Cruddy prints

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Cruddy prints

Postby cozmicray » Fri Dec 14, 2012 11:37 pm

Ordbot Hadron ABS ET 205deg BT 120deg .2mm layers

Small stepped object
What it should look like
Steps_RH_379.jpg
Steps as shown in Repetier host


How it was printed
Steps_376.jpg
21mm x 21mm steps each step 2mm


Not a Z-Axis problem shown by Z-Axis dial guage measurements

Steps_Z_374.jpg
Steps Z-axis measurement


any suggestions?
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Re: Cruddy prints

Postby TLHarrell » Sat Dec 15, 2012 12:46 am

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Re: Cruddy prints

Postby cvoinescu » Sat Dec 15, 2012 12:54 am

I have no suggestion for the lifting, but the horrible melting at the top happened to me too, with PLA, when the previous layers did not have time to solidify. It's worse on layers that take less time to print. Skeinforge has the option to increase the layer time to a set minimum, exactly for this reason. It has two choices: slow down so that the layer takes at least that minimum time to extrude, or it do the layer at normal speed then circle around it, waiting for the time to elapse ("orbit"). "Slow down" doesn't really work for me: with the hot nozzle so close, the previous layers remain molten; and my nozzle doesn't extrude cleanly at very low speed. "Orbit" works much better. A fan blowing on the work helps tremendously; PLA requires vigorous cooling, ABS only a little. With the fan on, I found that a minimum layer time of 10 seconds is plenty for PLA to solidify. (I don't have much experience with ABS yet.)
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Re: Cruddy prints

Postby orcinus » Sat Dec 15, 2012 2:03 pm

Your bed temp might be too high. Try setting it to drop off after the first layer.
Also, try tweaking the extrusion multiplier. ABS always has some die swell, but some filaments can swell to ridiculous extents (150% the nozzle diameter, even). So try dropping the extrusion multiplier to 0.7-0.8 and see if that changes things, then play around with it until your infills are flat.

Also, like cvoinescu says, the layers might not have time to cool. It's an easy thing to check - just reduce the printing speed and see if things change.
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Re: Cruddy prints

Postby Turbo442 » Mon Dec 17, 2012 5:56 am

cozmicray wrote:Ordbot Hadron ABS ET 205deg BT 120deg .2mm layers


any suggestions?


Couple of quick thoughts.

For the print to come out that bad you most likely have a couple of things going wrong at the same time.

Things I might consider:

1. Is it possibly a roll of PLA and you think it's ABS? If its ABS you would be printing much higher, I run at 240. 205 sounds more like PLA. Drop your bed to 65 and try again. Try dropping your extruder to 200.

2. Is your x or y axis missing steps for some reason after the driver heats up? I have seen prints turn to mush when the drivers really start missing steps. (Belts too tight, current set wrong, carriage too tight.)

3. Try printing 4 of these at the same time, that will give the print more time to cool off between layers.

4. PLA tends to resist lifting, that corner that is lifted could have happened when cozmicray lifted the warm print from the bed.

What type of extruder?
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Re: Cruddy prints

Postby cozmicray » Mon Dec 17, 2012 3:25 pm

I added a small fan cooling unit
Fan_381.jpg
Cooling fan


extruder is a mBot Mk 7

Three tries of the print each got knocked off.
Started cooling at layer 7 just before end of first step

Its NOT PLA, I have a roll of PLA totally different smell

My bed is glass with blue painters tape over it
(the only way I have been able to get prints stick)

Bed set at 120C gets the top of bed to about 85C (measured by contact thermocouple)

People are mentioning missing steps
My drivers have heat sinks on and are not hot at all.
Is there some way I can monitor for missing steps
Are steps missing on this driver/ motor common?

Tnx
Ray
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Re: Cruddy prints

Postby bdring » Mon Dec 17, 2012 3:41 pm

You can usually check for missed steps on axes by moving to a known location before and after the print is done.
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Re: Cruddy prints

Postby Turbo442 » Mon Dec 17, 2012 7:15 pm

cozmicray wrote:I added a small fan cooling unit
Fan_381.jpg


extruder is a mBot Mk 7

Three tries of the print each got knocked off.
Started cooling at layer 7 just before end of first step

Its NOT PLA, I have a roll of PLA totally different smell

My bed is glass with blue painters tape over it
(the only way I have been able to get prints stick)

Bed set at 120C gets the top of bed to about 85C (measured by contact thermocouple)

People are mentioning missing steps
My drivers have heat sinks on and are not hot at all.
Is there some way I can monitor for missing steps
Are steps missing on this driver/ motor common?

Tnx
Ray


Have you done the PID tuning of the extruder hot end with the M303 command? Your extruder should be able to maintain + or - one or two deg C after running the M303 command. Google it for instructions.

205C is not hot enough for ABS. The default pronterface setting for ABS is 230C. I run at 240C. Your setup may be just hot enough to extrude at first, then as the print continues, your hot end cools off a bit and your filament drive gear is slipping.

If the current on your drivers is set too low you will miss steps as well. It may not be the issue, just something to consider.
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Re: Cruddy prints

Postby brnrd » Tue Dec 18, 2012 12:10 am

I don't think this is due to missing steps. It looks like the part is not able to cool down because he's in effect printing a small piece. It's better at the base where it's wider and it gets worse as the part gets narrower. What's happening is that the nozzle and heating block is hovering over the piece all the time so that the part is not able to cool down. The extrusion temperature might also be a bit high. Some things that can improve this:

1. Try printing 2 or 3 pieces at the same time. This will allow each piece to cool down while the nozzle is working on the other pieces.
2. Turn down nozzle temperature a bit.
3. Turn on the cool option in slic3r to slow down the print when each layer is less than 40 seconds. I don't think turning a fan on with ABS is a good idea since it will usually result in the part coming off the bed.
4. Use PET tape or Kapton tape instead of blue painters tape over the bed.
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Re: Cruddy prints

Postby blah_59 » Tue Dec 18, 2012 1:02 am

Are you printing it with solid infill? If so, I may actually be able to help this time instead of asking for help. Try either 1) Turning down the flow rate to .9 or maybe even .8 or 2) try upping the filament diameter setting. It looks kind of like when I was doing a solid block calibration and too much plastic was coming out.
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