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Prusa I3 BOM Help

Posted by Zerker 
Prusa I3 BOM Help
July 30, 2013 06:36AM
Hi all,
new to RepRap, live near Hamilton, and looking to build a Box Frame Style Prusa I3.
I've been going Prusa's GitHub trying to get as much of the BOM from there for what I guess you would call the original build.
however it seems to be missing some information, is there anyone here more fammiliar with the Prusa I3 that might be able to fill in the blanks?

from the Wiki I see no one has a firm grasp on the exact amount of fastners required for this.
I've even tried translating Prusa's Norwegian BOM but it still makes no sense.

form the Vanilla branch I did find an incomplete BOM for each of the main parts, however it is missing the Z axis or Frame parts, any input very much appreciated

==The gregstruder==
Plastic parts needed:
-Extruder body
-Extruder idler
-Extruder large gear
-Extruder small gear

Other parts needed:
-1 NEMA17 motor
-1 hotend
-1 M3x8 grub screw
-6 M3 nuts-
3 M3x40 bolts
-1 M8x20 grub screw
-1 M8 hobbed bolt
-4 M8 washers
-2 M8 nuts
-3 608 skateboard bearings
-3 M3x10 bolts
(optional) 2 short, stiff springs or silicone pads

===Assemble the X axis (P2)===
Plastic parts needed:
-x axis motor end
-x axis idler end
-x carriage

Other parts needed:
-1 NEMA17 stepper motor
-1 T2.5 belt
-3 M3x10 bolt
-1 belt drive pulley
-1 M3x8 grub screw
-1 ??? bolt
-1 ??? bearing
-7 linear bearings
-7 M3x25 bolt with nut and washers
-2 smooth rods

===Assemble the Y axis(P2)===
Plastic parts needed:
-y axis motor holder
-4 y corners
-y axis idler
-y belt clamp
-3 y bearing holders

Other parts needed:
-1 23x23cm 12mm plate (9"x9" 1/2" thick for people in inchy countries) (may be thinner)
-1 heated bed PCB, with wires attached
-1 glass plate covered with Kapton or PET tape
-1 NEMA17 stepper motor
-1 T2.5 belt
-2 M3x10 bolt
-1 belt drive pulley
-1 M3x8 grub screw
-1 ??? bolt
-1 ??? bearing
-3 linear bearings
-3 M3x25 bolt with nut and washers
-2 405mm smooth rods
-22 M8 nuts (substitute 5/16" for M8 in inchland)
-22 M8 washers
-12 M10 nuts (?? in inchland)
-12 M10 washers
-4 140mm M8 (5/16") threaded rod (longer is ok)
-2 430mm M10 (??/16") threaded rod (longer is ok)
-9 3.5x12mm wood screws (or shorter if your plate is thinner)
Re: Prusa I3 BOM Help
August 02, 2013 05:54AM
I did some more Digging around and found a Site that lists Bills of Materials, and I found this link:
and I bioled it down to a Fastner/ Bearing list excluding extruder :
Item Qty
M5 Hex Nut 2
M2.5 x 10mm Machine Screw 6
Bearing 608 2
M3x8 Grub Screw 4
M3 x 10 Bolt 5
LM8UU Linear Bearing 10
M8 Nut 36
M8 Bolt 40MM 2
M3 16MM Machine Screw 10
M2 Hex Nut 6
M2 Hex Bolt 6
M8 Washer 34
Bearing 624 1
M3 40MM Bolt 4

I still feel like I'm missing something
Re: Prusa I3 BOM Help
August 02, 2013 11:50PM
Hi Zerker, I think your 8mm nut count is too high in the second list. There were two (at least) variants of the I3. One used 10mm threaded rod on the y axis and the other used 8mm. 10mm obviously gives you a stonger machine. You still used 8mm threaded rod for the shorter x axis rods on both variants.
Re: Prusa I3 BOM Help
August 03, 2013 05:14AM
everything I see for the Box version so far seems to work off of the original design which did use M8 threaded rod.
I want to make sure I'm going to have the correct printed parts for the box build, but the more I look into it, looks like I could almost do exactly the same as the single plate,is this right?

if so I have the RepRap Magazine issue 2 which has the build guide for the Einstien variant, so i could just build that but with plywood

sory if that sounds retarded, I ussually dont get time to research reprap until after midnight.
Re: Prusa I3 BOM Help
August 04, 2013 04:27AM
I think it's almost inevitable that you'll end up with a few (comparatively incidental) extra parts when you're done.
I'm building a single plate i3 (my first build of many I hope), and I am not at all concerned that I'll have a small box of bits purchased 'in error' by the time I am done.
I don't consider them 'redundant purchases', but rather as forward thinking purchases for the NEXT build.

The part that surprises me the most is how SMALL my surplus box of bits is at the moment....
OK, I have a small army of spare 608ZZ bearings that I'm certain will come in useful some day, but precious little else!
(That may well end up being a case of 'famous last words' though as I don't yet have a working printer... My build is heavily 'budget constrained' so I have at least a month before I'm printing anything even if all goes perfectly.... I suspect that will end up being closer to 3 months. The anticipation is KILLING me!)
Re: Prusa I3 BOM Help
August 04, 2013 03:19PM
First good luck with your I3 build.
The reason for wanting to put together a BOM is so I don't run too short or forget something entirely rather than buy too much.
From looking at


It looks like I would need almost the same parts as the Einstein variant only the y carriage bearing mounts and the Belt holder are different. As these parts would be to fit the same belt size and the same smooth rod and bearing size I can get printed the ones on the wiki and rest should be able to use the files from the Reprap magazine article

Re: Prusa I3 BOM Help
August 04, 2013 06:08PM
Thanx for the good luck wishes... I haven't need the luck yet, but I'm pretty confident I'll want all I can get by the time I've purchased the last of the needed parts. (I'm down to only needing the stepper motors, a hotend and some PLA / ABS)

One of the problems we 'beginners' face (if I'm allowed to use that term?) is that there are many variants of each machine and this makes it difficult for anyone to produce an accurate-to-the-last-washer BOM.
However, that 'problem' is not a huge one to overcome when considering the big picture.
Some examples (keep in mind that the version I am building is the single plate):
- The guy I brought the RP plastic parts from (digiknow) included two different versions of the Z axis idlers
- The Y carriage plate I've purchased uses 4 * LM8UU bearings while most I've seen use 3
- The Y carriage plate I've purchased is marked for a belt guide that attaches with 2 screws but the RP belt guide I have uses 3. (Oh no!!! I have to drill the plate slightly differently than marked??? LOL)
- When I was at the inaugural Akld Reprap meetup at Mike_P's house, I saw an I3 with a Y-Idler that incorporated a kewl belt tensioner. (This will probably be the FIRST part I print once I get thru the expected teething issues)

If I had been concerned about getting the exact quantities of the exact bits I needed from the outset, I would have taken the route of a complete kitset rather than sourcing parts individually. (And that would probably have meant taking the I2 route instead of i3 since the i2 is far more readily available in kitset form).

So far in my build, the only part I 'under-ordered' was the LM8UU bearings (due to the Y carriage plate needing 4). I suspect Mike was bemused when my first order to him only included a SINGLE LM8UU bearing (to bring my total up to 11 since the other 10 came from Digiknow).

I've kept an accurate BOM of all the parts _I_ have used in my build thus far in a simple spreadsheet. I've separated it into columns for X-Axis, Y-Axis, Z-Axis, Extruder, Electronics and 'Other'. Since I purchased all my threaded rod in 1000mm lengths, I extended my Y-axis from the stock build. (I cut the M10 threaded rod in half giving me around 500mm). To cater for this, the corresponding smooth rods needed to be longer too so I purchased 490mm lengths from Mike_P. The 4 remaining smooth rods (X and Z axis) needed to be somewhere around 350mm each (I forget the exact lengths), so I purchased 2 * 760mm lengths from Mike_P with the intent of cutting them in half. Those 'hardened' rods are EXTREMELY hard! I had to use a cut-off wheel to get the job done. (The smooth rods just LAUGHED at me when I showed them a hacksaw blade, and the jaws of a huge set of bolt cutters were equally unsuitable to the task!)

The only significant thing I have noted in the construction thus far is that the slots in the RP plastics for the captive nuts are a bit small for the corresponding nuts. I've had to take the 'heat-up-the-nut-to-melt-it-into-the-plastic' approach to get them in! For the majority, this has worked nicely, but the 2 * M5 nuts on the X carriage that control the Z-axis lift proved to be troublesome. I suspect I have FAR too much friction on the Z-axis threaded rods due to some of the molten plastic still 'fouling' the Z axis M5 threaded rods. I'll probably have to do something about that as I suspect I'll end up missing steps on the Z axis motors if I don't.

Anyway.... I'm assuming you're in NZ (since this IS the NZ section of the forum after all!)
If you're ANYWHERE in the greater Akld region, you might want to pop along to another 'meetup' @ mike_p's house on the 18th August! (He's out in west Akld, which makes it rather a LONG trip for me... I'm in the Pukekohe area! Any further south and I'd be outside Akld!)
If you live anywhere near me and want to attend the meetup, then I could pick you up on the way if that'd help?
Re: Prusa I3 BOM Help
August 05, 2013 02:27AM
Great reply from theRevva. The cute idler y belt tensioner is [www.thingiverse.com]. It's a good idea to just get going with your build. it is inevitable that you will end up with a few things you don't need and you are bound to miss something that you do. Sourcing it yourself is IMHO hugely more satisfying and will teach you more. It also opens you up to all the variants. It is almost inevitable you will find some part later on that is better and once your printer is up and running you can print it and improve. i'd love to say mine is up and running perfectly but it's not. Everything is great except the Z axis which is dragging it's heals. In fact some of the noises it's making sound like a horse loosing a shoe!
Re: Prusa I3 BOM Help
August 05, 2013 02:31AM
Another thought. I have found that the 3mm nuts sold by Jaycar are larger than standard and don't fit. Maybe try another supplier. My local hardware (Hammer hardware) was spot on exact.
Re: Prusa I3 BOM Help
August 05, 2013 04:16AM
LOL @ Oatridge...
Those 3mm Jaycar nuts fit PERFECTLY...
They just require the use of the correct 'tool' (which in my case was a small propane burner...) I held each nut in a pair of needle nose pliers and gave it a good 'warm up'. After that, they literally FELL into their respective slots in the PLA parts. My problem was that the M5 nuts for the Z axis were a lot closer to the correct 'fatness' to begin with, and' being of a larger thermal mass, they held the heat somewhat longer. Therefore, they ended up doing a bit TOO much of a 'melt' on the X carriage ends.

I suspect a new pair of X carriage ends will be on my list of bits to print shortly after the aformentioned Y-axis idler.

Anyways, getting back to the OP topic.
Another area where I've seen 'variations' in the i3 BOM is on perhaps the most BASIC of RP parts.
The 4 * corners (that the Y axis threaded rods are attached to) look to have different variants. I've seen some where the 8mm smooth rod is 'cable-tied' to the top of each post, others where the smooth rod slides into a hole, and the variant I have which uses an RP cap affixed using a pair of M3 machine screws and captive nuts.
While the version I have uses additional M3 hardware, it's not hugely worrisome to me. I grabbed a few hundred M3 screws, 100 * M3 washers, 100 * M3 nuts and 50 * M3 Nylock nuts.
While I will definitely have HEAPS of M3 hardware left over, I'm not going to quibble about the additional $20-$30 I spent.
It will all come in handy on my second build, third build (or perhaps hundredth build?)

In my mind, it's the more 'specific' reprap parts that I am concerned about.
For example, the hot ends, and to a lesser degree the hobbed bolt for the extruder drive.
These parts are far less ubiquitous in the marketplace. (I doubt we'll be able to pop in to Bunnings / Mitre 10 to pick up a spare J-Head anytime in the next 5 years. It WOULD be nice if we could though! ).
Re: Prusa I3 BOM Help
August 06, 2013 12:21AM
Mental note: buy gas torch for assemby :-). One thing Bunnings does have and at a cheap price, is a good range of springs. I picked up a couple of packets of C-562 springs which are perfect for attaching the heated plate to the Y bed.
Re: Prusa I3 BOM Help
August 06, 2013 04:11PM
Now THERE is an invaluable piece of info!!! (I'll head to Bunnings tomorrow)

I hadn't even _considered_ the mounting (and the follow-on levelling) of my heat bed yet!

Speaking of heat beds...
My Y-carriage plate not only uses 4 * LM8UU bearings (as opposed to the 3 I've seen on most others), but also expects the heat bed to be mounted on each of the 4 corners.
From what I have read, I'm pretty certain that will make the process of getting it perfectly level just a wee bit harder compared to the 3-way mounting option. Oh well, life's a b**ch smiling bouncing smiley.

BTW Oatridge...
My H/B is a Mk2a... I'm unsure of whether I should mount it with the heating tracks underneath, or on top?
My 'suspicion' is that the tracks should be on top (i.e. Directly underneath the glass plate I 'scavenged' from an old Brother printer / scanner / copier).
I'm also wondering about installing a thin sheet of 'thermal insulation material' between the H/B and the Y-carriage (although doing this will slightly reduce my max build height). I'll cross that bridge when I get there!
Re: Prusa I3 BOM Help
August 06, 2013 11:49PM
Heated bed interesting point. Just looked at my three working printers. Two with PCB tracks up and one down. The down is slower to heat! I think up should be best. I have stuck some fibreglass insulation directly under the heated bed as well. This seems to speed things up and I notice the heater cycles less. All my printers use 4 point. I call one edge the datum and set and lock it. Then I work around the edge and set the others, repeat twice and finally tweek the overall Z height using the middle as the reference point. I initiall tried vernier calipers but just got frustrated so ended up with a paper "feeler guage".
Re: Prusa I3 BOM Help
September 14, 2013 04:25AM
started ordering parts so i figured i might as well start making this into a sort of build log.

so far
480 Watt ATX PSU $FREE
RAMPS US$28.99 [www.aliexpress.com]
Arduino MEGA (Clone) US$14.24 [www.aliexpress.com]
5x A4988 Stepper motors (no pin headers or heatsink) US$24.84 [www.aliexpress.com]
roughly NZ$84.00 spent on electronics

went into Jaycar to buy some header pins for the stepper boards, picked some up thought they looked a little big for the holes in the board, showed the guy there the board and he said, "no,no,no they wont fit, we wont have anything that small here". I had my three year old with me and he was touching everything so i didnt try it out. got home, and realised the pins and sockets on RAMPS are a standard size, tried the steeper board on the header pins and a perfect fit. Back to Jaycar tommorrow, i wont be asking for advice there ever again though.
Re: Prusa I3 BOM Help
September 16, 2013 12:20AM
Good buying so far, keep it up and you will have a great value printer. Plus you always know where to get spares.I've got quite a bit of stuff through Aliexpress and haven't been dissaopointed, just watch the postage, free is good!
Re: Prusa I3 BOM Help
September 16, 2013 04:39AM
FYI [www.buyincoins.com] ramps for $18.99 USD, free shipping.

Was being discussed online tonight... haven’t personally tried one.
Re: Prusa I3 BOM Help
September 16, 2013 05:42PM
buyincoins seem to have very good value stepper drivers as well. Thanks for the tipDust.
Re: Prusa I3 BOM Help
September 16, 2013 10:24PM
They also have really cheap jheads... once again quality unknown. Who wants to take a gamble and do a review?
Re: Prusa I3 BOM Help
September 17, 2013 02:07AM
Yeah you got to be careful with the RAMPS Boards. I checked out the cheap ones on AliExpress and some of them don't have the jumper pins or jumpers for micro stepping.
I could have paid less for my one (its even cheaper at the mo, it's all on sale it seems) but it stated it was tested and all the buyers had good reviews for it. Same with the stepper motors I bought the ones Dust recommended as they were tried and tested and 100% good feedback from buyers for that product.
Still waiting for the motors to arrive. Paid an extra US$1.00 for fast shipping.

I soldered my stepper boards myself (first attempt at soldering, so keen to test that the motors work lol)

The j-heads are clones. The guy who designed them did a review on the eBay and makerfarm ones. The easy way to tell is the Chinese knock offs have only four vents in the PEEK instead of the recomended five. Blog post is well worth a read and goes over most of the downsides, the recent run of jammed j-heads are mostly clones.
Re: Prusa I3 BOM Help
November 24, 2013 10:28PM
I'm looking for more parts. here is what's next on my list
Heatsinks, Purchased : [www.aliexpress.com]
Fan for stepper drivers, can't decide 60mm, or 2x 40mm fans.
Multimeter (I need to set my stepper driver current and I want as low a chance to fry them as possible, I read somewhere that the cheaper boards dont have a stop for the trim pot, will a $20.00 multimeter be sufecient or should I just get a good one now anyway?)
I've found that as Dust said in another post, the motors I have purchased have leads that are too short, the wire is 24 AWG, and Jaycar say this is too small for them to carry. will anything do, I figure given the low load this should carry to go from stepper driver to stepper motor, there is not going to be any kind of heat concerns, is there a different gauge I can use? also, I can't seem to find anything less than $50.00 for 25 meters through Element14. I did find these on aliexpress
the wireing kit looks nice, but with shipping the price is at a point that I think I can crimp my own cables thanks.
Re: Prusa I3 BOM Help
November 25, 2013 01:25AM
Check out surplustronics.co.nz They have been around along time, do alot of mail order on line etc and supply schools so have a reputation to protect. I often buy stuff there. I see thay have a good range of cable.
Re: Prusa I3 BOM Help
November 26, 2013 02:01PM

Multimeter (I need to set my stepper driver current and I want as low a chance to fry them as possible, I read somewhere that the cheaper boards dont have a stop for the trim pot, will a $20.00 multimeter be sufecient or should I just get a good one now anyway?)

A cheap one should do fine - adjusting the pots is not that critical really


This is ok from Jaycar - its what I used...


Waitaki 3D Printer
Re: Prusa I3 BOM Help
November 26, 2013 05:52PM
I took a trip down to Jaycar and grabbed some simmilar wire.
I'll borrow a multimeter and grab one from China. as soon as my heatsinks come in, I can wire it all up and test the electronics, I'm just short hotend and heated bed wont be getting HBP straight away, my current PSU does not have enough AMPS on the 12v rail to run everything, it will do RAMPS and hotend, but I wil either need an additional PSU for heatbed or just buy and wire a whole new one to do everything.

next I plan to start buying the smooth and threaded rod, is it ok to use Mild for threaded and stainless for smooth? they shouldn't touch so a reaction should not be an issue, will mild be strong enough for threaded rod?
Re: Prusa I3 BOM Help
November 27, 2013 04:09AM
Hi Zerker, To answer your last question...
There's no real problem with using either and there are plenty of RepRaps made that way.
But here's why you might want to consider spending a bit more on stainless and proper linear guide rail.

Zinc plated mild steel threaded rod is not usually made to the same quality as stainless threaded rod. The threads are rolled into the rod and the pitch can vary a bit.
Because stainless threaded rod is a higher value product a bit more care is usually taken.
In time the zinc plate will go white. Particularly if you are in a humid or dusty location. The ends of the threaded rod where they are cut will also go red.
None of which is particularly concerning but if cosmetics are important then stainless threaded rod doesn't add that much to the cost.

For the smooth rod you can use drill blanks but you need to keep them oiled or they will rust.
You can also use stainless rod.
Keep in mind that if you are using recirculating LM8UU ball guides these are designed to roll on an 8mm rod. Well actually the diameter should be between 7 and 14 microns under 8mm. I don't know what the tolerance on the stainless rod is but I doubt it's anywhere near that tight.
Linear guide rod is also made from high carbon tool steel and is case hardened and then chrome plated. This is important because the balls actually bear on a very small surface area and will happily deform the surface of a soft stainless rod.
One of the nice things about the RepRap designs is that you can typically build them as rough as you like. You could probably use wooden dowels and the printer would still work.
I am constantly having to unlearn years of engineering training to realise that things don't have to be perfect to work perfectly well.
But if you want to be able to print high quality then you need to stack everything you can in your favour and buy the best quality components within your budget and take some care in the assembly.

Makershop - Reprap parts, adding new stock almost daily.
Re: Prusa I3 BOM Help
January 16, 2014 01:29PM
heat sinks, GT2 belt and 20 tooth pulleys, LM8UU bearings all arrived. I've found a local source foe stainless threaded rod that is half the price bunnings wanted to charge. still haven't tested the electronics yet as I've had the PC farming Litecoins which i will use to buy my jhead once i can figure out how to sell them for US$ and get that on to PayPal.
i still need fastners, skate bearing and smooth rod sources.

for frame i will be using this design instead of the boxframe design on the wiki
this should mean i have less issues making it square and still have the same dimensions and rod lengths with more rigidity. bunnings sells a full sheet of 12 mm untreated ply for 48.00 (rouanded up as i cant recall the exact cents :p )
i should only need 600 by 900 though.

for smooth rods is there an aliexpress supplier that people have used?
Re: Prusa I3 BOM Help
January 18, 2014 02:37PM
am looking into smooth rod through aliexpress also. some of the prices are 20-30 dollars cheaper (delivered) than anything I can find in nz. makershop.co.nz has the lowest nz price I can find so far.

Im also still looking for someone to print my plastics :-(
Come on folks snt that what the whole reprap community is about?

I now have:
threaded rod

Edited 1 time(s). Last edit at 01/18/2014 02:48PM by jloomb.
Re: Prusa I3 BOM Help
January 18, 2014 03:50PM
I'd be happy to help out with printing plastics
Re: Prusa I3 BOM Help
January 18, 2014 06:09PM
have pm'd tomas02.........
Re: Prusa I3 BOM Help
February 14, 2014 02:39AM
time for a bit of an update.
came across some extra funds so i have purchased linear rod from aliexpress, the listing was for the exact lengths and quantities for the box frame build so i snapped em up. i will post the link once they have arrived and i decide if i can recommend them or not.
found bit not yet purchased what i think is the cheapest supplier for stainless threaded rod locally (Hamilton) expect to pick that up on tuesday, yay for annual leave.
motors still untested, now that i have most of the parts on order or at least decided on, i should really get onto that, time in the workshop is a bit. tight at the mo, wife films for a youtube show all day sat, i get one day to spend with her and the kids and about three hours to myself, during the week i'm either with the kids or at work (i work nights she works days) so progress is slow but getting there.

last couple things to do before full assembly.
buy :
pick up threaded rod
plastic parts.
Re: Prusa I3 BOM Help
February 19, 2014 05:51PM
plywood sorted. bunnings checkout operator couldn't find the right price so gave me the one that most closely matched the dimensions, got 1200 x 1200 x 12 mm untreated for NZ$42.42 and they even cut it down for me so it would fit in the car, for free.

called EDL Fasteners for a quote on stainless threaded rod. $15.26 for 1meter M5, 1meter M8 And 1 meter M10. that lot was going to cost me $32.32 from allfast solutions.
i tend to like it when you find a shop that sells things for less than half the price of others. i would deff recommend EDL fasteners to anyone who cant find it cheaper. called them on the phone got an order number and picked it up same day took all of about 30 mins including travel time :p
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