How to print a curvy object??

[uma 0]

Folks,

Here is another challenge. I tried printing a galaxy S3 case using UM2. See the results for the problem i am facing. The model seems to be a reasonable curve in CAD. Even in Cura when i switch on support material the curve doesnt seem to be supported. However, when i printed on UM2 the results were dismal.

Has anyone printed such curvy objects? What is the thumb rule to print curvy objects along Z axis.

My settings

Layer Height: .2

Speed: 35 mm/s

Material: PLA

temperature: 225

Heated Bed: 70C

Thanks

 

[IRobertI 520]

Printing fillets like that can be problematic since it becomes such a big overhang. What I'd try to improve on it would be to print thinner layers (0.1mm), reduce the temperature of your bed to 60C and try turning the fans on sooner.

 

[gr5 2,172]

You need as much fan as possible. If there were a 200% setting then you would want to use that. By default fan comes on very slowly and not full fan until 5mm or so. If you make the fan go from off to 100% on the second layer you will get underextrusion because the head will cool to fast and it takes 30 seconds for the PID temperature controller to compensate. So I recommend having the fan come on even for the first layer. You will need a warm bed (70C) if you print first layer with fan on.

This will help a lot but it won't be perfect. It will be better.

OR FLIP IT OVER

I don't know any way to get this perfect. I guess you would have to flip it over - that would make good curves but the hidden side will be a bit stringy. You will want 100% fan for that also when it bridges the back of the phone. You will need at least 4 layers to get the top layer perfect as each layer will get better (they will all be a bit low and slightly underextruded but each layer will get better).

 

[gr5 2,172]

print thinner layers (0.1mm),

 

That can help also - as each layer is touching more of the layer below on those curved overhangs.

 

[illuminarti 18]

Print with thinner layers, so that the overlap on each layer is a smaller proportion of the extrusion width. Also be sure and set a minimum layer time of at least 10 seconds, since the part is low to the bed, and so the fan probably isn't on full. I'd also try lowering te bed temp to 60 - and maybe even lower the extrusion temp - basically you need the plastic to cool as quickly as possible to prevent it sagging.

[jonnybischof 60]

I'd try lowering your temperatures.

Try 60°C for the bed. You may have to stick with 225°C for the first layer in order to get it to stick, but immediately after the first layer is done, lower the temperature to about 190°C (depends on filament quality! UM blue doesn't seem to like going lower than 200°C, but that should already work).

Then, you have to play with the fan speeds. I can't say much because I don't have a UM2, but you can make a comparison yourself...

The cures would also look a lot better if you used smaller layer height. For example, if you youse 0.05mm layer height instead of 0.2, you will have a four times better resolution.

You can even go 0.025mm layer height, but then the print takes ages to complete.

I was also going to mention flipping the part & adding support, because you want the visible faces to be as clean as possible. The inner faces are not so important because they'll be covered by the phone.

/edit:

Either I'm too slow or you guys are too fast

By the way: You can try lowering the bed temperature even as low as 50°C. But then you have to watch the print carefully - it might warp more than with 60°C.

-> The lower the bed temperature, the better the cooling. Your bed keeps the whole part at bed temperature, which means it's always going to be soft during the entire print.

 

[alluvian 0]

Couldn't you also flip it over like GR5 suggests and turn on support? Cura should support the back then, and if you rough up the inside by scraping out support that should not be such a big deal.

I would think cleaning out support would end up being better than the unknown of dealing with the bulk of the print being printed on a fairly long bridge.

I speak from only ignorance and watching videos and reading though. I am still 3d printerless as I wait for the tax monies.

 

[yellowshark 153]

Thanks guys, I came across this thread yesterday and used it last night on a piece of geometry that I have been struggling with; result not perfect but much better. The piece is a thumbnail high and when I print it full size I think it will come out better.

 

[gr5 2,172]

Make sure the bed isn't at 75C as this is too hot. 70C works great for me. Other people say 60C is even better but I haven't tried. 75C is definitely too hot.

 

[yellowshark 153]

BTW settings were...

Bed 55 for layer 1 then dropped to 35

Extruder 205 layer 1 then down to 200 then about half way dropped to 195

Fans set to 100% from layer 2 onwards

Speed 20 m/s

Layer height 0.05

Left the door fully open