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Author Topic: filament speed wrong?  (Read 1810 times)

Alex

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filament speed wrong?
« on: February 02, 2013, 08:22:55 PM »
Hello everybody,
I finished assembling my bukobot Vanilla today and wanted to do some testprints. Now I ran into a problem that seems to be connected with  slicer settings but I dont know what is wrong: Please see the attached image - the whole-area in the first layer shouldn't be there - it just seems as if the filament is not flowing fast enough...
I am using the red PLA(?) sample from the bukobot-kit.
Profiles are taken from the ones i found in the forum posted by an admin - see attachment (Using: filament = Black PLA, print = Basic, printer = Bukobot 8 Vanilla)
Except I set the Heating bed temp to 60

whosawhatsis

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Re: filament speed wrong?
« Reply #1 on: February 02, 2013, 10:35:26 PM »
Try re-flashing the firmware. You can download our pre-configured Marlin here: http://bukobot.com/_media/marlin_x1.zip

You will also need the Arduino software, which you can get here: http://arduino.cc/en/Main/Software
You will also need the Sanguino library, which you can get here: http://code.google.com/p/sanguino/downloads/detail?name=Sanguino-0101r1.zip&can=2&q=

Alex

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Re: filament speed wrong?
« Reply #2 on: February 03, 2013, 12:49:28 PM »
Thank you for your quick answer!
I found that the true cause of the problem was me though: I did not tighten the filament retraction installation enough so it seems that temporarily the Tatsu drive gear had no grip...

Problem solved.

Another question: It seems like the extruder fan is not active. Where do I activate it? Cables should all be correct. When I activate it manually in Repetier host in the Manual Control Window during a print there does not seem to be a difference..

whosawhatsis

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Re: filament speed wrong?
« Reply #3 on: February 03, 2013, 04:56:10 PM »
The fan should never be turned off. We recommend connecting it directly to 12V at the power input to the Azteeg board (just screw it into the terminals with the wires from the power supply).

Alex

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Re: filament speed wrong?
« Reply #4 on: February 03, 2013, 05:36:36 PM »
Alright, thank you.
I soldered a female connector to the fan wires and connected it to the azteeg x1 "fan" pins - which do not seem to be supplying voltage... do they?
I will just screw the fan to the input as you said - but that would be a nice to know thingy - because the Reptier host software seems to provide fan adjustment settings..?


whosawhatsis

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Re: filament speed wrong?
« Reply #5 on: February 03, 2013, 05:46:54 PM »
The fan connector is connected to a transistor that allows it to be turned off and on in software. Our hot end design requires constant cooling on the top of the nozzle, so it should never be turned off and should just be wired permanently on.

buildrob

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Re: filament speed wrong?
« Reply #6 on: February 03, 2013, 11:03:33 PM »
There are two ways you might use the software controlled fan connector:
a) wire it to your main extruder fan and change your job start Gcode to turn it on (M106) and your job finished Gcode to turn it off (but be careful about turning on the extruder in Repetier's Manual Controls without also turning on the cooling fan), or
b) wire it to a second fan for cooling PLA prints (improves bridging and overhand performance). The slicer can then turn this fan on after its printed the first few layers (otherwise the print doesn't stick to the bed as well).

I mode some notes on the wiki how to get this working: http://bukobot.com/pla-print-cooling-fan
« Last Edit: February 04, 2013, 06:41:34 AM by buildrob »

Alex

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Re: filament speed wrong?
« Reply #7 on: February 04, 2013, 06:44:47 PM »
Thanks buildrob
Isn't the fan also cooling the hot end in the picture of the wiki?
Probably its not possible to prevent that completely right?


jit

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Re: filament speed wrong?
« Reply #8 on: February 04, 2013, 09:36:04 PM »
This whole part of the design has been bothering me for a while.

If we want to cool the plastic we just laid down, we should have a tool for that.

We have a tool known to the G-code interpreter as T0, which is the first extruder.  If we have a second extruder, physically offset from the first (in this case by about 75mm), it is known as T1.

Why not have another tool, let's call it T2, which is physically offset from T0 by 37.5mm (putting it halfway between T0 and T1 on dual-extruder machines).  This tool is a dedicated fan with a nozzle on it.  The nozzle directs cool air to the target area, which is [37.5, 0, 0] relative to the T0 nozzle.  The firmware knows how to turn the fan on when needed.

After the extruder nozzle(s) have finished with one layer, tool T2 is enabled.  This tool is a very broad brush compared to an extruder nozzle, so it can quickly sweep the entire layer.  A simple raster scan of the layer is done, then T2 is turned off and we go to the next layer.

The slicer software would need to be modified for this.  We can't reasonably expect the slicer gurus to put this feature in when nobody's hardware supports it.  So somebody needs to build the hardware first.  We can do this.

We could take advantage of such hardware without needing any help from the slicer.  We just create a G-code fragment that turns the T2 tool on, does an X-Y raster scan of the entire platform, and then turns T2 off.  All that is needed then is a simple program that reads in the G-code for your print job and inserts this code fragment after every layer.  It will take longer than the smart slicer would, but would allow us to use this tool while we wait for the slicers to catch up.

For those with single-extruder Bukobots, there is one complication.  The design suggested above would miss a strip 37.5mm wide at the left edge of the platform.  This could be fixed by a dual-nozzle design, where one air nozzle directs a second stream to the other side of the extruder and aims it at a point 37.5mm to the left of the extruder nozzle.  The slicer software would need to be modified to take advantage of this (but not the simple G-code fragment mentioned above).

The Azteeg controller already has everything needed to support all this.  One would need to buy one additional fan, some screws and nuts, and some wire (with connector) to hook it up to the Azteeg.  Everything else we can print.

Bukobot Duo v1

whosawhatsis

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Re: filament speed wrong?
« Reply #9 on: February 04, 2013, 09:59:21 PM »
I could implement that now just by (ab)using some configuration options in the slicer and firmware and using slic3r's multimaterial AMF support (or maybe just some hand-written layer change gcode), but it would cause more problems than it would solve. Doing that sort of cooling would allow the nozzle to ooze a lot while the cooling was occurring. There would be bits of plastic where there shouldn't be, and other bits missing where that plastic should have been. Generally, you want to extrude as continuously as possible to maximize print quality. We're experimenting with partially cooling nozzles when they're not in use to limit oozing, but it adds a lot of time to prints due to repeatedly waiting for them to heat back up, and it still doesn't remove the problem entirely.

The best use of a print-cooling fan is to blow near (but not on) the nozzle to cool plastic immediately after it is extruded (rather than after the layer finishes) using the existing extruder movement. Another option would be to mount a larger fan (or even an array of small fans that would sit in front of or behind the extruder so that the platform could be moved to the front/back, moving the entire print under the fans on layer change) that would cool the entire print at once when the nozzle moves away. The key difference is that these methods require taking less time away from extruding plastic, which will improve both print speed and quality.
« Last Edit: February 04, 2013, 11:38:26 PM by whosawhatsis »

Alex

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Re: filament speed wrong?
« Reply #10 on: February 05, 2013, 08:55:16 PM »
I tried to get better results without additional fan today - just by slowing down the printing process. Have to say that using just 50% of all extruding speed values did not make a huge difference. How do I insert a waiting time after each layer? Does RepetierHost / Slic3r support that or do I have to insert G-Code? If the second is the case can anybody give me an example?

Regards
Alex

whosawhatsis

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Re: filament speed wrong?
« Reply #11 on: February 05, 2013, 09:40:44 PM »
Sort of. Slic3r has an option to automatically insert custom gcode on each layer change. The code G4 is dwell. If you want to dwell (hold still) for, for instance, 10 seconds, you would use the following:

G4 S10

Alex

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Re: filament speed wrong?
« Reply #12 on: February 05, 2013, 10:19:14 PM »
Thank you I will play around with that and see what happens... as you said (above?) it is likely that filament will come out the nozzle while the waiting time - so it would be a good idea to move it to a (free) waiting position during that time wouldn't it?

whosawhatsis

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Re: filament speed wrong?
« Reply #13 on: February 05, 2013, 10:21:42 PM »
That would be a good idea, but that ooze is still going to be hanging from the nozzle, and there will be a gap where that plastic was supposed to go. I really don't think dwelling between layers is going to have the effect you want.

jit

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Re: filament speed wrong?
« Reply #14 on: February 07, 2013, 12:26:43 AM »
Alex, have you tried this?

Instead of printing one part, print two of them.  Put them at opposite corners of the platform.  If Slic3r is halfway sensible, it will draw all of a layer on one copy before moving across the platform to draw all of the same layer on the other copy.  That would give you some dwell time for each copy, without having the extruder sitting around drooling  --  it would be busy all the time, but half the time on the other copy.

They don't even have to be the same part.  They could be two different objects, but if all their layers are big enough, perhaps you will get enough time off on each layer to give you what you want.
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