CNC router bit suggestions

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olie25
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CNC router bit suggestions

Post by olie25 »

this question goes out to all those that have the benefits of a CNC router! until now i have used 1/2 ball nose end mills for profiling cores/sidewall. Im wondering if those who have used these machines for a while have suggestions for something better or am i on the right track?

thanks
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Head Monkey
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Post by Head Monkey »

Here's what I use: http://www.happymonkeysnowboards.com/Mo ... outer_Bits

You want to use bits designed for wood, not metal which is what your typical endmill is for.
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olie25
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Post by olie25 »

the current software im using doesn't allow for very creative tool paths, im pretty much stuck to the side to side profiling will the steps left of the core/side wall be an issue thats why i always used a ball nose
bobbyrobie
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Post by bobbyrobie »

Olie,

what type of software are you using?
olie25
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Post by olie25 »

im using stock shopbot software its a vectric product off the top of my head i cant remember exactly witch version it is. its ok but there has to be better options out there.
olie25
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Post by olie25 »

its not Aspire, probably vcarve pro
rnordell
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Post by rnordell »

I have also used Partworks3d (shopbots licensed version of the Vectric Cut3d software) for cutting cores. It works ok, not as much tool path control as FeatureCam or other higher end CAM packages but ok none the less. I've played around with several different types if endmills (Onsrud and others) but the one I last used I picked up at Home Depot http://www.homedepot.com/Diablo/h_d1/N- ... ifications It is a 1/2" x 5/16" carbide hinge mortising router bit. The down cutting action of the bit prevents the core from lifting and helps keeps the core flat against the vacuum table. This bit cut the bamboo core with the sidewalks attached very cleanly without having the sidewall detach from the core. I think my feedrates were 2.7 ips at 18000 rpm, .1875" roughing pass with 0.050" finish pass (35% step over?) I use either a 1/4" or 1/8" straight 2 flute endmill (make sure it is sharp! I have ones I only cut UHMW with) for cutting the base material.
strangesnowboarding
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Post by strangesnowboarding »

olie.
ballnose has a very small point of contact for making large relatively flat passes.
i use cheapo bits from HomeDesperate or online for better (carbide).
something more an one inch wide is ideal, i think i have a 1.25, 1.75 and 2.5 in bit set for surfacing.
http://mcdn.toolking.com/catalog/produc ... er_Bit.jpg
similar to this, check your local retailer to see what they have available.
twizzstyle
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Post by twizzstyle »

I am about to make my first pair of skis since building my CNC, so I've got some unknowns about bits too. I've got a huge selection of end mills, but I don't think those are appropriate.

I got a nice 1.5" bit for core profiling (same one Mike has listed on his Happy Monkey wiki). What I'm more anxious about is sidewall profiling, since that has always been my biggest challenge using the planer.

Should I attach the sidewalls to the core, then profile the core/sidewalls together? Should I profile the sidewalls as a slab (it's a 2" wide slab) then rip it into 4 sidewalls and attach to the core during the layup?

I'm leaning towards profiling the sidewalls separately since I know folks have done that with success, but what bit would be best for that? And maybe more importantly, how should I hold the sidewall down?

My current idea is to use some spray adhesive to glue the sidewall down to some MDF, and then clamp the MDF to the CNC. I'll have to peel it off afterwards, and clean the glue off, but without a vacuum hold-down system I'm worried about the sidewall lifting up when it gets thin.
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MontuckyMadman
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Post by MontuckyMadman »

hot glue dawg
sammer wrote: I'm still a tang on top guy.
twizzstyle
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Post by twizzstyle »

MontuckyMadman wrote:hot glue dawg
That's all I ever did with the planer (with sidewalls on the core) but even with TONS of hot glue it was always a disaster. Maybe with the CNC the upwards loads on the material won't be as much.

iIll just do SUPER light passes and let it cut for 3 hours :)
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MontuckyMadman
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Post by MontuckyMadman »

no hot glue to hold down material to cnc instead of spray nasty.
Machine the sidewalls for the difference of your edge step and attach after.
sammer wrote: I'm still a tang on top guy.
MadRussian
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Post by MadRussian »

if MDF is sacrificial you can use much stronger adhesive like loctite superglue. I test this method successfully with wood. Didn't try P-tex yet. Also IMHO very important router speed and feed direction
twizzstyle
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Post by twizzstyle »

MontuckyMadman wrote:no hot glue to hold down material to cnc instead of spray nasty.
Machine the sidewalls for the difference of your edge step and attach after.
Yep that's the plan. So ok, hot glue it is, and then as far as the bit, same one I'm using for the core? 1-1/2" straight cut? I figure a normal upcut endmill will want to lift it up too much.
twizzstyle
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Post by twizzstyle »

Ok I may need some more guidance. Just did some tests with old scraps and didn't have great luck.

Granted this was a 1/2" wide strip, the 2" wide slab may do better.

I hot glued it to some mdf about every 12" or so, with a 2" long healthy bead of hot glue. For tool paths, I'm having it do some roughing passes going side-to-side, but always the same direction so it's convention milling (not climb), and then some finishing passes tracing the profile going tip-to-tail, again conventional milling only.

Taking off 1/4" of thickness with the roughing pass was too much and after a few passes it popped the hot glue off. I changed it to 0.1" depth roughing passes, it seemed to be doing ok but was going to take HOURS to cut so I got impatient. Then I tried seeing how it would do without the roughing, and just going straight to the tip-to-tail profiling. It got one whole pass, second pass it exploded.

So do I just need to be patient and let it cut for hours? I'd guess the total time would have been about 3 hours. I am running at 10,000rpm (slowest my router will go), and 50ipm. I was using a 1/2" 4-flute endmill (up cutting)

As I posted earlier I have a 1-1/2" straight cut router bit on its way, will that work better? Should I do something different for tool paths? I want to make sure I do this right before I ruin a whole slab of sidewall :(
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