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fusion360 surfacing strategies

CaptnBlynd

Plastic
Joined
Oct 12, 2015
I am practicing with my home student mill (sherline) using machining wax. Using fusion360 (because it is not thousands of dollars) I have been trying out different patterns and tool combinations for a specific challenge, A hemisphere. A simple half ball shape about 1" diameter. This is the shape I find to be the hardest to get a smooth finish on.

About the best I've used so far:
Adaptive pocket to clear the bulk. 1/4" end mill.
Parallel. 1/4" end mill.
Spiral. 3/16" ball end.

This is not giving me the smooth clean lines I'd like. It is all practice and I'll melt it back down. Nothing specific to a job. Just learning the various approaches by doing. Working in wax, really tolerant material that shows the least detail well. When I get done I can see the paths for all 3 operations at one point or another on the hemisphere.

Any advice of tool/operation combinations for a smooth half-sphere? Any tweaks to path set-up you'd use? I'm not honestly certain that a completely smooth half ball is possible with 3 axis and standard bits.
 
There are videos made by nextgen cam about hsm works (almost identical) that explain and cover all the surfacing strategies. I definitely remember a video where they set limit angles for different paths when surfacing.
 
Here's an article on surface finish articles and Fusion 360.

A hemisphere is one of the times the scallop cutterpath could work out really well. You'll have the same cusp everywhere, without the self collapsing corner and snail tracks. Otherwise a combination of 3D ramp and spiral(or parallel) with complimentary slope angles would do a nice job.
 
I am practicing with my home student mill (sherline)

Part of this may be because the Sherlines require some backlash to reduce binding on the leadscrew. You can usually adjust down under a thou, just keep an eye on the adjustment and make sure nothing binds along the entire travel of the table. I have Sherlines as well and did fight this for a while until I dialed everything in as much as possible.

It won't remove mechanical backlash, however there is backlash compensation in the .ini file for your mill. You can measure the actual backlash and set it in the .ini. This way the control will help compensate for some of this and improve your finish/size.
 








 
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