Cruddy prints

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Re: Cruddy prints

Postby orcinus » Sun Feb 24, 2013 8:08 pm

Three probable issues i can see:
- Z axis wobble
- you're extruding too much
- not enough cooling / speed too high

Using other people's configs without any tweaking is generally not a good idea.
There's simply too many variables in the hardware... Sometimes it takes 5m or more of spent filament just to tweak in for a particular PLA make/type.
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Re: Cruddy prints

Postby SystemsGuy » Sun Feb 24, 2013 10:10 pm

So something's not right on your bot - and I agree with Orcinus - just jumping on a config is only half the battle, you have to have your firmware tweaked... That said, I think you may have mechanical problem - I happened to run off a herringbone for a friend last week, using the same config, and here are my results - and I'm printing as hot and as fast as I can, not really shooting for quality on these...

gear1.jpg
120mm/s Infill, 100mm/s perimeters. .15mm layers.


gear2.jpg
As above, moving too fast for this small a layer.


tiny-3.jpg
.1mm layer, 80mm/s perimeters, sitting on a US quarter coin






orcinus wrote:Three probable issues i can see:
- Z axis wobble
- you're extruding too much
- not enough cooling / speed too high

Using other people's configs without any tweaking is generally not a good idea.
There's simply too many variables in the hardware... Sometimes it takes 5m or more of spent filament just to tweak in for a particular PLA make/type.
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Re: Cruddy prints

Postby cozmicray » Sun Feb 24, 2013 10:35 pm

Nice gears

I built the Ordbot back in Aug 2012 and have been working with it since then
to get parts to stick and print half decent.

On a lot of forums -- log all my changes -- what is the magic

Standard ATI kit hadron with mBot Mk 7 extruder

Need printer fairy to come down and touch my printer???
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Re: Cruddy prints

Postby cvoinescu » Sun Feb 24, 2013 11:28 pm

cozmicray wrote:I built the Ordbot back in Aug 2012 and have been working with it since then
to get parts to stick and print half decent.

On a lot of forums -- log all my changes -- what is the magic

Standard ATI kit hadron with mBot Mk 7 extruder

Need printer fairy to come down and touch my printer???

My first attempt was on an eShapeOko, which is not even designed as a 3-D printer, using a J-Head MK-VB (an original one from hotends.com) and a random Wade-like extruder I bought as a kit on eBay, attached to the Z rail of the eShapeOko with an angle bracket from the hardware store, held to the bracket by a single screw (the bracket doesn't quite fit). It worked practically perfectly from the third attempt (first attempt I got the steps-per-mm way wrong and over-extruded; second attempt I did not have a fan at all and the printed PLA remained jelly-soft and got distorted). I used PLA on Kapton tape on an unheated but thermally insulating surface (a wardrobe shelf from Ikea, foil-covered chipwood). It sticks just right except for the tallest and narrowest pieces. I printed at 185 Celsius, with the fan running gently and blowing from about 5" on the print and the barrel of the J-Head.

So, I don't know. Did I get touched by the printer fairy, or did I just choose the easiest, tried-and-tested, most likely to work solutions and went with them?
Last edited by cvoinescu on Mon Feb 25, 2013 10:35 pm, edited 1 time in total.
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Re: Cruddy prints

Postby SystemsGuy » Mon Feb 25, 2013 8:32 am

Well, I'm not the printer fairy, nor do I play one on TV! :P

Post up your firmware settings - configuration.h and configuration_adv.h. I've got zero experience with the MBot extruder, I use a J-Head on my own design, but it looks to me like it's more than just extrusion problems...

You are printing on 3M Blue Painters, tape correct?
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Re: Cruddy prints

Postby orcinus » Tue Feb 26, 2013 4:23 am

There is no magical printer fairy dust that makes prints turn out well, i'm afraid.
Just a lot of trial and error. Those that get it right from the get go can count themselves lucky, as far as i'm concerned.

I waste and have wasted hours of time and meters of filament getting things to look alright. I eventually got there, but i still need to go through a lot of trial and error tweaking whenever i change some parameter (filament, object size, speed, object shape, you name it). With all due respect to everyone in the community, i think that people who claim they get brilliant prints every time, on the dime, with very little tweaking, are either flat out lying or don't tend to look at their prints too closely.

Also, forget the idea of having a single, do-it-all slicing profile. You'll have to experiment with the parameters of your slicer-of-choice for pretty much every combination of speed, filament and object to get the results you want. I keep separate profiles for combinations of different filament makes, colors, fills and speeds and even that doesn't work at all times.
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Less Cruddy prints

Postby cozmicray » Sun Mar 03, 2013 5:32 pm

Well doing a bit better

HB_Gear_1.jpg
Herringbone Gear for extruder PLA


Transmisson_Gears.jpg
HB gears for Transmission PLA


R-pi_case.jpg
Raspberry Pi case PLA
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Re: Cruddy prints

Postby SystemsGuy » Sun Mar 03, 2013 6:16 pm

I still think there's something mechanically not quite right. Would you mind printing these? Smaller should just fit inside the larger.

orcinus - I sort of agree with you - but at the end of the day, it's temps, feeds, and speeds. We all share pretty much the same mechanical platform - which in general means x / y / z acceleration, jerk, and speed should all be pretty close.

The big variables come with the hotend, extruder, and the PLA - in my mechanical mind - the tool, the spindle, and the material. Those are probably "big" enough to make the difference between an acceptable print and an unacceptable one.

I do have very specific notes on each spool of filament I use, and I have a couple of test STL's that I run on new spools to get the filament packing density and temperatures dialed in - but other than that, I don't change much.

I do switch back and forth between KISS and Slic3r depending on the model - and have a number of different profiles for each depending the quality vs speed I'm looking for.
Attachments
37.7x37.7-square.stl
(4.53 KiB) Downloaded 647 times
40x40-Square.stl
(4.25 KiB) Downloaded 652 times
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Re: Cruddy prints

Postby brnrd » Sun Mar 03, 2013 6:35 pm

The top surfaces on those prints are not closed. Assuming that the correct feed diameter was entered, the extruder steps per mm in the firmware or the extrusion multiplier in slic3r need to be corrected.
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Re: Cruddy prints

Postby orcinus » Sun Mar 03, 2013 6:57 pm

I'm not entirely sure that's a calibration issue.
Look at this photo up close:

Image

The shell layers (2) in the top layer that are 100% overlapping (in fact, they seem smooshed together too much, if anything).
But at the same time, the infill is sparse (the photo above doesn't have any infill in the top layer, the RasPi case has too sparse a top layer infill).
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