3d carving

[Stephen50]

I remember watching a training video pertaining to a project where the rough cut was to deep for the finish cut to produce a clean cut. My problem is similar, I used Design and Make model 50268B (Chinook Salmon), the size of the project is an oval width 18 inches x 9 inches in height A 1/4 inch end mill depth was used the bottom of the cut is 28/32 when the rough cut was complete, I noticed what I will call steps were approximately 1/8 to 3/16 in height as the bit reached zero plane. Using a 1/8 inch ballnose when the finish cut was complete I noticed ridges spaced 3/8 to 1/2 inch apart. I 'm going to do a second finish cut with the same bit smaller step over, see if that will eliminate the ovals that the first finish cut left behind. Tried taking a photo the imperfections didn't appear. I'll take any and all suggestions.

[scottp55]

Stephen,
It IS difficult without a pic..resize pic a bit smaller and save-as and try again?
What was the machining allowance for the Roughing Toolpath?
You CAN try the same toolpath with a smaller stepover, but that doesn't sound like the problem because of the "ridge" spacing.
DON'T remove it from the clamps!
IF running at a lower stepover doesn't remove the Ridges because they're to deep, you can still save it by cheating your Z-Zero down a hair. If it's a dished model then you will wind up with a very small lip on the perimeter of the dish...but easily sanded out usually.
In SB3 it's easy to drop Z-Zero. Z-Zero as normal, then type MN(M ove N udge) and in the pop-up window in Z go negative .01" and then Continue...spindle will bump down .01" and that's the new Z-Zero until you Z-zero with your Plate again. Moving down by increments of .01" if necessary(but "Lip" on dish will keep getting larger).
No need to run the whole file, just see if it's solving the problem.
Pic and a screenshot of both roughing and finish toolpath set up would be very helpful.

Oh, TJ is giving a free online training for anyone on "Intro to 3D" tomorrow at 1PM Eastern tomorrow. The Q&A session after the formal class is great for stuff like this.

http://www.talkshopbot.com/forum/showth ... 3D-Carving

scott

[Stephen50]

The photo illustrates the ridges left after the finish cut.

[adze_cnc]

For your roughing toolpath what is the value for the "Machining Allowance"? I'm going to venture that it is 0.00

If that's the case then it's no wonder there are striations. They're not leftovers from the ball-end mill but rather the roughing end mill. In that case Scott's suggestion is pretty much your only hope.

Steven

[Stephen50]

Scott55; Thanks for your response I completed the cut last night and the ridges disappeared. I'm assembling a folder with the numerous recommendations I've received for the different problems I've encountered, during the deign, modeling, and creating toolpaths for my first 3d project. Thanks again everyone my confidence level has risen dramatically during this endeavor.

[scottp55]

Stephen,
Just for the sake of future readers searching Forum for solutions to problems in these threads(and my own curiosity),
can you state what the problem was(Zero Machining Allowance set like Steven said as an example), and what you did to get a good cut?
I'm interested myself in how far you may have had to Nudge your Z-Zero down if Machining Allowance was set at 0.0 with a .25"EM.
Congrats on saving the cut!!

I learn more from my mistakes than if I had perfect cuts every time:)
For instance in Hardwoods, I prefer a downcut EM for roughing as there seems to be less chance of splintering, and then I can set my Machining Allowance lower(.015-.02") which allows me to put a Linseed/Beeswax "Butter" on the wood before my finish cut for 20 minutes before carving and then spreading the excess around before cutting. It seems to give a smoother finish,I can run without DC as it acts like flypaper for the fines, and the slurry seems to be driven into the pores, which is good for large pore woods like Walnut. Virtually done when it comes off machine:)
scott

[Stephen50]

Matching Limit Boundary offset set at .02
Matching Allowance set .04 inches

Utilized -.01 twice to remove the ridges sanded the few marks which weren't removed with the two negative passes

[scottp55]

Thanks Stephen!!
Hmm....should have been fine with those settings.
NICE to know .02" removed marks!!
Big Leaf Maple(I'd call it a soft Maple but the grain is worth it) I've had to go more of an allowance, because Downcut roughing compressed Quilted fibers, and an Upcut ripped them out....
Grain goes every which way and fairly soft fibrous wood, so sometimes have to Nudge Z-Zero for a .01" pass.
Always important to Z-Zero from the same exact spot on material surface(or spoilboard and even Z-Zero Plate on our machines).
A friend of mine up North hand carves Salmon and Brook Trout and was worried about my detailed machine carving:)
Told him to keep carving 24+ inches, AND undercut...and to keep carving out of Eastern White Cedar(Juniper) and he ain't got no competition from me

Show a pic when finished please?
Thanks again!!!
scott