Incorrect width dimension on printed object

HI, I have a prusa i3 hephestos by BQ and have made by first print.
the common 20mm cube but on X axis, is has 18mm width.
I am using 1.4.1 firmware by BQ, where/what can i change to correct this issue ?

Use the reprap calculator to calculate the correct steps per mm for your printer ([prusaprinters.org]). You can then send an M92 instruction to your printer to set the correct steps per mm for testing ([prusaprinters.org]). Once you've got the correct value, you'll need to change your firmware configuration to apply it permanently.

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[3DKarma.com] - suppliers of quality, affordable 3D printer kits and filament for the UK market.

Hi 3dkarma,
I'll try that, thanks.
Regarding changing firmware, the 1.4.1 marlin version by BQ is not available to edit, all I could get was an .hex that I had to flash to the printer :/ How can I change firmware configuration if no source is available ?

EDIT: I found that in Repetier-Host there's an option Firmware EEPROM configuration, I guess this is the place to change the conf, right ?

Edited 1 time(s). Last edit at 03/31/2015 07:38PM by Carlcox89.

I tried to Write EEPROM settings and it said the new value (upon clicking reload values) but when i disconnected and connected printer it loaded the previous 80 value

I'm not sure if repetier host will correctly set eeprom values for marlin firmware - if it thinks it's talking to repetier firmware, it might do something different. The g code reference at [reprap.org] states that repetier host uses M206 for setting an eeprom value, but marlin uses M500. Looking at the eeprom section of the g code reference, you could try first setting your steps per mm to the correct values, then send M500 to the printer. After a reset, if you still don't have a correct value, send M501 to the printer to retrieve eeprom values. Use M503 to check the values stored in eeprom.

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[3DKarma.com] - suppliers of quality, affordable 3D printer kits and filament for the UK market.

I think I got it. The new values are stored now and the 20x20 cube came almost perfect.
ALMOST. .. because it has weird opposite corners (the bottom left [where the printer begins the print] and Top right)

[www.dropbox.com] (left and right corners in the pic)
[www.dropbox.com]

However I printed this thin wall cube ( it as round corners tho): [www.thingiverse.com]
and it came out perfect! No weird corners..they are smoothly rounded

The only difference from this last this thin wall cube is the rounded corners , the first 20x20 cube has sharp corners , so it seems that the printer isn't able to do sharp corners, how to correct this?

From the domed look of the top of the cube, it looks like you're over-extruding a little. Drop the extrusion multiplier down in 2% increments (98%, 96%, etc.) until you get a nice smooth top layer. This should also take care of the rounding of the corners. Also, make sure you randomise the start and stop points in each layer.

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[3DKarma.com] - suppliers of quality, affordable 3D printer kits and filament for the UK market.

Quote
3dkarma
From the domed look of the top of the cube, it looks like you're over-extruding a little. Drop the extrusion multiplier down in 2% increments (98%, 96%, etc.) until you get a nice smooth top layer. This should also take care of the rounding of the corners. Also, make sure you randomise the start and stop points in each layer.

Cant find randomise start/stop points for layers option on Repetier-host using Cura slicer

Edited 2 time(s). Last edit at 04/01/2015 09:03AM by Carlcox89.

Randomise start/stop points might not exist in Cura.

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[3DKarma.com] - suppliers of quality, affordable 3D printer kits and filament for the UK market.

I reduced the extrusion multiplier and the top face looks better. However I cannot seem to get the corners better and neither print circles

Tried to print this: [www.thingiverse.com]

got this: [www.dropbox.com]
(stopped middle print since I saw it was way off)

I'm starting to get sad... either cura , either slic3r.. with hephestos default print profile i get all prints wrong

I decreased extrusion multiplier but now i'm having problems with top layer...
is this related to extrusion multiplier or something else ?
Because i tried then to increase it from 85 to 90 and then 95 and then 100% (left to right in the pic ) and this is what i got... the top layer doesnt get better
[www.dropbox.com]

Quote
Carlcox89
I decreased extrusion multiplier but now i'm having problems with top layer...
is this related to extrusion multiplier or something else ?
Because i tried then to increase it from 85 to 90 and then 95 and then 100% (left to right in the pic ) and this is what i got... the top layer doesnt get better
[www.dropbox.com]

Ok, i solved this problem setting the infill to 30%... it seems Cura has this issue if using less than 30% infill it creates this holes in the top layer.
Now i'm starting to like my printer.
Only a couple more adjustments and its good to go

Anyone knows why this happens to the cylinder ? (it's the starting point.. it creates a vertical line) in the gcode it doesnt appear
[www.dropbox.com]

At the end of each layer, your extruder should retract a couple of mm to prevent oozing and blobbing. At the start of a new layer, it will reverse the retraction. If you've got a blob on the inside of the cylinder and a divot on the outside, it is possible that you've either not got retraction turned on, or that you need to increase retraction slightly and add a little bit of extra length on restart. Easy enough to do in Slic3r, but I don't know the specific Cura settings.

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[3DKarma.com] - suppliers of quality, affordable 3D printer kits and filament for the UK market.

Prints start to get better and better and I couldnt be happier
[www.dropbox.com]

3dkarma thanks for all your help!
I was able to do bridging perfectly and now the only two things that need to be fix are these vertical lines (I have retraction enabled) and the bottom layer quality that isnt perfect..