Gas station without pumps

2019 September 19

Printed 3DBenchy

Filed under: Uncategorized — gasstationwithoutpumps @ 13:32
Tags: , ,

One of the standard test pieces for 3D printers is 3DBenchy, a design with several somewhat difficult features created by (licensed CC-4.0-By-No).  I finally got around to printing it earlier this week on my Monoprice Delta Mini using Hatchbox Gold PLA with a layer height of 0.07mm and the 0.4mm brass nozzle that came with the printer. It took 4 hours and 25 minutes to print at that resolution.

I’ve been trying to figure out how to get Cura 4.2 to dump the entire settings used to generate the Gcode, but I’ve been unable to do that—it seems to record only the differences from the standard settings. So far the best I’ve been able to do is to extract settings from the output G-code:

;Filament used: 3.85238m
;Layer height: 0.07
;Generated with Cura_SteamEngine 4.2.0

M82 ;absolute extrusion mode
G21;(metric values)
G90;(absolute positioning)
M82;(set extruder to absolute mode)
M107;(start with the fan off)
G29 P5 Z0.3 V4; (Level the bed with 5x5 array)
G1 X55 Y0 Z5 F3000;(Move to the outside of the bed.)
G92 E0;(reset extrusion distance)
G1 E5 F500;(Prime.)
G92 E0;(zero the extruded length)
G1 Z0;(Down to printing height.)
G2 X0 Y55 I-55 J0 E20 F2000;(Draw a priming arc.)
G92 E0;(zero the extruded length)

adhesion_type = none
build_volume_temperature = 0
default_material_bed_temperature = 50
layer_height = 0.07
layer_height_0 = 0.14
material_bed_temperature = 40
material_bed_temperature_layer_0 = 50

alternate_extra_perimeter = True
brim_width = 3
cool_min_layer_time = 3
fill_outline_gaps = True
infill_sparse_density = 25
line_width = 0.35
material_initial_print_temperature = 195
optimize_wall_printing_order = True
top_bottom_thickness = 0.42
xy_offset_layer_0 = -0.05
zig_zaggify_infill = True

That is enough to recreate the settings in Cura 4.2, but if the default values change in later versions of Cura, I won’t know which to reset. Some of these settings are irrelevant, also, as the brim_width doesn’t matter since I didn’t use a brim, for example.

Print speed is the default 60mm/s with walls and top/bottom at the default 30 mm/s and travel at the default 120mm/s.

I chose to print at 0.07mm (70 µm), since I read somewhere that multiples of that thickness are best for the Monoprice Delta Mini.

Bottom view shows the shiny surface from using a glass plate with hairspray as an adhesive.

The top surface looks pretty clean, but stringing can be seen from the stern and between the uprights of the wheelhouse.

The top view looks pretty good from this angle also, but some blobbing can be seen inside the bow.

The port bow shows smooth sides, but some stringing on the hawsepipes and poor bridging at the top of front window of the bridge.

The view from the stern shows bad stringing for the rear window. The 0.1mm writing on the stern is barely legible with angled lighting (not really with this flash).

The starboard view shows bad stringing between the uprights of the bridge and some blobbing on the back of the bridge, as well as some layer marks near the top of the arch.

Many of the calibration checks (measured/ideal) are hard to do with calipers, because there are not well-defined measurement points or other parts of the print interfere with placement of the calipers. I skipped some measurements entirely as impossible to measure with the calipers.
roof length 22.9mm/23mm
chimney cap diameter 6.4mm/7mm
depth of chimney hole 11mm/11mm (hard to measure accurately)
chimney inside diameter 2.4mm/3mm (hard to measure accurately)
length 60mm/60mm (hard to measure accurately)
width 29mm/30mm (hard to measure accurately)
height 48.2mm/48mm
box height 15.65mm/15.5mm
box width 11.8mm/12mm
box inside width 7.8mm/8mm
box depth 9.1mm/9mm
box length 10.75mm/10.81mm
hawsepipe diameter 3.95mm/4mm
front window width 9.95mm/10.5mm
rear window outer diameter 11.35mm/12mm (horizontally)
rear window inner diameter 8.9mm/9mm

The z-heights look about 0.5% too big and the x-y dimensions about 2% small (though I don’t trust the measurements—I’d want to use a rectangular block for re-calibrating).

I think that the biggest problem is stringing, which may be fixable by increasing the retraction, though bridging at the top of the front window is also flawed. Retraction is enabled and is the default 6.5mm @ 25mm/s.

I’ll be asking for advice on the 3D-printing subreddit, since asking for help on Benchy prints seems to be common there.

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