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3 D Printed items

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In the past few weeks I've bought a few 3 D printed items. All have been visible body/engine parts. The accuracy etc has been great but the surface finish is a real problem. Have just bought a bonnet and grill for a wrangler  which are fantastic, however the surface finish is lumpy to say the least. To get it flat is a major job. I've got through sanding sticks that would normally have lasted months lasted 20 mins. Why is this and more importantly is what is the future of 3 D printing???

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All depends on what you want. The two common ways are FDM (filament deposition method) I.e. pushing a reel of material through a hot nozzle and laying shapes down and SLS (selective laser sintering) which is where you blast a laser pattern into a vat of resin or powder and harden the shape that way. 

Sls can be like glass, huge quality due to the fine layer but generally very weak compared to traditional material. Resin does tend to be weak while beautiful and accurate, but powder can be quite strong sacrificing surface finish. FDM is often stronger but will have definite ridges and surface defects.

Also depends on what material you're using. For detailed bits I tend to favour HIPs as it's lovely and soft, I can print very fine layers and it's a joy to sand. Next is abs as it's still nice and soft but takes a bit more effort to sand smooth. That said you can monkey with that with acetone to blend layers. 

For strength I like nylon (FDM or the sintering like shapeways) or onyx, which is a carbon fibre blend developed by markforge. 

I think the real push for printing at the moment is strength and speed, detail is slow and slow isn't sexy enough for the current market. 

I'm happy to print parts in as high detail as I can if you want to compare. 

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Depends on the material it is printed with. 

Sounds like these are printed in PLA, which is a very hard plastic, and a disaster to sand down. 

I've  finished these parts by using a plastic primer, followed by spray filler. Both from Motip brand, found at automotive parts shops. That gave me a decent enough finish.

But pictures could tell us more if you have them.

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2 minutes ago, Ray_ve said:

Sounds like these are printed in PLA, which is a very hard plastic, and a disaster to sand down

^^ spot on. In my opinion regular PLA is a fairly useless material for any working part. Good for cheap trials and tests. PLA+ is better but still the surface finish is awful.

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Lots of clever people around to help print whatever you need ?

Interesting question re the future tho 

I used to think 3D print was anchored in ever improving cheap, eco friendly polymers ...

The truth is it will only happen when we don’t buy what we have 

So how much would we pay for a 3D kit ?

Or part ?

Answer both and you’ll beat every Government current pricing military or space bred parts 😂

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I recently bought my first 3D printer, an Elegoo Mars resin printer.  Instead of lasers, it uses a HD LED screen to blast liquid resin with UV light, causing it to harden.  The detail I can get is pretty good.  Way better than my friend's FDM printer.  However the finished prints are more brittle - last week his printed bumpers survived the trials of the UK Scaler Nationals (several hours of non-stop crawling over hard rocks) while mine shattered in a big head-on impact with a rock towards the end of the event.  I need to experiment with different resins.

I know people who have got very good finished results from FDM printers by using narrower filament and increasing the layer density.  The trade-off is a much longer print time.  One acquaintance with an FDM printer could print off a bracket in less than 30 minutes which would take about 2.5 hours in my resin printer.  But it took my friend almost 20 hours to print a bumper on his FDM printer that didn't look as good as my 4 hour resin print of a bigger item.

I think 3D printing is the future for small-volume parts (like RC hop-ups) and as it matures quality and strength will improve, but there will always be trade-offs between detail, speed and strength.  The tricky thing for a beginner is working out what material and printer type to start with.

I don't know if places like Shapeways offer resin-printed parts, it's been a long time since I looked, but for cosmetic-only items I would definitely consider that.

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15 minutes ago, Mad Ax said:

I recently bought my first 3D printer, an Elegoo Mars resin printer. 

That one is still on my Christmas shopping list. ^_^

I have the 'regular' FDM 3D printer. Its fine for anything bigger then 5cm but not for high detail due to its 3mm material spools and 0.4mm head. Converting it to a finer head and layer height is more work then I care to put into it. I typically use 0.25 to 0.3mm layer thickness which is a rough finish.

On a hobby convention, I saw a Dremel 3D FDM printer make a new body for a matchbox car. That used a very fine layer thickness. 0.1mm or maybe even finer. It took 12 hours to make the 6cm body as it was printing at snale speed, but the amount of detail in the printed part looked excellent to me with minimum finishing effort.

But I hope to make better resolution small parts with the Elegoo Mars. It would nicely complement my current printer.

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1 hour ago, Ray_ve said:

But I hope to make better resolution small parts with the Elegoo Mars. It would nicely complement my current printer.

If you haven't already, watch my threads and those of CarterTG in the TC Designs forum.  CarterTG seems to have a lot of commercial experience printing with resin and FDM but I'm a complete beginner, however they are probably good threads to pick up some advice.  I've had some very very detailed and attractive prints with are nonetheless useless because parts of them have failed; I've had others that will be usable but ugly due to the amount of support material.  I'm having to really think hard about how my prints will be supported during the design process, which may not be something you think about so much with FDM.

I also get a little z-azis line in all my prints which probably lines up with the thread size on the built plate, meaning I might have a bad bearing or something.  It doesn't affect what I'm doing but might be an issue if you were printing small action figures or something.  I don't know if this is a common issue with the Mars, I haven't looked into it since it doesn't bother me.

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I’ve finished PLA with sanding and filler primer and had great results.  I’ve also had occasions where I’ve not worried about the finished and just used the piece.

i think the bigger issue is building the strength into the part and printing it at the appropriate orientation to reduce the likelihood of it failing.  Do resin printers have the same issues in terms of weakness across layers?

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Professional print quality from places like Shapeways are pretty good. I do a lot of 3D printing on my 2 FDM printers. 
Quality is in many things and many factors. My first prints were ok, my recent prints get smoother and smoother. 
But it takes time to dial everything in, but it is possible to get really good and smooth finish.
I cannot comment on your specific prints, but I can say this.

Look at it like sculpting a piece of wood. Or machining a piece of steel. You can do this fast or slow, rough or fine. How much detail are you willing to put in over the time it takes to make?

Kinda the same with 3D printing. 
One of the biggest chances I saw in improving print quality is slowing down the print speed.
But things like quality of the filament, layer thickness, layer height all have their place. 

In the end, the difference if you wanna paint it, is the amount of work involved to get a smooth surface. What I noticed is that the more detail in the print against the more time to print.
The less time the paint prepping takes. 

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