Hi, all,
The recent update on Crowd Supply (regarding the difficulty in mass-producing parts with 3D printers) reminded me of some RepRap/RepStrap innovations from a few years back:
- https://web.archive.org/web/20150318000301/http://justindunh am.net/making-cast-resin-3d-printer-parts/ https://web.archive.org/web/20150318000301/http://justindunham.net/making-cast-resin-3d-printer-parts/ - http://reprap.org/wiki/Clonedel - http://reprap.org/wiki/Moldmaking_Tutorial
This was before cheap, mass-produced 3D printers became widely available, so many people were bootstrapping their RepRaps by purchasing 3D-printed parts from others. At some point, someone realized that it was a lot faster to 3D print a set of parts, make molds from them, and then use those molds to make additional part sets, than it was to separately print each set of parts.
I'm not sure how complicated the parts of the laptop case are, but if the parts could be re-designed to be optimized for resin casting, it might cut down on the production time. Of course, I've never done any resin casting before so I don't know how feasible this would be in practice. Also, I have no idea how fast modern 3D printers can run now, so the speed advantage might not even exist any more.
Anyways, I just though I'd mention this on the off chance it might help speed things along.
Keep up the good work!
On Thu, May 25, 2017 at 1:33 AM, Forest Crossman cyrozap@gmail.com wrote:
Hi, all,
The recent update on Crowd Supply (regarding the difficulty in mass-producing parts with 3D printers) reminded me of some RepRap/RepStrap innovations from a few years back:
oo interesting
https://web.archive.org/web/20150318000301/http://justindunham.net/making-ca...
hmm, currently offline (as in *archive.org* is offline!)
http://reprap.org/wiki/Clonedel http://reprap.org/wiki/Moldmaking_Tutorial
ooo niice. very clear. i like it.... except that the resins are listed as not being as strong as ABS (which i've tried and it failed miserable) and not quiiite as stiff as PLA.
now, unnnfortunately, the design of the laptop, whilst it is quite light (1kg) really is rather long - 230mm deep and 330mm wide - which means that it's relying on the stiffness of PLA (and the PCBs) for its structural strength.
i didn't realise at the time when i said i'd provide a DLP option that resins are not as stiff (and a lot more brittle) than PLA, so that one's going to need some thinking about / research, hum...
This was before cheap, mass-produced 3D printers became widely available, so many people were bootstrapping their RepRaps by purchasing 3D-printed parts from others. At some point, someone realized that it was a lot faster to 3D print a set of parts, make molds from them, and then use those molds to make additional part sets, than it was to separately print each set of parts.
I'm not sure how complicated the parts of the laptop case are,
pretty complicated but also designed to be injection-molded. it *should* be doable... but resins i think might not cut it.
but if the parts could be re-designed to be optimized for resin casting, it might cut down on the production time. Of course, I've never done any resin casting before so I don't know how feasible this would be in practice. Also, I have no idea how fast modern 3D printers can run now, so the speed advantage might not even exist any more.
well the $150+$40 shipping truly dreadful taobao-knockoff i just finally managed to get up and running after three WEEKS of redesigning its parts, is currently running at an amazing 150mm/sec with only minimal degradation in quality: bulging at sharp-turn (90 and 180 degree) corners.
which i am kinda blown away by. but... then again... i _did_ totally replace the entire x-end and carriage mechanism with a horizontal arrangement, put a 50mm triangle in one strategic corner of the frame (only one so far), replace the glass+MK2 printbed PCB with printbite + a MK3 aluminium 3mm plate....
none of which will really dramatically increase the cost so is a positive sign.
Anyways, I just though I'd mention this on the off chance it might help speed things along.
appreciated. do you also have a 3D printer and would you (or anyone else) like to give this a shot, see what happens? i'd be interested to know how much "bend" there is in the back base part and the left end part for example.
l.
On Wed, May 24, 2017 at 8:33 PM, Forest Crossman cyrozap@gmail.com wrote:
I'm not sure how complicated the parts of the laptop case are, but if the
parts could be re-designed to be optimized for resin casting, it might cut down on the production time. Of course, I've never done any resin casting before so I don't know how feasible this would be in practice. Also, I have no idea how fast modern 3D printers can run now, so the speed advantage might not even exist any more.
I've got a tiny bit of experience here, for what it's worth. For our open source SMT pick and place machines, we used 3D printed molds for mass-producing a particular part on the machine. They were cast in medium to low durometer urethane, but the process is somewhat similar to other types of resins.
The main problem we had were that the molds took a while to clean. The material oozed out of the top in a few strategically placed holes. Those would clog constantly and required a lot of labor to clean, however, probably still MUCH less than if the parts were 3d printed. So it was slightly annoying, but less annoying and quicker than 3D printing that particular part. There are prototyping shops in China that can do this in limited runs, with great results. No idea about cost though.
The surface finish was actually quite nice. It was basically an inverse of the 3D printed part. It looked 3D printed, but under magnification, you could see that the the ridges were backwards. If the master parts were 3d printed via an SLA process, then those lines would disappear, and the accuracies would be much better. We usually got very small air bubbles on the surface of the part, but it was casted upside down so they were never seen.
Probably the main detractor for resin casting in this particular case is going to be how the parts are designed. Unless a part was designed to be cast, it's probably not going to be cast. lkcl has already spoken that he did not want to redesign any of the parts if he could help it. For that reason alone, I'd guess that it's probably off the table.
I'm definitely not an expert though, this is not really my area. Just figured I'd share my brief experience.
On Thu, May 25, 2017 at 1:54 AM, Neil Jansen njansen1@gmail.com wrote:
On Wed, May 24, 2017 at 8:33 PM, Forest Crossman cyrozap@gmail.com wrote:
Probably the main detractor for resin casting in this particular case is going to be how the parts are designed. Unless a part was designed to be cast, it's probably not going to be cast.
they were designed to be cast, although some of the parts would require a very unusual pair of molds, where assembly and disassembly would need *two* moves (first sideways and **THEN** upwards) to split them apart.
the idea was to have a generic "block" into which mold parts with fixed outer dimensions were placed (held together), with mold parts having three sides *MEETING AT ONE SPECIFIC CORNER* and the other mold part having three sides meeting AT THE DIRECT OPPOSITE CORNER instead of the more traditional "top and bottom" mold parts.
but the molding isn't the main concern, it's the materials strength. does resin have enough strength and stiffness to not fall apart if it is used to span a distance of 330mm?
l.
arm-netbook@lists.phcomp.co.uk
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Forest Crossman -
Luke Kenneth Casson Leighton -
Neil Jansen