3D Printing

[KaanE]

Good afternoon (here)!

I do not know where should I post this so I'm asking here. I have just purchased a Creality Ender 3 3D printer on which I'm going to print a few items, a few of them being helmets and armours I'm going to sand/finish later for moulding and casting purposes.

Anyway, to the question. Is it worth printing in 0,1mm/layer such big items, like a helmet or is it better to print it at 0,2mm/layer and save around 40 hours, instead of spending 80 hours for 0,1mm quality finish?

I mean, I do not think I am going to spend 40 hours sanding and finishing it before moulding to have it smooth, but maybe I am wrong and it can be a nightmare to level the 0,2mm layers.

So I am asking people with experience. All my experience has been sculpting from clay and/or fiberglass, with lots of sanding for a smooth finish, but never with a PLA item.

Thank you very much!

 

[xeno]

I think the question should be printing 0.1 or 0.3 layer height, that was is commonly used for the bigger items.
(I tend to use 0.1 for most items)
Also you might want to look into another materials then PLA, like ABS (with enclosure) or PETG, these materials sand much more easy then PLA,
PLA tends to gum sandpaper and needs wetsanding.
With the others you can use power sanders and drill holes much better

Best is to do a layer height test and material and see the time it takes to smooth the surface.

when there are mostly smooth large shapes, then a higher layer thickness could work, and when there is texture or detail, then go lower.

 

[KaanE]

I think 0.3mm is not worth for just a few hours less...

I'm sorry, I'm not using ABS, it warps very easily, can produce very dangerous fumes because higger temperatures can melt the teflon tube, and it's not biodegradable.

I have also read about using XTC 3D or even common epoxy resin over the finished print to make it easier to sand, but I'm afraid it may cover some detal (for example grooves on the Mando helmet).

 

[Iskelderon]

Wouldn't touch ABS with a ten-foot pole!
PETG is just as easy to sand as ABS and as long as you don't buy inferior no-name filament (cheapo PETG often won't adhere to the build plate the way it should) it won't pull that Goldilocks crap on you.

 

[JiminSTLouis]

This is what I use to smooth my PLA prints. Brush on a thin layer, cure with a UV light, sand off the shine, and repeat 1 or 2 more times as needed. Here are the results off my Ender 3.

 

[KaanE]

What layer height do you use?

 

[JiminSTLouis]

What layer height do you use?

Usually 0.15mm unless I want something to look nice right off the printer, then 0.06mm. That’s what I used on my J2 antenna.

 

[KaanE]

It looks really smooth when "resined". I can't believe it... Wow!

 

[JiminSTLouis]

It looks really smooth when "resined". I can't believe it... Wow!

Thanks. The antenna wasn’t smoothed at all. That’s right off the printer and I was rushed to finish the J2 for Wonderfest.

Here’s the hull before any prep work.

 

[JiminSTLouis]

Also, just for clarification. It took more than just the resin to get that final finish. I also had to use bondo spot filler to conceal the panel joints. But the resin did a great job covering up the print lines, which I think is the intent of your original question.

 

[KaanE]

Thats exactly the question. The printing lines as the joint lines will require a little bit of bondo/filler and sanding. That's where I have experience hehe.

Looks like 0,15mm is a really fine print for a big thing like a helmet (not for a warhammer) if the plan is to smooth it out later. I was also thinking about 0,18mm... I need to find the perfect ratio for finishing/printing times...

Also, yes, I understood it that way. Not just a single layer of UV resin but a few.

 

[xeno]

Thats exactly the question. The printing lines as the joint lines will require a little bit of bondo/filler and sanding. That's where I have experience hehe.

Looks like 0,15mm is a really fine print for a big thing like a helmet (not for a warhammer) if the plan is to smooth it out later. I was also thinking about 0,18mm... I need to find the perfect ratio for finishing/printing times...

Also, yes, I understood it that way. Not just a single layer of UV resin but a few.

Save yourself some trouble, the resin is a sort of substitute for bondo, but a lot of resins will keep a sticky top surface, as oxygen impairs curing, you would have to do it in a bucket of water or something
but like I said, some have seen it as the cure to all print line problems, while it is just another kind of "Bondo"
safe yourself the trouble and use Bondo from the start

 

[Dsimdude]

I think the question should be printing 0.1 or 0.3 layer height, that was is commonly used for the bigger items.
(I tend to use 0.1 for most items)
Also you might want to look into another materials then PLA, like ABS (with enclosure) or PETG, these materials sand much more easy then PLA,
PLA tends to gum sandpaper and needs wetsanding.
With the others you can use power sanders and drill holes much better

Best is to do a layer height test and material and see the time it takes to smooth the surface.

when there are mostly smooth large shapes, then a higher layer thickness could work, and when there is texture or detail, then go lower.

... and for those of us who are still among the uninitiated, what do you mean by "wet sanding?" Are you literally talking about sanding with a damp piece of sandpaper, or do you mean something else?

 

[xeno]

... and for those of us who are still among the uninitiated, what do you mean by "wet sanding?" Are you literally talking about sanding with a damp piece of sandpaper, or do you mean something else?

Yes, sanding with adding water to the sanding paper
Usually this is done when sanding really fine like 600 or higher grid sandpaper, this a "special" sandpaper thet wont fall apart with water, you can have a spray bottle or a bucket of water to continuously adding a bit of water to get rid of the sanded off grime from the object, so it won't clog up.

PLA is a material that easily turns soft when sanding, the temperature that turns it soft/gummy is low, and the water helps to cool, and stop the paper from clogging up

 

[Iskelderon]

Keep in mind that bondo, resin and even plain sanding will also kill "desired" gaps, like panel lines.

But as this screenshot from a model builder video shows, panel line scribing chisels are great to have in your arsenal anyway:

 

[Dsimdude]

Thanks for the info, guys! I always learn something new on this board...

 

[JiminSTLouis]

... and for those of us who are still among the uninitiated, what do you mean by "wet sanding?" Are you literally talking about sanding with a damp piece of sandpaper, or do you mean something else?

I tried one section using only the bondo but found applying and sanding it was more difficult than the resin (and messier).

Whatever works best for each individual.

EDIT: I was using Bondo spot filler in a tube.

 

[Iskelderon]

I tried one section using only the bondo but found applying and sanding it was more difficult than the resin (and messier).

Whatever works best for each individual.

EDIT: I was using Bondo spot filler in a tube.

Depending on the situation, automotive spray filler can also be a viable option.

 

[JiminSTLouis]

Depending on the situation, automotive spray filler can also be a viable option.

Yup... after the resin smoothing I used the automotive filler primer to see where I needed to bondo (prime, fill, sand, repeat). I tried the filler primer to fill the print lines but wasn’t happy with the results. I think for the 4 foot J2 it would have taken many cans. And it would still need bondo for the panel lines/gaps.

 

[KaanE]

I have used bondo lots of times, and a lot, in fact I used to sculpt from bondo, and if you have to do small recessed lines, like on a Mando helmet, it can be a nightmare to get them straight and with an even depth. Also, you could mess lots of proportions because you do not sand the same depth everywhere, you may leave more bondo here and less there... That's why I am trying to stay away from bondo for final refining. It's okay for the big sculpt, like the basic shape, but not for smaller details like grooves, at least not practical.

Spray filler is a good option for the finishing layers, to get it very smooth, but not to cover the whole roughnes of a 3d print (not resin 3d print) unless you spend lots of cans.

What about using epoxy resin, the classic one used for rotocasting, the yellow creamy colour? It cures with the chemical mix, is not sticky, sands pretty well and can be applied really thin. Also not expensive and doesn't cure as hot as poliester fiberglass resin, which could mess the print.