Ski Builders Forum

I'm about to start core profiling on a CNC shopbot and just wondered what type of cutting tools people are using to generate the profile tapers. Thanks in advance for any info.

3-axis machine? For core tapering, I use a 3/4" diameter "Bowl & Tray" bit.

https://www.toolstoday.com/p-4945-bowl- ... ords=45984

Yes, 3 axis machine. Thanks for the info

I use a 1.5" straight flute.

Amana RC-2250. Works great and has indexable/replaceable cutters.

twizzstyle wrote:I use a 1.5" straight flute.

I used bits like twizz for quite some time on my router bridge and they worked great.
I have 4 sitting in the shop now waiting for me to mail them away for resharpening.
Once they get a bit dull they can make your core blow up really fast!

Just ordered one of these to try. Gotta run down to Eureka tomorrow and pick it up.

https://www.amanatool.com/rc-2241-inser ... r-bit.html

Will post a bit of a review after it's had a bit of use.
Was torn between it and the RC-2242 with the curved edge.
Was finally sold when I found the inserts for the 2241 were pretty standard 12x12x1.5mm carbides and available just about anywhere.

sam

I'm interested in how you like the rc-2241. It's nice that is ~$50 less than the rc-2250. One thing I like about the 2250 is it still has cutters on the bottom surface that will cut all the way to the centerline of the tool. Because it cuts to the centerline you can plunge and don't always have to ramp your cuts down into the material.

I'm scratching my head a bit as to how you're using spoil board cleaners for profiling? On a rail/router bridge I get it, as you're effectively mimicking a 5-axis (or 4-axis I guess) router, but on a 3-axis machine, I don't see how a big wide flat bit gets you anything but trouble?

On most cnc software you can select your machining plane with code like g17, g18, g19. You can then cutter size compensation the tool on the z axis so your profile is still correct. Or you can even get lazy and not even learn to write code and just about any cam software will do it all for you

A bigger tool actually produces a flatter finish when ramping with a 3 axis machine.
That said, i only use 20 and 25mm tools but that is because i get them super cheap.

Dig it!

The scallop height on a 3axis machine from a 1.25" spoil board cutter is pretty small when looking at what it is doing while cutting a ski core. I was curious so I drew it up in CAD to measure it. Assuming a 10mm thickness change over a length of 800mm (about half the length of a slalom ski, 12mm underfoot, 2mm at tip), a 0.75" stepover of the bit results in a scallop height (from bottom of curved surface cut by bit to the "ridge" between passes) of 0.0015625". If the stepover is decreased to 0.375" the scallop becomes 0.00035". Worst case stepover of 1.25" the scallop is still only about 0.007". If the ramp angle is steeper, say a 10mm change over 400mm, now a 0.75" stepover with the same 1.25" bit jumps all the way up to 0.003125".

Ummm, yeah bro.
I think you are over thinking it all. Just try to picture it in your head.
I've spent 20 years running big cnc milling centres and even with all the new cadcam programs around I've found the guys i have taught who can picture it in their head properly go on to be good cnc tradesman.
Learn to right programs from scratch without cam tools and you will rarely have problems.

No problem here visualizing it in my head. Just trying to put some numbers to scallop height so people can understand the variables that go into producing it, no matter if you use cutter compensation, handwrite your g-code, or generate it with a CAM program. Regardless, scallop size is a function of cutter diameter, cutter shape (flat endmill v. ball endmill), toolpath stepover (% overlap), and the angle of the surface being cut relative to the rotation axis of the cutting tool. If surface roughness from the scallop height is trying to be controlled the effects of a flat endmill can be minimized with proper tool selection and toolpath generation, or it is best minimized with a 5-axis machine so that the axis of the endmill is always normal to the surface being cut.