Switch to the Engraving bit, much cleaner edges.
You will have to play with depth, to get the “Feel” you want.
Out of my league, I am sure someone else knows why.
I would recommend the 120 mcetcher for cast acrylic. The 90 seems to dig too deep and clogs up a bit. I also use a blower during the etch to clear acrylic dust.
From Carbide 3d Page: 90 Degree or 120 degree tip?
The 90-degree tip has better penetration in very hard or anodized materials.
The 120 deg tip provides slightly wider lines in softer materials such as fiberboard but has less penetration in harder materials.
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I’ve done a lot of engraving in faux ivory and saw this issue. My hypothesis was that the bit, not an MCEtcher, was turning in the holder. The other part of the issue was that the lines were not all being cut in order, that is the machine would skip to another area and return later to finish an area already begun.
My solution to the turning in the holder was to switch to another spring-loaded holder that locks the bit from rotating. I’m not sure how the MCEtcher handles this but I suspect the bit is free to rotate, albeit slowly, within the holder.
My parallel lines were all created “by hand” versus using a texturing algorithm created within CC or some other app. As a consequence, CC would skip around to different areas, as mentioned above, which would allow the bit to rotate enough within the holder that any, even minor, eccentricity would lead to gaps such as you see when it returned to filling in an area begun earlier.
I have not tried a built-in texturing function, perhaps it automatically finishes an entire filled in area before moving on which may eliminate this issue irrespective of any minor rotating of the bit. When your lines are being engraved does the process continue in order or are some sections left blank to be revisited later?
So, yeah, follow up for anyone interested. Those heavy lines are, as I, and bpedit, kind of theorized. They’re all caused by the engraving tool path doing sporadic ‘chunks’, doing areas, jumping across the piece, doing a section there, and jumping back. It doesn’t start at a specific spot and simply work across the whole part. Contouring first with an engraving bit did nothing.
So, unless someone knows how I can alter and optimize the GCode to basically make it start in one corner and sweep upwards, I think the only way I can eliminate this is gonna be with a second pass at a 90d angle to the first… doubling the machine time.
Was the defect pattern exactly the same ?
Did you try the Texture first on the fill area with the McEtcher, then a Contour with an engraving bit second ?
I use 60 IPM, a DOC of .015 with 2 turns into the McEtcher. I don’t get debris build up.
It’s not debris build up. It’s “first cuts”. I don’t know how else to explain it. Every time the Z axis comes up, and rapids to a new spot, the first cut it makes is gonna be "strong, and every other cut in that area is normal. I’ve watched the bit from an unsafe distance, lol. It’s not a build up.
I haven’t tried the “texture” option, as I said. I did a Contour first, to see if is was in fact debris from the initial contour. Then did a standard engrave. Made no difference. I was using DoC of .01. I’m not sure what specifics I can try. A “finishing pass” at 90d to the original did nothing but make NEW harsh lines every time it rapided to a new spot and laid a fresh line. Linear won’t work, and separate linear passes did not. I can try the Cross Hatch and Mirror paths that come with engrave, but I don’t think that’s gonna be it.
I’m probably gonna try your “non Pro” Contour and Pocket, as well. But it looks like the Engrave paths aren’t immediately what I can use.
Edit: Yep, exactly the same. Hell, it’s damn near a style at this point, luls
I have had to lubricate the McEtcher because it would “stick” on initial contact.
If you manually press the tool onto a safe surface, does it depress evenly ?
I don’t think what you’re seeing is a “strong cut” on the first pass in a new region. From looking at your pic it appears that, when starting a new region, the spacing is off leaving a larger space between lines versus a heavier line as you would expect from a heavier cut.
Perhaps I wasn’t clear in my earlier explanation. What I suspect is happening is the the bit is rotating in the holder. This rotation is minimal between adjacent lines but accumulates over multiple lines to the degree that the bit is substantially rotated when returning to finish an earlier area. If the very tip of the bit is not perfectly centered on the shaft the result is a displacement from the shaft centerline compared to the last line from the earlier engraved region.
My evidence for this, as mentioned, is that when I switched to a different holder which locks the bit from rotating (while still allowing compression) the issue went away. This comparison is using the same bit. Curiously, the locking holder is less well machined with a bit more play which is why I wasn’t using it to begin with.
Perhaps trying many bits would yield one perfectly centered at the tip. Before the locked holder solution I tried a few and, though some were better than others, they all produced similar results. BTW, none of these were MCEtcher bits but from a company specializing in engraving bits.
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I don’t think I was clear. The bit hasn’t rotated, because this will be the very FIRST cut. Quite literally, after doing contours, when nothing has been filled, it will do one of these harsh lines. It then engraves, let us say, an inch of normal-looking fill. It then rises on the Z, moves an inch, starts a new section, and again, that very fist cut, is harsh. Lets say after doing an inch there, it rapids back to where it left off. That cut is NOT harsh. It’s fine. I’ve watched the whole process. Anytime it cuts the clean acrylic, the very first cut is harsh. Any cut that’s adjacent to a previous cut, that gets to step over, is fine. The harsh lines aren’t the machine coming back to finish a new area, it’s when it starts a new area.
It’s aggravating. Gonna have to start playing with step over, for sure.
I missed this. Maybe this is my solution… Will try. Thanks.
Late to this party… I have used several different DDE bits succesfully including Carbide’s own MC etcher.
My work method is this: Z zero is set off the material surface rather than using the baseboard.
(FWIW, I have engraved aluminium, glass, slate and acrylic and all without issues)
Adjust the DDE bit from the zero point of no spring tension, so that there is a very slight spring tension. I usually opt for a spring tension that makes the bit work effectively at a depth of around 0.5mm. If the tension is too stiff, it can be easy to lose control of the DDE bit’s accuracy, in my experience. I then set the engrave start height position to 0.5mm without any stepover. I use a pocket toolpath and work from the outside in.
Ensure that you lubricate the tip of the DDE bit. My technique is to lightly flood the area with CT90 oil so that the workpiece is covered in oil and the DDE bit is residing permanently in a light oil bath while it is engraving. Cut onto the material area to be cut from outside of it. (this is vaguely analogous to ramping in) Cutting the other way can chip the diamond if it traverses a material edge.
My approach is to use a really light touch combined with a light spring tension and complete lubrication. If the engraving is insufficiently deep (not usual on most materials) I run the same toolpath but set the Z zero height 0.5mm lower. It appears to be key when using DDE bits to keep the friction as low as possibly manageable while still getting the bit to engrave the surface. For this reason I also keep the feed speed relatively slow. YMMV.
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