[Arm-netbook] video of laptop casework demo available

[Luke Kenneth Casson Leighton]

http://rhombus-tech.net/community_ideas/laptop_15in/news/

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[Paul Boddie]

Post by Luke Kenneth Casson Leighton
http://rhombus-tech.net/community_ideas/laptop_15in/news/

It looks rather promising, and I can see how the limitations of the printer
might make prototyping difficult: I've also had people print me things, and it
has required a lot of "post-processing" on their part to get mechanically-
acceptable results.

I imagine that this would be adapted to more scalable processes once
prototyped, however, which would infuriatingly eliminate some of the precision
issues experienced during prototyping. Or would you first go through an
iteration or two of higher-specification 3D printing first?

Paul

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[Luke Kenneth Casson Leighton]

Post by Paul Boddie

Post by Luke Kenneth Casson Leighton
http://rhombus-tech.net/community_ideas/laptop_15in/news/

It looks rather promising, and I can see how the limitations of the printer
might make prototyping difficult: I've also had people print me things, and it
has required a lot of "post-processing" on their part to get mechanically-
acceptable results.

yeah tell me about it. i learned only recently that you have to
switch on "antiooze retract".

one of the problems i'm encountering is that the inner walls are
really quite thin. repsnapper isn't too smart, so it goes "i'll draw
that inner part - 1mm thick - as a square, and right next to it i'll
draw *another* inner part buuuut, because they're separate, i have to
go zip-zip-zip (from 1st square to 2nd and back) to get the bit of
oozing plastic off of the nozzle".

uuunfortunately, that "bit of oozing plastic on the nozzle" can be as
much as 3-4mm long. it accumulates *per layer* on the exterior of a
wall 1mm thick that's being built up 0.2mm at a time.

you can tell what's going to happen, can't you... :) yep you guessed
it: that "bit of oozing plastic" makes the corner of the inner wall
eeever so slightly higher by 0.2mm than the surrounding sides being
built up... by the time you get 10mm high the corner is a whopping *4*
millimetres higher than the height where the printer head is
travelling!!

that ends up with a corner pushing the bed down, causing no end of
problems including the entire part breaking free of the heated bed.

by switching on antiooze retract, the zip-zip-zip which causes 3-4mm
of plastic to be dumped in a corner is replaced with "bzzz-zip-bzzz"
which is:

* z-axis going backwards a couple of millimetres
* x-y positioning to the new location
* z-axis going forwards a couple of millimetres

and it carries on from there. it seems to work and produces much
better quality work.

*if* however the walls on the parts i was printing were, say, the
quotes normal quotes thickness - most people print 3D parts with walls
*at least* 5mm thick, and *especially* if they were being printed as
solid parts (which i am not), then there would *not* be the problems
that i'm encountering.

looking at the parts that make up the mendel90, almost all of them are
completely solid. holes are at least 8mm in diameter. any "interior
walls", the smallest thickness i can see on any of the 100 parts is
about... 4mm.

by contrast, i'm printing *hollow* parts where the walls are in some
places only 0.7mm thick. certainly, the interior support struts are
only 2 runs of the print head back-and-forth.

so it really really does depend on what you're doing, paul. i can say
that now, after working with this mendel90 for... five months? :)

Post by Paul Boddie
I imagine that this would be adapted to more scalable processes once
prototyped, however, which would infuriatingly eliminate some of the precision
issues experienced during prototyping. Or would you first go through an
iteration or two of higher-specification 3D printing first?

right. ok, the plan is as follows:

* phase 1: get 3d printed parts working (as +ves)
* phase 2: split all parts into two -ves
* each 1/2 part will be subtracted from a "block"
* this "block" will fit inside a metal container
* the two 1/2 -ve parts will be fitted inside the metal container
* low-viscosity injection mold plastic will be used to create a prototype part

phase 3:

* the two 1/2 -ve parts will be printed out on flash-thermal resin (on a DLP)
* the two 1/2 -ve parts will then be flash-cast to metal.
* the resultant 1/2 *METAL* parts will then be used for *production*
injection molding.

the reason for using high-accuracy thermal resin to cast the molds in
metal is that - i hope - they will be much more accurate, so will not
require polishing.

if they *do* require polishing (i.e. not look good enough) then what
i will do instead is investigate some casting methods that give the
cast parts a "sandy surface" look, meaning that any blemishes simply
won't show up as significant.

$USD 20k on polished injection molds when they're only going to last
2 to 3 thousand units before they wear out due to abrasion - it's
silly. there has to be a better way.

l.

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[Luke Kenneth Casson Leighton]

On Mon, May 4, 2015 at 6:00 PM, Luke Kenneth Casson Leighton

Post by Luke Kenneth Casson Leighton

Post by Paul Boddie
I imagine that this would be adapted to more scalable processes once
prototyped, however, which would infuriatingly eliminate some of the precision
issues experienced during prototyping. Or would you first go through an
iteration or two of higher-specification 3D printing first?

* phase 1: get 3d printed parts working (as +ves)
* phase 2: split all parts into two -ves
* each 1/2 part will be subtracted from a "block"
* this "block" will fit inside a metal container
* the two 1/2 -ve parts will be fitted inside the metal container
* low-viscosity injection mold plastic will be used to create a prototype part

so *right from the start* i have to design each part so that it can
*either* be 3d-printed (as a +ve part) or that it can be split into
two -ve halves.

these two halves will fit together, creating an inner space that can
be filled with molten plastic... *but*, the tricky part is that it has
to be possible to remove the two halves without destroying the plastic
inside it.

so, having an inner space that goes round a corner is not possible to
do, because at least one of the halves of the mold will be stuck. the
two halves have to come out of the plastic *straight* - no overhangs
are allowed.

i don't entirely know if this is ok, but i am counting on it being
possible to pull one of the mold halves out at one end first, followed
by the other. the reason is because i have some screw-holes and
insets which i am *hoping* will not be destroyed or damaged when one
half of the mold is pulled away from the plastic.

... we shall have to see!

l.

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[Paul Boddie]

Post by Luke Kenneth Casson Leighton
* phase 1: get 3d printed parts working (as +ves)
* phase 2: split all parts into two -ves
* each 1/2 part will be subtracted from a "block"
* this "block" will fit inside a metal container
* the two 1/2 -ve parts will be fitted inside the metal container
* low-viscosity injection mold plastic will be used to create a prototype part

You're braver than I thought. ;-)

Post by Luke Kenneth Casson Leighton
* the two 1/2 -ve parts will be printed out on flash-thermal resin (on a
DLP) * the two 1/2 -ve parts will then be flash-cast to metal.
* the resultant 1/2 *METAL* parts will then be used for *production*
injection molding.
the reason for using high-accuracy thermal resin to cast the molds in
metal is that - i hope - they will be much more accurate, so will not
require polishing.
if they *do* require polishing (i.e. not look good enough) then what
i will do instead is investigate some casting methods that give the
cast parts a "sandy surface" look, meaning that any blemishes simply
won't show up as significant.

I think Bunnie had some interesting/amusing things to say about surface
blemishes when they were making the moulds for Novena:

https://www.crowdsupply.com/kosagi/novena/updates/1330

Post by Luke Kenneth Casson Leighton
$USD 20k on polished injection molds when they're only going to last
2 to 3 thousand units before they wear out due to abrasion - it's
silly. there has to be a better way.

A while back, I became interested in these matters and surfed around looking
at UK-based companies offering injection moulding services. Maybe I should dig
some of those links out and see if there are any collaborative opportunities.
Interestingly, I think one of them was actually publicly-owned (by a local
council) and was technically a non-profit.

Paul

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[Luke Kenneth Casson Leighton]

Post by Paul Boddie

Post by Luke Kenneth Casson Leighton
* phase 1: get 3d printed parts working (as +ves)
* phase 2: split all parts into two -ves
* each 1/2 part will be subtracted from a "block"
* this "block" will fit inside a metal container
* the two 1/2 -ve parts will be fitted inside the metal container
* low-viscosity injection mold plastic will be used to create a prototype part

You're braver than I thought. ;-)

or just ignorant of what could all go horribly wrong...

Post by Paul Boddie
I think Bunnie had some interesting/amusing things to say about surface
https://www.crowdsupply.com/kosagi/novena/updates/1330

yyeah :)

Post by Paul Boddie

Post by Luke Kenneth Casson Leighton
$USD 20k on polished injection molds when they're only going to last
2 to 3 thousand units before they wear out due to abrasion - it's
silly. there has to be a better way.

A while back, I became interested in these matters and surfed around looking
at UK-based companies offering injection moulding services. Maybe I should dig
some of those links out and see if there are any collaborative opportunities.
Interestingly, I think one of them was actually publicly-owned (by a local
council) and was technically a non-profit.

yes please!

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[Paul Boddie]

Post by Luke Kenneth Casson Leighton

Post by Paul Boddie
A while back, I became interested in these matters and surfed around
looking at UK-based companies offering injection moulding services.
Maybe I should dig some of those links out and see if there are any
collaborative opportunities. Interestingly, I think one of them was
actually publicly-owned (by a local council) and was technically a
non-profit.

yes please!

OK, I'm not sure if any of these are useful, but I found them educational when
I was trying to figure out what kind of services people were offering. My
starting point was actually wondering what the state of the industry was in
the UK: plastics always seemed to be a common feature of industrial estates,
at least up in the north of England, and I wondered whether it still was.

I found the following interesting because they make the fact that the customer
owns the tooling a virtue. Maybe that isn't the normal practice, or maybe it's
because they're so confident of their own abilities that they make a virtue of
it...

http://www.omega-plastics.co.uk/

The following people are the publicly-owned company I refer to above. I just
found it interesting that such organisations are still around and haven't been
closed down by the powers that be:

http://www.moorlandplastics.co.uk/

The last time I made anything with plastics was at secondary school,
unbelievably, so I sought out more recent guides to the technology. Here's one
I found rather useful:

http://www.bpf.co.uk/Plastipedia/Processes/Injection_Moulding.aspx

Perhaps I surfed many more companies' sites and didn't think it worthwhile to
note them all down. Nevertheless, I hope you can get some ideas about possible
routes to production from some of this.

Paul

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[Hrvoje Lasic]

Luke,

1) We print 3d parts with one professional company doing it on good
equipment. I can give you contacts if you like and you can ask for quote.
Usually best scenario is to print several parts on your printer and when
you think you are done, pay for better prints (for example if you need to
shoot video or present it to investors you need the best you can get, don't
spare on this).

2) I had several bad attempts with the mold makers but I think I found
qualified one in China (this is specialized shop only in molds, the guy has
been working on parts of HTC, Apple etc.). if you like I can give you
contact and you can send him parts for quote to see if you can lower cost
for mass production. He can also produce. As a rule of thumb, if you are
going to China for mold go in Shenzen area, the best molder makers are
there and opposite and if you go to i.e. Ningbo area good chances are that
you are going to finish with bad quality parts, looking cheap. If you are
not sure what you are looking in term of finishes, go to some mobile phone
store, find some telephone (that you have exact model that you can point to
molder so you have same reference) and ask molder if he can do that and
that type of finish. I am not a mold specialist, but making several
thousands pcs of one mold is way too low. Mold should last at least 100k
pcs, depend on the quality of material can last 200, 300k pcs. Again, speak
to qualified molder, ask for quotation and ask for number of produced
units, ask for advice and second opinion. if they still reply you this low
number ask why.

Hrvoje

Post by Paul Boddie

Post by Paul Boddie

Post by Luke Kenneth Casson Leighton
http://rhombus-tech.net/community_ideas/laptop_15in/news/

It looks rather promising, and I can see how the limitations of the

printer

Post by Paul Boddie
might make prototyping difficult: I've also had people print me things,

and it

Post by Paul Boddie
has required a lot of "post-processing" on their part to get

mechanically-

Post by Paul Boddie
acceptable results.

yeah tell me about it. i learned only recently that you have to
switch on "antiooze retract".
one of the problems i'm encountering is that the inner walls are
really quite thin. repsnapper isn't too smart, so it goes "i'll draw
that inner part - 1mm thick - as a square, and right next to it i'll
draw *another* inner part buuuut, because they're separate, i have to
go zip-zip-zip (from 1st square to 2nd and back) to get the bit of
oozing plastic off of the nozzle".
uuunfortunately, that "bit of oozing plastic on the nozzle" can be as
much as 3-4mm long. it accumulates *per layer* on the exterior of a
wall 1mm thick that's being built up 0.2mm at a time.
you can tell what's going to happen, can't you... :) yep you guessed
it: that "bit of oozing plastic" makes the corner of the inner wall
eeever so slightly higher by 0.2mm than the surrounding sides being
built up... by the time you get 10mm high the corner is a whopping *4*
millimetres higher than the height where the printer head is
travelling!!
that ends up with a corner pushing the bed down, causing no end of
problems including the entire part breaking free of the heated bed.
by switching on antiooze retract, the zip-zip-zip which causes 3-4mm
of plastic to be dumped in a corner is replaced with "bzzz-zip-bzzz"
* z-axis going backwards a couple of millimetres
* x-y positioning to the new location
* z-axis going forwards a couple of millimetres
and it carries on from there. it seems to work and produces much
better quality work.
*if* however the walls on the parts i was printing were, say, the
quotes normal quotes thickness - most people print 3D parts with walls
*at least* 5mm thick, and *especially* if they were being printed as
solid parts (which i am not), then there would *not* be the problems
that i'm encountering.
looking at the parts that make up the mendel90, almost all of them are
completely solid. holes are at least 8mm in diameter. any "interior
walls", the smallest thickness i can see on any of the 100 parts is
about... 4mm.
by contrast, i'm printing *hollow* parts where the walls are in some
places only 0.7mm thick. certainly, the interior support struts are
only 2 runs of the print head back-and-forth.
so it really really does depend on what you're doing, paul. i can say
that now, after working with this mendel90 for... five months? :)

Post by Paul Boddie
I imagine that this would be adapted to more scalable processes once
prototyped, however, which would infuriatingly eliminate some of the

precision

Post by Paul Boddie
issues experienced during prototyping. Or would you first go through an
iteration or two of higher-specification 3D printing first?

* phase 1: get 3d printed parts working (as +ves)
* phase 2: split all parts into two -ves
* each 1/2 part will be subtracted from a "block"
* this "block" will fit inside a metal container
* the two 1/2 -ve parts will be fitted inside the metal container
* low-viscosity injection mold plastic will be used to create a prototype part
* the two 1/2 -ve parts will be printed out on flash-thermal resin (on a DLP)
* the two 1/2 -ve parts will then be flash-cast to metal.
* the resultant 1/2 *METAL* parts will then be used for *production*
injection molding.
the reason for using high-accuracy thermal resin to cast the molds in
metal is that - i hope - they will be much more accurate, so will not
require polishing.
if they *do* require polishing (i.e. not look good enough) then what
i will do instead is investigate some casting methods that give the
cast parts a "sandy surface" look, meaning that any blemishes simply
won't show up as significant.
$USD 20k on polished injection molds when they're only going to last
2 to 3 thousand units before they wear out due to abrasion - it's
silly. there has to be a better way.
l.
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[Luke Kenneth Casson Leighton]

http://rhombus-tech.net/injection_mold/

paul, thanks. hrvoje, could you put links/info on there so that it's
possible to refer to in the future, easily?

soft tooling (lower cost) is what i was referring to. hard tooling
(what you are referring to) lasts much longer and, obviously, costs a
hell of a lot more.

i'm looking for practical ways to get prototypes ready at a lower cost
even than soft tooling.

l.

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