GeneMpls
11-28-2013, 12:04 PM
I have been a Sbotter for a year now- on my second SB- a 2007 PRS and
having a ball. I am making an 8 foot long Mustang... found a model on
Sketchup and got it into Aspire and split it on the centerline and sliced it into
one inch layers. I have learned a lot and this far it has progressed nicely.
The Mustang fuselage is quite slab sided and lends itself to this.
At this scale (about 25%) each half of the fuselage is 4 inches wide. The
first inch on each side will be an thin wall square aluminum tube armature-
the first layer outside the armature is 2" Duna HDU and the outermost layer
is 1" Duna. So far so good.
I machined the 1" layer first and that went just as planned. The highest
point on the model is the surface of the foam- so not machined. The problems came when I started on the 2" layer. I used a .5 inch round nose for roughing(and finishing)- roughing went well. When I tried the finishing pass I had problems with the bit (which has a .75 cut depth) slamming into pieces of the foam which was left by the roughing- causing the bot to loose its zero.It seems like the roughing left way more material than it should have.
I had to abandon raster cut and use the offset strategy to avoid the bit slamming into foam that was not roughed out. And beyond that problem-
the nice flat surface that mates to the next slice was machined down a .25
or so- which did not show in the preview.
I (miss)spent 30 years of my life repairing and restoring Corvettes and am
not concerned about the large stepover BTW- a DA sander and polyester
prime will make quick work of that. Thanks for any thoughts. Gene
P.S. I see that picts don't show much detail- roughing was at a .05 machining allowance and I did not use the boundary vector offset- made my own offset
manually.
having a ball. I am making an 8 foot long Mustang... found a model on
Sketchup and got it into Aspire and split it on the centerline and sliced it into
one inch layers. I have learned a lot and this far it has progressed nicely.
The Mustang fuselage is quite slab sided and lends itself to this.
At this scale (about 25%) each half of the fuselage is 4 inches wide. The
first inch on each side will be an thin wall square aluminum tube armature-
the first layer outside the armature is 2" Duna HDU and the outermost layer
is 1" Duna. So far so good.
I machined the 1" layer first and that went just as planned. The highest
point on the model is the surface of the foam- so not machined. The problems came when I started on the 2" layer. I used a .5 inch round nose for roughing(and finishing)- roughing went well. When I tried the finishing pass I had problems with the bit (which has a .75 cut depth) slamming into pieces of the foam which was left by the roughing- causing the bot to loose its zero.It seems like the roughing left way more material than it should have.
I had to abandon raster cut and use the offset strategy to avoid the bit slamming into foam that was not roughed out. And beyond that problem-
the nice flat surface that mates to the next slice was machined down a .25
or so- which did not show in the preview.
I (miss)spent 30 years of my life repairing and restoring Corvettes and am
not concerned about the large stepover BTW- a DA sander and polyester
prime will make quick work of that. Thanks for any thoughts. Gene
P.S. I see that picts don't show much detail- roughing was at a .05 machining allowance and I did not use the boundary vector offset- made my own offset
manually.