Let's Make Robots!

Kossel Build

03/11/14

I'll fix pics when I get home.  Was trying image hosting to relieve Juliette.  Didn't work.

Well, post came.

I finall have "all" the pieces for my 3D printer.  I sourced a few of the major parts and ended up buying the rest from www.builda3dprinter.eu.  And today that order came in.  So, let me review.

 

The problems start off right away.  It appears that builda3dprinter (here after, B3DP) provided me with a MK V end effector and I bought MK IV J-Head that was advertised as an MKV.  Point to you eBay.  So, I've got to figure out how I can salvage the situation with the least amount out of pocket.

Damnit, can't fit it in the hole.

3/11/14

Ok.  So, I broke down and ordered a geared stepper-motor for the extruder.  I was a little under budget and felt it was a better choice rather than struggling trying to get the current motor I had to work with what B3DP sent.

Here is the BOM thus far

Regarding the J-head, I'm still undecided what to do.  Hoff and Ossipee have given me some good ideas, but no solution seems "perfect."  I'd either have to request new printed parts or buy a different J-head.  I think I'm going to play around with ordering another pneufit plug that'll fit my J-head, then, drill out the center of my end effector.  This should make everything work.  But it'll put replacing my my effector at the top of the do list.  If anyone has suggestions, I'm open to ideas.

I'm not sure how I feel about B3DP yet.  I'd like to say that I like the kit, but they weren't real upfront with exactly what pieces were being shipped.  For instance, I now realize there are endless variations of J-Heads and end-effectors.  But when I first started looking at their products I looked for details of what's in their "kits" to no avail.  So, I assumed, "Well, they must just ship standard pieces and that is why it doesn't state exactly."  Wrong.  I'm not even sure there is a "standard"?  Oss, Hoff, TinHead, Jinx, someone correct me if I'm off base.

I'm researching the names of all the pieces I've been sent and I'll catalog them for the next guy before I'm done. 

But the one that got me was the extruder--the extruder from build3dprinter.eu is built for a stepper-motor with a 8mm shaft.  Actually, the parts are from the original design which called for a geared-stepper motor and a spur-gear with 22 teeth, with a 8mm diameter shaft.  The "common" NEMA17 has a 5mm diameter shaft.   I've seen a few extruder designs that use a regular stepper and a 5mm diamter spur-gear, but that is not what comes with the B3DP kit.

The other "gotcha" was the lack of information on the end effector.  I'm still searching for the name of the effector that comes with the B3DP kit.  I'll update when I have exact information.

3/13/14:

Started putting the pieces together:

Jig Setup & Traxxas Ends

The manual states I should tap and drill the Traxxas ends and the carbon rods.  I bought a metric tap and die set from Harbor Freight, but when I examined the pieces I received from B3DP I noticed the headless bolts were too small to catch the inside of the carbon rods.  Also, I wasn't sure how to use my tap and die; this devolved into the realization I had the wrong thread sizes.  Makes sense, I was using a US tool and parts from everywhere else but the US.

Well, I lucked out.  According to the B3DP manual you don't need to tap anything.  Just screw the headless bolts into the Traxxas ends, then use slow-setting Epoxy to glue the ends into the carbon rods.  Screwing the headless bolts in the Traxxas ends went great.  Um, gluing was another matter.

Not much to say about setting up the jigs for the carbon rods and Traxxas ends.  Just follow the instructions on pages 3-6 of the Blomker guide.  I used a square and a speed-square, the square to align the rails flush, then the speed-square to align the machine screws at one end.  I've read that the arms can deviate from the 180mm outlined by the guide, but they should all be the same length.  My goal was to identify rods longer than the others and file them down a little. 

 

Gluing Traxxas Ends (and a big F'up)

I bought some cheap slow setting epoxy from Harbor Freight.  I mixed it with a chop-stick (a favorite tool) and began to apply it to the Traxxas ends.  Then, I f'ed up. 

I dropped one of the Traxxas ends into the epoxy.  I tried cleaning it in alcohol and acetone.  But there was still some residue that prevented the ball-joint from moving as freely as I wanted.  Sigh.  I went ahead and ordered more Traxxas heads, so, if anyone needs an extra because they dropped it in epoxy, just let me know.  I'll have eleven extras.

One more note, be sure to wipe excess epoxy from the Traxxas end and rod joint.  I was worried about an improper seal between the two and left the globulated extra.  It leaked into the crevices of the 1515 Beam.  Of course, I thought, "I'll just make sure to turn the yucky part inside when I put the pieces together so it's not noticeable."  Well, the nuts bolting it to the plastic pieces are also on the inside.  In short, it caused a lot of problems.  I'd wipe them off before setting them in place on the jigs if I could do it over.

 

Bottom Triforce Assembly

 

I didn't like the name "Bottom Assembly" so, I renamed this step: Triforce assembly.  For the most part, smooth sailing.  Just make sure you barely screw the nuts on.  If they are too tight you can't get the plastic lips to close around them.

NOTE: The plastic pieces have an "up" side and a "down" side.  Refer to the next section for explanation.

The little circular tabs on the bottom Triforce assembly are for printing purposes and may be removed with a sharp knife and steady hand.  In the absence of a steady hand, a lot of blood and an emergency-room visit will suffice.

Also, don't screw any bolts down too tight until you press all pieces together.  I had reviewed the section in the Blokmer guide, pages 28-32, but I realized the need for give from all sides was greater than expected.  You'll notice towards the end of my video I was struggling not to look like a complete idiot trying to push all the pieces together.

3/15/2014:

Adding the shafts to the bottom Triforce was a little tricky.  First, it should be noted, there is an "up" and a "down" to the Triforce pieces:

 

Of course, I didn't realize this until I already had bolted the bottom Triforce down and started trying to shove the first shaft in place.  I quickly pulled the bottom apart, flipped the odd piece I had so all my plastic pieces had the two-prong guide at the "top."

Now, I've seen and read a dozen different ways to press the 1515 into printed plastic.  I tried my heat gun, but was really wary I'd deform a piece and I would have to wait 5 weeks to get another from B3DP.  I ended up using the following tools:

To press the rods in, I started the rod into the first nut.  Then, when it started to get tight, I put a little bike oil (the green bottle) around the edges, flipped over the assembly, and put it in my lap.  I pressed the end of the rod I had started against the tile floor and beat on the receiving end (assembly) with a balled fist.

Well, this worked great.  A little too great.  The rod slipped past being flush.  This is where the screwdriver and hammer came in.  I simply left the assembly in my lap, but raised the rod off the floor.  Then with the tip of the screw driver against the end of the 1515 rod, I tapped against the screwdriver with the hammer.  This allowed me to align the 1515 rod flush with the bottom plastic of the Triforce assembly.

3/16/14:

Carriage Assembly

 

Carriages assembly went pretty well.  I had to tap the holes for most of the bolts on the carriages, since there was printer-webs still in the holes.  But after the holes were clear it was pretty straight forward.  I followed the guide from B3DP.  

A few notes:  If you haven't sorted your bolts, might be a good idea to do it now.  If all your bolts are lumped together digital-calipers are a godsend.  You just measure from directly under the head, to the end of the shaft. 

There are three nuts that will need to be pressed into the plastic of the carriage assembly.  I used a heat gut to soften the plastic of the intended holes, then pressed the nut slightly in place, and end by placing the tip of a flat-head screwdriver over the nut and hitting it with a hammer.  This method worked well.  One exception, there are three nuts, but two of the bolts are 25mm and one is 16mm.  The 16mm bolt is not long enough to catch the threads of the nut unless you tap it deep into its hole.  I hope this picture makes it clear:

 

3/21/14

Motors and Endstops

 

Bottom endstops and motors went smooth.  

Only bits of advice on the motors are: Make sure you tap the holes in the plastic to prevent any plastic shards from misaligning your bolt as you try to screw it into the motor hole.  

 

Also, don't tighten any bolts down until all your bolts are started correctly.  I found they often were misthreading, which I attributed to such a harsh angle.  

 

Oh, one more bit, purchase a long 2mm Balled Allen Key for this process.  As you may notice at the beginning of my video I tried with a short, balless Allen key to no avail.

 

4/2/14:

I've been waiting on another Ramps 1.4 board to come from China, since the one I bought was no good.  So, I figure I better catch up on documenting.  

Carriage Arms and Effector Assembly

 

Two notes

1. The carriage assembly is pretty straight forward, just make sure you follow the instructions and don't get in a hurry.  But the effector I had a little difficulty putting together.  Mainly, the round part of the J-head wouldn't fit into the hole.   I simply use a heat-gun to warm the plastic enough to provide it with some give and shoved the J-head into place.

 

 

Top Triforce, PSU, Ramps 1.4, and Attaching Effector


Ok.  Working on putting things together I started getting a little peeved at B3DP.  First, there are three parts they do not include in "The Rest" kit, but also don't mention in the "What's not included" section.  They are the spring, safety pin, and Allen-key for the auto-level.  Also, the Kossel build for the auto-level includes a switch that looks like this,

The auto-level bit is a little tricky to put together.  You will need to source two parts are you own, that is, the B3DP is not going to provide them: The safety pin, Allen-key, and springs.  I ordered an Allen-key off eBay.  The safety pin I "borrowed" from my wife's things.  And the springs I pulled from some old pins.  After much fiddling I was able to piece something together.   

 

 

 

 

 

 

 

In fact, this above image is a direct image link to the switch listed in "The Rest" section on B3DP.  Buuut I was given four switches that look like this:

This should not have bothered me too much, since the three for the end-stops worked like they should.  But when it came to the auto-level, the Allen-key crook was supposed to catch the metal arm of the above shown switches, guiding it down to the button.  Well, I found that when the Allen-key came to sit on the button, instead of pressing it down it would slide either to the left or right.  And it didn't seem to matter how much tweaking I did, I couldn't get it to sit right.  In the end, I bought the "appropriate" switch at Radio Shack for $3.

Still, it would have been nice to get what was advertised.

 

 

 

 

Here is what my auto-level looked like after tweaking.  Now, it is isn't mounted, but I tested it with a MM to make sure it was working as I wanted.  

 

The PSU went together pretty easy.  

For the US,

  • I tried buying a cheap computer-power cord from eBay.  Um, I sliced the end off and found more copper in telephone wire. I went ahead and sacrificed one of my old computer power cords.  Not as long as I'd like, but it had some enough copper for my liking.  Then, Green <---> Ground  White <---> N(eutral)  Black <---> L(ive).  Also, if you are using that fasttech.com PSU, I noticed it came to me with the 240v as default.  So, make sure you flip the switch on the side.

 

After wiring my PSU to the Ramps I turned it on and looked for blue-smoke.  Nothing.  Waahoo!  But I had another problem.  The Mega underneath wasn't getting power.  Well, I scratched my head for a bit and then actually read the Ramps manual.

Apparently the diode that had been tapped to the underbelly of my Ramps is what enabled it to be powered from a 12V PSU.  So, I soldered it in place.

After soldering the diode in place everything appeared to be working.  I continued to wire everything else up like proper.

 

Here, I switched gears and put the top Triforce together.  No tricks there.  After, I got a hankering to actually put the top on and the belts in place.  It took a little courage, since B3DP sent me my timing belt in one role.  I had to make some cuts and was worried that they had given me just enough belt and if I made a cut that was a little off would have to wait on another belt.  But it was in vain, I had enough.  

To cut the belts I just strung them up as shown and left about four rubber-teeth past the end of the linker groove.  The little extra room can be adjusted when the top Triforce is put on.  There are three tension bolts for this purpose.

 

(Sidenote, from here on I'm using a lot of pictures, since the Kossel is a little difficult to video given its size)

This is what the belt should look like when in place, except the should go below the carriage or it will knock into the end-stops before carriage. 

 

I then tightened the top Triforce and quickly hooked the ramps up.  I uploaded the Marlin firmware and was able to get the motors to respond to one direction.  The problem came when I tried to hook the cooling fan to the Ramps.  Waaa-waaah.  

Apparently, the power control FETs on the Ramps were bad.  I couldn't get any voltage from two of them.  So, I took a break for a few weeks. I'll get back to it whenever the new Ramps comes in.

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Just be careful when drilling out printed parts. They state on their site that they are 50% infill. "Most" prints "should" have at least 2-3 solid perimeter and top/bottom layers as well, but if you have to take off a lot of plastic you'll find you might not have much to work with when you get down past the "shell". The RepRap Wiki is usually the place to go if you want the "official" BOM. Wow, this post used a lot of quotes. Lol. One small drawback of open-source projects like this is wading through all the forks, but the rewards are still well worth the work. Good luck Ladvien.

 

"Official" Kossel end effector from Github Repository. (Looks like a match to the B3DP site part.)

https://github.com/jcrocholl/kossel/blob/master/effector.stl

 

B3DP end effector:

B3DP End Effector

 

PS: Since thermoplastics tend to shrink as they cool (The cause of parts warping that you may have heard about) It is not uncommon to have holes that are tighter than you would hope for. This is actually preferrable to a loose hole. (I know what your thinking) and a bit of tweaking and parts cleanup is all just part of the game at this stage. ;)

Thank you for the warning.  I think I'm just going to leave the brass cap off my J-Head, shove it up into the hole (you gotta do that sometimes), then, screw the pneufit in like it is supposed to be.  I believe this might get me through to a time when I could print a different effector that will match my J-Head.  Not sure if I will be printing anything worth using anytime soon.  We'll see.

And about too tight holes (yes, I was thinking that) I was going to apply a little heat from my heat gun and see if I could slip the J-Head into place.  Again, we'll see when I get there.

 

Thank you; and Hoff; and Oss for your input.  Probably saving me hours of frustration :)