[V1-4 & 38] Mold with depth increment (solved in RC1)

[pixelmaker]

If I cut a mold with a depth increment and scanline toolpath every second toolpath has a offset of one stepover.
This means that there is a step at the last DI at the side. And because the offset the cutter has to cut 2 DI at this step, this breaks me a tool.

ralf

[dh42]

Hello Ralf

Added to the bug list
http://www.atelier-des-fougeres.fr/Cambam/Aide/Bug_report.html

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David

[tau]

Ralf,

i just briefly played with your file:

even the generated boundary shape of the MOP's looks strange in some areas (some "dips" as well)?!

[pixelmaker]

even the generated boundary shape of the MOP's looks strange in some areas

look at the toolpath from the side. If I work with a 10mm cutter and a stepover from 40% (0.4) I get a step of 4mm at the side of the last increment.

ralf

[dh42]

Hello Ralf

I think this problem is solved with V1.0 (since R14) because alternating X and Y half stepover offsets for scanline roughing has been removed.

Can you confirm ?

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David

[pixelmaker]

hello David

the depth increment with a endmill cutter is now ok.
If I change the cutter to a ballnose cutter there is no depth increment.
Every depth increment is cut to target depth, in this case 5 times to target depth.
This is a new bug in V1. Since i made an update i can't say since which release the bug is there.

Ralf

[dh42]

Yes, well spotted ; the bug exists also on R13_3 and R14 for ballnose and bullnose. (not tested on older V1 version)

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David

[pixelmaker]

Please write it in the bug report

[dh42]

Hello

I'm testing the R16 that correct the problem with missing machining levels, but I found something I don't understand (and it's the same on 0.98)

I'm not a "mold" user so maybe it's a normal thing, but on the file, target depth (TD) is set to 0 (SS = 15) and with a endmill the bottom most toolpath is at Z = 0, but with a ball mill, the bottom most toolpath at Z = 1.5 (radius of the tool) and all machining level are shifted from the radius of the mill.

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David

[pixelmaker]

hello David
that there's already an R16, I can only see from your statement. I rewrote the link from R15 to R16 and it downloads.
I'll check it out tomorrow. I have work to do today.

ralf

[10bulls]

I am treating this as a bug.

I think an extra tool radius roughing clearance was added to the depth for ball nose + scanline + roughing, possibly to help with the offset scanlines 'feature' that was recently removed.

But I cannot think of any good justification for it, and it seems it would just cause confusion.

If extra roughing depth clearance is needed, it can be added with the 'Roughing Clearance' property.

I don't use '3D Mold + Scanline + Ballnose + Roughing' much though, so feedback welcome!

[Bob La Londe]

I make 99% molds using 3D methods so maybe I can add some insight.  

3D waterline roughing is the fastest most of the time if it works.  For a variety of reasons it often has not worked in the past.  This leaves either of two options.  Scanline 3D roughing, or scan line 3D finishing with an HSM approach  if there is a good place to approach the cavity from so the initial plunge (or later plunges in the cut) do not result in excessive engagement.  The biggest issue with 3D Waterline Roughing is that it doesn't work all the time.  Its next biggest issue is that it doesn't address cutter engagement issues, but uses the same hard right angle stepover that is a problem with other operations.  

The later approach (scanline finish) (DOC=0) as a roughing pass is often very fast.  If its planned well, the cutter can take the abuse, and there are not further details that require a smaller cutter you can sometimes finish a mold cavity in a single pass.  Unfortunately it often won't work for simple logical reasons.  

This leaves scanline 3D roughing.  It almost always works, but it has some issues as well.  The two biggest are that you must get the final depth exactly right (less roughing clearance). If its set deeper than the cavity it continues to make full cavity passes after it has completed its task for as many increments remain until it would have reached its target depth.  The other problem is that it covers the entire range of the cavity on every pass regardless of whether or not it has already cut that area of the cavity.

Ultimately a 3D waterline rough that works more often and uses a constant engagement (HSM so there are no deep sideways moves exceeding stepover engagement) clearing method at each layer with a spiral mill to depth option as needed would be the fastest way to rough a cavity most of the time.  

[10bulls]

I make 99% molds using 3D methods so maybe I can add some insight.  

I hear you Bob and I am very grateful for your insights.

I am the first to admit waterlines shortcomings.  I really like using waterline rough, followed by waterline finish (or two, with progressively smaller ball radius cutters), finished with a scanline finish just to smooth the last bits out.
But computing can be slower than a bag full of rocks (and temperamental) and I know it can be improved.  Plans are afoot to tackle this and I'll very much appreciate your input when we get around to testing this.

Thank you!

[Dragonfly]

I don't have so much experience but it seems to me current waterline methods are more similar to slicing for 3D printers. Don't know how fast are the dedicated 3D slicers though. And I think it is because of this problems occur when actually removing material with a mechanical tool of given physical dimensions.

I have examined how other 3D software (ArtCam and Aspire) approach the task. Especially for finishing.
In 'Aspire' for example besides the scanline method there is one other which I've tried and like it very much. Basically it is a pocket within a given boundary, just like the standard CB pocket with Inside+outside offsets. The stepover is defined by the user and it actually determines the quality of the finish. The generated tool paths are then projected onto the 3D shape and the final G-code is like a pocket but with the tool tip following the relief in Z along each concentric tool path.

And, adding an angle option for the scanline method will be very useful. I implement this by using the transformation matrix for the object and the MOP respectively but it seems to me CamBam could do a temporary transformation while generating the tool paths while the object is not permanently modified. Sometimes I have to use two copies of a 3D object (or two separate project files) and with large 3D shapes it makes file sizes quite big slowing down open/save and work.

[Bob La Londe]

Sometimes I have to use two copies of a 3D object (or two separate project files) and with large 3D shapes it makes file sizes quite big slowing down open/save and work.

I 've found that if I hide the layer with the 3D objects processing is not slowed down as much.  I'll often create an outline of the 3D object in a different layer for keeping track of its location when the 3D object is hidden.