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Printing issues ...
Looks like:
Z axis too many steps per mm. This will cause the print head to get further and further away from the part, until you get gaps forming like that. To check, measure the part, and compare to where it THINKS that the Z axis is. If the part is longer, then your Z axis needs to be recalibrated.
Extruder too few steps pre mm. This will cause the extruded filament to be too thin, and will
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SupraGuy
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Reprappers
Well, I kind of think that if the point of building the reprap is to make parts for the reprap, then it's kind of a waste.
That said, if you buy a cheap kit, you'll end up doing exactly that for a while. As I type, my i3 is making a second set of feet. The ones I got were crappy, so I modified the original design to something that suits me better, make a set, then put them on the printer. Now I'
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SupraGuy
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Reprappers
Does the problem follow the rods, or the bearings?
I suppose that it's possible that you got some rods that were rolled out of spec. Maybe they're 21/64" or something like that. (That's the size of the drill bit that I use to make clearance for an 8mm rod, because it's something like 8.33mm when converted, which is tight enough to hold things with minimal shimming, but loose enough to actuall al
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SupraGuy
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Reprappers
At least for Marlin...
Look in the Configuration.h file for a line like the following:
#define DEFAULT_AXIS_STEPS_PER_UNIT {80.0,80.0,4000.0,128.5}
It shoud be about 2/3 of the way down the file. This is the list of values is for the various axes of the printer. 80.0 steps per mm for X, 80.0 steps per mm for Y, 4000.0 steps per mm for Z, and 128.5 steps per mm for the extruder.
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SupraGuy
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Reprappers
I don't have that kit, but some general principles:
1. Probably underdriven. There should be a current adjustment on the Z motor driver, on the Polulo drivers, you can measure voltage from the pot to the negative terminal on the power supply which will tell you what the peak current of the driver will be. Since the Z axis is driving 2 motors, it should be about double what they are for the X and
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SupraGuy
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Reprappers
Have you properly calibrated your extruder? Have you set the correct filament size?
That looks like it's extruding too much material. Alternately, if could be your Z axis missing steps, but that looks like it's way too early for that to be this much of a problem.
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SupraGuy
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Reprappers
The off-center of the threaded rods for the Z axis isn't much of a problem, as the angle that they form from the motor to where they hold the X carriage up doesn't really change, so changing the couplers won't make a significant difference, unless the point where the rods support the carriage is significantly off center from the axis of the motor, which is not the case in any of the designs that
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SupraGuy
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Reprappers
I've read that. I did miss the bit about people complaining about holes too large though. My point is still that it's stupid to say that too small is okay, the slicer needs to attempt to make things as accurately as possible. Having an OPTION for the compensation method would be better, or better yet, have it as a variable amount, so that it can be tuned to your printer/filament.
My verticle and
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SupraGuy
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Reprappers
If so, that's stupid.
If I wanted to machine things, and drill them out, then why would I even use a 3D printer? It would be then far better to just get a CNC mill and blocks of plastic. If you have to adjust your models to get the dimensions that you want, then the models aren't portable, since they can't then produce the same thing on a different printer, or if they're used for different machi
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SupraGuy
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Reprappers
I would just add this:
Circles aren't always circles.
This was a major pain, since so many of my parts were crap, and I had a lot of my i3 jury rigged with zip-ties holding de-laminated pieces together, and things that were really difficult to keep square, endstops that won't stay still, and belts that don't want to stay tight, I tried to use the printer to make parts that didn't suck so bad. M
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SupraGuy
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Reprappers
Seems like it should be fine. I set the bias current on the polulo to 0.85V, should be about as much current as the steppers that I have can handle.
For the time being, I set the max Z speed to 1.25mm/s in Marlin, which seems to do fairly well, but it takes some time to do any significant Z movement. I'll probably increase that a little, and then just let it be. It works well otherwise (Just fin
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SupraGuy
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Reprappers
Okay, I've got my printer pretty well configured, extrusion seems good (Just made final adjustment for feed rates) X/Y/Z movement is all as close as it's ever going to be, or at lest close enough for anything that I plan on ever printing.
If I'm in pronterface, all axes move smoothly. I can move the extruder around without any trouble at all.
The only time it's a problem is with the G code that
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SupraGuy
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Reprappers
And for the nozzle size, resolution isn't quite the right word.
Like a rounded, dull pencil, you can still draw exactly where you want, but maybe not as fine a line as you want. This isn't like an old low-res printer (Like back in the dark ages of dat matrix) which can only print at certain intervals. The 3D printer can place a line of your nozzle thickness to within the resolution allowed by th
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SupraGuy
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Reprappers
If you have a 200 steps per revolution stepper motor, 16X microstepping on your RAMPS board, and are directly driving an M5 rod with 0.8mm thread pitch, then 4000 is the correct value for steps per unit in the Marlin config.h.
It sounds to me as though there may be another issue there with your Z axis travel, possibly an issue with missed steps.
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SupraGuy
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Reprappers
Uh, check your filament diameter. Common ones are 3 and 1.75. Sounds like 1.75 may be the correct value.
Also check your nozzle diameter, as it appears that your lines are a bit too far apart. It may not clear up everything, but it's a start.
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SupraGuy
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Reprappers
I sometimes have a similar issue, because the steppers do not keep up with the command to raise the extruder to 5mm. Sometimes the motors just make noise, but the command to drop back down works, and the result is as you describe. I usually wait for the hotend to finish heating, then immediately re-home the Z axis to move it to its correct location. it's not a good solution, but works.
I'm still
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SupraGuy
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Reprappers
Ok. when does it hit the bed. the gcode generated by slic3r by default moves the Z axis up 5mm after the bed heats, and before the print head heats, then moves if back down to the layer height after the hotend is at target temperature. Does the hotend hit the bed then, or does it happen over time afterwards?
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SupraGuy
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Reprappers
First things first, have you tested that Z is going the correct direction?
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SupraGuy
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Reprappers
There is a good reason to park the nozzle at the "all home" position. Since you are using stepper motors, the printer really only knows where the all home position is, and not REALLY where the print head is at any other time. It might know that it TOLD the motor to move the print head to position X/Y/Z but it doesn't actually know if it happened, and if you reset the printer, it no longer knows w
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SupraGuy
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Reprappers
Have you enabled the controller in the config.h for your firmware?
33 is the correct board type for the Marlin firmware for a RAMPS 1.4, so that part is okay, but near the bottom of the file it has an enable/selection for LCD controllers. The comments should be fairly easy to interpret without being a programmer. (Hard for me to say, since I am one though.)
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SupraGuy
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Reprappers
Thanks for replies.
Yes, I own a decent set of calipers and a good square. The rods for my Y axis are indeed exactly parallel, and the X axis was exactly perpendicular at the point where I initially built it. I've had to tighten nuts a couple of times, and the X axis has subsequently drifted by about a mm or so, which I intend to rectify asap. (It is of course that I tend to tighten the nut on t
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SupraGuy
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Reprappers
Okay, I've got things calibrated, but print quality is still kind of ... well, crappy.
I've got my X, Y and Z axis settings very close to exact, parts up to 90mm across have less than 0.5mm variance from expected dimensions in either X or Y sizes. I have not yet tried printing anything higher than about 25mm high, but this is also well within expectations.
Last time I tightened some of the fram
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SupraGuy
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Reprappers
I think that you're misunderstanding what the LCD is connected to, and how the Arduino works.
The Arduino is its own computer. It just happens that it gets its power from your Windows PC via the USB cable is all. When the arduino is powered up, it starts running its loaded program, in this case, the printer firmware which you downloaded to it. That printer firmware is what turns on the LCD scree
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SupraGuy
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Reprappers
Are you hitting the X/Y limitations of your print bed? It looks like the skirt is trying to print out of bounds, and it's bouncing off of the limiters.
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SupraGuy
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Reprappers
I contacted the seller, and was told that though the specs say 0.3mm nozzle, it really means 0.34. Well, I kind of thought it was smaller from the results that I got, but I'll see what changes if I set that up.
I've re-calibrated the moving axes, and the belt holder for the Y axis completely broke, so I've jury rigged it with hot glue and zip ties. (There are a LOT of zip ties holding my printer
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SupraGuy
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Reprappers
Okay, I see that there are a bazillion topics on print quality, and I've spent some time reading and searching, but I don't want to hijack someone else's thread. my other thread on my build started as more of a rant, and not really appropriate for the business of actually getting good results.
So, I know that I have some tuning to do, but there seems to be a number of things which can have an ef
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SupraGuy
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Reprappers
Well, after a rather sleep-deprived weekend, I got what I'd term my first successful print out of this thing (Though the scale is still off somewhat.) and now the Z axis is messing up again. Possibly just a heat issue, so I'll do some isolation testing. The Z axis motors always did make some unpleasant noises when homing, but were usually okay moving, but the last couple of tests, they got a bit
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SupraGuy
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Reprappers
Well, there was absolutely nothing wrong with my PC hardware. I installed 7 on it as well, just to test, and it runs that with excellent results. I installed Linux on a 120G solid state drive that I have as "extra" (I'm sure that I'll find a better use for the 2TB drive that was in there.)
Current status: I have my first 3D print now.
The extruder is a POS. I did something dumb... I trusted tha
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SupraGuy
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Reprappers
Yes, I am aware of that (Pronterface reports the serial output something like "dangerous extrude prevented")
I've taken steps to get around that. For the first few times by simply heating the hot end, and when that didn't work, I set up the min extrude temp to be 18 deg C... I've also tried plugging in the extruder motor to known working drivers, which is when the X stepper driver stopped drivin
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SupraGuy
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Reprappers
Well, pretty sure that the seller actually knows something about the workings... but is obviously more interested in getting stuff out the door to make money than in providing good quality parts, I suspect that the printed parts are basically made from the cheapest plastic that he can pump through his own 3D printer, and he's obviously not too concerned if there's a missed step in a part here and
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SupraGuy
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Reprappers