Side Ooze

Not sure what the technical term is, but I’m trying to solve an issue where holes oriented on the Z axis have a reduced diameter, reduced by about 0.5 mm (which is coincidentally, the nozzle diameter of the hot end). So for example, a 2mm diameter screw hole prints as 1.5 mm. Obviously I can account for this in my CAD by adding 0.25mm to the radius, but I’d actually like the drawing and the print to match closely so that if it is an object I want to have printed in one of those expensive powder 3D printers (after doing all my tweaking on the LB Mini), I don’t have to go through and reset all of my screw holes to actual size.

I’m relatively new to 3D printing having had only limited, largely frustrating, experiences with some other kinds of printers at a makerspace. I’ve been looking at various threads here on optimizing print quality but I’m not having any luck with this. This could be because Cura directs the print head right down the center of a line, making it inevitable that there will be “side ooze” of half the nozzle diameter, or it could be that there is a setting I haven’t messed with properly.

Some things I’ve tried include measuring the diameter of my filament (e-sun white HIPS) and adjusting accordingly (2.95mm incidentally). Adjusting the flow rate (upward after adjusting filament diameter because I was getting a lack of flow). Stating the nozzle width as 0.4 mm instead of 0.5. Slowing down the print speed. Setting initial layer thickness to 0 (my prints are invariably 0.45 mm too thick BTW). Setting the initial layer line width to 100% down from 125%.

Anyway, any further suggestions would be great.

(Note – I do love this printer compared to the ones I’ve used before – no glue sticks, no taping, and the prints work every time – the only failed print I had was an overnighter where the filament tied itself into a knot).

Most likely the issue you’re seeing is your layer height setting.

For standard abs settings in cura, your layer heights at 0.18mm per layer. You can set it for as low as 0.05mm per layer in the Z in the expert menu if you’re willing to accept longer print times for your increased quality print. Since each layer in the Z is 0.18mm, holes in the Z direction will not be as exact as in the X Y direction.

You’ll also find holes in the XY plane usually come in small due to the nozzle width.

Best bet is to print a hole and pin test such as the following:

http://www.thingiverse.com/thing:62304

Print it oriented flat on the bed then print it again in the vertical position. Take some calipers and measure the different from the actual solid model and make a chart and add that offset to your design.

The other option I use often is to get yourself a full sized drill set similar to the following:

http://www.harborfreight.com/115-pc-cobalt-drill-bit-set-61886.html


This will give you drills in very small increments and you can drill out your printed hole to the EXACT diameter you want. That’s probably the quickest and easiest way.

-Jim

Thank you for the info. After thinking about it, I decided to drill out my holes just so that if later I have the piece printed on the machines they have sculpteo or the like, I don’t have to edit my drawing. I suppose I should start looking into a small drill press to make that process more accurate.