MakerGear Forum

Hi everyone,

I received my M2 printer about a week ago. So far, most of the prints have been coming out in excellent quality. However, a print that I attempted this morning in PLA came out in very poor quality.

Here's the solidworks file of the pic:

http://imgur.com/PhAuNP8

as you can see, it's simply a large ring with four rounded cylinders attached with 1.5mm holes in the end of each cylinder

Yet, on the M2 print, the cylinders turned out warped near the bottom, and the 1.5mm holes didn't form :

http://imgur.com/C7DgtDg
http://imgur.com/zKQrDaB

Would anyone happen to know what I could do to solve the printing problem? Here's the printing stats I used incase these may be the cause of the problem:

Print bed temp: 65 C

Nozzle temp: 215 C

Layer thickness: .05 mm

Perimeter speed: 30mm/sec

Infill speed: 45mm/sec

Travel speed: 45mm/sec

You need to print any model with high degree overhangs with support (I'm assuming you didn't turn on support). Conventional wisdom says you should use support for any overhang > 45 degrees, but I have had good results printing up to 70 degrees in PLA with a custom fan shroud. You also have the added difficulty of trying to print a rounded surface against the bed. There is only a single thread of contact between those cylinders and the bed. That will not give you much bed adhesion at all and you are likely to see warping.

Even with support, curved undersurface quality will not be awesome. Here are some pictures of a similar case, using dual extrusion with nearly solid dissolvable support. You can clearly see the difference between bottom and top surfaces. viewtopic.php?f=13&t=2221

If it were me, I would print the cylinders separately, standing on end, and attach them to the base. You could model in countersunk flats into the base to index the cylinders to make gluing easy. If you're using PLA, IPA Weld-On #4 or other plastic solvent works fantastically, and the weld will be as strong as the rest of the part. Or if the cylindricity (cylindricality?) is not super important, make the base flat, with 45 degree chamfers. You can even get away with small fillets against the bed, as long as there is a substantial amount of contact.

On an unrelated note, 0.05mm layer heights is also likely to cause you enormous headaches. It is possible, but requires exquisite tuning, both of extrusion and mechanical setup. I would stick to 0.2mm until you get your part to print to your liking, then investigate lower layer heights, not dropping below .10mm. (I find there is very little to distinguish between .15 and .10, even). If surface finish is important, I find myself turning more and more to finishing techniques rather than low layer heights, which can hide a host of defects. XTC-3D or heavy fill primer is excellent. Low layer heights will also weaken the strength of the part along the Z axis.

Just had another look at your model photo. What are those (non-cylinder-end) dimples? Are those through holes?

jsc wrote:If it were me, I would print the cylinders separately, standing on end, and attach them to the base.

Another good (better?) choice is to split the model horizontally, through the center. Look up some of Ed Nisley's posts on how to put matching holes in the surfaces of the two attaching faces just the right size that you can use a short piece of filament as a pin both to align the pieces and to help hold them together.

Good design is 90% of the battle. Just as there are certain design practices that you need to follow when designing injection molded parts, so you need to follow certain guidelines when designing 3D printed parts. It's just that 3D printing is mostly a hobby thing, and I'm not aware of any book on good design practices for it.

Even with support, curved undersurface quality will not be awesome.

Agree 100%. I did some testing with an egg shaped object, and i never could get the rounded underside to come out perfectly smooth, even with support enabled. There will be pock-marks.

If you don't want to split it up into parts, be sure to turn on support in S3D and hit it with extra cooling, (I just use a desk fan), to cut down on the globbing under the overhangs. But your better choice if you have the time is to rework the design. (I'd likely cut it in half, print each half with the flat side down, and the little end-cap pinholes will probably bridge okay without support. Then just superglue (and clamp) the two halves together.)

And if those other little dimples are actual holes that go through, get a drill bit in that size.

Thanks for the support guys, I decided to print the four cylinders and attach them to the main body. The "dimples" were intended to be holes where a screw would go into and tighten down on a carbon fiber rod (that slides into the top of each cylinder) to secure the carbon fiber rod in place. I've decided to use a better method by simply beefing up the cylinders and making a slot down the middle to clamp down on the CF rod when some screws are put in place.

Let me guess: quadcopter?