Compost shredder

by thymark, published

Compost shredder by thymark Jun 7, 2014

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73873Views 14634Downloads Found in Outdoor & Garden


This is the first working 3D printed shredder for kitchen food waste. Perfect to make compost.
Printed from PLA.
How to assembly : http://issuu.com/marcusthymark/docs/boom_assembly/0
First version breaks at 25Nm torque, second version at 50 Nm torque.
The version uploaded here is number 3 and hold up to 74 Nm torque. ( Then break )
Shredding some chicken bones : http://youtu.be/A4rg--VEXVM
How to assemble vid : http://youtu.be/j4a-f51Ypc0
Metric ball bearings : SKF SS6006

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What size are the bearings since the BOM seems to be missing now.

This is a old project and unfortunatelly I don´t know why all teh info was deleted. Because I know that the metric one work great, I have for now deleted the Imperial version from teh page. Until I find time to go through the model. I hope stefi01 have for you the answer you are looking for.

Thanks for the reply. Luckily for me you had all the info i needed imbedded in the cam files and those gave me all the sizes and what not. Thanks for your time.

see my remix of this, its the same bearings for the american size bearing

Thanks for the reply.
Thymark was looking all the info up for me, but in the mean time all the needed info is in the zip files [standard and ,metric] including drawings for the bearings as well as the bearing names :) 20 bucks for 4 bearings kind of hurts.

Thanks for the reply.
Thymark was looking all the info up for me, but in the mean time all the needed info is in the zip files [standard and ,metric] including drawings for the bearings as well as the bearing names :) 20 bucks for 4 bearings kind of hurts.

Hi thymark,

Did you delete the details about printed parts? number of parts, print density etc.

Has anyone tried it with, like, bigger "animal" bones? Asking for a friend.

Comments deleted.

I find it works especially well for this purpose.

That's fucked up man

Comments deleted.

I think you could improve the design by adding some kind of walls for avoiding the food falling down. By the way, it's a very cool project :D

Have you tried shredding copy paper or mail? How does it perform when shredding paper?

This is so cool!

Is there a reason for the fins on the sides being so much thinner than the spacers they sit on, or? :)

Could you use this to crush cans for recycling?

Jun 28, 2016 - Modified Jun 28, 2016
remyspencer - in reply to ByteSlinger

If you print the shredder parts in ABS or another tough plastic, I think the shredders should hold up for typical aluminum cans. Depending on the type of can you're trying to crush it might not be strong enough though. Probably you want to make the shredder parts out of a sturdier material for crushing/shredding metal. I saw one where someone made the shredder parts out of a very tough wood, but best would likely be machining them out of steel. I haven't put everything together yet so I'm not able to measure the strength of the 3D printed shredders. I'm making mine out of ABS using the designer's recommended densities.

under the pictures of the parts, can you put the quantity we need to print? i just downloaded the nut for example "inch" and i have no idea how many to make. the same goes for "spacer" and reading the list on the description doesnt link the pictures to the name.
can you show one picture of all the parts on the table? or somehow tag each picture with the name and qty?

Apr 7, 2016 - Modified Apr 7, 2016
stefi01 - in reply to smartstuff2buy

2 sides for the bearings, i found this was way under scale and it should messure at 160mm x 90 to 92mm and i made mine at 16mm thick and missed out the outer part as was not needed, 4 x gear wheels, 1 of the long inserts into the gear wheels and 3 of the shorter, the ends have a hexagon shape and theres a circle bit in the middle which slides into the gear wheels, 2 x sides which is the red sides in the pic's .
8 crushing teeth things and 8 spacers, i did find all was out of scale though as did many others on these coments. my gear wheels are 78mm in diameter by about 10mm thick ( the gears,not the spacer thats added to one side) , the hexagon shape on the x3 and the x1 part that slot in to the bearings are 24.50mm accross. dont know how long as its fitted into the 1 inch shaft, the shredder teeth are 80mm diameter and 13mm thick, the spacers are 13mm thick and 52mm in diameter, hope some of this helps.

when i download the files, you did not name them to match the part list that says how many quantity of each to print :(
its hard to know how many to copy/paste inside my print area if i dont know what each 3d picture is named when looking at the part list. :(
can you update the parts to be named the same?

Hi everyone,

Do you think I can shred plastic bottles with this if I print it with XT or M-ABS ?

Please let me know

Would depend on the bottle/infill/tension of the gears, but likely not. Best bet is to have the teeth CNC'd or laser cut from steel.

Where can I order the metric 2x2 tubing?

I just reprinted everything in inches.

Hey Thymark, I'm planning on making this.
Everything looks good, you did a great job.
Do you have any tips stil?

will you make a hopper for it.

Agreed, this needs a hopper

Aug 7, 2015 - Modified Aug 7, 2015

i agree with someone else, this is hard to know what to print when you "download all."
can you please rename everything, for example if there are 10 parts, could you make the name of the file shorter (the full name does not show up in my robo 3d R1 printer's queue list.

if you make the titles like this, it would help us all...
i'm afraid i'm going to print both metric and inch because i have many long files with titles that dont match your instructions.













for example, i printed 2 spur gears, and now i see a nut as the 2nd print, but i dont see it in your list. so i dont know how many to print, also it is not laying flat so i will have to do that, which is easy but i'm a noob, i wasnt sure at first that i had to move it.

i really like your project, just trying to help make it easy for beginners and others.
i tried to space out those sample titles but this comment box is merging them all together.

I will do two folders one will be INCH and one Metric. So if somebody click on download all, there will still be clear what is what. I do it in one hour later ( prom this post )

I know you are busy, but when you upload the 2 folders ( I will be needing inch )
but can you please label them with "part 1, part 2, part 3" because some of the images look identical, such as shaft1, and shaft 1+5.
also the spur gear and spur gear 15mm look identical in the 3d picture when I load them in the program of my robo 3d r1 using MatterControl v1.3

I have a table full of parts and not sure which I need to print to finish it, since I tried to change the names of them when I edited it, and printed 2 at the same time, so I changed the name to like spur x2 or something.
thank you for your time

thank you!
i printed 2 spur gears, it tooks 4 hours and 20 minutes on low quality. when i rotated it, i renamed it, and then i printed. when it was done, i wasnt sure if it was inch or metric :( i think it was inch.

if i looked correctly, some of the parts, like "cup" and a few others will be the exact same file, good for both metric and inch right?

Hey Thymark! I'm hacking together a hopper to help load more compost in at one go. I'll post pictures soon, but I thought I'd let you know what a much-needed upgrade that will be.

Important question: is there any difference between the bioshredder.stl and bioshredder_inch.stl?
I think I printed the metric one by accident, the look the same to me though.

only difference is the metric files will take metric hardware better. in this case its the steel tube. though if you already have imperial steel tube and it fits, there's no real issue. otherwise you'll need to order the metric sizing.

im thinking of doing this print hollow and then casting it in aluminium just dont know how bad my shrinking will be or how well plastic will melt but one way to find out

That will be a great idea. i am casting a lot using printed parts. Just burn the plastic out before pouring molten metal in.

please upload a youtube video showing you casting parts.

Question can you make this 2x bigger? I like the design and function. Yet I have no modeling exp, software or the time. I'm in Afghanistan and it would help if someone could help me with figuring out how to make this design at least 2x bigger or 4x. It would help compost all the wet and food trash on base into a single garbage can instead of waste more garbage cans. Right now we're just dumping the trash into acid which is toxic to the environment. I am asking for someone to assist. Thanks for reading.

Doubling the size of some of these components (the frame) would make it impossible to produce on many common 3d printers.

"impossible to produce" i think you mean "difficult". Use the openscad library "puzzlecut" to cut into pieces.

Has someone tried milling coffee? Thank you!

this doesn't get the grounds nearly small enough, the gap between the rollers and the teeth is large enough for beans to slip right through. Might work to get the husks off of coffea berries, though I doubt it.

Anybody try to recycle pet pla or abs on it ?

How should i react to your question to not be rude or disrespectful. Please take any pair of scissors at home which you use to cut paper and any kind of kitchen knife. Now please cut the kitchen knife using the pair of scissors on two pieces. ( cut the blade and not the handle ) After this experiment you can understand that you cant use cutters made out of that same or similar material like the object which is cut.

To be fair, you could definitely destroy the knife with a shredder made of the same material as it.

Comments deleted.

Anyone have any kind of estimate on how much plastic they used, or time for pcs? I know it is a lot of plastic and would be the biggest endeavor I have printed if I decide too.

I used about 400 [2 190m spools] meters on the dremel idea builder. Not sure how much that is in weight. But make sure you have access to all the other parts before you start. It's not entirely clear unless you watch the videos first, but you need square lengths of metal to exact specs, bearings to exact specs, etc. None of which I have any idea where I would even find. I've printed the bearings on my printer though after a few trials and error, gotten them to work. Now I'm printing the shafts as one solid piece, instead of just the ends and trying to find square metal that fits them perfectly.

Steel shafts are available at hardware stores and the big boxes (in US, Lowes, Home Depot) for example see

The challenge will be to ensure the right fit (1" may not always be 1").

A year ago I gave up on the mini shredder (steel) unit as it:

  1. Was too small to digest garden waste. Needs to be 2X to do garden waste
  2. Had too many parts which would make it too complex and expensive for a consumer product (even using "Ikea model")
  3. I drew up a single shaft part (integrated blades + shaft + spacers) to be cut out of a single piece of steel. Machine shops willing to do that (even ones in China) wanted hundreds of $ to cut one part.

A number of thoughts on short cuts:

  1. I don't think you need a bearing for plastic on plastic using a hand crank. The stress and friction just aren't that great. A bushing will do.
  2. That eliminates the complexity of the bearing housing (walls, housing). Ergo, a printed housing may not be necessary (think sheet metal, block of wood, cut from thick sheet of plastic, acrylic, etc)
  3. It might be MUCH simpler to design all parts around a 1" (or metric equivalent) steel tubing shaft. That is, one piece outer shaft bits of blades and spacers that fit over the square tube, square bore gears, square bore bearings (I know I'm contradicting myself per #1 above) and the hand crank (just run threaded rod through it and bend to your desire)

I can be reached off line at [email protected]

Your idea is interesting and thats why I challenge you to do it better and not only write how you can make it better. All the parts ( blades and spacers are made to fit on the steel tube, and ball bearings are easy to buy on ebay. All the screws, pipes can be purchased at hardware store. I will really like to see your version doing that same stuff like my version or better.
I can even pay you the cost for filament, if you can bring this design be more easier to build and share it here with us.


Working on that now. Hope to have drawings and perhaps a print or two by the end of the week.

I am happy that you see it like a challenge and not like a insult. Take your time.

So, I see there are 3 "made"s for this model. Evidently I have made a mistake along the way, and wondering if anyone has any ideas. After unzipping the files I ended up with some very long named files all mixed together in a folder and it wasn't immediately obvious which ones I needed to print. So I read through the comments and the instructions, and things only cleared up slightly...still had a folder full of files that aren't named in an easy fashion. Separate folders for different versions, and quantity of print for the model in the file-name would help tremendously! Anyway I put together from the instructions a list of parts and quantities to print and a few days later I have what should be all the pieces, but fit together they do not. I'm not sure what went wrong, possibly when removing all the unnecessary/confusing characters from the file-names, I mixed something up.

Basically the question I'm trying to figure out is: The square part of all the "shaft" pieces. Should that fit snuggly into the square part of the "spacer" and "bioshredder" pieces? Mine are all very sloppy with about an 1/8" gap if pressed to one side [or 1/16" all around if held in center]. Is this supposed to be loose like that to allow movement when shredding? I think more likely I have mixed pieces, but would rather ask the question to those who have printed and assembled this already if they had this same gap before I start printing more versions.

Thanks in advance!

Thanks for the upload, very nifty idea indeed...

When you click on download all, you get both, the INCH one and the metric one. Just read the instructions and download just the parts writen for the metric one or INCH one and there will be no confusion.

This is way to cool !!! I have seen this kind of shredder in a scrap yard in action OMG this is so cool!!

How does it handle corn on the cob cores?

Hi jamangic
I will say, it can /barely/ handle them. I would not recommend using this for many corn cobs, or if you must, cut them lengthwise with something first.

I dont know, somebody need to test it.

thank you very much

Hi, I have just one wish, when you use the CAD files don´t delete my logo.

You can now download the source files in STEP file for metric and inch. The metric version is whole assembly and the inch are just inch parts, so for inch you need both, metric and inch.
That same is for orig. SolidWorks 2012 files.
All in folder "Thing files"

Would you be able to send the .sldprt files please?

Oct 27, 2014 - Modified Oct 27, 2014

HEY !!! Great news I just added 3D printed hand crank for Metric compost shredder and just uploading for the imperial shredder too.
Check the photos...

Does this work to salvage print to remake the filament?

In my opinion you could make the shredder more efficient by making the second drum run slower by adding a tooth on it's gear. This way you would get more shearing effect between the drums and less clogging.

You could experiment with different ratios and see how it feels.

This is how the real shredders work i believe.

video is online............ see description for link

Aug 11, 2014 - Modified Aug 13, 2014

video is processing and can take some half a hour to be online : http://youtu.be/j4a-f51Ypc0

Please post assembly instructions. I am strugging to assemble using the PDF that you uploaded.

will ABS run the risk of the parts smelling and decaying after multiple uses?

I have problem understanding the instructions. For example:
2x printed bearing holder thin.stl ( 0,25 layer, 0,4 infill )
does that mean does 0,25 means and 0,4 means. Yous said for infil 1=100% what does 0,4 means then 40%? is the "," actually "."?

the 0,4 does mean 40%. "," is used in several countries in place of the "." marking decimals. Similarly, the "0,25 layer" means 0.25mm layer height

Thank you for the explanation.

are there any instructions on how to put this together i have printed most parts but unsure of how it all fits :(

I will upload today a video how to assemble, give me some hours...

thanks so muck thymark i love this shredder already and i havent even put it together :D

wanted to do it fast ( the video manual ) but I found some older videos which I am now editing, but the manual is following soon.

How's that video coming along? Sorry to pressure you but I'm printing the shredder as we speak, and would like to know how it all goes together. Great work by the way!

I will upload a PDF file how to build it, The video is not going good, I have deleted some parts of the video be mistake. So need to make it again. But check it here in 3 or so hours then you find a link in description.

I have to say that instruction pdf is not as helpful as I would have liked. What would really help me out is if you added an exploded view (like this: www.mhhe.com/mayfieldpub/tsw/explode.gif). no pressure though.

Hey peoples, I made a small change on metric shredder. Download and print with the new file bioshredder spacer 2.STL

Just guessing from the looks of it, I think amateur wine makers could use this to masticate the grapes.

Just thought you should know, the food safety of PLA and ABS are really questionable at best.

I will uploade more versions of this. with sieve or smaller blades, with hopper and so.

im soooooo going to make one

This is probably the coolest thing I've seen today! (it's still early, so don't get too excited!) Well done though! As soon as my coffee kicks in and my printer cooperates I have this on the list!

How about polycarbonate instead of PLA? Isn't PC stronger?

isnt abs the best?

yes and no. Yse ABS for the shafts and PLA for the blades and housing.

you can try it, it will works for sure.

Very cool thing. I still have one question: Is it possible to use it for old candles to get little pieces of wax?

yes you can shred candles. If you want a small pieces of wax you can print the blades smaller ( thinner )

ok, thanks a lot

How much PLA did this take in total? VERY COOL!

near 1 kg

Mix this with a cider press and you can have a tasty beverage machine!


There are lot of videos.

Can it handle fresh apples? this would be great for making cider!

yes it can

great design- Thanks.
The part "bioshredder_spacer" has no square cut-out as the INCH-version of the same part has. Is that intentional or a mistake?

thymark - in reply to rol

That was intention, but possibly I will be changing the metric one to square too.

this is cool, it reminds me of the giant one they made to eat couches

This is awesome! How does it do on cardboard box material? News Papers? Is the tolerance between the blades too wide to do paper products?

cardboard is doing great. paper not so much, even big shredders have problem to crash paper.

The nice thing about this design is that it puts all the PLA's strength on the axis where it's needed. The layer bonds are coplanar with the direction of force, so they are protected from delamination. If you print the gears at 100% infill, they will be extremely hard and resistant to wear. (And when they do wear down... big deal, you print more for almost nothing!)

Exact, I am printing the gears with just 60% infill but of course 100% is better and hold more.

Nice. Looks an aweful lot like an MMD Sizer. You got an engineering background?

Haha ROTFL Demolution man

Awesome design... I noticed you had to use a bunch of c-clamps to secure the device while shredding... any thoughts to adding small mounting plates with screw or bolt holes around the perimeter so that it could be secured to a surface?

I am just working on it, adding some hopper and mountings.

yes fucking yes finally

LOL..i had this same thought.

it might be interesting to see what would happen if did some metal casts of the load-baring parts (ie: lost-PLA methods)

I can send you one if you want to test it.

Would you be able to send the .STEP files for this? Or better yet, .ipt or .sldprt if you have either of those. I would like to machine this.

one what? I can't metal cast anything... (I have a reprap though...)

Then I have not understand your comment.

Love this thing!

Really cool project! I want to make one with metal gears/shredders to shred up some of my old printed parts. Any idea where I could find metal gears for that? Thanks!

I am selling shredders for that purpose. http://www.filamaker.euwww.filamaker.eu

zpj - in reply to thymark

Actually if this can shred bone it might be able to shred plastic. Or you can maybe use a coffee mill or blender

Just added imperial version in INCHES.

Even in the US, 3D printer enthusiasts use metric. I wish the rest of our country would follow our example!

If God wanted us to use metric he would have given us ten fingers.

Metric or GTFO!

Me too, it is simple.

Would it be possible to reinforce that printed coupling by threading a couple of M3 screws down it's length, sort of like rebar? Is are the walls thick enough to have room for that?

Hi, how i write you on youtube, it will break more easy if you take more material out and add some screws.

Any chance you could also include the master files for those of us who may want to change some of the dimensions for locally available materials... in the US, finding metric parts can be much more difficult and expensive. Particularly for the steel shaft!

Your local Ace Hardware store should carry a wide range of metric hardware as all the ones I have visited have.

McMaster-Carr and Amazon carry lots of metric parts.

Hi, yes I will be using Grabcad for that. Before the STEP files on Grabcad I will upload here an imperial units shredder for you all.

Terrific, thanks! :) Yes, it's POSSIBLE to find metric hardware and shafting, but it's not nearly as EASY as just going to the local home depot and getting something in an imperial dimension... so having something one could modify or published in imperial would increase the possibility of others being able to make/use this excellent design. :)

Great, thanks! :-) Very much looking forward to it and making one!

It is impressive how strong your 3D printed shredder seems to be. Clever design and cool project! Thanks for sharing the 3D-files. :)

So i am doing some small changes,
1st : the two front gears will be 15mm thick and not 10mm
2nd : one shaft will be 5 mm longer.
In next 24 hours will be a PDF manual online with all the tech data.
I have just done the destruction test, and I need to say it was not easy, video is coming.
Breaking point at 73 Nm torque.
If somebody have print all 4 gears in 10 mm , it will work with them too, or maybe write here if somebody want them.

In two days I will be uploading new video to show what the 3rd version can do, and one what it cant doo. and a PDF and video manual for assembly. For those who want it easy I will be selling the ball bearings, screws and that 2 pipes on http://www.filamaker.euwww.filamaker.eu for Wholesale prices and will be offering printing the plastic parts vie http://3Dhubs.com3Dhubs.com

i like this thing...
Have you considered getting rid of the high speed, sealed ball bearings? The drive shafts are the weakest point and could then be made much larger in diameter.

The thing is so that if you put out the ball bearings and use just plastic on plastic than in cutting process you need to use more torque, so there is no winning on that side. The version 1 and 2 what is in video use ball bearings with 20 mm hole and can hold up to 50Nm torque. This uploaded version number 3 use ball bearings with 30mm hole in it, so I can imagine a veggie which cant be shredded. Of course no wood or bones or not cooked meat. But for that i have some stainless steel shredders.

There will be some added friction with plastic bearing surfaces. You think it will be so much that the strength and torque potential gained from much larger shafts (perhaps >55mm dia) would be negated? I can't see that happening but I'm just an observer from afar..
I'm also assuming there would also be lubrication, like paraffin wax. The bearing surfaces might be widened, further distributing the load.
If plastic-plastic friction would be severe, perhaps it is already evidenced by wear at the gear teeth.
Plastic-on-plastic may not be the only option. There could be a plain metal bearing of some kind, like short lengths of tubing... or oil-impregnated sintered bronze sleeves..
Ultimately, even if the shafts are very strong, some other component becomes the weakest link. A chicken bone will find it ;-)

I dont know what will ABS make but you can make a experiment, take two pieces of PLA and rub them together, in a very short time they become elastic/sticky and that will be the end. Using some sort of lubrication means that you need to add it each time inside. And there where is place for lubrication is place for food remains, so a disassembly will be needed each time to clean it. The next problem with the piece of pipe is that same like i write d before and that is friction. Take a piece of metal and rub it on PLA, you can count possibly on one hand how much is needed to make it elastic/sticky. Maybe ABS will work different.
This is what I know but I am total open for that to see what different versions come out and how the Maker community find some better solutions, this is just a base to start with.

It sounds like PLA is prone to "galliing". It happens with steel against steel, aluminum / aluminum and with certain combinations of materials. I'm unsure of the details, but I've read that some plastic gear sets use alternating resins, like acetal / nylon to prevent galling.
ABS against ABS is very slippery under normal conditions. There's no softening and sliding mechanisms run smooth with a bit of candle wax.
My very first spools of PLA arrive soon. I've never used it. I did not expect it to behave as you describe but I'll be on the lookout for that. Out of curiosity, have you noticed wear or stickiness on the gear teeth?
Version 3 will probably survive some cooked chicken bones... don't get your finger bones in there.

The gears looks very fine,no problem there. But i need to do more shredding. The beauty of hand cranked shredders is the safety, you dont crank further if your fingers go inside. With the stainless steel ones which i produce is good to use gloves, then it dont hurt if you crank a little your finger inside but this one is too much safe. hahahaha. Have fun with the PLA, you will probably not go so soon back to ABS when you try PLA it is different and the plastic smell - there is no plastic smell...

Wow !!!! Congratulations !!! ready to test it ;)

Thank you Julien...

I'm shocked!! I am in awe! Thought can only metal shredder - but not plastic! Thanks for the video!

Thanks, lot of people think that same so i was in need to change it.

hi. cooool stuff. should abs also work? i dont own pla. greetings smuk3d

Abs is better, but to prove it I will be printing the main shaft from ABS and test the breaking point.

What happened with this test?

No time, but I will be doing that later. For this time 70Nm torque with PLA is enough to work just great. ( I dont like the stink of ABS )

Firstly awesome device, just shows how tough PLA could be. I think the idea of introducing bolts into the cutting faces would be a great and really enhance this device and widen its application.
Great work!
Secondly i bet once this project is finished you wont want to eat another chicken again. LOL!
Whats for tea! F@$king Chicken!