Print quality after mechanical adjustments  

Re: Print quality after mechanical adjustments

Okay so managed to get some time today and work on the Prusa, first step was to do the calibration again, and this time I started with a Z height of 400 on the 3rd print after inspection I decided to go to another 35 on the Z so that was on print number 4.

Overall the height looks to be perfectly set now compared to 1, 2, 3.

On print 4 I did a tune at mid way through the print that can be seen by the mid section belt going around Marvin, just to see if the Zit and Blobs would go away with minimizing extruder flow via the prusa LCD setting, did not see a difference so reverted back whilst printing to 100% flow.

Also had set the extruder temp down by 5 so instead f 215 it was set at 210 to see if the stringing went away on the Marvins ears and eyebrows, No joy on that.

So now look like I have to dwell into the printing setting on Slic3r or S3d and look at the retraction and coasting settings.

If anyone would like to chip on the zits and blemishes that can be seen on the circled areas I would be more than grateful.

Re: Print quality after mechanical adjustments

Quick question before I start working on software side of things , I checked my extruder calibration, and I was under extruding for sure, eye balling I would say am off by 3mm.

Question one, would that affect the quality of the final print ?

Question two if I was to calibrate the extruder I would need to flash the Eprom, would the Repetier software work ? as Opposed to recompiling ..

Thanks.. :geek:

Re: Print quality after mechanical adjustments

Okay after reading more into the forum looks like just using the pronto interface would do the trick on the flashing the Eprom.

My extruder was under extruding by 7mm, after measuring.

So Eprom was at 161.30mm can obtain this info via pronto interface via Command M503

My calculation based on 100mm comes to 93mm

Calculation comes to 161.30 x 100 / 93 = 173.44mm

Pronto Interface set via command:

M92 E173.44

Then ran the M500 to store the new extrusion command.

This is the final print from the SD card after all calibration has been on the machine.

Next step would be printing it via Slic3r Prusa edition and seeing the end result.

Re: Print quality after mechanical adjustments

You would think paying attention to building and then reading would make sure you did not miss out on something, well yesterday, by chance whilst doing some calibrations on the z axis as per jeffs method and after several attempts to get the thin sheet 75x75 from his thread here http://shop.prusa3d.com/forum/prusa-i3-kit-building-calibrating-first-print-main-f6/life-adjust-z-my-way-t2981.html .

I spotted that one of the Y axis rod had popped out of its place for some reason, the zip tip was completely loose.

The following images are of the the sheet being calibrated with a popped out Y axis rodded that caused an ever so slight un even finish when calibrating on various heights.

After installing the popped out rod and tightening down the zip tie and rechecking all other components of possible miss alignments and recalibrating the machine once again in all aspects, the following print is the final result, the 400 section was first printed at the top half of the sheet in the image, and whilst printing I kept looking at the table sideways keeping and eye on the extruder nozzle and the plastic density, I noticed that the plastic had minuscule hair like like sticking up and after a few MM I felt it by finger touch and was not really 100% smooth.

I then adjusted the live Z to 395 and kept on seeing the print, and the minuscule hairs went away and and the touch super smooth.

The pictures shows clearly I had a mirror like finish smooth to the touch, even the 400 was a near perfect layer print.

After that I created a small test cube with a top hole dimensions on Fusion 360 for tolerance check.

First cube was printed via S3D in medium quality at 20% infill, size of the cube as per the Fusion 360 set are 10x10x10 hole size 5mm depth 2.5, after checking with a digital caliper it read 10.54x10.52x10.54 / 5.55 depth hole size 2.55

Reprinted the same cube in high quality with 30% infill, and final print yielded 9.99x9.99.9.99 / 5.00 depth with a hole size 2.5

Prior to all this I printed Makers Muze tolerance gauge and the best I got to was from 0.5 / 0.4 / 0.3 that twisted perfectly.

Makers Muze tolerance gauge found here https://gumroad.com/l/OxKwn

The reaming tolerances are 0.2 / 0.1 / 0.05 which were fused together prior to my final calibration above, will do another test print now that I believe I have everything setup correctly and post my findings.

Re: Print quality after mechanical adjustments

Well having thought I had the calibration done right, turns out that it worked perfectly fine on small first layer prints, whilst moving on up to a larger print, for a small project I did for a friend, the first ayer clearly shows that the heat bed is skewed, dont mind the image, the right side corner is the bottom left of when the project was printed, flipped right side up.

I have highlighted the area in the middle with a box, that was the area I used to do all my calibration prints, which ran perfectly well in my earlier posts, but the minute you go out of that boxes area you will notice the uneven finish due to bed being skewed.

After messing around on the mesh bed leveling and re-aligning the Pinda probe, looks like I am going to have to unscrew a couple of things to ensure better results.

A quick Digital caliber gauge check revealed that the bed was lower on some corners then other corners, i.e some screws were tightened down a little more then others resulting in a non level bed.

Tomorrow, objectives :

First step would be to realign the pinda probe with a feeler gauge to 0.75 as this was done by eye balling.
Second step, use digital caliper to measure the Heat bed gap between the Y carriage and heat bed on all points so they all match.
Third Step after Second step heat the bed a couple of times and let it cool down to get any twist out and remeasure again second point to make sure all is ok.
Third step, use dial indicator to check all X/Y axis for any possible skewing.
4th Step redo calibration XYZ then run Calibration file and live adjust Z.

Run final Gcode file and see results. Will post my findings.

Re: Print quality after mechanical adjustments

Couple of things I found out today, spotted that the X axis belt was too tight, as small black shavings showed up in the channel and on the motor.

Reference the images here.. After readjusting the belt again the shavings completely disappeared, and the overall smoothness got even better.

Now that all the belt tensioning are correct, proceeded to check the main deck frame, for any sign of twist and work my way up to the heatbed.

Since the base had the felt pads stuck on during my build it would be not possible to see any twist in the lower deck, pads had to be removed and main deck orange blocks needed to sit on a flat level surface.

After removing the pads noticed that the LCD screen holder was touching the surface, so had to remove the LCD screen to work on the lower deck, upon inspection, there was a twist on the back left corner, with a feeler gauge that could pass under it at 0.45, all other corners were okay, so fixed that and put everything back together.

I took a digital caliper and checked all for corners of the Y carriage to the heat bed, front right corner was off by -0.12, so lessened the screw tension a little and that gave me identical readings on all 4 corners of the Y carriage to the heatbed.

Now that I am sure that everything is mechanically sound and remeasured, I decided to reset the Pinda probe to heat bed level using shims to a height of 0.75mm.

Ran the XYZ calibration and then ran the default Calibration V2 that came with the prusa, automatically the Z level was way off, so used Live adjust Z to have it come down to -800um to get the first layer sticking correctly.

Then printed Jeffs square to check the correct first layer Z level setting, as can be seen here the first print had the back end of the square not sticking correctly, all 4 Mesh Level bed correction are set to 0.

Dont mind the 595 that should be -800um as per the Z level set.

After which I adjust the Correct Mesh bed compensation on the back to -35 as per this image and the layer turned out better.

A couple more prints on with more Correct mesh bed compensation...

Finally came to Z level set at -835um after messing around alot on the Mesh Level bed compensation and running another XYZ calibration with another Z level calibration. With mesh bed back compensation set to -35

Final print of Jeffs Square, measured out at 0.21 can be 0.20 with Z level set at -825um but there is a reason as to why I did not go that path.

After messing around so much on the calibration and mesh level compensation, it has come apparent to me that the Mesh Bed Compensation 4 point adjustment has some what of an in between calculation, obviously 4 points of correction meant that it would be an in between adjustment as opposed to a more accurate 8 point mesh bed adjustment, 9 with the middle of the bed.

Say for example Front Center/ Front Right / Right Center / Right Back / Back Center / Back Left / Left Center / Front Left hence forth the 8 points accuracy plus +1 center middle of bed making it 9 as opposed to the 4 points found on the LCD.

This image of the final print clearly shows, that the front center required a mesh bed adjustment of say +15um in the front center and -15um on the Front Right and Center Right and Back Right as well as Back Center.

If I was to adjust the 4 points it just seemed that it would cross paths to a point where the adjustments did not make it any better.

As far as my findings go, the only way to resolve this is via software now, as I believe I cannot build the printer anymore perfectly then where it is today, the heatbed is the obvious culprit now, and if I was to apply the theory of RC nitro engines, then no 2 stock motors are alike since some come better in performance due to the better overall tolerance from one build to anther.

I still admire how precise this printer is and what it can achieve, this minor thing with the heatbed can be obviously overcome with code, which IMHO would be a good point for Prusa Research to incorporate in their future firmware release and or Slicer Prusa Edition.

There are 1001 and one reasons for this minor issue, probe sensing, metal sensing, temperatures etc etc, just too many to pin point the exact culprit of it.

As far as am concerned, it negligible unless your constantly printing the maximum bed size area all the time. I did not even spot it till I had a med level sized project.

Reading on into the forum PJR has obviously started hashing it out, on his thread here http://shop.prusa3d.com/forum/prusa-i3-kit-building-calibrating-first-print-main-f6/hyperfine-bed-leveling--t4330.html

For me this thread has come to a conclusion, hope someone finds the thread useful.