What did I do wrong?

Hmmm, interesting. I wouldn't normally print vertically like that. Go flat and see if it prints the same way.

When I import the STL to SketchUp, I do notice that there are a number of "open" triangles, as well as many interior planes, usually at the mid-point within your 2x4s. Slic3r is pretty good at repairing those.

It's possible that Slic3r tried to generate support material for the top cross-beams, but that would have been as thick as the whole wall...

Weird. Print flat and show us your results.

When I had a chance to get back to my printer this weekend I had decided to pause on walls and print some flat parts from a known good model to see what it would do. I got a Tardis model to print. I was able to make a real nice panel of one of the doors. Decided great lets make it work, and told it to print the other 3 walls. Did a great job. Then I told it to print the base, and again it did a great job. Went in to tell it to print the top two pieces and the head must have clogged or something as it decided to not feed anymore material. Thing had me so confused. I pulled out the material from the extruder and found it chewed the side of it up on that bolt thing. I pulled it out and cleaned it up. Then went in and made sure it was not clogged Put it back in and thought i would be good to go. 3 hours later and still messing with trying to get the Z distance fixed. cannot keep it on the glass. I have pulled the Z stop down atleast 1/8" and for some reason it still is too high. Was fine before. I have made sure the nuts were seated in the parts and it is still hight. What did I do now?

OK NOw I am really confused. Took a couple minute break, and came back and rehit the Home thig and it seemed good. I have it printing the two top files and when the string of gooey comes out the end instead of a nice steady string that is smooth on the bed it is sqiggly. I look at it close with an LED Flashlight and it is off the bed too high still but instead of it being a mile away it looks like it is about the thickness of the string too hight. I set the depth using a piece of paper with a slight drag when it was cool, and used a set of calipers in four corners of the glass to the x axis cross bars. It is as level as it can get (Or atleast as level as I could get it) Wish there was a way to adjust it without it changing so drastic. Any upgrade or anything I can do to get the bed up or the head down like just a tiny big? Any tricks?

Quote:

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Originally Posted by Tachout

Wish there was a way to adjust it without it changing so drastic. Any upgrade or anything I can do to get the bed up or the head down like just a tiny big? Any tricks?

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:) You are ready to join the Auto_Bed_Leveling cult! Once you get that setup and dialed in, just about every print's first couple layers go down clean and crisp. If you have other problems like bridges that are too big or slopes at too steep of an angle you will have problems. But just getting the first couple of layers down every-time without a fight is nice....

OK Got up this morning walked into my office and found the parts made great. Wahoo! I am printing the last parts of the Tardis I am making and here is what I have so far

http://i127.photobucket.com/albums/p...ps2834b6bf.jpg

Once it is done it is supposed to have a 9 volt battery in it, some LEDs and light up somehow. Not my model, it is one I downloaded off the net, but it is really coming out. I am not a Dr. Who fan, but my oldest daughter is. She is like 30 and it sounds like christmas when I showed her a picture and told her that once completed, it will be in a box on the way to her. Thank you everyone for your help.

Roxy I will have to look into the Auto_Bed_Leveling. It is a pain every time I have to set it.

Well heading out to the garage while it prints the last parts. When it gets too hot out for me to do Fiberglass work, or what ever, I will probably come in and start getting a Home Model ready, as I want to print one floor plan real bad to see how it comes out.

This is a classic retraction problem. Slic3r should be retracting the filament before crossing open space. What you're seeing is ooze created by an incomplete retraction. Bits of plastic build up on the destination surface, and then on the built-up ooze, creating the oddly beautiful mess you're seeing.

Unfortunately, the 66 oz.in. motors that Colin is shipping these days are not ideally suited to a reprap machine. I think they're these motors: http://www.circuitspecialists.com/ne...2bygh4807.html

The problem is the high resistance and complex reactance. 19 ohms resistance and 32mH inductance are WAY too high to retract rapidly. Typical reprap motors will be closer to 2 ohms and 2.5mH. The high inductance severely limits the current rise rate in the coils, and at 12V, it just can't retract at the high rates Colin has in his slic3r config files. It tries, but the motor ends up skipping some steps during the retract. If you reduce the retract rate to 10 mm/s, you should get better results.

It still won't be perfect, but it'll be better.

clough42, thanks for shedding some light on the motor retraction limitations with these motors. How would you know the motor is skipping steps, is there something you can listen for when the motor? I would never have realized this and will try 10 mm/s.

I'n not speaking for the OP, but my first print with retraction set to 10mm/Sec is promising. If nothing else, the print went a hell of a lot quieter, too. I'll probably keep the setting for that reason alone, at a sacrifice in printing time where a lot of retraction is used.

EDIT: That "quieter" probably means what I was hearing before was the motor skipping. The large gear appeared to be rotating backwards like it should, but it likely wasn't rotating as MUCH as it should.

But a question - couldn't a "too low" setting on the driver for the extruder stepper motor also be a limitation on the high speed retraction?

Maybe. It all depends what is limiting the current. There are several factors. By default, I think Colin's instructions call for setting the reference voltage on the driver to .39v. This equates to a current limit of 2.5*.39 = .975A (for a Pololu clone board). The motors are rated for .5A. This is one of the reasons they get so hot. It's more complex, though, because the resistance of the coil is 19 ohms, so at 12V, the resistance will limit the current to .63A, which is why the motors don't actually burn up. It also means that if you have your driver current set above .63A (ref voltage of .25v) I don't think you'll see an actual current increase. (Microstepping makes this more complicated.)

The killer, though, is the inductance. 32mH is really high for a reprap motor. This won't affect holding torque when nothing is moving, but it limits how fast the current can rise in the coil at a given voltage. As you step faster, the time for the current to rise gets shorter and at some speed, it can't rise enough before the next step and you start losing torque. At some point, the motor can't overcome the load and you skip a step (or twenty).

I think this is what is happening during the retract.

Most of the time, Slic3r is configured to retract 1 or 2 millimeters when moving between islands. It should quickly retract, move and then quickly advance the same distance it retracted and start printing again. You should see the gear turn backwards some distance, and then move the same distance forward when printing resumes. In my case, it was stuttering and clicking as it retracted, and then running smoothly when re-advancing, creating a blob. When I slowed it down to 10mm/s, it started retracting smoothly and re-advancing the same distance. (There may be something here involving nonlinear loading and gear backlash, bit slowing it down seems to help.)

If you print something with gaps that the nozzle has to cross (like the oozebane object) you can see the retracts. Try it at 10mm/s and watch how the gear moves. Then turn the speed back up and see if it's missing steps.

My Itty Bitty Belted Extruder (http://www.thingiverse.com/thing:389105) uses a lower gear ratio (4:1 vs about 5:1 for the Greg's) and it uses a NEMA 14 motor with about 1/3 the torque of the motor that Colin ships, yet it's able to easily retract at three times the rate without issue. So I don't think it's a torque (or current) issue. I think it's the motor winding inductance that's limiting the step rate.

Keep in mind that I'm entirely self-taught here, so if someone with more experience or formal education wants to shed light on this, I'm all ears.