Any of those you pictured is good. The pla is the weakest but still
probably OK depending on the exact design of the part. abs, asa, petg
all definitely good.
I haven't looked at the model in question, but, to make a working
battery cover in general, you don't always have to *exactly* copy the
original injection-molded ABS part. You can usually find ways to alter
the design a little to replace very thin bits with chunkier bits, and
adjust certain parts that would result in not enough layer-to-layer
surface area, and still fit and still get the same job done. I think
that was even mentioned in this thread about making some tabs shorter
and thicker. So, even pla could be fine, depending on the exact design
of the part.
But the rest would definitely be good. Especially ABS or ASA if you can
get it acetone vapor smoothed. The vapor smoothing process slightly
dissolves the surface, which just as a side effect also joins layers and
neighboring lines at least all over the surface, and a battery cover is
almost all surface.
https://www.youtube.com/watch?v=TlY833mR6Os
Like this one, Those bendy snaps should by rights just break right off
because of how they are essentially tall thin towers of layers with a
tiny x/y cross section. But you can see its glossy. He did acetone vapor
smoothing on it, and I bet that's what made those snaps actually
functional now.
A 200 cover doesn't have any "live" parts like that but that example
just really shows what I wanted to describe well.
There are plenty of examples where you can see that with plain fdm
printing, even in pla, you CAN get perfectly good battery covers. This
one looks perfect.
https://www.youtube.com/watch?v=QOLB9szKRsk
It just is a bit hit and miss unfortunately, but if the design is
tweaked to improve the chances, it's much easier & more likely to get a
good functional result even the first time.
--
blw
On 7/2/20 2:05 PM, B 9 wrote:
Thank you, Brian for all the info. You are officially a Source of Good
Bits!
https://craftcloud3d.com/ is FABULOUS. Unlike the other sites I found,
they didn't force me to create an account to get estimates and the
prices seem much lower. I'm seeing I can get a battery cover for my
Tandy 200 for $11.04 (PETG) or $11.54 (PLA or ABS), including shipping
and no extra charge for black. That's almost worth it, if I knew it
wouldn't break as soon as I try to use it.
image.png
Lee: Good suggestion on checking the library. I don't know if they're
open yet in my area, though.
—b9
P.S.The URL craftcloud.com <http://craftcloud.com> redirects to some
Korean live/work "hive". Weird.
On Wed, Jul 1, 2020 at 9:21 PM Brian White <b.kenyo...@gmail.com
<mailto:b.kenyo...@gmail.com>> wrote:
Different printing methods cost different amounts. The basic service
at shapeways is something called SLS , which is laser-sintered nylon
powder. It produces very good results in terms of both dimensional &
shape accuracy and the toughness of the part, but it's expensive.
The kind of printers people have at home are either FDM or SLA, and
there are tons of services that offer those.
SLA uses uv light to harden a uv sensitive resin. This produces
super-accurate output, but generally too brittle for a useful
mechanical part. Though there are a few special resins that are a
bit stronger and might work well enough for a battery cover. The
problem with a battery cover is it has tiny shapes that just break
off, and on top of that, it has shapes that you intentionally have
to stress and flex in normal use, without breaking.
FDM is the real common one where a nozzle squirts out melted
plastic. This is good for mechanical parts that aren't stressed too
hard, but isn't super accurate, is pretty weak for small parts. It's
just barely good enough for something like a battery cover if the
printer operator is knows what they are doing and gets good layer
adhesion and no warping and uses a tougher material like petg. The
materials used for fdm are tougher than the uv resin, so they can
bend a little before breaking, but the layers and lines is a
weakness unless the printer (both the machine and the person)
actually knows what they're doing. The problem is a lot more people
own a printer than know how to get good results out of it.
If you take an STL fild and go to CraftCloud.com, you'll get
presented with something like 20 or more types of printing, most of
them not good for a battery cover, but at least FDM, SLS, SLA
(maybe, with the best resin), maybe MJF. (MJF turned out not to be
accurate enough for the pcb2molex carrier, but a battery cover ca
tolerate a bit more variability than that carrier). You upload the
stl, select the printing method and material, and finally it shows
you some quotes from different print shops that can produce the part.
But none of these are magic. What you get is only accurate within
some range of variation. SLA is very accurate, but probably not
strong enough. SLS will also be accurate enough and strong enough on
the first try, but costs more. For FDM, it's cheaper, but will
probably need a few iterations before you get a very good result.
Generally for FDM, you burn through all those trial & error by doing
it yourself, not by paying some service.
There are a TON of small shops out there able print by FDM or SLA.
Aside from craftcloud, there is 3dhubs and several other similar
marketplace type sites or just google. But it's not cheaper when you
wait 2 weeks for a part that isn't good enough, and you end up
trying 4 times to get a good one.
--
bkw
On Wed, Jul 1, 2020, 6:41 PM B 9 <hacke...@member.fsf.org
<mailto:hacke...@member.fsf.org>> wrote:
Thanks, Lee! I appreciate the expert insight. I hope Steve is
able to rejigger the hook tabs with slightly less overhang.
$15 for 50¢ of material sounds crazy, but I don't have a 3-D
printer. Are there any 3-D print services that aren't so
expensive? My local makerspaces have closed their doors to focus
on PPE right now.
—b9
Lee Olivares <l...@braains.net <mailto:l...@braains.net>> wrote:
> The “vertical” hook tabs are on the weak side, simply by
nature of their geometry and the limits of FDM, but they’re
certainly functional. Unfortunately re-orientation of the model
isn’t a great option to improve their strength, nor is beefing
them up, simply because of the size of the slits in the case.
>
> However, making them with slightly less overhang would
prevent some harmful leverage without affecting function, and it
would permit “scooping” the three engagements on the short side,
since the tolerances there are pretty tight as it stands.
>
> Managed to fracture one of the vertical “hook” tabs removing
the support, and it’s a snug fit but a really great design.
>
> Thanks!
>
>
>
> - Lee
> - 909.437.0250
> - Destroying technology problems.
>
> > On Jun 28, 2020, at 21:39, Lee Olivares <l...@braains.net
<mailto:l...@braains.net>> wrote:
> >
> > Resident 3D Printer repair guy here: that’s expensive,
you’re looking at .50c in material for an FDM PET print.
> >
> > It’s about an hour on a Prusa MK3S @ .2mm, I’m fairly
certain my buddy gifted me an M200 so maybe I can do some
comparison shots.
> >
> > Printer is hot and ready so I’ll just crank out a sample as
a reference, wait 2hrs before making any purchases.
> >
> > - Lee
> > - 909.437.0250
> > - Destroying technology problems.
> >
> >>> On Jun 28, 2020, at 20:04, B 9 <hacke...@gmail.com
<mailto:hacke...@gmail.com>> wrote:
> >>>
> >>
> >> Very awesome! One of my M200s is missing the battery cover
and looks a bit janky with the flexible plastic I cut to fit in
its place. I got cost estimates from xometry and shapeways to
see how much it'd be and it seemed the cheapest options were $15
to $20 bucks. For example, here's Shapeways' prices, but you
have to add $3 for black plastic and then there's shipping on
top of that.
> >>
> >> <image.png>
> >>
> >> —-b9
> >>
> >>> On Sun, Jun 28, 2020 at 7:15 PM Steve Glenner
<steveglen...@hotmail.com <mailto:steveglen...@hotmail.com>> wrote:
> >>> The M200 I just got was missing the battery cover, so I
designed up a replacement and 3D printed it. I donate the model
to the community in case anyone else needs one:
https://www.thingiverse.com/thing:4508352
> >>>
> >>> Tandy Model 200 Battery Cover by SteveGlenner
> >>> I bought a second hand Tandy Model 200, but it was
missing the battery cover. So here is a replacement battery
cover. It should be printed with supports as there are some
overhangs but otherwise the settings probably aren't critical. I
printed mine in black ABS so it matches the rest of the bottom case.
> >>> www.thingiverse.com <http://www.thingiverse.com>
> >>>
> >>>
--
bkw
