Smartrap Build

Hi,

So I've started building a SmartRap...

For the most part it's been fairly straightforward and looks like a pretty great simple little machine though I'm trying to go for a totally rock bottom build price -- I'm hoping to put together a few to give to friends if i can get them cheap enough and stable -- so I'm going to be hitting issues that I suspect other people who don't cut corners won't.

For anyone interested (esp wrt pricing) I'm in California, USA.


For first build, I decided to pick up parts from someone selling them on ebay. Paid about $26 with shipping. Parts received are of PLA & pretty good quality, though the perimeters are a little wide (holes were slightly too small & needed to be cleared with a drill, the bearing mount for extruder was a little large, etc). That caused a few minor challenges -- the rods required a bit more force to get into X & Y ends and I put minor splits in a couple of them -- drilling out 8mm holes i figured would be too challenging as the parts would want to grab onto the bit, and clamping the odd shaped parts would have taken a bit of work (plus I don't have any 8mm bits handy)… so I just wiggled and hammered a bit. Repairs were easily handled with some soldering iron patching though. The extruder bearing required carefully pressing into place with a vise.

For most of the motors, I found some cheap NEMA 17 steppers on ebay (i bought 10, so prorated shipping worked out to about $3 each)
[www.ebay.com]

which turn out to be ~17 ohm, 12.5mH, 34mm -- not super strong, and due to higher resistance & inductance they want higher voltage / lower current than standard motors used for repraps, but with some tuning seem to be running axes just fine. They aren't strong enough for the extruder though so will probably need to make a modified base to deal with X / Z being these 34mm and extruder needing a 40mm. Also, it think it not unlikely they will end up limiting printing speed (though for these builds i'm not too worried). The other issue I've found with them is that due to their slightly shorter shafts, the fishing line gets very close to slipping off at one end of travel. I may look into adding a bushing / sleeve.

For tests on the extruder drive, i initially tried to use a QU-BD drive gear that was sitting around, though it was slipping way too much. I'm not sure if it's partially a print tolerance thing & possibly when i had to press in the bearing it ended up slightly offset, or whether there's a size issue with the drive gear, etc… I may try attempting to print a new plate & try to merge in something like bdring's tweaks to the QU-BD extruder (adding a spring and lever). though it's pretty questionable I'll get to it. For now, i've flipped the gear upside down -- I think I can probably work out shifting the motor a small amount to get it things to generally work.

For rods, I'm using 8mm O1 tool steel drill rods from McMaster. I'm using the old dimensions from earlier BOM, so 2 x 250mm, 2 x 240mm, 2 x 220mm, so was able to get a set of rods from 2 x $5.70 rods. I'm not going to deal with hardening them, so my bearings will likely etch grooves in them over time (though may also try printing a set of PLA bearings)

I'm playing around initially with using OhioPlastic's J-Head Lite. I picked one up and a bunch of parts a while ago and eventually got it working reasonably well on a few short prints; i think this'll be a good platform to give it a longer run. Fits nicely into the extruder mount, though at present takes a little fiddling to get the PTFE tubing centered properly above it for initially feeding the filament into the hotend.

i had an extra RAMPS / Arduino set lying around, so using those… due to the smaller 34mm motor height, the RAMPS board won't fit under the X carriage, though that should be pretty easy to take care of when i swap out the extruder motor.

At this point I still need to get the fishing line run through for my X axis (parts I got only came with 1 small hook for fishing line -- or possibly i lost the second -- and haven't printed a new one), i need to replace the extruder motor & get that all working effectively, need to replace my Z nut (the only ones I had around were half height), and get endstops wired.

Oh -- one other minor concern from my build is that the 8mm bearing cover plate for the Y axis seem to be flexible / loose enough that it's pretty easy to twist the rods, and after doing so the machine's alignment will remain slightly off. Not sure it that might end up causing some issues with prints.

tymm,

I'm planning on building this one too. Have been waiting for the right time before getting a set of printed parts. Now that the machine is in production (v.5), maybe its time?

Do you know what version of the printed parts you got?

ah, i think i put together a 0.4.5 -- the y plates from 0.4.6 and beyond look different than mine; those may well take care of my Y issues

Sounds very good tymm,

I hope all will be ok.

I will post a new video tomorrow ( tonight if all is ok) with a full build , from box to print ( this is the name ) . Maybe it will help ?

I'm also about to update thingiverse models ( github is already up to date). There's some changes from the actual model . Mostly little changes to ease building , but there's also a new system for Y axis to fix the glass and be compatible with a heated bed like MK2 ( 214x214).

The video will be with last model ( which is in fact in production now).

Detailled documentation is still to come ... so long to write

thx

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the Smartrap project

[smartfriendz.com]
[www.thingiverse.com]
[reprap.org]
[github.com]
doc assemblage: [reprap.org]
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