Sprayed-on 3D Printed Pattern Filler

[Scott_M]

If you are using prusa slicer, ( I am using Orca based on prusa ) there is a setting called "Fuzzy Skin" on the "others" tab that causes the toolhead to "jitter" on the outside wall it is adjustable by a few settings that make it finer or coarser. It almost eliminates layer lines, especially when layer heights are smaller.

In this picture I was not trying to eliminate the layer lines ( I have it set to a fine fuzzy skin ) I was just trying to make it look like the finish of the textured plate it was printed on. It worked very well. The large diameter is 1 3/8" the o ring groove is for a 1" o ring ( for size comparison )

I am not sure how that would affect applying a surface coat or if it would make it harder to pull from the sand. But I think it would be worth a try to print a test piece with the default settings of Fuzzy Skin ( kind of coarse ) and see if it helps you any.

Food for thought

Scott

 

[petertha]

The fumes require a commercial respirator though, which I really dislike wearing for long periods of time, and thus the push for some water-based filler solution.
The auto body skim coat seems to adhere well to a 3D print.

The strong odor is from the polyester resin base. I stopped using it eons ago for laminate composite work, but its still predominant in the auto filler/putty world because its relatively inexpensive & it works.

There are epoxy based systems too, but they get spendy. The fillers are probably similar, but epoxy is considered better for certain applications that require it. These fillers are not entirely odorless either (or necessarily safer), but some find the odor less & more tolerable.
https://www.aircraftspruce.ca/catalog/cmpages/quickPoxy.php?clickkey=10343
There are products like these formulated for plastics, but no personal experience
https://www.aircraftspruce.ca/catalog/cspages/puttyFlex.php?clickkey=10343
Despite what you may read, be careful about thinning fillers into a slurry with acetone or whatever solvent. At minimum it it buggers up cure time, more often it degrades the material to a gooey mess. Thinners are not really reducing viscosity in the classic sense where the solvent evaporates & binder cures normally. In typical resins, solvents sever the intentionally long molecular chains into small ones, which have a hard time getting together again. The properties will be altered, always for the worse. If it works in a tiny % degree, it just means the system is tolerant, but still not considered best practice.

There are other products I have seen in the FX world, but cant seem to find right now. they may be urethane based. But I recall cost was comparable to epoxy & usually shelf life is short.

 

[GreenTwin]

If you are using prusa slicer, ( I am using Orca based on prusa ) there is a setting called "Fuzzy Skin" on the "others" tab that causes the toolhead to "jitter" on the outside wall it is adjustable by a few settings that make it finer or coarser. It almost eliminates layer lines, especially when layer heights are smaller.

View attachment 152278

In this picture I was not trying to eliminate the layer lines ( I have it set to a fine fuzzy skin ) I was just trying to make it look like the finish of the textured plate it was printed on. It worked very well. The large diameter is 1 3/8" the o ring groove is for a 1" o ring ( for size comparison )

View attachment 152279

I am not sure how that would affect applying a surface coat or if it would make it harder to pull from the sand. But I think it would be worth a try to print a test piece with the default settings of Fuzzy Skin ( kind of coarse ) and see if it helps you any.

Food for thought

Scott

I need to drill into the details of what the Prusa Slicer program can do.

I am aware of using finer layers, at the expense of adding significant time to print.
For larger prints, fine layers can make print time excessive (days).

I think the XL nozzle is probably on the large side, just due to the sheer volume that the printer is capable of printing (14 inches cubed).

I will check it out.

.

 

[ddmckee54]

I agree with what petertha said about thinning the fillers with acetone, with one addition.

The whole idea/advantage of a 2 part filler and/or glaze is that it doesn't shrink. You thin it with acetone and you just took that advantage away because now it's going to shrink as the acetone evaporates. Autobody glazing putty used to be lacquer based, and you can still get it that way. If you were sloppy and applied it over a deep scratch where it was too thick, the top would dry and skin over. You'd sand it and paint it and it looked fine. A couple of months later you'd have an irate customer coming back because his paint job has now developed grooves and scratches.

 

[T140CLIVE]

I have seen some recent discussions about how best to fill 3D printed patterns, so that the lines don't mirror over into the molding sand.

I think some have mentioned some methods here previously, but here are my ideas based on some recent discussions I have seen.

One person mentioned "high volume" auto body paint, but the grooves on my 3D printer are too deep for that, especially on curved surfaces.

My thoughts are that a water-based filler needs to be sprayed on with a slurry sprayer, in a very thin layer, that is thick enough to not run, but thin enough to give even coverage.

One problem I have had using sheetrock wall patching compound to fill patterns is that it sets up in just a few minutes.
This short set time is great for patching sheetrock, but not so good for patterns, unless the pattern is on the small side.

One person has reported success with the sprayed-on filler, but I don't have any details, and so I am going to try it.

.

This works well

https://www.amazon.co.uk/MOTIP-Fast...d=5bf3352d3fab3d1fa61932d0ab2d9371&th=1&psc=1

 

[ddmckee54]

There are a variety of what are effectively high-build primers available in both polyesters and epoxies, these give you the highest build. These will do an admirable job of leveling the layered playing field caused by a filament 3D printer. They'll add to the highs, and some of that high will flow into the lows as the primer dries/cures Just search for "spray putty", or "high build primer". Another hint, when searching for those fillers look for autobody suppliers not just some Ebay/Amazon re-seller - then you'll be getting the good stuff. The "high-build" primers that you get in most spray cans aren't going to be much better than any other spray can primer. They may have a few more solids, but they still have to be sprayed through that disposable nozzle.

If you need to maintain a tight dimensional tolerance then these high-build primers aren't going to be what you want to use as they will increase the size of the part every place they are sprayed. And the thickness of that primer layer will only be as good as the person/device doing the spraying. But then again, if you need to worry that much about the dimensions, you REALLY should be using a resin printer and not an FDM printer. You'll STILL get layer lines, but they'll be a couple of orders of magnitude smaller.

Thanks Scott_M for the Prusa slicer Fuzzy Skin tip. Looks like I've got ANOTHER reason to ditch my Symplify3D and go to the Prusa slicer. Were those parts printed large end down? If so, what's the top layer look like? What does the "Fuzzy Skin" setting do to your dimensions, do you know if they compensate for the jiggle in the outside layer?

Don

 

[Scott_M]

Hi Don
Yup I left Simplify shortly after getting my Bambu P1P. It came with Bambu studio which was a fork of Prusa and then went to "Orca" which was a fork of Bambu studio and Prusa but all open source. I like it a lot !!
Yes those parts were printed big end down on a textured plate. It was also a .6mm nozzle with a .4mm layer height so the layer lines are much bigger.
The hole through the middle was modeled at .3125" and measures .311" The big O.D. was modeled at 1.375' and measures 1.380"in one place and 1.375" in another with 2 fuzzy surfaces touching. The small end should be 1.00" and is within a couple thou wherever you measure.
So yes , it does compensate for the jitter pretty well.
This was a test piece to test texture, on the final run I will switch to " one perimeter top and bottom" to get the plate side cleaner looking ( no perimeter laps showing )
The small end will be hidden so only the 1/4" side of the 1 3/8th and the plate side will be visible so I will use adaptive layer height as well and make the first 1/4" .16mm layer height and the rest .3mm.

 

[vk7krj]

Nobody has mentioned vapour smoothing yet- a quick google search using "pla vapour smoothing" brings good results.
It's a very good way of producing an excellent finish on 3d printed parts with minimal physical effort.

 

[Scott_M]

In a home shop vapor smoothing is doable for ABS using Acetone. But printing ABS requires an enclosed printer with temp control. Pats printer is an XL, 14" square. they don't come enclosed. not sure if he added one. But still trying to keep an ABS part that large from warping would be hard.
PLA is much easier to print and less susceptible to warping but not friendly to vapor smooth unless you are willing to use dichloromethane in your shop. Or a steam bath of methylene chloride. I am not
Abs is the only semi safe material to vapor smooth but it has more VOC than most FDM materials and is hard to print without warping at large sizes.
I do not think it is a viable option for Pat ( the OP )

Scott

​

 

[GreenTwin]

I appreciate any and all suggestions, but I think Scott is correct about vapor smothing not being a good solution for me.

I use PLA excusively, and have had good luck with it.

.

 

[lee webster]

My prefered method with my Ender3 is to print a part at 0.2 layer height, scrape the surface fairly smooth with small, sharp tools (stainless steel dentists picks, poor quality but cheap), sand the print using a modified electric toothbrush as a sander, dust off and fill with polyester car filler. I can sand and fill quicker than my Ender can print. I then spray the part with primer/surfacer and sand again. Sometimes I get a part that looks better than a resin print. I could use resin prints to make parts if they didn't have a habbit of warping so much, perhaps it's the water washable resin?

 

[GreenTwin]

I tried mixing Durham's putty with sodium silicate, and I smeared/scraped that onto the dog.
That was a big mess, and not smooth, and cracked off when I tried to sand it.
It did set by itself with just sodium silcate (no water added).
Strike 1.

I tried a 2" sandpaper disk in a low speed angle drill, and that melted the surface, and left it extremely rough.
Strike 2.

I tried a coarse 2" sanding sponge in the same low speed drill.
Strike 3. It made the same very rough surface as the sandpaper disk.

Last attempt, I tried a find 2" sanding sponge, slowed way down to perhaps 10-20 rpm, with medium pressure, and sweeping movements, and finally, that seemed to actually cut the plastic without melting it.
I worked on the top of the dog leg, which was one of the worst areas.

I used the fingernail scratch test, and scratched the area before sanding it.
Very audible sound scratching perpendicular to the grooves, and you could feel the ridges very well.

Worked on the area for a few minutes with the fine sanding sponge on very low speed, and eureka, it worked very well.
The sponge cuts off the tops of the ridges without any melting, and the surface becomes quite smooth to the feel.
The fingernail scratch test was barely audible.

I think I have found a method that is going to work well, and it is a dry, simple, and fast method.
It does take a firm pressure applied while sanding, but nothing excessive.
Speeding up the disk faster than a very low speed starts to melt the plastic, so the speed must be kept low.

With this method, I think it would be easy to use shellac to finish sealing the 3D printed part, and then sanding between a few coats of shellac.
I like shellac because it dries fast (as fast as 15 minutes between coats), and provides a hard surface, and a durable finish.
You can shellac one pattern while sanding another, and by the time you finish sanding, the shellac has dried, and you can sand that.
Shellac lets you work in real time finishing patterns, instead of spraying on paint, and then having to let that dry overnight.

The small diameter disk, which has a rubber backer disk, is semi-flexible, and it was pretty easy to work curves and such.
And this worked well with the roughest area on the dog print, which is pretty rough, and so it would even easier on non-curved surfaces, which are much smoother.

With the fine sanding sponge, it is easy to blend everything into a smooth continuous surface, unlike some sandpaper disks that tend to cut multiple flat plains into something like wood, which then has to be blended into a continuous surface.
The small diameter gets into tight spots pretty well.

There is a potential that wet sanding method could also be used with a sanding sponge, but I think a dry method would be much easier/better, and would allow immediate shellacing after sanding.

This is very exciting.
I have been trying to solve this puzzle for a while.

.

 

[GreenTwin]

This method does not appear to generate dust, and so as I zoom in on the surface, it is as if the plastic that is getting cut off is settling down in the grooves, and acting as a filler, which would explain why the surface is so smooth.

I need to find a magnifying glass and look more closely, but I think that is what is happening, and the shellac would fix the dust in the cracks, which is a good thing.

.

 

[Bazzer]

I have seen some recent discussions about how best to fill 3D printed patterns, so that the lines don't mirror over into the molding sand.

I think some have mentioned some methods here previously, but here are my ideas based on some recent discussions I have seen.

One person mentioned "high volume" auto body paint, but the grooves on my 3D printer are too deep for that, especially on curved surfaces.

My thoughts are that a water-based filler needs to be sprayed on with a slurry sprayer, in a very thin layer, that is thick enough to not run, but thin enough to give even coverage.

One problem I have had using sheetrock wall patching compound to fill patterns is that it sets up in just a few minutes.
This short set time is great for patching sheetrock, but not so good for patterns, unless the pattern is on the small side.

One person has reported success with the sprayed-on filler, but I don't have any details, and so I am going to try it.

.

My buddy and I have done a few 3D printed patterns and then sprayed and filled. It works super well.

The fuz of the model in the photo is printed in 7 sections (done on a Dremel 3D20) at fine settings, the sections are then joined together on a tooling mandrel.

The printed surface is flatted back, you cannot do this too much otherwise you build up heat and the pattern starts to move, then spray the pattern with polyester spray filler, in the UK this material is called U Pol Reface, not sure of brands in the USA but there will be many.

The resulting pattern is indistinguishable from a machined pattern that has been finely finished.

The fuselage that you can see in the photo is a sprayed in the mould finish, it is not over painted after demoulding, you cannot do that if the pattern and thus mould was of poor quality.

Use Polyester spray filler.

 

[GreenTwin]

"Sprayed-in-the-mold-finish".
That sounds pretty sophisticated.

The thing about a pattern for an engine is that it does not necessarily need to look good, it just needs to be smooth.
The smoothness helps to prevent the sand from sticking to the pattern, as does paste wax or something similar.

One school of thought I am contemplating is to get the 3D printed pattern as smooth as practical in a reasonable amount of time, but not perfect, and then cast a permanent aluminum pattern.

The aluminum pattern could be touched up easily with a 2" sanding spong in a tool and die grinder, as long as it is not deep grooves.

The grooves are way really need to be fillled, and of course the peaks flattened.

I worked on JasonB's Cretors-like flywheel that he sent me, which I printed in 3D, and the sanding sponge appears to be sort of "micro-melting" the surface of the print, because the print gets smooth, but nothing really comes off in the process except a very slight amount of tiny plastic fragements, such as from the sharp edges on the print.
And the sanding sponge does not appear to be wearing away, as it would do with metal.

If enough force is applied to the sanding sponge, and/or too much rpm, the surface begins to get dark streaks in it were the plastic is noticably melting.
With just the right amount of force, the tops of the ridges appear to be melting off in the same color as the print, or whitish, and reforming down in the crevices.

Anything protruding up from the surface of a casting, such as a permanent aluminum pattern, can easily be removed with a sanding sponge in a tool and die grinder.
Crevices can be deep, and almost impossible to sand out with a sponge, and so it is important that they be filled on the 3D pattern.

I am going to try to stick with shellac before I try anything more exotic.
I have a gallon of shellac, and don't have any polyester spray.

That is an impressive plane.
I need to take a photo of the control line plane that is in my attic, that I built years ago.

.

 

[GreenTwin]

I am going to go look for some videos on the latest Prusa slicer, and how to adjust it with the XL.

I think I would be willing to trade off some time in order to get a smoother print.
Its not like I am on a schedule or something to make patterns.

.

 

[ddmckee54]

Regarding vapor smoothing PLA, the solvents that you have to use are pretty nasty so you really DON'T want to be around the fumes any more than you have to. It can be done, but unless I had a lab grade fume hood, I wouldn't want to try it.

 

[Bazzer]

What are those solvents?

 

[petertha]

then spray the pattern with polyester spray filler, in the UK this material is called U Pol Reface, not sure of brands in the USA but there will be many.

Nice F3D. I bet some of your buddies know some of my buddies LOL

U Pol sounds a lot like Duratec, which is a real workhorse sealer commonly used in composites industry. Its very tenacious, high solids, finishes very fine. I've seen expensive plugs & molds surfaced with this & nothing else other than mold release. Pulling molds or some degree f flex like boat/aircraft structures is very demanding of finishing systems. But Duratec is polyester based. If OP is having odor issues with with a small blob of Bondo, this will be very much worse. Typically its sprayed, but I've seen spot repairs & weekend warriors use a foam brush. But you will know it when the lid is off.

https://www.fibreglast.com/category/Duratec

My cabinet maker friend made a plug (male positive shape) using what he called catalyzed lacquer sealer applied on CNC milled MDF. I didn't think it would survive de-molding but it actually worked fantastic. I had a little bit left over to play with & I was impressed. It comes in many flavors. The bottom line is these products have evolved dramatically past decade, either by their purpose or safety/VOC/whatever. So your Daddy's primer is not what is on the shelves these days. Trouble is none of these products are cheap so its hard to experiment.

https://hpifinishingsupply.com/?post_type=product&s=sealer

 

[Bazzer]

Nice F3D. I bet some of your buddies know some of my buddies LOL

U Pol sounds a lot like Duratec, which is a real workhorse sealer commonly used in composites industry. Its very tenacious, high solids, finishes very fine. I've seen expensive plugs & molds surfaced with this & nothing else other than mold release. Pulling molds or some degree f flex like boat/aircraft structures is very demanding of finishing systems. But Duratec is polyester based. If OP is having odor issues with with a small blob of Bondo, this will be very much worse. Typically its sprayed, but I've seen spot repairs & weekend warriors use a foam brush. But you will know it when the lid is off.

https://www.fibreglast.com/category/Duratec

My cabinet maker friend made a plug (male positive shape) using what he called catalyzed lacquer sealer applied on CNC milled MDF. I didn't think it would survive de-molding but it actually worked fantastic. I had a little bit left over to play with & I was impressed. It comes in many flavors. The bottom line is these products have evolved dramatically past decade, either by their purpose or safety/VOC/whatever. So your Daddy's primer is not what is on the shelves these days. Trouble is none of these products are cheap so its hard to experiment.

https://hpifinishingsupply.com/?post_type=product&s=sealer

Duratec is a great product but is a little harder than Reface.

I think that Duratec has a slate filler where as Reface has a chalk filler that sands out a bit easier. I have seen huge mouldings released off of Duratec.

Are you out of SA? There were some guys from SA at the World Championships, Wilcox (father and son)