[Model and reality measures not matching]

Manually design a test-file: for example a rectangle of 50mm x 50mm x 0.5mm high, plus a cube of 10mm x 10mm x 10mm. These don't waste too much material and time. Put these in your slicer and verify if their dimensions are still okay. Try printing and see what comes out. This should give you an idea in which direction to search.

I designed and printed a 5mm cube.

In cura everything is fine (5 x 5 x 5), but printed object is stretched in X (6.4 mm) and Y (6 mm) axis, Z is right.

I think belts are well tensioned, maybe too much, but surely not loose.

EDIT: After measuring different small objects it seems that they're scaled about 25% on both X and Y.

Sounds like the calibration factors for your printer need to be adjusted. I don't know your printer, but there should be somewhere in your setup that translates mm to stepper motor steps. If that is messed up, you will see parts which are scaled up (or down) consistently. If you can find the place to adjust the "steps per mm" for X and Y, then change the X number to one that is smaller by the factor 5.0/6.4, and change the Y number that is smaller by the factor 5.0/6.0 then re-run your test. Should get you close.

[Losing Layer 1 On 2nd Extruder After Dual Color Merge]

I think if you have your two stl files set up correctly, you should not get a brim for the second model. Basically, merging two models means you get a single model which is printed with different sections having different colors... but still, a single model. That model just has one brim. In my experience, you get both extruders laying down filament at the layer 1 level (0.2mm for me) but only one brim (laid down by extruder 1). Watch the Z height during the print the height of the first instance of using extruder 2 isn't at the same height as the first instance of using extruder 1. My guess is that they are the same and you just expected (incorrectly) a brim from extruder 2.

[printing with the 2nd extruder ONLY ??? in Cura 2.6]

Hey DaHai8 !

thanks a lot!  

after some tweaking, I got it! Now I can print with only the 2nd Extr....!!

BUT:  I can only use Cura 2.4 , cause the representation of the graphic for "layers view" does not work (Open GL etc...)  The "compatibility mode" is'nt just fine )-:

And by the way: Do you know, how I can configure the "machine settings" for the dimensions of the printhead in Cura 2.4 ?

see also --->  

https://ultimaker.com/en/community/39281-cura-not-using-user-set-machine-print-head-size?page=1&sort=#reply-183614

@ eldrick:

thanks for the hint !! ... but I do not know, how I use this :( 

what shall I  type in there ???

In my experience, a "Regular Expression" (REGEX) is a perl search and replace expression. You don't need to put anything in there. I suspect that Cura is allow you to use REGEX's to build complex substitutions. Yours is pretty simple, so just leave the box unchecked.

[Cura 2.6 - bogus M104 S200 after first layer prints, despite specified temperatures.]

(Tried a reply and forgot to check the "Not a robot" box, so sorry is this is duplicated.)

Cura 2.6 has a lot of settings that are hidden and will assume a default value if another value isn't specified by the user (like "Initial Printing Temperature"). I would guess that that is where your M104 S200 is coming from. To track it down, open the Settings Visibility and do a search for Temperature, then check all of them to make them visible. Go back to your main page and look for a temperature setting with a value of 200. Change it to something more appropriate (like 220) and recompile. See if the M104 S200 is gone (and you find something like M104 S220).

[Cura 2.6.1 feedback]

First post so not sure I am going this correctly, but wanted to comment on the latest Cura (2.6 and 2.6.1).

- Build surface issue:

I'm using a dual extruder set up in with Marlin (Prusa i3). The first extruder is set to cover the entire build surface (200 x 200) with the second extruder placed with an offset of -35mm relative to the first extruder (so it can actually cover from Y=0 to Y=165). When I load a dual extrusion print and set both parts to be printed by extruder 1, the build surface shows the back 35 mm of surface as greyed out (not available). (It should should ALL the surface as available.) When I choose extruder 1 for the first half of the print and extruder 2 for the second half of the print (as it should be), the build surface now shows both the front 35mm and rear 35mm as unavailable (should show the front fully available and the rear 35mm as unavailable).

- Material issue:

I have set up my printer defaults to print at 215. But I have also set up some custom material entries that have different temperatures (an ABS for example, that has it's print temperature set at 235). So when I tell Cura that I would like to use the new material (print temp 235) I would have expected that the slicer settings (normally printing at 215) would be overwritten to the new temperature, but that doesn't seem to be the case. Am I missing something?

Great slicer, by the way. Thanks for those who do the work!