Improving my print quality

Hi! I've recently built a Prusa Mendel i2 and over the last few days have gotten it to print rather reliably. Now I'm trying to improve my print quality and was wondering if anyone would mind giving some suggestions.
My setup uses PLA, no heated bed, .4mm nozzel, and 1.75mm filament. I've attached images of my latest print that I made that has a .2mm layer height, .25mm first layer height, 195C print temperature, a 205C starting temperature, .2 fill density (rectilinear), concentric top and bottom fill pattern, and was sliced with Slic3r. This file I used was this Trilobite from Thingiverse.

The trilobite was rotated on the bed so the front to back of it was on the X axis with the head on the right side of the machine. There are noticeable ridges on the right side of the print, there are some minor gaps, and the very tips of the head of the trilobite seems to be incomplete/slightly melted and deformed.


Thanks for any suggestions!

print speeds?

A cooling fan may help your overall print quality.

Do you have bearings on your Z-axis lead screws? Your prints have Z-wobble, and a bearing guide on the lead screws usually makes Z-wobble worse.

Are you talking about the the bearings that the Z screw goes into at the bottom of the printer?

yes, ones like in the attached picture. I run a Prusa Mendal variant and had this bearing setup with helical Z couplers, top mounted motors. Completely eliminated my Z-wobble by removing the lower bearings and swapped the helical Z-couplers for solid printed ones. It's better to let the lead screw wobble than to restrain it and transfer the wobble to the print head carriage. The bearing holes should be large enough with the bearing removed for the ends of the lead screws to wobble around a bit.

If your lead screws are 5/6" and not 8mm, then there is a center line off set between the lead screw and the stepper shaft because most aluminum Z-couplers are for 5mm to 8mm, and the instructions just say to tighten them more for 5/16".

Edited 4 time(s). Last edit at 12/27/2013 10:30PM by Dirty Steve.

Interesting, doesn't that create a lot of stress on the coupler?


Oh and I forgot to mention my speeds. I've changed them since I posted this but I don't think there was anything over 60mm/s and I'm pretty sure I had perimeters set to 50mm/s

it does add the weight to the couplers, I think that aluminum helical cut couplers wouldn't last very long and snap at the coil cut. I haven't had any problem with solid printed couplers. You may need to up your Z-axis current a little to compensate if you are seeing any lost steps.

I modeled my own couplers because I couldn't find any that are 5mm to 5/16". There are similar ones for 5mm to 8mm depending on your lead screw size. I use a little bit of 2 part epoxy on the motor shaft and lead screw for assembly, they have never slipped.

[www.thingiverse.com]

What type of couplers do you currently have on you machine?

Edited 2 time(s). Last edit at 12/28/2013 01:08PM by Dirty Steve.

Originally (these were used on the trilobite print) I had these couplers:[www.thingiverse.com] but they crumbled under the pressure I had to put them under to keep the z axis from slipping. Now I'm using some rubber tubing with hose clamps and haven't had any slipping. The z wobble is still slightly there but not nearly as prevalent. It's possible it might of been due to backlash though since I discovered I didn't have my belts nearly tight enough.


I'm now combating these little bumps that appear on the surface of the print and minor spill over of filament on prints with slight overhangs.

Usually backlash won't look like wobble. Couplers should be printed with 100% infill.

Are your lead screws 8mm or 5/16"?

I also run my Z motors with thick rubber washers with the screws lightly tightened so that the motor itself will absorb some of the wobble with the rubber washers.

Edited 2 time(s). Last edit at 12/28/2013 05:19PM by Dirty Steve.

They are 8mm.

I'm pretty sure the original ones where just badly printed with how the crumbled. I got all of the printed parts and rods together from a seller on eBay. The printer is basically a clone a Makerfarm printer. It's been an interesting build since most of the documentation he provided was out of date in relation to the printed parts he was supplying (like the template for the MDF base plate having the holes placed meant for Y sliders with a different mounting hole orientation) and all of the rods have been too short (and badly cut) with the claim that they improved "look" of the printer.

I've noticed that the belt tightening has actually made the ripple worse. My circle test was too short for it to be noticeable but on taller prints it is definitely there.

I've been working on other issues and haven't gotten to printing the new couplers and remove the bearing on bottom. I may have to modify your coupler carriage to be a bit longer though since my rods are a tad short and the stepper has a damper on it causing them to not meet super closely.

I've also noticed a bit of wobble as the printer moves and I'm going to print some brackets to fix that.

I'm running my printer right now with no screws on the Z axis steppers. Seems to have helped my rippling more than the printed couplers did. I'm doing a lot of test prints today to try and get some issues to sort out so we'll see if it's going to be consistent.

I'm having issues with my extruder flow rate I think. Some times I get these little blobs on the side of the print or strange build ups and the sides of prints. I'm also concerned that my first layer is to close to the bed. It's not very think but it is really wide and almost see through (my filament is white)


EDIT
From the looks of it this latest cube only has ribbing on the back of it on the Y axis.


EDIT EDIT
Attached some pictures of the deposits

Edited 2 time(s). Last edit at 01/01/2014 05:42PM by jaeg.