ABS and arches

See the picture below of a part that is about 40mm across. As you can see it was printed in this orientation. The top of the hole has not joined well. It was printed without support material, but I'd actually expect a hole like that to print fine if I was using PLA. It's printed at about 40mm/s at 225degrees.

I'm guessing with ABS it is laying down the edge and it is warping. No idea how to fix it.

:-)
hi there

One way to fix it is...avoiding it.
Many printing issues can be solved by avoiding.

In this case, I saw many times 3D prints designers are using a teardrop shape instead of a round hole.

Or, if the situation allows it, use a hexagon shape which points upwards.

Both will greatly reduce the bridge because you're actually printing a bridge, not an arch.
Arch would have meant moving Z axis while moving X.



As for the other options, I think you should start reading about "how to make perfect bridges" :-)
It's a .. tough chapter on 3D printing.


good luck and don't give up

I won't give up I like the idea of hexagonal holes. I made this one round because I tapped it, but I'll go hex in future, I imagine I can tap that too

Lower your temperature, that's all you really need to get good holes without support. You might be extruding too much?

Edited 2 time(s). Last edit at 10/21/2014 10:42PM by ggherbaz.

I'll give it a go
I've created a cube with hole in to experiment. Is there anything that indicates my temperature is too low? Besides it not melting of course

Bad layer adhesion, clicking of extruder, thinner extrusion. Those are the most common ones.

Have you checked your "real" temperature? You might think that you are extruding at 225 but reality might be something else. Just test by 5 degrees each couple of layers until you find your lowest temperature and adjust from there.

One more thing, you don't mention what kind of printer you have, ABS don't like open frames because of cool drafts, keep the printing area at least 90 degrees.

It's an i3, open to the elements at the moment, printer 2 will have an enclosure I think for sure

I've tried a few things regarding the real temperature, I was worried about this a while ago because I was having various issues. I've got one of those thermocouple based hand held temperature devices which I've had a few issues with itself. So what I've done is start low and bring the temperature up bit by bit until it started moving. Lowest seemed to be about 215, although 220 gave me a stable slow moving thread. I print at 225 usually on that scale, and 235 for fast prints.

Ok, good to know that you have already found your extruding temperatures. So 225 is perfect, but because you have an open frame the problem might just be that the filament is cooling too fast.
If you have the time do 2 simple tests:
1 print the part with a skirt about 4mm away from the part to keep heat from built plate around the part.
2 without the skirt put a 150~200 watts incandescent bulb about 6 inches away from the part.

Damn, did you suggest a bulb the other day? I have it on my list but completely forgot about it!

I need a hot bulb pointing at me right now, I've got a flu (possibly man variety) so freezing if I step away from bed right now :/ I'll amuse myself looking for high wattage angle poise lamps on Amazon

I use this method every time I print with ABS, the lamp with the 200 watts is pointed at the part I print (my printer is enclosed though) and I keep the chamber between 90 in cold days to 110 in summer times.
Don't waste your money with expensive reptiles heating lamps, uv's or ceramic, just a plain cheap incandescent bulb will do, besides 200 watts consumption is 200 watts no matter what type you use.

But don't forget to get or "change to" ceramic bulb socket, unless you want to do a fire claim with your insurance company ;-)

Funny you mention that, I looked at lamps and of course everything is low power green stuff now. So I immediately thought of either medical heat lamps which led me to terraria (sp?) and reptiles.

Good call on the ceramic housing though, I hadn't thought of that being an issue.

Most of the cheap clip lamps out there (Walmart, dollar store,etc.) Are rated for only 40 watts, but that is just because of the socket, so unless you got a lamp rated for 200 watts bulb you need to replace the socket to prevent melting the cables and risk of fire.