X-axis prints 0.2mm smaller

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X-axis prints 0.2mm smaller

Postby nidalp » Tue Jun 02, 2015 4:25 pm

This test object has it's X dimension printed 0.2mm smaller.

What could I do to fix this?
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Re: X-axis prints 0.2mm smaller

Postby gCreate_Kyle » Wed Jun 03, 2015 6:56 am

Hi Nidalp,

Check your belt tension and for friction in the extruder carriage.

And dial in your extrusion multiplier. You may also want to log the average diameter of your filaments.

I don't recommend changing the steps per mm in your firmware. This will cause your dimensions to be off over long distances.
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Re: X-axis prints 0.2mm smaller

Postby nidalp » Mon Jun 08, 2015 10:04 pm

Well, spent 3+ hours yesterday working on my gMax, removed the bed, realigned entire frame, made sure that base is square, Z guides are vertical and aligned to one another, aligned Y axis rails and mounted bed carriage on them so it doesn't wobble at all and moves smoothly. About 80% of those big nuts that keep the frame together were so loose that I could turn them with my fingers, and this is after I've been having this printer for a year or so (note to self: don't ever again buy a 3-D printer that has 3D printed parts keeping the frame together). This is 3 rd or 4th time I've been tightening these nuts.

Today I went on and aligned bed (Z-axis) so that all 4 corners and center were within a hair width from the nozzle. Checked that with paper. Made 4 turns on each of the 5 points (you need to do minimum 2, better 3 and 4th for final check) to make sure bed surface is levelled with the nozzle as it moves around. I use a piece of glass attached to acrylic that came with gMax originally.

Then I made sure that belts are tight and have enough tension. You can't go too far with pulling X-axis belt, Z-axis rods get visibly bent if you overdo it. I have CNC router with XY belts and those are so tensed (is that a correct word, eh?) that when you flick them you hear a note. Those are driving on 16mm rods while gMax has 8mm rods so you can't do the same thing on gMax. But I made sure gMax belts are well tensioned.

Anyhow, still getting those 0.2mm off on X-axis.

Overall print quality hasn't changed noticeably, also. I tinkered with extrusion multiplier, with filament diameter (set it to 1.7 mm since that is the actual diameter of Colorfabb PLA I'm using), with layer heights and some other things. Of course, I didn't try all possible combinations or even all reasonable ones, but I did spend good 2 hours playing with it.

I've got some improvements, but not such that I can for example print 60mm x 80 mm x 8 mm cover and be sure that all holes on it will fit the PCB I want to put in there, at least to some degree. Usually I have to use xacto knife to make holes fit buttons and stuff.

I also downloaded firmware from gCreate site, only thing I changed was to set serial speed to 115200 so I can use Pronterface on Linux. Compiled it and uploaded to my gMax. Made backup of original one before that, of course :) I was using Pronterface to do all this work.

All in all, only thing my gMax is good for, so far, is printing models just for fun where it is not important if they are accurate in dimensions or even in some details. I'm aware that Gordon printed heap of parts using gMax (I can't even get that hex nut holder to print to the quality of the ones I've got with my gMax) and that others have printed some pretty fine pieces. However, my gMax is just a big disappointment for me at this point. It must have mutated into zombie or something while it was being shipped here. Or something. Whatever.

I'm out of ideas and I guess it's time to move on to something different and use gMax parts for some other projects. Cheers.
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Re: X-axis prints 0.2mm smaller

Postby gCreate_Kyle » Wed Jun 10, 2015 9:24 am

Hi Nidalp,
I did not realize you had the 1.0. You should convert the top end of your 1.0 to the 1.5 design. It is a much more rigid design as it does not use 3D printed pieces to hold the frame together.

Get two of these for the base of the uprights http://www.amazon.com/80-20-4-Hole-Inside-Bracket/dp/B00FPMP38C/ref=sr_1_10?ie=UTF8&qid=1433964183&sr=8-10&keywords=80%2F20+bracket Look around for a deal from a knock off brand. 41 dollars is a steep price for that part.

Drill/tap the top of the uprights. Or you could use 2 more L brackets for the top cross bar.

Print new z-axis motor brackets.
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