Shell Development - bobbybudnick/SFS-Mobile-Internet-Device Wiki

This page tracks development of the shell, or first layer plastic case around the device. This page mainly covers making a shell with a 3d printer but if you are good with a dremel tool there is nothing stopping you from modifying an existing project box. If you would like a shell printed or modifications to a shell please create an issue.


New shell and printer
Instone 3D Inventer Pro

Settings to start with
currently using 20% fill/rectilinear supports/10mm exterior brim

Slic3r tips
rotate 90 degrees for device shells
change support to rectilinear for easier removal

Finishing tips
carefully slide the device into the shell
colored tape can be used to match the filament color and fill in gaps
for better cellular performance/cooling the bottom can be left untaped

Spool notes
spool naturally becomes more difficult to unspool when low on filament
some clunking may be acceptable for higher speeds
speed can be set on printer proportional to how much is left on spool


Stringy prints/sometimes bad layer adhesion/extruder clunking
spool naturally becomes more difficult to unspool when low on filament
change to 205c for second layer - no effect
adjust speed - 35% fixes problem - make speed proportional to spool remaining
change nozzle - not tried
z-axis calibration - should only be for first layer problems
some clunking may be acceptable for higher speeds
separation starts with supports so speed can be adjusted to only print weak supports

Prints balling up at print head
clean nozzle and bed with alcohol - did not work
try brim - worked well
try raft - not tried
try 25% speed - improved but not enough
height calibration - improved but not enough
adhesive on bed - not ideal
new filament due to water contamination - expensive

Weak or no manual extrusion
replace nozzle

Weak or no automatic extrusion
check position of extruder gear on motor shaft and tighten tiny allen lock key
check cleanliness of extruder gear and roller and bottom and top pathways

Poor bed sticktion
clean with alcohol
replace kapton tape if needed

Erratic touchscreen
check connection of ribbon cable to display board

Poor spool geometry and clunking
clunking comes from poor feed to the extruder usually because the spool cannot turn
the spool also cannot interfere with the print bed going up or down
if spool pulls from bottom it will tend to move toward user
if spool pulls from top it will tend to move away from user
add teflon pads to inside side of spool holder to space spool from print platform
add teflon pads to back printer wall to deal with when the spool is pulled that way
70% speed helps
may be best to feed spool from bottom and use foam/kapton ramp and teflon pads

Various problems
remember when in doubt slow it down!

Model 16 Changelog

original design
add notches
move button access hole towards tail 15mm
add sleep switch access hole

Model 22 Changelog

expand width by 5mm
equalize wing widths
move cellular hole down 10mm
expand sd/reset hole down 10mm
add charging hole
add screen power button hole
add cooling holes
expand charging hole

Model 20 Changelog

increase width by 8mm
decrease wing width by 20mm
increase width by 5mm
increase length by 5mm

Model 21 and 23 Changelog

reduce wing widths by 6mm
reduce top hole height by 10mm and increase width by 10mm
increase overall width by 5mm
reduce side hole length by 20mm and reduce height by 5mm
increase side hole length by 19mm
increase top hole height by 10mm