Please be gentle with me as I'm a noobie with less than a month on a CNC
Making an attempt at a 3D model and while I've gotten some good advice over at the Axiom forum but need pointers on where to go from here...
The piece I did (9x10x1" Spanish cedar) was rough and profile cut with a 1/4" EM...100 ipm @ 12000 RPM...The finish pass was with a 1/16th BN 100 IPM @13000 rpm and an 8% stepover...both had a "plunge rate" of 15 IPM (not clear on what this means)...
Generally happy with the cut except there's a combination of glass smooth areas (about 90%) and "fuzzies" on what I'm calling the "downhill" sides of the cuts...Having a hard time wrapping my head around how both can happen at the same time and what to do about it before I set up for V2 in a nice curly cherry piece...
(and for you pixel peepers: yes...I fixed the profile tool path in the file
I'm guessing that the downhill sides is a climb cut? Conventional cutting will cut smoother, but with 3D, you often have no choice.
Try cutting at an angle?
Maybe increase RPM a bit?
Smaller stepover?
Side grain will be better that end grain. End grain is tough no matter what you do. Even on a table saw - hand plane - end grain is just downright difficult.
I would LOVE to know how to make that problem go away.
REALLY sharp tools help but don't eliminate.
A coat of shellac will stiffen the fuzzies and make them easier to remove my sanding - but that's only after carving and getting the fuzzies.
Some woods are more susceptible than others, HARD and DENSE woods are better - Pine is horrible. Cedar is a soft wood.
Overall - what you have looks GREAT - at least as good as you will get on the cedar.
Imagine the Possibilities of a Creative mind, combined with the functionality of CNC
Thanks...suspected that it had some to do with it being cedar but that's what was handy for the test cut and was/is pretty tight grain...just surprised/baffled that most came out so smooth and those areas didn't...yes it was a climb cut in an offset direction because of the circular nature of the piece...grain orientation is something I'll have to study on that piece and keep in mind when I can.
On my previous / 1st attempt at a 3D cut I had a second finishing pass with a 1/32" BN that got rid of all the fuzzies...added 12 hours to the cut time but came out looking silky and sweet...Jumping from a 1/4" rough to a 1/16th single finishing pass was an attempt to get the cut down to "reasonable" times...still trying to get my head around what is "reasonable" and find a balance...guess it's just going to take making more sawdust to be able to judge that
Your carve result is very good for that material! It's not uncommon to have fuzzies on portions of a dimensional carve as Leo mentioned. Rather than "adding 12 hours to a carve", sanding them off is much more efficient time-wise. Especially if using the 3M Sanding discs - I use the 180-grit (yellow) on all dimensional carves to make quick work of it.
"Not a true cedar, Spanish Cedar is actually more closely related to true Mahoganies (Swietenia and Khaya genera), as both are in the Meliaceae family. Density and mechanical properties can vary widely depending on country of origin and growing conditions; (specific gravity can vary from .30 to as high as .60 in some instances). Some of the wood available at present comes from plantations: where younger, faster-growing trees, produce wood that is lower in density, and paler in color than wood cut from trees taken from forests in the wild."
Leo wrote:Interesting note about the Spanish Cedar not being a true Cedar - more closely related to Mahogany. I never knew that.
Learning something new everyday...thanks for that little factoid Michael
Started V2 in a piece of Birdseye Maple and hovered over it till it came to that fishes head where the fuzzies showed so bad on V1...Looks better but I think Leo's thoughts on end grain are spot on...still some evidence that it's happening again...lots less but still there.
At least with the Birdseye I'll be able to sand it a bit if I need to...I'm afraid to touch some areas in the Spanish Cedar version...way too fragile.
I did add a 2nd finishing path to the updated file "just in case"... 1/32" BN @ 6%...I'll look at it when this pass is done and make a decision then but I'm currently thinking what the heck...if I start that pass at 7pm it'll just be finishing up when I get up tomorrow and not anymore work on my part
Thanks for the warning...That'll be interesting to read.
I had the impression that this was a common practice in the CNC community...hadn't heard of those sorts of problems...(yet) and in the short time I've had my machine I've done a few overnights and several 8 hr runs where I only dropped in occasionally to monitor the progress...no problems yet ...(knock on wood
I've never tried this myself, but would it work to give it a coat or 2 of varnish or some other high solids finish, on the table, let it dry and run a cleanup pass after it's dried? Not real efficient time wise, but I wonder if it would work or just make a mess?
As Leo says it would be nice to eliminate the chance of any fuzzies in any type of wood, if you should discover a way then please let us all know
Not sure if you need to step down to a smaller ball nose for a second finishing pass, I have often run the same file again as a clean up pass & generally it removes the majority of fuzzies. If I do run the finish pass again I will generally give the model a quick coat of spirit based shellac sanding sealer before starting the cut, stiffens up the fuzzies which helps remove then & being spirit based dries very quickly
It really comes down to what you think is going to be quicker & give the quality of finish you require, often it is quicker to just remove them by brushing or sanding.
I can't imagine going to a 1/32" BN for my first finishing pass but I'm game to try...I'll give it a shot tomorrow
V2 in Maple was better...not as clean as I would have liked but better. still just the rough (1/4" EM) and a single finish pass 1/16" BN at 8%...I'll try the 2 finish pass run tomorrow with a 1/32" on the 2nd finish pass...
Prepping V1 with a satin brushing lacquer to try the fuzzy removal techniques suggested...like the clear finish on it just wish I could stop looking at the "stuff"
It is best to use the largest ball nose possible. There are a few techy reasons for that, but I will not expand on that now, as I am at work.
Use a small ball only to get into details that a larger ball cannot fit into.
I would never use a 1/32 ball on a large dome - there is no benefit to that. Rather I would use a 1/2 ball if there was room to do so.
On your 3D I think the 1/32 would be fine.
****** Running the machine unattended? Sure fine. It's only a problem if you have a fire. Can you have a fire - of course you can! Are you willing to take the chance? Is it worth it? I don't do it *******
Imagine the Possibilities of a Creative mind, combined with the functionality of CNC
