Introduction: 3D Printer Part Recycling Grinder

Picture of 3D Printer Part Recycling Grinder

I was getting tired of cutting up failed parts and my research materials by hand. So I decided I wanted a part grinder to compliment my Filastruder. There are a few options for grinding up failed printed parts for turning them back into filament. I didn't want to spend $500+ dollars and also wanted something that was more effective than the other low cost DIY solutions I've seen. I don't have access to a machine shop anymore so I had to make something in my garage with somewhat basic hand tools. The design is based around this tooling restriction. It is smaller than I would have liked and took about 40hours to build.

The design relies on the plates for the spacing of the cutting faces (which are the most important part). The other faces are not as critical, so cutting using templates is accurate enough. The design is intended to be expandable in the future to grind up larger parts, and hopefully switch to a dual blade design.

The manufacturing technique I used is incredibly labor intensive and fairly time consuming. I feel most people who are capable of this kind of work will already own some of the tools I would've preferred to use. But for those of you who are poor and hate themselves just like me I'll go through the steps I took to build this grinder.

Disclaimer: If you choose to build this you will soon understand I am not joking about hating yourself. You will be sweating and bleeding a lot during the massive amount of time you will be working on this. Hand sawing and filing is a very slow and very labor intensive process. You need to be capable of high intensity work for hours at a time. If your not, you will be a lot stronger by the end of this project or you will give up. Don't start this without assessing your own physical and time limitations.

Step 1: Design

Picture of Design

I designed this grinder in Inventor. It is designed to cut similar to scissors with a progressively forward closing cutting faces. The end of the scissor faces has an acute angle to stop material from sliding out and not getting cut. It only has one set of moving blades for simpler manufacturing and construction. The design assumes the material always has the same thickness. So the only features that needs to be added are in a single plane. All the plates are held together with more bolts than are necessary to increase stiffness.

DXF files of the flat parts and Step files of all parts are included in the zip file.

Step 2: Tools and Materials

Picture of Tools and Materials

These are the tools and materials I used to complete this project.

Tools:

  • Vice
  • Drill press
  • Drill index (I used a cheap harbor freight set)
  • Wire wheel
  • Hacksaw (and a few blades)
  • Bastard file
  • Half-round bastard file
  • Triangular bastard file
  • A few needle files
  • Bronze brush to clean files
  • Center punch
  • Sledge hammer
  • Rotary tool (and some abrasive discs)
  • Ratchets and Sockets
  • Some Pliers
  • Crescent wrench
  • Some clamps
  • Printer

I would've preferred to have had a few more tools that would have removed most of the labor from this project. These are a band saw and a belt sander. This project would be relatively easy with both of these.

Materials:

  • 3/16" x 3" x 48" mild steel stock (~$20, I had to buy two 36" bars at $17.95 each)
  • 1/2" x 12" mild steel round stock ($5.77)
  • 1/8" x 1/8" x 3" mild steel stock ($2.21)
  • (2) 1/2" bearing 2-bolt pillow block flange (I bought this one, $21.35 for two shipped)
  • (2) 3/8"-16 x 4" steel bolt
  • (4) 3/8" steel washer
  • (2) 3/8"-16 steel nut
  • (4) 1/4"-20 x 3" steel bolt
  • (8) 1/4" steel washer
  • (4) 1/4"-20 steel nut
  • Paper
  • Glue
  • Rubbing alcohol

The fasteners totaled about $3.00. To build the whole thing the cost of materials was about $52.

Step 3: Print, Cut, and Paste

Picture of Print, Cut, and Paste

Print out 1:1 scale drawings with hole centers marked. Make sure to print enough for a cut out for each part that needs to be made.

Cut out each part along the outer edge of the geometry. Don't cut out the holes because the center lines are needed later.

Now test layouts of the templates to decide which will work best to minimize cutting and/or waste material. Once you have decided how to lay them out clean the surface using a mild solvent such as alcohol. The surface needs to be cleaned thoroughly or the glue won't stick. Completely cover the back of the templates (including the edges) in glue to ensure it does not move during later operations. Place the template onto the clean steel surface and lightly press them flat. DO NOT press or slide the paper to hard or you will introduce dimensional inaccuracies.

Now wait 10-15 minutes for the glue to dry before moving to the next step.

Step 4: Cut and File Parts

Picture of Cut and File Parts

After the glue has dried the parts are cut out with the hacksaw. The goal for cutting is to remove as much material as possible to minimize the amount of filing needed to finish each part. Leaving 1-2mm around the perimeter was the goal for me before I began filing. It takes some practice and a lot of patience to cut close but not too close to the final dimensions. The sawing can also be quite tiring so take a lot of breaks and switch to filing for some time to rest your arm.


Once you have cut in an edge filing is done in two steps. First use the more aggressive half round bastard file to remove material quickly. Then use the flat bastard file to flatten and improve the surface consistency. This will also take some practice to do quickly and accurately. The most important thing to do while filing is maintain the flatness of the surface you are filing. If you file of the edges in an attempt to move faster it is easy to remove too much material and to get the face perpendicular to the plate face again.

Step 5: Drilling Holes and Removing Templates

Picture of Drilling Holes and Removing Templates

I have a small drill press in my garage, but this step can also be done with a hand drill. I chose to use my drill press because I didn't want to wait for batteries to charge constantly. It still chatters a lot and the finish and accuracy was similar to that of a hand drill.

The steps to drill the holes are:

  1. First use a center punch to start each hole.

  2. Drill a smaller pilot hole, I used 1/8".

  3. Using a file, clean up the burs on the back of the part after drilling.

  4. Drill the larger hole.

  5. Again, use a file to clean up the burs.

To make drilling easier use cutting fluid. A heavy engine oil works well for this. I didn't have a heavy weight and just settled for 5W-30. Use a cheap paint brush and a tin can to avoid making a mess.

After all the features have been added to a part, the template can be removed. This was done by grinding it off using a wire wheel. Do not remove the template from the cutting blades yet, they need to have key ways added.

Step 6: Cutting Keyways and Hex Flats

Picture of Cutting Keyways and Hex Flats

The keyway in the shaft is made using a rotary tool and a small abrasive wheel. Slowly work the slot down and check its dimensions against the key you already cut. I rounded off the corners of the key that are in the shaft to make fitting easier.

The keyways on the blades are made by filing out the bulk of the material using a more aggressive triangular file. Then finishing them up with some needle files. Test fitting along the way until it fits perfectly over the key. Each blade needs to be at a different angle, so make sure to put the keyways at 90 degrees to eachother.

To make the hex drive on the end of the shaft you need to add flats that are 7/16" apart and 120 degrees separated. I don't have a special trick for this. File one flat. Move to the other side and file a flat parallel to the first. Measure the distance between the flats and remove material evenly from each side. Now file the other ones. Use a deep socket to determine how close you are. You should be able to see if you are parallel to the flats in the socket. Keep filing the parts the socket runs into until it fits.

Step 7: Fitting and Assembly

Picture of Fitting and Assembly

Now that the parts are all cut to shape they can be final fitted together. This is not an exact manufacturing process and the bolt holes are only drilled to standard fit, so it is likely that there are going to be holes that don't align properly. To compensate for this some of the misaligned holes are drilled out to the next largest size.

Steps:

  1. Stack the plates in the order they will be when assembled.
  2. Attempt to thread one of the bolts through.
  3. Mark where the bolt stopped with your finger.
  4. Hold the bolt next the outer faces of the plates to see which plate it stopped at.
  5. Drill out the hole to the next largest size you have.
  6. Repeat with each bolt until everything fits.

I don't have any pictures of how to put the blades and shaft in. It isn't too difficult though. I did it by leaving the 3/8" bolts in and spinning the plates out of the way. The sliding in the shaft into place, followed by the blades and spacers. Spin the outer plates back in and mesh them with the blades. (I need to add some pictures of this, I'm just happy with it being assembled right now)

Step 8: Testing and Final Thoughts

Picture of Testing and Final Thoughts

After some testing the grinder showed it is capable of cutting up some printed parts. I able to cut fairly thick (~1/4") solid printed PLA walls. I didn't test anything but PLA because I don't have anything else. But it should cut most of the common printed plastics. It may have trouble with polycarbonate.

The downside to this design is the maximum part size that it can bite into is small. The blades separate to about a 0.5" square opening. Which only allows very small parts or some pre-cutting to get the blades to bite. This was sort of intentional because the Filastruder works much better with small pellets. And to get smaller pellets the opening size was reduced. If I were to redesign it I would make the blades longer to allow larger pieces to be cut without the need to pre-cut.

Now I need to figure out the best way to mount it so something. I didn't have a plan for mounting when I started this, but it shouldn't be too difficult to add more holes for a good mounting solution.

If someone wants me to add something I'd be more than happy to. I am fairly new to righting the things down that I do, so any suggestions would be helpful.

EDIT: Added a video and photo of grinding PETE. While doing this I found a flaw in the design that I'll discuss in the next step I'm adding.

Step 9: Future Work

While grinding PETE some of it became wedged in a few places and required the grinder to be disassembled. One of the blades spins flat against the outer wall and plastic wedged into the gap. It could get into this gap because I couldn't tighten the plates as much as was needed. This was caused by the plates all being the same thickness and some of them collided when tightened. I came up with two things to fix this problem:

  1. Lapping the faces using grinding compound. I did this and it worked very well at reducing binding with minimal surface pitting.
  2. Adding another set of stationary cutting blades to space all of the blades off the outer walls. I think I'm going to do this and it will remove the binding issues.

Another problem that became apparent after testing with the flat PETE was the material getting hung up on stationary blades. This explains why almost all commercial material grinders use counter-rotating blades. I might iterate on this design to improve the grinder's ability to handle strange shaped and larger parts. For now it fulfills my needs of making small parts into small enough bits for a Filastruder.

Comments

mrblank5 (author)2017-06-10

this is great

Jehu_McSpooran (author)2017-03-18

Have you tried this grinder on something hard like a broken iphone screen?

Pa Lemur (author)Jehu_McSpooran2017-03-21

Nope. But I guarantee it would not be successful at cutting through an iphone screen.

The process that makes the glass on Iphones makes it very hard and fairly tough. It might crack and explode, but it will probably just deform the steel in the grinder. Its only 1018 mild steel, and even hardened steels would have a had time with phone glass. If it were just the screen without the glass it might work. But again I wouldn't recommend it.

Jehu_McSpooran (author)Pa Lemur2017-03-21

Dang. I get a lot of iphone and ipad screens and glass from repairs and need to shred them. Usually I can crush an ipad screen with my hands or use a pair of aviation shears for the plastic backed ones. I might still make one and see if it works anyway.

Tho1294 (author)2017-03-14

i'm sorry but i can not print the dxf file on paper with scale 1:1

can you send me the image in an other format, thanks you.

Pa Lemur (author)Tho12942017-03-21

I added pdf's of the templates I used to make the grinder. All the hole centers are marked already.

When you print them double check you have the size set to 100%. If you don't it may adjust to something like 98% to fit the 8.5x11" paper.

Pa Lemur (author)Tho12942017-03-21

I don't have pdf's right now. But I'll convert and upload them when I get home so you can print them.

Shouldn't libre office be able to read a dxf?

ed-romes (author)2016-09-22

That's a good start so when you decide to go dual blades use two matching gears placed tooth to valley as one turns left the other turns right and you have your counter turning blades and a better gripping power !! It has been suggested grinding up soda bottles to make the filling but then you will need a way to melt and extrude the plastic !! Good luck

pskvorc (author)2016-08-27

Nice instructable. Provides excellent conceptual design for further development in size and capabilities.


While the following question may appear off-topic, it isn't so far off that I think it is out of place.
Can "milk carton" plastic be used for filament material in a 3-D printer?
I have long wanted to use plastic milk cartons for 'something else' AND simply "chew them up" so they don't occupy so much space. If that plastic could be used for 3-D printer filament, I would get serious about making something like this device to chew up milk cartons.

Pa Lemur (author)pskvorc2016-09-05

I made a top level comment about this just now. But I'll answer to make sure you see this.

HDPE is an ultra low surface energy polymer. It only has about 50% more surface energy than PTFE (teflon). So its not sticky at all, including with itself. The only way that HDPE bonds to itself is when it is completely melted, it has not cold-welding ability. So it does not work as an FDM plastic. It also doesn't really have a glass transition temperature, or its really close to the melting temperature. Which means you can hold it above Tg to improve interlayer adhesion because it is incredibly close to the melting point and you might melt the part.

I worked around another research group that focused on printing HDPE, and they had very limited success. The prints would usually fail after 3-4 layers from either falling off the print bed, or just not sticking the previous layers. They never had a successful print in the years they worked on it.

I think modifying the surface energy by adding another polymer would help. But I'm not familiar with what polymer blend well or what can be done to increase surface energy. Doing this would kind of defeat the purpose of having a readily available recyclable material though.

*Surface energy is how much extra energy the outer face of a material has. High surface energy means it really wants to make the face get smaller or go away, so its 'stickier'.

pskvorc (author)Pa Lemur2016-09-06

Great info! Thanks.

Paul

Flegeance (author)2016-08-27

I tried a food grinded and a food processor they did not work for hdpe milk jugs

Pa Lemur (author)Flegeance2016-09-05

That's unfortunate, a lot of people have been suggesting using a food processer. This grinder works great for HDPE I just got around to testing it.

Pa Lemur made it! (author)2016-09-05

Finally got my car and garage put back together so I could do a followup on this.

Lets start with the things I changed/added to it after this Instructable:

1. I added another stationary blade to each side. This spaced all of the moving blades of the outer plates and reduced binding.

2. I lapped the plates using some valve grinding compound. Which was a little aggressive, but still improved clearance.

3. Made a base that can be attached my workbench with space for a catch basket. This is shown in one of images I attached.

How it performed:

1. It was able to cut EVA and HDPE easily.

2. PLA was also fairly easy, but sometimes a drill was not enough and I had to use a ratchet. I didn't get a chance to test ABS, but it would be very similar to PLA. The major difference between the two is impact strength and thermal properties.

3. I was able to cut PETE, but it is incredibly difficult. I think the cutting surfaces weren't tight enough so it would slip into gaps and bind. Testing this plastic broke one of the blade spacers in half, by binding against it and bending it out the bottom.

Now for things I would do differently:

1. Use precision ground plates, or grind them flat yourself. Cold rolled steel is nowhere near flat and caused a lot of clearance issues. Which were mostly sorted out by lapping, but not completely.

2. Gear by 2-3:1 using a chain drive. It would be much easier to use if the torque was multiplied a little.

3. Find a cheapy 1/4-1/3HP electric motor to run it continuously. I only have a battery powered drill which get irritating when I can kill it in ~20 minutes.

Side notes for those interested:

1. HDPE is not a printable plastic using FDM. Many have tried and many have lied about success. HDPE is very low surface energy plastic, so it hates bonding even to itself. The only time it adheres to itself is when it is all melted, it has no cold-welding ability. So it is theoretically possible to print if the part is kept a few degrees below melting, which causes the interlayer portion to melt when the next layer is laid. I've worked around a research group that focused on FDM of HDPE, and they haven't solved it in a few years of trying (but they are trying to run it through a makerbot instead of a good non-proprietary research printer).

2. The two materials in the attached photo labelled R1 and R2 are the materials I developed for my Masters thesis. They are intended to be made into filament, printed, solvent debound, thermal debound, and sintered. I had mild success at producing metal components and still work on it sometimes outside of work. These materials are what I intended this grinder to be used for. They are much weaker than virgin polymers because of the 55vol% powder content reducing the effective cross-sectional area. So the grinder cuts them up easily, instead of me sitting with a pair of wire cutters like I did for the other 100 samples I tested (ggrrrrr).

3. I am going to make an attempt at making a small batch polymer melt blender for samples of about 40mL. I'll probably put up an Instructable for it also, but it will be a while.

Pa Lemur (author)Pa Lemur2016-09-05

.....And all the formatting didn't work as intended. Each header has 3 points below it, sorry for the confusion.

Waste Of Space (author)2016-08-27

Seeing as you finish up with a square drive end on the main shaft, did you not thing to use square shafting rather than round and then use square centre bearings.

Pa Lemur (author)Waste Of Space2016-09-05

I tried to find some square center bearings that were large and mounted in a flange, but came up short. It would have also added a lot of work when making the holes in the blades. So I stuck with a circular shaft and dealt with a key and making a hex drive.

belsey (author)2016-08-18

I can see what you mean in your intro, when you cautioned would-be makers about the stamina needed to complete this project... I admire the super human patience your grinder required! I've been thinking of something like this, a bit bigger, for food scraps to feed to worms or compost piles. Either to be attached to a mixer or with a hand crank, but instead of steel, those blades would be made out of glass or ceramic which could just be thrown in the dishwasher every so often... However I think that project will have to remain a dream for the foreseeable future.

BambiB (author)belsey2016-08-28

I don't grind anything for my compost pile. Just toss it in and throw a little mulch on top. The worms are very happy.

belsey (author)BambiB2016-09-05

True, that works, but it does go faster when everything is chopped up...

BambiB (author)belsey2016-09-05

True. For ultimate breakdown speed, put it in a blender with water and make a slush out of it.

Personally, I have a couple of 50-gallon planters I just toss the stuff in and periodically throw some wood chips on top. In a matter of months, it's all top grade potting soil. Guess I have better things to do with my time than spend it pushing food scraps into a tiny shredder.

DarrenB57 (author)belsey2016-08-27

A meat/vegetable grinder would probably be more suited for your purpose. imho. You can buy one new for less than the raw material for this project.

belsey (author)DarrenB572016-09-05

I have a meat grinder, but it's a hassle to set up and clean... that's why I was thinking it would be nice to have something like a fairly simple, like a rough grinder with a hand crank, set above a bucket, which could be hosed down every once in a while. But it's not really worth the expense and effort to make, especially since, and BambiB said, the worms don't complain about the extra chewing work.

Pa Lemur (author)belsey2016-08-18

I would caution against using ceramic as a cutting material. To cut like this grinder you need a material that has good compressive and tensile properties. Ceramics suck in tension. Also the faces would need to aligned perfectly for ceramics because of the materials low flexibility and elongation at break. So they wouldn't bend enough and the cutting faces would easily fracture.

If you want to make something food safe and/or washable I would recommend a hardenable stainless steel. It will be harder to work with, but will produce a very functional grinder.

Likeswater (author)Pa Lemur2016-08-27

Stainless steel comes in several varieties. "316" is very corrosion-resistant, but "304" is easier to machine. It may be more suitable for at least part of the food grinder. It's not like you're going to leave it outside or on the beach. :) Wicki the two. If you have access to a water cutter it may not matter.

belsey (author)Pa Lemur2016-08-19

Yes, that makes sense... but then I'd have to hate myself that much more to work with stainless rather than a piece of good old scrap steel! I guess there are no shortcuts (besides just buying a food grinder, but where's the fun in that?).

HGWenviro (author)belsey2016-08-18

While you're dreaming, I'd recommend stainless steel. Still washable but super tough, not brittle, teeth/plates could be sharpened periodically with a grinder. Maybe power it with a pulley to an old stationary bicycle?

teddlesruss (author)2016-08-19

Just wondering if the blades could be short lengths of flat with just an angled cut at each end and a small recurve near the cutting end to trap the material being ground sort of like:

/````````````/ (centre hole &
/,,/````\,,,,,,,\ key etc here)
(only one end shown, rotate flat
stock 180deg and repeat)

That way you can just cut each end exactly the same, even use perhaps an angle grinder and a template to get to the approximate shape and finish with files and lapping.

Keep the fixed cutters shape pretty much as it is, and the suggestion of mesh to screen the shreddings is a great one too as it would save a lot of material going through multiple times when it's already fine enough.

I think the cam shapes of the dual cutter grinders are for shedding of the input material from the underside as far as I've been able to work out and a single cutter grinder probably doesn't need that - and it would save a lot of filing if it was possible.

Pa Lemur (author)teddlesruss2016-08-24

I'll respond to all your comments here to keep it simple. I think I understand what you mean about the blade shape. It is probably possible to make the blades out of a small piece of rectangular stock with a relief cut into the outer edge. I chose to make large circular blades for a few reasons:

1. I wanted a small cutting face to reduce required cutting force. The biggest feature that can be captured by the blades is a 0.5" cube.

2. By having the cutting gap only open just before the blade cuts material doesn't fall through the grinder as easily and there is a higher chance of smaller pieces being cut (this is just a guess).

3. The extra material gave me space to have bigger keys and avoid failure.

4. The most important reason to have the larger blades is to keep them in contact with the stationary blades for their whole rotation. The whole thing is held tightly together and the constant blade-blade contact keeps everything aligned. Without this the rotating blades would easily fall out of alignment and cause it not too work. The overlap might be achievable with a different blade shape, but I stuck with what I have seen in other grinders.

The mesh screen has been suggested a few times. I chose the blade thickness to be the size i needed the pieces cut into. Larger pieces can get through by lining up with the blades, so I was planning on feeding the material through a few times to reach the needed consistency. I might test the screen later if I find this method annoying or ineffective.

Having the grinder cut on the upstroke might work (in combo with the screen). The downside to this would be if 2 blades engage simultaneously. If its 2 thick pieces, you'll need over ~100ft*lbs to cut through it. This is where another part of the design comes from. I only wanted 1 blade to be cutting at a time. Which is why they are all 90° to each other. It can still be difficult to cut through large solid pieces with only 1 blade, so I would suggest not doing multiple blades that can engage simultaneously. Unless you are going to add reduction to the drive.

I hope this gave some insight into some of the design decisions I made. If you have anymore ideas/questions feel free to ask!

teddlesruss (author)Pa Lemur2016-09-04

Ah okay I'm sort of thinking ahead to when I (hopefully!) get a start in 3d printing myself, I know I'll be getting a few misprints to recycle. %) I've been pondering how to do that, then saw filament extruders, which led to shredders/cutters such as this one, and I was hoping to come up with a shredder design that was extremely simple to manufacture. If all my ducks line up in a row and I get as far as recycling old prints and plastics, I'll definitely make those design decisions part of my design process. TY by the way for your Instructable because it's definitely given me a good starting point.

teddlesruss (author)teddlesruss2016-08-19

Just one more thought - make the LH fixed cutters a 180deg rotation of the RH side then you get two cuts per rotating cutter. (It shouldn't matter if material gets cut on the upwards side and falls back down with the next down rotation, should just make for better throughput, yes?)

teddlesruss (author)teddlesruss2016-08-19

Should mention I have respiratory issues so sustained efforts like filing are problematic hence I always look for the easier ways to do things. And I want to do 3D printing and recycling/reclaiming so this kind of 'ible is very interesting to me.

_soapy_ (author)2016-08-20

I've often told people that with a set of rules and some metal you can make nearly anything, it just takes time! And here, you've proved that.

I've been planning to cut one of these for ages, I'll have to pull my finger out. I've got a CNC plasma cutter, so I have no excuse!
Now I can use your design to vet my own I have literally no excuse!

JohnH508 (author)_soapy_2016-08-27

since you have a cnc plasma cutter, I'm sure you won't mind sending the author a few more plates so his dream of a larger grinder can come true. He took the time to teach after all.

_soapy_ (author)_soapy_2016-08-20

Argh. This isn't some procedural generation thing! Files, not rules!

oldmanbreadboard (author)2016-08-27

That should have read "a hopper of some kind." Apparently, I am not using my brain or my eyes, or both.

oldmanbreadboard (author)2016-08-27

I can see you got tired, calling the files such names. Questioning the marital status of their parents. Tired old joke, sorry. Great instructable. You show how people can do things with few other tools if they use their best tool, their brain. In my childhood I spent quite a few hours in a blacksmith's workshop. It was amazing what he could do with just heat, lots of muscle, a hammer, and his brain full of knowledge.

If you live near a junk yard, an old washing machine motor, geared down with appropriate pulleys and a drive belt would make your grinder rip through plastics. The motors are incredibly strong when geared to slow the speed down. It is probably already in the works, but I also suggest a hopper of some if only as a safety barrier. If your finger gets snagged on a ragged piece of plastic, in it goes. My next door neighbor cut off two fingers trying to pull a ragged piece of plastic from underneath a running lawnmower.

johnh631 (author)2016-08-27

A good way to cut and shape ,is to use an angle grinder with 1mm cuttind discs,ceramic ones are the best,and the flap discs which have different grades of grid for grinding to polishing .

A centre lathe and mill are'nt too hard to make,pillow block bearings,tube heavy enough to have tread for a big chuck,the bed can be square sectin hollow stock havy but not much is needed,most hobyist types have 600mm beds,threaded bar,sliding tool post holders and bits can also be made useing a cutting wheel on a grinder,and if done it can make parts(with care) to upgrade its self.tools re-make tools.

what kit ,from remelt to 3D printer and sofware do you have,i have been interested in it but never looked to hard.

your grinder could be made larger ,fitted with a geared down pulley set to chip garden wast,branches etc.

MarkinDetroit (author)2016-08-23

Great job! Just like it used to be done, not everything has to be 3D printed, CNC or laser cut.

Pa Lemur (author)MarkinDetroit2016-08-24

Thanks! I have to admit, this project did convince me to buy a belt sander. Filing is quite terrible when you need to remove any significant amount of material.

TerryA33 (author)2016-08-22

Great work mate time to get the hands busy

mosix (author)2016-08-22

amazing!!

RumBot (author)2016-08-18

I like it. Do you have the DXFs for the flat parts?

Pa Lemur (author)RumBot2016-08-18

Thanks, I added dxf's to the design step.

MarkC327 (author)2016-08-18

Could your use this on HDPE? I have a collection of milk bottles that need to be shredded? Like the concept and the Instructable is very well documented. I think I may have to make one of these. Thank you.

Pa Lemur (author)MarkC3272016-08-18

HDPE is a very soft plastic, so it would easily shred it. It was trash day today so I don't have any HDPE that I can use to test it. In a few days I'll throw some HDPE into it to verify.

WilliamC181 (author)2016-08-18

Adding angle-iron mounting flanges bolted into the sandwich and using screw clamps or bolts would better stabilize the machine so you could focus on grinding.

Pa Lemur (author)WilliamC1812016-08-18

That's part of the plan. I wanted to make it independent of the mounting solution so I can modify it without having to also modify the mounts. Quick-grips work for now, but your right they aren't enough to keep if from moving during use.

BuildAnything (author)2016-08-18

Nice cutter. I can offer you machine shop services if you need them in the future. I am in the USA. Just let me know. I somewhat retired from my own shop so have plenty of material and machines laying around. Would be happy to contribute to projects.

Tvixen (author)2016-08-18

Great work mate .....

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Bio: I have an MS in Mechanical Engineering from Oregon State University. But I got a job as a software developer so I feel the need ... More »
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