Just a little bit smaller...

I'm trying to print the extruder block, it don't seem so bad, but its all a little bit smaller...
The hole for the m556 bearing it's 0.2mm smaller than original and so all other..

that's the gcode by slic33 (only the first lines):

..........................
; generated by Slic3r 1.0.0RC3 on 2014-03-14 at 11:07:35

; layer_height = 0.25
; perimeters = 2
; top_solid_layers = 4
; bottom_solid_layers = 4
; fill_density = 0.2
; perimeter_speed = 20
; infill_speed = 20
; travel_speed = 60
; nozzle_diameter = 0.5
; filament_diameter = 1.75
; extrusion_multiplier = 1
; perimeters extrusion width = 0.75mm
; infill extrusion width = 0.75mm
; solid infill extrusion width = 0.75mm
; top infill extrusion width = 0.75mm
; first layer extrusion width = 0.50mm

G21 ; set units to millimeters
M107
M190 S60 ; wait for bed temperature to be reached
M104 S200 ; set temperature
G21 ; set units to millimeters
G90 ; use absolute coordinates
M83 ; use relative distances for extrusion
G1 Z5 F200 ; lift nozzle
G1 X2 Y50 F2000; Go to wait for warm position
M116; Wait for all
G1 E1
M109 S200 ; wait for temperature to be reached
G90 ; use absolute coordinates
M83 ; use relative distances for extrusion
G1 Z0.250 F3600.000
G1 F1800.000 E-3.00000
G1 X52.075 Y64.440 F3600.000
G1 E3.00000 F1800.000
G1 X52.225 Y64.320 E0.00998 F360.000
G1 X53.455 Y63.550 E0.07541
.....
Can help me to understand where I do my mistake?
Some image...

Quote

; extrusion_multiplier = 1

Have you done a single wall test as to check you extrusion width?

afiar mine is set at 0,79 as to get it right

Erik

I usually end up drilling the holes out to the size I want - I had to do this with several of the original parts that came with the kit too. I've not yet found a way to get hole sizes accurate. I tried setting the extrusion width to nozzle diameter + layer height as someone suggested, but that made the horizontal holes come out elongated.

Edited 1 time(s). Last edit at 03/14/2014 08:32AM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Vertical holes printing too small is a Slic3r bug that has never been tackled by the developer, Sound/Alessandro. Most other slicing programs have a similar problem. For any vertical hole, the nozzle path is offset by half the extrusion width, and he doesn't seem to want to change this - see: [github.com]
Theoretically, that's fine; but the problem is that the area on the inside half of the circle is smaller that the outside, but gets the same amount of material, and no compensation is made for this, so it always squishes in a bit more than it should. It's the same problem you get when you print a 90 degree internal corner; there is too much material in the corner segment, which squashes out, to make the corner not as sharp as it should be. The answer is to either offset the path, or reduce the flow rate at this point.

Jean-Marc/emaker (RepRapPro director) has written a compensation routine, for the older 0.9.9 version of Slic3r. He pushed it to the Slic3r main, but it was never rolled into the main version. The developer felt it wasn't necessary, despite nearly everyone complaining about it! We use this version to slice in-house, and it's available as source code here: [github.com]
This lets us have 3D files with correctly sized holes; we don't have to compensate in the design files for slicer/printer inaccuracy, as it should be. Though it may have other problems!

However, this can make reprinting parts a little more difficult. The best compromise is to select 'External perimeters first' in 'Print Settings > Layers and perimeters > advanced'. That way, the inner layer won't push the outer layer even further into the hole.

I hope that helps.

Ian
RepRapPro tech support

@ormerod168 No, I have done the thin wall test but just to test the print quality, I don't have a digital caliper, but with my caliper the thin wall seems to be of the correct size of 0,75mm. If I have understood the test correctly, if the size of the wall correspond to the size of the "perimeters extrusion width" it should be ok or not? I'm trying to understand but for me it's a really new world

@dc42 I try one other way, I just rescale all to 102% and it fit really good, the hole of the bearing are anyway a little smaller, but just a little forcing it it goes well, but it so strange... I don't really understand why, but even the hole of the screw now are accurate both as diameter and also as distance between two holes... I'm a little ....

But the problem is for any kind of print, it's all a little smaller not only the ones of the omerod kit...

Now I'm trying to print some other object at 102% just to test...

Quote
ian
(...) However, this can make reprinting parts a little more difficult. The best compromise is to select 'External perimeters first' in 'Print Settings > Layers and perimeters > advanced'. That way, the inner layer won't push the outer layer even further into the hole.
I hope that helps.
Ian
RepRapPro tech support

O yes it's very interesting I try to print as you suggest, I hope they will implement the corrective routine also for the new version, I will try to compile the code but I'm not a programmer, can't find the binary anywhere?
But my problem isn't only for the hole, all the dimension are a little bit smaller..., rescaled to 102% from slic3r I have the correct size, I don't know why!!!

Quote
raffybuffy
@ormerod168 No, I have done the thin wall test but just to test the print quality, I don't have a digital caliper, but with my caliper the thin wall seems to be of the correct size of 0,75mm. If I have understood the test correctly, if the size of the wall correspond to the size of the "perimeters extrusion width" it should be ok or not? I'm trying to understand but for me it's a really new world

I just think it sounds a bit strange that your perimeter extrusion with is 0.75 - what are the setting in slic3r\print settings\advanced\default extrusion width? - mine is set as zero (auto)

Erik

Quote
ormerod168
...

I just think it sounds a bit strange that your perimeter extrusion with is 0.75 - what are the setting in slic3r\print settings\advanced\default extrusion width? - mine is set as zero (auto)

Erik

The default extrusion is set to zero as your, why do you think that is strange? I print with 0.25 layer height and the nozzle diameter is 0.5, I have understood that the correct setting for the perimeter estrusion width is 0.75 isn't correct?,

@dc42 I don't have notice any non circular hole in my printing. Of course not are perfectly circular, but a good approximation, but I lack of experience I own this printer just from two week....

Quote
raffybuffy
The default extrusion is set to zero as your, why do you think that is strange? I print with 0.25 layer height and the nozzle diameter is 0.5, I have understood that the correct setting for the perimeter estrusion width is 0.75 isn't correct?

Quote

..Extrusion Width Ratio is placed under the advanced options, so it's not necessary to change it at all and you shouldn't do it only if you really need a particular extrusion width. Just be careful not to set it to a smaller extrusion width than your nozzle size: the results are undefined in that case...

[forums.reprap.org]

Erik

I have done a lot of measure, to try to understand how print with the correct dimension, as method I use (just why all start from my tentative of printing it correctly) the iamburnys_ZGearHexnut (many thanks to him ) measuring the dimension in netfabb (typically the hole of the hexnut and the hole for the bearing, but also any other dimension) so I understood that the dimension on Z are alway correct the problem are on x/y plane.

I checked all the the settings and I found an incorrect parameter for the stepper motor of the extruder (M92 E433) that I have put in during the commissioning of the omerod, measuring the lenght of the pla, I don't know how but now seem changed (perhaps changing from abs to pla?), so I set the new value (426), this had a good effect on all the job.
I tried to change many parameters but I don't have find a way to print an object with the dimension as in netfabb at least for the hole extruded on Z (really all the measures on xy axis are not very precisely), but I have notice that all the measure in netfabb are a little more bigger, I suppose to compensating the mistake.
Anyway I will oversizing any hole to have a chance to get a good job.