3F 8mm YG1 @ 12krpm
1.290 doc
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Interesting, Pretty similar I think to my results except that Black probably shows way more imperfections.
Can you add some detail on the tool-paths, feeds per tooth, ramps etc… Looks like a FDOC based on the shaving hairs around the first picture.
I’ll see what I can share later but it looks like the 3F needs curve testing as well. A good cut shows very consistent machining marks.
The 8mm shanks definitely moved around less than the 0.250 tool.
I feel like I have gotten marginally better surface finish by using a conventional finish pass with a 20% of diameter stepover, but it really could have been placebo effect as the difference was small.
I have only gotten smooth (near mirror) finish in extruded acrylic by sanding the edges by hand: 220 -> 320 -> (400) -> 600 wet -> 1000 wet -> (1500 wet) -> 2500 wet -> 5000 wet, (steps in parenthesis may sometimes be skipped). Yes, time intensive but worth it depending on the importance of the finish quality…
The following pics show surface finish after using onsrud 65-000 series (Super-O) and a Yonico 14103Q Carbide v-groove (2-flute)…
No finishing, just endmill:
After finishing with the sanding method above (only to ‘2500 wet’ though):
Can you find the polished one? (It does have a finish blemish though…):
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Same part rotated 90 degrees between photos. 2nd shows chatter from V wheel deflection as the spindle moved in the Y direction. It looks worse than it is but at least its consistent!
Parts straight off the machine, no post processing. The top 1" is final OD, the bottom 0.0290 is +0.010 radial and was cut with a 4mm 2F, ready to be setup for the flip and final machining.
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now I am eagerly waiting for a shot of the curves, where both X and Y moved, to see if you end up in the same place we left that thread 
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@Vince.Fab thank you for posting these. I feel a lot better at what i’m able to achieve sans any 2sided machine on an XXL without nearly the number of mods as you.
I got a maintenance kit along with the new C3D router. We’ll see if i can get any more resolution with some tune ups.
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0.250 hss straight sf. 0.500 depth/0.020 step. 1.000 depth/0.005 step. No spring
Datron 8mm sf 0.500 depth/0.020 step, 1.000 depth/0.005 step. No spring
I ended up going to an 0.002 stepover on the actual parts for the best finish. That’s what I want to try the curves with again. Tolerance and smoothing were set in the tenths range.
Linear rails would make a huge difference, maybe someone with a Pro can test as well.
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I hope the V wheels in the kit are the heavy duty ones that come on the HDZ as they are beefier then the factory v wheels that came on my machine. I would also run them slightly tighter to reduce their deflection even more. Just don’t go caveman on them. Running steel core belts may help some as they are more rigid then the fiberglass core but Vince has more experience then I do with the performance difference between the two so I am curious on his opinion regarding them.
I don’t even machine plastics but I am glued to this topic as I want to absorb any and all machining tactics information I can. Did you ever finish setting up your linear rail SO3 with Daniels story plates?
This machine is a stock s3 with Z plus, white steel cores, and SMW plate plus stiffeners. Its running the HD wheels and I haven’t been able to beat the precision the white steel cores offer without any step adjustments in grbl. Consistently sub ± 0.003 without Fusion adjustments either.
The fully linear S3 needs motor extensions soldered for the flipped setup but almost ready to go.
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I have a very big surprise coming !!! stay tuned!
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Smooooth. Gotta try 3F again I guess
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I also found this, no idea if it would be useful to you:
http://www.sdplastics.com/acryliteliterature/13196EFFFabTBEdgenSurfaceFinishing.pdf
I may have gotten overly excited, but still an improved result. New Router, Tightened V Wheels, and Some EVO cutting oil added. Finishing was done at .04 DOC, .035 WOC. .004 Feed per tooth at 20k.
I thought it was a really good result while it was sitting on the machine, but the oil was deceptive. Still this is my best result to date. And I’m beginning to understand why @Vince.Fab decided to 2-side machine his.
material was two pieces of .75" fused together this time. The left side is the top of the cut and it is very good, if this was consistently the finish all the way to the bottom, I wouldn’t bother with sanding. And it’s good to know I can achieve an acceptable finish if this were only .75" thick acrylic. But after .75" in depth things start to get a little wonky.
After a quick sanding of 220, 320, 600, 800 the difference in cut quality is clear in the bottom half of the cut.
Next time I’m going to try this cutter to eliminate the Amana Unicorn bit variable.
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@Julien here’s a curve if you were curious.
It’s not able to achieve a mirror on curved letters, but I actually prefer the visual consistency of the cut on curves (Less of a visual juxtaposition)
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Using the LMT Onsurd Bit.
Visually, the only difference I can see in the geometries of the LMT vs Amana bit is the LMT is a bit “flatter” at the tip where the Amana comes to more of a point. So I wasn’t expecting MUCH difference but the LMT did produce some interesting differences.
In fairness, I was cutting much more curved shapes this time around, but in short the conclusions that I’m drawing are:
- Finishing results on both bits are almost identical with the top half of the of the 1.5" cut being pretty consistent but then loosing it >.75" down, with the LMT producing less of a Mirror finish.
- Roughing results on the LMT were more visually acceptable, but not smoother. When the Amana roughed it attempted to polish the cut more then the LMT does so the end result was a visual juxtaposition in black that is very noticable. However, when the LMT roughed the cut was more matte all the way through pretty much to the point where it looks uniform enough from a distance.
The LMT also produces more audible chatter to combat that I tried various combinations of RPM and feed rate. Results pictured below.
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I am improving… best result on a straight edge yet. Biggest change here is that the finishing pass went from .04" DOC to .125"… it seems to like more depth. This is the LMT bit btw.
Question, why on some of my contours does the bottom (right side of the image) show roughing marks at the bottom of the cut? I used to think this had to do with getting some double sided tape on the bit, but now I think it has to do with the Rough at Final and Finish at Final settings in F360 along with whether the finish stroke was moving climb or conventional. This is the same letter just the opposite side.
I’m finding that it’s possible to get better results selecting portions of a contour and instructing that part of the contour to be cut either climb or conventional. But this gets very tedious with something like letters and I still haven’t found a way to deal with inside corners and tangentially expanded toolpaths on portions of a contour.
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