Part shine & outer perimeter speed
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Hi all,
I'm trying to get a more consistent finish on the exterior of my parts while minimising loss in build rate. My parts mainly have a matt finish, but where the printer slows down the outer surface shine appears. Do most people prefer to slow the outer perimeter right down to bring back the shine, or increase small perimeter speed/reduce slow down on short layers?
Currently running a V6 with stock 0.4mm nozzle, heater, and thermistor. I run a track width of 0.44mm, layer thickness of 0.25 and have been working to maximise my speeds on my new build.
I run a linear extrusion correction that covers the range of 40-250mm/min on the filament speed which is approximately covering 10-90mm/sec print speeds. I have noticed that as speed increases you loose shine (increase in shark skin effect) on the extruded material (extruded into free space) and it gains in thickness (die swell).
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i think with lower speed the plastic can reach a higher temperature.
with fast speed there is a lot more plastic going through the hotend and it does not have the time to reach the same temperature. -
@veti Yes it can. But I don't think this is a too much flow for the hotend/nozzle problem. I would expect a strong kick up in the linear/non-linear extrusion graph if I was hitting on melt temperature issues.
My understanding of sharkskin is where there is a shear slip effect on the polymer/nozzle wall. When you have lower flow rates the the velocity gradient from the wall to the centre of flow is smoother. At a critical point as flow rate increases you get a much more chaotic flow at the boundary.
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https://makeshaper.com/2017/12/04/matte-glossy-pla-prints/
thats is what i based my thinking of and the fact that i have observed this when printing at different temperatures.
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It's all related. Raise in temperature will reduce the viscosity of the material which will may mean the snap point where the melt begins to slip along the bore increases. Likewise maintain melt and increase through put and you will also hit against that slip point.
I'm already processing at 200C on the polymer and staying below 10mm3/sec.
Back on point. What are your perimeter/outer perimeter/and infill speeds and thicknesses? Do you see differences in surface finish on your part as geometry forces different scan speeds?
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since i print mostly with stealthchop2 on my maestro. my speed is below 80mm/sec
and i print the outer perimeters with 1/2 speed. (i am assuming you mean mm/sec as well because 40mm/min is really slow) -
Cheers.
40-250mm/min on a 1.75mm filament is 14.6-91.1mm/sec head speed with 0.44 track width and 0.25 layer thickness.
...however in my first post I did say in error 40-250mm/min equated to 10-90mm/min head speed in error! Fixed that now.
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I think I'm going to need a new temp tower. The vase mode one isn't great for hot and fast!
