Picture of MilkRap (Milk Crate RepRap)
This instructable describes how and why I made a RepRap Prusa Mendel V2 integrated into a Milk Crate (Dairy Crate).

Step 1: Background

Picture of Background
I have been a Maker in the purest form since I was a kid, and I am so glad that there is now a name (and community and movement) for what I am. Just a few years ago I would have to refer to myself as a "guy who liked to take things apart to see how they worked and also build stuff". Just saying "I'm a Maker" is sooo much easier. I purchased a RepRap Prusa Mendel V2 kit from the good folks at Maker Farm (thank you Colin for all your support) about 8 months ago and immediately fell in love with the machine and with 3-D printing.  But a few things about the Prusa struck me as opportunities for improvement. In particular was that to build a Prusa, the first thing to do is make a frame out of thin air (not literally of course, but constructing the frame from threaded rods is a slow process requiring lots of measuring, cutting, joining, leveling, and plumbing). So I began thinking of ways to build a Prusa into a rigid frame that was easy to construct (good) or already constructed (better). I am also an avid fan of recycling and finding alternative uses for objects borrowed from other industries. Then, I either saw or remembered seeing piles of milk crates sitting behind a convenience store getting dirty and abused, or milk crates being used as shelving in a college dorm, or as a  step stool in a mechanics garage, etc. It struck me that milk crates are everywhere you look and are also built to be very strong. As it turns out, the interior dimensions of a rectangular milk crate is big enough to insert the working parts of a Prusa Mendel and achieve the same build area in the X and Y direction and......... 
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gmdownes (author) 1 year ago
I am posting some unsolicited observations about sourcing parts for a MilkRap build (or any "xxxxxRap" for that matter. I will also post links to parts I self sourced if anyone is interested. Perhaps my experience will save someone some time, money or headaches.

I am a cheapskate by nature - something that fuels my DIY spirit - so I have spent countless hours looking for the cheapest way to build a 3D printer. In fact, when I was designing the MilkRap, lowest possible cost was one of my two major design goals - the other was easiest/fastest possible build.

As a result of my time spent scouring the web for the cheapest components I came to the conclusion that buying direct from places like ebay or a Chinese website like AliExpress.com can perhaps save you a few bucks but they come with potentially higher "prices" in other areas: Delivery time, quality, completeness, correctness and accountability.

Delivery times for some Chinese websites (even things on ebay coming from china) can be up to a month or more depending on where you are located.

Quality: I am an expert on this as I have purchased the same component from many different factories in china. What I can tell you is this; if there are 100 factories in china that all make product "X", they will all use different levels of quality components in the manufacture. So like a box of chocolates, you never know what your gonna get.

Completeness: I recently bought a set of Nema 17 stepper motors (used) on ebay for cheaper than a new set would havfe cost from a reputable supplier who I had purchased from before. When the motors came they were six prong outlet when my printer needed four. Not a huge deal, but it would take some soldering to fix. Also, they did not come pre-wired. I would have to buy a double ended plug for each motor to get them to work (actually two sets for each motor to convert them from 6 prong to 4 prong.) The set I could have purchased from the reputable supplier was about 30% more expensive, but came correct, new, and pre-wired. I originally thought I wouldn't mind soldering the connections, but when I was done I wish I bought the more expensive ones.

Correctness: A different time, for a different project I purchased an AC to DC power converter from AliExpress. The description on the website clearly stated that it could be used with either a 220V input or a 120V input, so I bought it. For my application, I specifically needed a power converter that can be used for either input voltage depending on what was available wherever I was. However when I plugged it in to a 220V outlet the huge spark and smell of burnt electronics told me instantly that the product had been mislabeled on the website and was not actually build to handle 220V input.

Accountability: American companies (for the most part) have all figured out that accountability (i.e. customer support) is a huge part of getting return business and favorable reviews. China on the other hand, has not. Trying to explain a problem to a foreign company is hard enough, then you try to get a refund - Yikes!

So, in brief, if I had to do it again I would stick to American suppliers with good reputations (check the web for company reviews). I have had a very good experience with the folks at Makerfarm.com. This is not to say other companies wont give you just as good of an experience, its just that I have really only delt with Makerfarm. They should have everything you need, more or less. If you need custom raw materials like PTFE tube or steel round bars, McMaster Carr and Grainger are the place to go. They have really good pricing, no minimum order quantity for most products, and one time I ordered from them in the morning and it was delivered that afternoon (How did they do that !?!?) Both of those companies are a makers best friend - they carry everything under the sun.

Partial MilkRap self sourced BOM.

Black rectangular milk crate 24 quart $7 + $12 shipping

Mk2 j-head hot end $49

Printer board rev d. $87

Mk1 heat bed $19

Nema 17 used motors $52 for 5

Minimalist direct drive extruder $0.0

Lm8uu linear ball bearings $5.25 for 10

Mk7 drive gear $12.5

Atx 500w power supply $20

Steel rods came from McMaster Carr online

PTFE tubes for Bowden extruder came from McMaster Carr or Grainger, I cant remember.

Glass plate for top of heat bed came from Lowes (I found you do not need to use borosilicate glass, soda lime window glass has worked just fine for me)


How hard would this be to do with a i3? thanks

Ok I'm new to 3d printing, have never printed. This milk crate design looks like a great way to start. One problem, where's the special plastic crate mounting parts? In a 3d printer that I don't have yet? Is there anyway to get them made, or even the cad blueprint file? Or am I looking at a one off design never to be recreated? PLZZZZZ I need answers

reprap printers are designed to be as printable as possible, so, they are supposed to spread virally, with friends printing parts for friends. If you have a friend with a 3d printer, they could print the parts, if you have a library nearby with a 3d printer, you may be able to get them printed there, or, if you are the first person in your area to try to build one, you can buy the parts online, possibly on ebay, and start the reprap spread in your area.

I'm hoping to use the new 3d printing facilities at my university to print the necessary parts, and then print parts for my family :-)

Uphiearl1 year ago
I have a borrowed Replicator 1 and have been having a ball. I did not like printing with ABS so I tried PLA and WOW. Everything started turning out great! I found I don't use heat on the HBP it works better.
So now I am ready to gather the parts and see how INEXPENSIVE I can make it for. The MilkRap looks good. I won't need the HBP so that's a little off the build price.
I will keep track of the build and see how it goes.
BTW...I am going to use the Makerbot Replicator 1 to make the plastic parts. I think I can do it for less than $200.
gmdownes (author)  Uphiearl1 year ago
Great news!! I am very excited for you. I assume you are using a 3D CAD modeling program to create the parts. I personally prefer ABS because you can create small pieces and join them permanently and easily with (home made or store bought) ABS cement (hint: it's just acetone and ABS).

I found the most expensive parts of these machines is the circuit bird and motors. I haven't found a way to get that price down yet, which is hard to understand since you can buy an arduino for $10.

If I were going to make another Milky I would make the z-towers out of steel square tube instead of all that plastic. Steel is cheap and strong. Also consider using steel angle on the edge of the crate instead of the aluminum I used to save a few bucks.

I will post more thoughts as they come to me.

Good Luck!!!!

Hey, gmdownes. If you want a cheap 3D printer controller board, you can use a RAMPS board like this one for $29: http://www.aliexpress.com/item/1pcs-Mega-2560-R3-1...

It includes an Arduino mega, shield, motor drivers and an LCD. I have personally bought It from the seller and it has worked very well and use them in both of my 3D printers. The only downside is that you have to wait a while for it to arrive.

We require the files, please!
xtreker152 months ago

Can you clarify what files are the ones necessary to print this? There seems to be quite a few duplicate files and even a folder that says new. Can you clean out the old .STL files to make this much easier to understand.

mookiex21 year ago

I would really love to move forward with this, but I have a problem... How do you print parts for a beginners 3d printer when that person obviously doesn't have one? ie: It hasn't been built yet. Thanks all. Perhaps yu can guide me through this whole thing. It seems confusing to me and if I can't print parts then Where do I get everything?

Thanks Everyone

could you provide quantities for each plastic part required for fabrication? I found that not all files are in STL format, I dont actually own a 3d printer yet, and was hoping to build my own based on these instructions/ mendel i2 instructions and wiring, so is there any way to get all files in STL format? or any way to convert the format myself?

gmdownes (author) 1 year ago

Hello World!

Follow this link to all files MilkRap


Please feel free to ask any questions you have (after your due diligence) and I will try to answer as fast and accurately as I can.

The files are a bit of a jumble, but if you look enough you will find everything you need to build a Milky of your own.

Note that I did not use the "side by side" X axis smooth rod configuration shown in the main model. There is another sketchup file for a smooth rod holder where the rods are stacked vertically. Likewise, the Z carriage in my prototype is reconfigured to hold the hot end on the vertically stacked smooth rods (though I am not sure if the sketchup model for the carriage I used is in this dropbox folder.

Anyway, you will have fun figuring everything out.



Is it ok if I orgainize it all and put this on thingiverse giving proper credit?

gmdownes (author)  Flutter_Cuddles1 year ago

That would be awesome. I will be in your debt.

samern1 year ago
That would be great. Please advise when you post the files and I will load them and fiddle with them and then post back a finished product. Those who want me to print t parts can also let me k ow separately.

samern1 year ago

In the absence of the STLs, I think I can reverse engineer the MilkStrap using some basic components I already have. It should be easy enough to fashion the components:

20mm 80-20 extrusions for the towers

20mm 80-20 extrusion along the bottom to hold the towers together

Bearing mounts on the extrusions for the Z leadscrews. Z motors can be bolted to the towers.

8mm rod for X and Y and a basic carriage out of Thingiverse take care of business there.

I'll give it a try and see where I get and if successful I'll post an 'I made it' and make parts I print available.

gmdownes (author)  samern1 year ago

Samern, (and the entire community)

I simply can't apologize enough for not posting the STL files. But as this was the first iteration, many of the parts were modified by hand a lot or a little between being printed and integrated into the machine. As such, I didn't want to post a bunch of files and have people commit to the project and get stuck. Another point of hesitation is of course all of the things I learned on iteration one that I would make better in iteration two (still in my head). I am positive there are a great many areas for improvement. Let me know if I can answer any questions for you as you go. P.S. I LOVE the idea of using thingyverse parts... We are all in pursuit of Occam's razor.

If you could post them anyway I will take it upon myself to test print, correct and repost. That being said here is what I would do:
A makerslide along the bottom with a single threaded rod for X or Y. The same for the other horizontal axis and finally 2 more for Z. This way there is no gantry. If you don't want to use makerslides you can put your table on lm8uu pillow blocks and mount smooth 8mm rod with aluminum clamps on the crate ' s exterior. That's even easier and and the rod will self reinforce the crate frame and make it very rigid. Might try that too. The carriage itself can be any of the bunch on Thingiverse.com and the threaded rod can pass through an embedded nut in the carriage. I've put two of these on top of each other if folks want and are willing to cover the cost.

gmdownes (author)  samern1 year ago

I was thinking about this over the past 12 hours and have realized that the reason I have not uploaded any files is that I was working so feverishly and not taking notes, that going back and trying to figure out what .STL files were the final iterations would be very taxing. So I have decided to instead post the entire Sketch Up model. I had not posted the model previously because I do not delete previous iterations of parts as I work, so the model space contains several iterations of parts next to each other, which can be confusing if you are trying to decide which iteration to print. If I went back into the model now, even I would need to really study the parts and perhaps make test prints to figure out which one I ultimately used in the finished work. I also noticed that after converting some .STL files into .SKP files I found on the web (like Thingiverse) and importing them into my model, the model surfaces began acting funny (not ha-ha funny) and became more difficult to work with. I don't think it is a virus, but rather just one of the many ways that Sketch Up lacks the ability to handle complex tasks.That being said, I know that many people would just really love to have a jumping off point and won't mind sifting through the rubble a bit. I will upload the Sketch Up model this weekend; that is what I would want, then you can tweak the designs and export any .STL you choose.

aruggiero11 year ago
I am hoping you are able to post either a link to or a folder of the stl files for the printer. i look forward to building and modifing my own Milkrap this September
Papa_Guido1 year ago

How do I get the files to print the parts?

Can you upload the files, please?

patanlorri1 year ago
Im totally new to 3d printing but thus far your build seems to be the most comprehensive iv found on this site, I'd love to ask you a few questions about software an equipment as iv decided to build a 3d printer. If you could an wouldnt mind please send me an email if your still onsite at patrickconran41@gmail.com
aruggiero11 year ago
I hope you're able to post the stl files before the end of the year. I'm excited to get started on this.
Claydiz1 year ago
Amazing! Great Job!
RealityInc1 year ago
Hey! I covered your project at 3D Printing Industry! This is a really great idea and I applaud you for it! http://3dprintingindustry.com/2013/12/06/milkrap-reprap-upcycled-simplified/
gmdownes (author)  RealityInc1 year ago
Wow. Thanks for the positive write-up. It gave me a good laugh at the end. Like I said in the (instructables) comments under the project, I really just want to get my idea out there to help move the conversation forward and fuel the creativity of others. When I saw the instructables contest it became a reason to finally get my idea (for the MilkRap) out of my head and into the physical realm. Luckily the rest of my life was at a place where I had time to complete the project - at the 11th hour or course. That is not the case anymore as I find myself consumed by other pressing, non-maker, issues. So I am extremely grateful to have had the opportunity to do what I could. Thanks again, I'm glad you think its cool.
gmdownes (author) 1 year ago
Thank you so much to the instructables community for your interest in my project. I apologize for not getting the files posted already. There are some changes I want to make to the original design before I post the files but I have not had a chance to do so. I am going to redouble my efforts and am shooting for 11/12/13 to get the files posted. Again, thanks for your interest and support.
wdoyle19801 year ago
Where can we download the STL files? I think my previous comment was deleted
profort1 year ago
I totally agree with last statement. Want to assemble all the parts before I build also. Can anyone print the 3D parts in hard plastic and sell them?
aruggiero11 year ago
Will you be posting the .stl files anytime soon? I have been thinking of doing a 3D printer and your version seems to be the best one for me to use.
bubbad4161 year ago
I'm really wanting to build this, but I need these files. Any time frame?
profort1 year ago
Any American suppliers able to provide some of these printed parts? Especially in Southern California?
profort1 year ago
Where would they fabricate them from steel or can I please buy them from you?
profort1 year ago
Where would anyone recommend purchasing the printed parts for this machine please?
profort1 year ago
What order should the parts be purchased to match assembly please?
profort1 year ago
Thank you again. This is amazing.
thinkyhead1 year ago
When I first learned about RepRap I was expecting someone had already done this. So glad to see it in actual existence!

One change I would recommend is to replace the 5/16" Z threaded rod with a metric M5 threaded rod, add smooth Z rods in parallel, and let the threaded rod hang loose. Because the 5/16" threaded rod pitch doesn't divide easily into the metric units used by RepRap firmware you will get banding in your layers from inconsistent layer heights, and trapping the top end of the Z rod causes Z wobble, because no rods are perfectly straight. The M5 threaded rod has a convenient pitch of 0.8mm, so it can support many layer heights with no rounding errors and no banding. It is also a bit more flexible than an 5/16" (or M8) rod, and leaving it loose prevents any wobble in the rod from being transmitted to the x-gantry. The smooth rods and bearings are then added as the main motion guides.

I look forward to seeing how it tests out when you start printing with it!
gmdownes (author)  thinkyhead1 year ago
I thought the same thing about it already being done. I searched the web prior to starting and found scant traces of folks talking about doing it but couldn't find a concrete example.

I hear you about the metric threaded rods. It would help the resolution. Likewise with keeping the tops of the rods free. That's the rub with these projects, there is always room for improvement. I wonder how Joseph Prusa finally came to the conclusion that he could either keep making incremental improvements to infinity, or go ahead and publish what he had so far.

My guess is that Josef probably said, "I can't eliminate any more parts, natch!"

I was rethinking the metric vs SAE thing, and actually I can't see any reason why SAE wouldn't be okay, since the pitch is set in firmware, as long as the thread pitch is nice and accurate.
wrsexton1 year ago
In reading the comments, I see you used a rectangular rather than square milk crate. Unless I missed it somewhere, I didn't see a comment about what impact this might have on either X or Y capacity, as you discussed with Z. I would think it would allow larger dimensions, unless limited by the hot plate. If that's the case, could you pair a couple of hot plates with a rectangular piece of glass for more capacity? (I'm old school so I always think bigger must be better....)
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