Print Failure Ball


#1

I was making a print of a large ball and the print started to fail in the 2nd half of the ball.

Ball is about 4.5" OD. The print is hollow but the shell is .160" thick. There is a .25" hole on the bottom. Layers were .05 mm high. With internal supports.

As you can see in the pictures, the failure started in the 2nd half. The layers started to have strands coming out. There were a lot of solid particles left in the tank afterwards.

I have cleaned the resin tank and currently making a smaller print to see if the issue is with the resin. Any advice is appreciated.


#2

That looks like your print started de-laminating at the point where the layer surface area and separation suction was greatest - and then the ripped off print debris ruined the print from that point onwards.

Is your part hollow? If so, what is the wall thickness , and do you have an air-hole at the top of the ginormous cup?

Also - are you using an LT tank or a standard one? If you’re using LT you musn’t use the metal spatula, it scratches the PET surface


#3

.160" Wall thickniess.
.25" Hole

Standard tank. But thanks for the advice on the LT tank, I have one but did not know that.


#4

Some of the supports were broken. I wonder if I just need to add more.


#5

That doesn’t look like original Formlabs resin, isn’t it?


#7

More supports might help - the supports don’t just stick the model to the build platform, they also help stiffen it so that it doesn’t move around in the peel part of the print cycle. If your hollow sphere is thin enough to be relatively flexible around the hemisphere and above, that could be enough relative movement to delaminate some bits of the layers as they’re peeled, leading to the lines and bristles of incomplete layers embedded in later layers.

May I ask why you want to print a sphere, as opposed to all the other ways to get a sphere? They’re a great challenge to print, and fun, but I have trouble coming up with justifications for printing them.


#8

looks to me like shrinkage.
Each layer is a concentric circle… at first, everything is fine, but as the circumference of that circle gets larger, the shrinkage compounds… eventually the wall starts to break away from the supports. The gap you see between the supports and the wall is how far out of spherical your part is.
Because of the compromised support, the part can move relative to the platform on peel.
once it starts to shift on peel the laser starts burning stretches of wall where the wall is no longer close enough to the tank floor to bond… and on peel the portion of the wall that is bonded pulls the unbonded length away like piece of spagetti… from there on things just get worse and worse.


#9

This did the trick. I added a lot more support and the print came out great.

Why exactly are spheres such a challenge?

What are you suggestions for other ways to make a sphere? Thanks


#10

The big increase in cross-sectional area (for solid spheres) as the sphere starts can be difficult, requiring a lot of support that you’ll have to remove later, and sand or polish, depending on your requirements. For hollow spheres, like this, you still need a lot of support to keep it stiff enough to print properly.

Now that I see you’re got negative feature details on the top it makes much more sense to 3d print it. I thought you were just making a plain sphere – the print defects were hiding the features. Sometimes you can just find something commercially available for a sphere in some material in some size.

For this project, you still might still consider alternatives like turning a sphere on a lathe before etching or engraving it, or printing a 2 or 3-part mold for casting a sphere in some material, so that you have some parting-line seams to deal with, but no support marks.

I’m glad to see the print is working better for you with more support!


#11

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