Using a Bowden cable on the reprap prusa cold end


This post is to document something that I thought was fairly standard , but after talking to a few people I discovered it isn’t. Some people (I’m looking at you jkeegan) even thought it wasn’t possible. I have been using thin hdpe tubing for some time to enable my extruder to unspool filament by itself.

The benefit of the tubing is that it removes the effect that pulling has on the carriage positioning. The cable has a small washer between it and the extruder, and butts against a 3mm hole I drilled in the handle of my extension cord reel. That arrangement allows all of the pulling force of the extruder to be focused on spinning the reel as opposed to lifting the z axis off of the bed.

I used this setup most of the time I was working with the cupcake, and just set it up again for my gen 6 prusa.

Downsides: it does probably require more torque. You also need to be smart about using as little hdpe tubing as possible, as it seems like the friction scales non linearly. You also want the line to be as straight as possible between the spool and the extruder. My setup in the video is about as long as you want it to be. I could easily see using 10cm of tubing and simply setting the spool on the top of my prusa. That ought to have very little drag compared to the current rig. PTFE tubing might be worth looking into as well

I may end up building a bracket to allow mounting the reel on top. That seems like it would be a pretty manageable setup.

Just because I know someone will end up asking where I got that reel from: home depot is the answer, but you can also find it at amazon here

The hdpe tubing I believe is used for cold water lines such as ice makers. I picked it up at home depot as well.

3d printed metal bike lugs!

This is the convergence of all of my interests: bikes, 3d printing and shiny things!

I saw it featured over on Hackaday, but it’s just too good to not repost.

This is a bike built up from carbon fiber rods and laser-sintered metallic lugs. There is a whole lot of awesome in that sentence. I’m surprised that it looks like it somehow prints with support and requires a ton of cleanup, but it is 105% awesome regardless.

Here’s the vid.

VRZ 1. a tack bike frame with 3d printed lugs from Ralf Holleis on Vimeo.

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Nail Files – Reprap tools list

I’ll admit it. I went into cvs and walked out with two packages of nail files and a snapple. What of it?

Despite the weird looks from cashiers, nail files are absolutely _perfect_ for cleaning up prints. You can do fine sanding, clean up seams, or round off those sharp corners from a kapton heated bed. The best thing? It’s less than $2 for a pack of ten. Pick them up with your groceries, or use them as a cart stuffer on amazon so you can get up over the $25 minimum for free shipping.

Wow, most of them on amazon are a bad deal, but you can pick up a gross of them for $9 with free shipping!

reprap tools shopping list – Irwin self-adjusting wire strippers.

reprap tools - self adjusting wire stripper
I’m really excited about some tools I have found recently, so I figured I would start a recurring series of posts about them. There will be some simple cheap ones, and some expensive ones. Hopefully they are useful to someone else!

If you want a sneak peek, then you can check out the amazon list I made.

Here is the first review: keep your eyes peeled for more!

Irwin Industrial self-adjusting wire strippers.

You can certainly get good results with a traditional wire stripper, but this is faster and can be done one-handed and in awkward situations. Once I unwrapped it, I ran around the house looking for wires to strip (not always a good idea) and happily found a few solid core and stranded wires. This stripper was like magic. You can set a depth stop or you can eyeball how much wire you would like to strip. It has a simple cutter (probably better for solid core) as well as a few crimpers built into the handle. The plastic covers on the steel handle really give the tool a solid feel in your hand.

The best thing is that this is roughly the same price as a good quality pair of traditional wire strippers. I got mine from amazon for about $16, and you may be able to do better off by shopping around. If you do see them in-store, pick them up and feel them. It is a solidly built tool.

Why?

I think the usefulness of this is obvious, but it will assist you in doing all of the wiring for your reprap. Your motors, endstops, power cables, heated bed, extruders and thermistors all need to be stripped / cabled and attached to your electronics. It is super useful beyond the reprap as well. Automotive, audio video, and home electrical all are made easier with this.

One last note: If you do end up getting this from amazon, then definitely browse through the rest of my reprap tools list. You might get that cart-filler to become eligible for free shipping, or you might find something that will knock your socks off.

Why Kapton rocks

I have never been a big believer in using kapton tape as a heated bed surface. I never saw much benefit, and whenever I used it I ended up cutting it or scratching it very easily trying to get the parts off.

When I use blue tape I generally heat the bed up to 90-110. I print the part, and then as soon as it is finished I pry it off with a chisel. This ends up with a lot of damage to the blue tape, but it is pretty cheap to replace, and easy to pull up a single strip at a time.

The turning point for me came when I tried to do the same procedure on my kapton bed. The adhesive simply wasn’t strong enough to keep the tape on the bed and it ended up bending and lifting and tearing. I knew that was not supposed to happen, so I stopped and looked at what I was doing, and realized that the point of kapton is that it loses grip as it cools. That means you need to cool the bed in order to get the part off! I feel silly admitting that it took me so long to see I was being impatient.

Now that I have that figured out I print, cool, and then generally I can snap the piece off fairly easily. I wipe the surface down with nail polish remover on a cotton ball before every print. Sometimes I still need to get the chisel out and put the tip under one edge of the piece, but once one corner pops free, the whole piece is free. No more prying from every corner.

My one complaint is that I only have 1″ wide kapton. 2 or 3″ would be much nicer. I’ve also been meaning to get some PET tape with a high temp adhesive to test against.

Ways i have messed up reprap prints

This is a running list of all of the ways I have broken a print. This doesn’t have anything to do with my machine calibration. That’s a whole other post in itself!

-I got a snag in the filament feed which stopped extrusion.
-My heated bed shorted out on a bulldog clip.
-With the print not centered on bed it hit the endstop a few hours into the print.
-I have tried to print from stls not positioned at z-0.
-My cooling fan for extruder unplugged midway through and then the extruder jammed up.
-With the firmware z speed not limited properly, i have lost steps due to rapid z moves.
-Filament strips and stops extruding.
-I have run out of filament.
-On a multi part bed, one part became loose and then slowly caused blobs to build up on other parts. It eventually knocked most of the other parts loose.
-Before I had my heated bed fully figured out I had a LOT of parts curl and then come loose from the bed midway through a print.
-I didn’t check the scale of one stl I downloaded from thingiverse and it ended up being about 4mmx4mm.

Got any more to add? post them below in the comments! I’m sure I’ll keep discovering more.