Dimension Acuracy

#1
I have a Gmax 1.0 with an upgraded Gamx1.5 + bed. The new bed is a lot more sturdy and stable. Once I leveled the bed I did not have to do it again. The older one, the Plexiglas one was a mess.

I never really paid attention to dimensional accuracy in prints until recently. What I noticed now, something that has been there for some time, I just did not pay much attention to it before, are having ripples or waives on certain vertical walls.

So after designing 4 intersecting rotating axis lines every 45 degrees (0,45,90,135, 180, 225, 270, 315, 360) I printed a structure 10mm tall, and 2mm thick. Measuring the thickness on each arm, showed that depending the position of the leg on the print, the measurements were from 1.86mm to 2.21mm. The designed dimensions were supposed to be 2.0 mm.

Here is a video of what I printed with some of the measurements. You should get the idea.

https://www.youtube.com/watch?v=-iLXxOiSzHE



The bed I had leveled with a feeler gauge to a 0.152 mm on four points around the bed. My first layer was 0.28 mm and the next were set to 0.10 mm, which is where I typically print. I tried the print with Cura and then with Slic3r. On the X and Y the dimensions come up relatively ok and straight lines appear straight. The problem happens on the diagonals. The dimensions deviate more on upper left and upper right movements of the print head where it also print straight lines with waives on the sides.

I have used CURA and Slic3r to print this. I even took the time to look into Marlin to make sure that the steps per min on the x and y steppers were set right, since I upgraded from gMax 1.0 to gMax 1.5 firmware. It all seems good in Marlin.

I am thinking about buying Simplify3D slicing program. I am starting to think that that could be one of my problems with dimensional accuracy.

Any thoughts?
 

AlexD

New Member
#2
Hi there,

Nice detailed post, I have not seen this problem before or even experienced it myself, however I have never checked my prints for similar problems.

First of all, I would make sure that the belts are TIGHT and that the Y Axis Rails are absolutely true to the frame, my first thought is that the rails MIGHT be trailing off in one direction.

Do the dimension differences gradually trail out?? It might help to do a REALLY slow print to try and identify if there is any kind of play mechanically in the printer that could be throwing it out.

S3D is a brilliant program but this more like mechanical problem, and if you have had it using more than one slicer then I don't think S3D will help (although buy it it's awesome :lol: ).

Thanks

Alex
 
#3
Problem fixed. The printer was getting old and had loosen up significantly. After tightening it up, replacing some parts, updating firmware, and squaring the all the axis, now it is better than when I first got it.
Moving on...