Rostock Adjustments need hints

[MorbidSlowBurn]

Hi,
I just posted my Rostock Max in the "show us your machine thread". I have had it up and running for about 3 weeks but not enough time to fully tune it. I am attaching a picture of a calibration cube I printed and it has a couple of issues but much better than the first two I printed. I have searched the forums and internet but have been unable to find a solution.


Rostock Specs:
Acrylic Frame with single extruder and Onyx bed with Borosilicate Glass.
Firmware is Polygonhell dated 02-18-2014 with mods for 16 micro steps.

First issue, when the printer begins to print it places a nice layer when moving towards the "Y" stepper but makes a thinner layer when traveling away. Initial layer looks good when moving in the positive X direction but thin when traveling in the negative X direction (can see on the perimeter of the cube print). I may have found the issue but couldn't find out how to correct it. My print head is not parallel to the build plate. I get the following measurements when measuring from the top of the printhead platform to the build plate (hole at each point of the platform): between X and Y steppers 20.4mm, Y and Z 19.7mm, X and Z 21.4mm. All bearings are adjusted so there is no slip and belts are adjusted.

Second issue is that on the last layer (most noticeable) there are gaps in the layer as seen in the attached image. The upper surfaces in the side holes do not have these gaps.

Third issue, just a notice and probably acceptable is that the first 10 layers have a flare. It starts with about 1mm on each side (inside and out of part) and slowly decreases until it is uniform for the rest of the print.

Calibration_cube was printed with the following configuration at 75% speed:
No cooling, Filament diameter 1.735, extruder temp 230C (all layers), bed 60C (first layer), 50C remaining
Layer height .2mm with .3 first layer, 3 perimeters with randomize starting points and 5 solid layers.
20% infill and the rest of the settings from the PDF instructions.

When adjusting the settings I went so far as to measure the feed on the extruder to tune in a 100mm advance on the extruder filament. EEPROM setting for Extr.1 steps per mm 573.00

Thank you for any help you can give me,
Mike

[img]http://i1299.photobucket.com/albums/ag6 ... 6edd37.jpg[/img]

[geneb]

You need to make sure that you've got the nozzle height at the base of each tower set correctly. The layer thickness change you're seeing may be due to a big error on one or more towers.

The infill error you're seeing is nearly identical to what I had going on - it was only recently discovered (by mhackney(sp?)) that this was due to binding of the plastic support arms to the aluminum u-joints or binding of the aluminum u-joints to the platform assembly.

Check the fit of each arm - you don't want any side-to-side movement, but the arm should fall to the vertical position under its own weight. The u-joints on the platform end should spin a bit when flicked with a finger, but should have no side-to-side movement.

g.

[MorbidSlowBurn]

Thanks for the insight. Now that you mention about the ujoints I remember reading a post on that. I will rework them as I know I am probably a little tight for fear of being too loose.

And with the leveling I did the full leveling process on the towers and I don't think that is my issue. I have printed at various locations on the plate with the same results. If I was out of level I would expect it to be more severe as I approach the "low" tower. What I really see is that the bed and print head platform are not parrallel. I see this being a bigger problem when I install my second print head as one will be lower than the other. When measuring the height of the platform to bed without moving the head, I am getting about a 2mm height difference at the three corner points of the platform. This implies to me that the extruder tip has a slight tilt (using my measurements and solidworks I estimate about 2 degrees out of vertical on the extruder). It is almost as if the ujoints at the cheapskate bearings are not parrallel. I will see what I can adjust when I rework the ujoints for less friction.

[MorbidSlowBurn]

I spent a couple of hours last night reworking the ujoints. They all are much smoother with movement. The hardest time I had was on the platform until I had the screws that hold the halves together tight while sanding (shaft slide to side so that only one ujoint was removed). The screws would create the slightest buldge after tightening that would bind the u joint. This was on the platform only as the chepskate ujoints would allow the arms to fall straight down under their own weight.

Now I do have another question. My ujoints I adjusted for vertical motion. I did sand the arms more to loosen them up but there is friction moving them side to side. What is the right amount of friction on them?

I leveled out everything, adjusted EEPROM and end stops while the bed and extruder was hot. The perimeter layer looks much better but the last layer still has the exact same gaps (same g-code from slic3r). I am going to try kisslicer to see if I get a different result.



And BTW I thought the PDF assembly instructions were great and they were a deciding factor for my purchase.