print quality, help needed

A few days ago I finished building my makerfarm i3 8" kit. I've printed several things and so far I'm happy, but there are a few little issues I need help with. My kit has a.50mm head, ramps and am printing 3mm abs. On several of my prints there are random abnormalities in some of the layers. I can't attach a picture because it's to large, but hopefully somebody knows what I mean. Is it normal to have abnormalities? I kind of assumed I would get prefect prints.

Very though to say without an image, try uploading your image on this site [imageshack.us] and then paste the link here. You should get very little abnormalities depending on the part.

Printed parts are not going to be perfect. That's even more true without fine tuning things. Matching your brand of filament to your extruder / hot end is one form of tuning. Getting the gcode to match the dynamics of your motors is another.

The first thing to do is to compare your parts to the printed parts on the extruder. There are certainly plenty of "odd bits" on the ones I have. If you see it on the extruder parts, it's normal. Past that, I'd shrink the image down and post it.

Sorry it's taken so long, here is a link to a close up of a bunch of abnormalities. I printed another one and it has the same abnormalities in the same spots so obviously it's in the software. How do I go about checking future STL files for issues like this and most importantly how do I fix it?

The second one I ran through netfab and fixed errors, but it actually made the second one worse, near the top it slid the last 10 layers over 1mm.

[imageshack.us]

Edited 1 time(s). Last edit at 10/26/2013 03:37PM by vetteguy112233.

Also this particular print had 4 pieces that it printed all at once and I noticed that when going from one part to the next it would leave strings of plastic. on this particular print it really shows up, when you snap them off at the end. I'm guessing maybe printing the parts separately is the only way to avoid this? Which brings me to my next question, how do I print items separately when there are multiple items in a print? This one was a grenade and I broke the handle and world like to print just a handle instead of all 4 pieces.

As for splitting images, I think I've figured it out. I use Sketchup, so I opened the file, ungrouped everything, selected the piece I wanted (making sure to get everything), created a new Sketchup document and pasted it into there. I then exported it as an STL file (in mm because for some reason INCHES didn't work???) which I opened in Netfab, corrected all errors and saved again. Then on to Slic3r to get the Gcode, then to Pronterface to print it.

This sure was a lot of steps, but it seemed to work. Am I overcomplicating things or is this what everybody has to do?

In Slic3r there is a check box for "print multiple items one at a time". The only problem there is hitting something with your print head or carriage. With short stuff it's not usually a problem. With tall skinny items it can be.

There are a bunch of buttons and boxes in the slicing process. The easy way to go is to try some small / simple / stupid parts and see what each setting does. It's a lot easier to see this stuff than it is to understand a convoluted description of what this or that box does in this or that case.

Like it or not, the world is metric. There will be fewer bugs in free software if you use metric settings. They are the ones that get debugged ...

Great info, thanks!

What about the picture link I provided. I've printed many things that seem to have these imperfections. I don't know if it's air absorbed into the ABS plastic or what, but I need to see if it's something I can fix. I just want to see a perfectly printed project.

I think you will find that your print defect relates to the "randomize starting points" setting in Slic3r. You may also need to tweak some extrusion settings (like filament diameter / temperature).

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One other (likely not applicable) thought:

How a part is designed / sliced does impact how it prints. Your extruder / hot end will only put out a 0.40 mm (say) piece of filament. If you design a cube that's 0.60 on a side, there's no way to print it cleanly. Some parts of some structures need to be carefully planned ....

Edited 1 time(s). Last edit at 10/27/2013 12:12PM by uncle_bob.