as it's thickness.

So if I had a piece that was 0.25" thick if I told it to cut to 0 it would not remove any material. If I told it cut to 0.125 it would go halfways, and 0.25 would be full material removal. If I told it to do multiple Z passes at 0.125 from 0 through .25 it would take two passes and remove all my material. I could also tell it to remove 0.125 from a depth of 0.125 and end up at .25 or full material removal. Clear as mud, right?

Practice! See how your CAM software behaves. They are all fairly similar and it doesn't take much to figure it out. Just don't practice on expensive hardwoods with 50$ carbide router bits from Centurion.....like I did. =/

Dan B
06-12-2013, 01:07 PM
I think you are on the right track. Think of it as "Distance from curve". Maybe these illustrations will help.

187866

187868

187870

Notice that by using a negative value, you can force the paths to be under the curve.

Hope this helps,

Dan

Treeline
06-13-2013, 10:20 AM
I think you are on the right track. Think of it as "Distance from curve". Maybe these illustrations will help.

Dan

Dan, I think I might about have it albeit with the new added wrinkle of a curve being drawn below a surface and requiring a negative entry in the "Raise Z etc." box.
Still, I think I have it, so bear with me as I describe what I understand and let me know if I indeed get it.

1. In either case, a curve line is all that is needed, not a curve line that is EXTended to an intended depth, because it is not necessary to determine the depth of a curve line since it's the entry in the "Raise Z etc." box that determines the depth of the cut along that curve. I think I have that right.

2. Then if the curve is ON TOP of a surface, the depth is determined by making a POSITIVE entry in the "Raise Z" box followed with the depth of each pass desired. The Safe Clearance entry is what protects the surface from being hit by the cutter while transitioning from one line depth cut to the next one.

3. Alternately, if a curve is drawn BELOW a surface, it's assumed that you would want to cut from the (sub-surface) level of that curve up to the surface, so you would enter a value that is the deepest part of that curve to the surface. Naturally, shallower parts of that curve would automatically break the surface during the cut.
In this case, the value would have to be a negative value because since "depth" is what the "Raise Z..." box is looking for, it would have to know that you are wanting a "depth" that is actually above the curve itself. Therefore, the negative value is the bottom of the cut (on the curve itself) and all other cutting is done upwards. While I wasn't thinking of using a curve below the surface for what I'm trying to do at the moment, I can easily see the advantage of drawing a curve below a surface specifically for when you want the depth of the cut to vary in depth from the surface. Really cool, that!
The only thing I'm leery of is if Madcam knows to START the cut above the surface when entering a negative value in the "Raise Z..." box. Obviously, if it were to start at the bottom of the cut, that would create all sorts of smoke and fire, but I'd like to assume that not to be the case and that Madcam will indeed begin the cut above the surface using the Safe Clearance entry from where to begin the first plunge to the first StepDown and then progressively all the way to the bottom of the cut.

So, am I a saved soul on this one or am I still missing something?

EDIT!
OK, wait, I looked at the diagrams in the previous post again and realized that I have it backwards. I switched the concepts in my paragraphs #'s 2 and 3.
If the curve is drawn ON TOP of a surface, then you enter a negative number to determine the overall depth the cut is to be made BELOW the curve.
But if the curve is drawn BELOW the surface, then you enter a positive number to determine the overall height ABOVE the curve (up to the surface) you want the cut to be made.
God I hope I'm finally there.

Dan B
06-13-2013, 12:52 PM
Your first point is correct. A simple 2D line will suffice. Your edit at the end is correct. I think you have it.

Dan

Dan B
06-13-2013, 03:31 PM
Here is a little trick when using the profile toolpath:

With your curve at the bottom, double click in the "material top" box and madCAM will automatically fill in this value.

188030

Also, the profile command will give you the option to machine on the curve:

188032

By using the "Profile" toolpath (instead of "Along Curve") with the "on curve" option, you can take advantage of this little trick for setting the tool to the top of the material.

Dan

Treeline
06-13-2013, 06:38 PM
Alright, thanks. It's nice to get one step further along the path to knowledge. I'll look at the "Profile" toolpath as well. It looks like a good trick.

Thanks again.