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Guess what :P

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Posted · Guess what :P

 

http://daid.eu/~daid/IMG_20120430_210742.jpg

My 2nd extruder bowden tube is slowly moving up. I'm not sure if the new clamp is weaker, or if the new tube is more slippery. But it explains the issues people are having with the extruder plugging. My primary extruder does not have this problem at all.

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Posted · Guess what :P

that's very up.

when I put the blue circlip on the tube I noticed two things.

1) you can put it on and all looks good. but you haven't put it on properly - force it on with pliers until it can grip no more.

2) you know you've got it on properly because it forces the bowden tube up by exactly 1mm. originally I tried to compensate for this by pushing the tube an extra 1mm down (this actually makes matters worse) thinking it would lead to a leak, but it doesn't. I can't explain why.

I've been assuming people are not putting the clip on tightly enough and this leads to bowden tubes popping off and all the other problems complained about. maybe that's not the case after all..

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Posted · Guess what :P

The left blue clip you mean? Because that blue clip is black :p

I'm pretty sure it's as far as it can be, I think I used tweezers to push it into place, and I think it snapped into place. (it's quite hard to get it in properly in an already assembled head with 2 tubes sticking out of it) But I'll double check to be sure.

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Posted · Guess what :P

Cool news;)

BTW

Daid, could you please share your Cura setup for tiny walking robo print??? (wall thiknes, infill%, speed) i am tring to print it but legs wall thiknes seems to low and every time I'm trying to clear the support I broke legs :(

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Posted · Guess what :P

I've used 50% support material (should be the default in Cura at the moment), other then that default settings with 0.1mm layers, and 2mm retraction at 50mm/s. I manually turned down the speed to 75%.

I rotated the model 90deg so the supported lined up differently with the model. Like this:

http://daid.eu/~daid/IMG_20120418_212319.jpg

it made the center support easy to remove as it was not attached to the legs at many points.

And then I took my sweet time to remove the support. Those legs are really fragile. I used a sharp knife to cut the support lose from the legs, and then you need to be really careful not to break the arms.

You could also scale up the model 20%, that would make it stronger.

Also note that RC2 has a bug in the support, where the first layer has too little material. So if you support doesn't stick or stay upright you could upgrade to the development version.

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Posted · Guess what :P
legs wall thiknes seems to low and every time I'm trying to clear the support I broke legs :(

I uploaded a newer model of the mech with slightly thicker knees (4/19/12) that should help to solve the "fragile legs" problem. I haven't had a chance to print the new one myself but just looking at the sliced layers it seems the knee connection is much more solid. Are you having problems with that model or the old version?

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Posted · Guess what :P
that's very up.

when I put the blue circlip on the tube I noticed two things.

1) you can put it on and all looks good. but you haven't put it on properly - force it on with pliers until it can grip no more.

2) you know you've got it on properly because it forces the bowden tube up by exactly 1mm. originally I tried to compensate for this by pushing the tube an extra 1mm down (this actually makes matters worse) thinking it would lead to a leak, but it doesn't. I can't explain why.

I've been assuming people are not putting the clip on tightly enough and this leads to bowden tubes popping off and all the other problems complained about. maybe that's not the case after all..

I've checked the clip, and it's tight. So that's not it.

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Posted · Guess what :P

What i've observed with the circlip is that after an initial "digging in" state where the tube appears to slip, the clip makes indentations and gets a good grip on the bowden tube, which prevents further slipping. SO what I've done is just run the printer, let it slip, then cleaned out the plug and tightened the hot end back up to the new higher height. Works well.

I know that won't help you because you are trying very hard to get the heads exactly level, but perhaps what you could do is something like that to allow the clips to dig in, then take apart both heads and cut both tubes down to exactly the same length.

An alternative might be using the printable bowden clamp? That thing grips REALLY good and has a wide grip footprint so it doesn't need to "dig in". I am not currently using that method myself but it seems like it would make more sense than the circlip.

good luck! And could we see some multi-color prints that you have made with the setup?

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Posted · Guess what :P

I took mine to pieces the other day to have a look at the tube. that clip has really dug in and made a circular groove in the plastic of the tube. no wonder it grips well now.

this was partly caused by me trying several times to get it perfect when initially putting it all together.

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Posted · Guess what :P

just an update:

I recently installed the printed bowden clamps and i must say it is much better than the stock compression fittings. What I did was:

-insert the bowden tube through the printhead-side of clamp (

http://www.thingiverse.com/thing:11864

) and extend it down too far.

-Then put the PEEK part on the end of the tube and thread the aluminum plate onto the ends of the head screws as it's holding the PEEK/nozzle assembly (don't tighten anything yet).

-Now, tighten the knurled part on top a bit so the bowden tube doesnt move freely, and then tighten the four screws holding the aluminum plate all the way.

-The bowden tube should remain firmly pressed into the top of the PEEK part as you are tightening. After tightening the aluminum plate then tighten the knurled part on top all the way. I used the "extra grip" insert to hold the bowden tube.

I left the white part of the circlip on just to guide the bowden tube down the middle of the wood hole, but you shouldn't have to. Or you could replace it with a circular printed part as it's just a guide and doesn't have to grip.

This setup is now working wonders on my printer. Granted, I don't have two print heads, but it should be possible to do it with two. You just have to modify the printed bowden clamp stl to have two threaded segments.

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Posted · Guess what :P

I really like the idea of printing in multiple colours, and admire your dual setup Daid. Now, could we extend it further?

I have strong belief in the following concept:

* One nozzle with 4 or more entry points for plastic of different colours extruded in the same tip.

* Flow regulators for each colour within the nozzle (using electromagnetism?) or as close as possible.

If the flow control is close enough to the tip you could get quite accurate x,y precision for colour changes and if you have thin enough layers you could mix the colours to fake almost any colour.

I wonder if such a prototype nozzle could be printed in one of those metal 3d printers?

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Posted · Guess what :P

Multi-input nozzles have been tried. The results suggest that good mixing is ESSENTIAL, and this is complicated by the fact that plastic is very viscous and doesn't mix well at the temperatures we extrude at. A tip that mixes the plastic automatically (like those epoxy nozzles) would be nice but that would be a fairly large volume of plastic you would be throwing away with each color, as you'd have to flush out what's in the mixer tip to make the next color. You could try to predict the upcoming colors and push in the appropriate filaments, but I just don't see that giving you enough of a solid color, more of like a shade of the previous color that was in the mixer. But that doesn't mean you shouldn't try it!

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Posted · Guess what :P

No, I wasn't thinking of mixing. I was thinking the flow control is so far out on the tip that there is little room for any mixing.

...besides you can make sure all the colour changes happens during infill of an object, then you will get rid of any unintentional mixing. My idea of getting all possible colours was not with mixing, but by changing the plastic you extrude with for every different layer. If the layer is thin enough, you won't notice and can fake all sort of colours...

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Posted · Guess what :P

maybe 3 extruder with R G B plastic would do the job? the question is how small can you go? you need to extrude a mix of R% G% B% plastic very very near one another, just like the pixel in old crt tv.

aftertought. you need also a 4th extruder for white and a 5th for black... 8-(

but after all I would be happy just with basic 4-8 colors...

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Posted · Guess what :P

Color mixing is quite difficult. But there was something about it on the RepRap blogs a week ago or so.

IMG_20120514_235612.small.jpg

Photo of my fixed dual head. What did I change?

We replaced the top 8A plate with a 8B plate, with 2 clips on it.

Then drilled new holes for the thermocouple board. With 2 thermocouple boards there is a little bit of a space problem, so I replaced the top strain relieve with the 2nd thermocouple board.

Finally we cut a corner out of the printer head on the left back, and rotated the top/bottom 90 deg, so we could access the lower clips while the printer heads where on the left. Now the fan holder fits on the right side, giving full printer space access again.

The good news: Adding a 2nd clip seems to solve the bowden popping problem so far. And I can print dual color again.

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