I am really happy with my carving but I am keep leaving bits of fuzz and small imperfections that I would like to correct. Attached is a couple of images and the file. What am I missing?
Donna Fall on square.c2d (320.3 KB)
Ed
Here are my thoughts:
- Make sure you are using a downcut end mill.
- Make sure your stepover isn’t too wide.
- Make sure your spindle is trammed well.
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Decrease your step over. As you can see most of your fuzz is in almost the same direction as your grain. Make sure you are using a sharp bit. I keep a medium sanding block on the machine and before I remove a project I run it over the surface to remove any fuzz from an upcut bit. I did not down your file so not sure what bit you used but you get top side fuzz with an upcut bit. However it is usually easy to remove. If you expect a perfect surface after machining you will always be disappointed. I use some sanding sticks to get into tight areas and remove unwanted bits left over behind. Not sure what wood you used but it looks like premium pine or poplar both of which are soft woods and will splinter easily.
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I am not so much worried about the splinters and fuzz on to but rather the missed spots in the pockets. Is it a speed and feed thing, a overlap, or depyh of cut. I always divide my cuts so the first two pass are bigger and the final depth is thin. I take the factory setting for overlap.
set the overlap of the final pass to 40%
makes a huge difference
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I find an upcut bit leaves a smoother bottom finish than a down cut, but it leaves fuzzies or blowout on the surface (depending on material), so I run a downcut bit on all surface cuts down a few tenths and have it cut slow and shallow, then I switch to an upcut bit and let it fly. Leaves nice smooth cuts top and bottom and only adds a few minutes to the overall time.
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I’ve started using compression bits. There’s a small upcut design at the tip and the rest is downcut. As long as you clear the upcut spiral in the first pass (or offset a finishing pass) then it’s almost always smooth as butter. A bonus with compression bits is that jobs run faster because you can run deeper passes.
The cost of a nice compression bit is definitely worth the time you save finishing after a carve.
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This was frustrating until I figured it out. Apparently ‘stepover’ does not work exactly like I thought it would.
Look at the attached file. Same 1/2" wide rectangle both use a 0.25" endmill. One with a 0.125" stepover and the other uses a 0.124" stepover. When stepover is set to 0.125" it looks like the machine assumes everything is perfect and ‘stepover’ as I would define it is zero. The half inch wide path is done with two passes of a 0.25" endmill.
The fix is to change the stepover to just 0.001" less than half the diameter and then the tool path will include a run down the middle that will clean up the fuzz you are seeing.
stepover_test02.c2d (10.5 KB)
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This is one thing that always confuses me. In the tool setup it says my step over is 15% This produces a 50% step over. If I have a 1/4" bit and a 15% step over the step over on the other screen it has 0.125". That is a 50% step over, not 15%. What I do is 1/8*0.4 = 0.01". Confusing.
What if you decrease the step over to something like 0.1? I wonder if it would do the same thing. I did try the 40% number and it did work out really well. I also figured out that if the board moves at all it shows up in the pocket. I had one of the hold downs not quite right and the board came up something like 0.01" and and that side was fuzzy. I had to really look to find it had moved!
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