Scaling problem - thin walls

[CCO 0]

Hi Team

 

We are having a lot of problems scaling our products down to a size, where we can 3d print it. 

We are using Autodesk Inventor Pro 2022 to design our products (industrial fans). 

We would like to 3D print models of our products, which are quite big. 

 

Our problem appears when we try to scale the model and the wall thickness of the sheet metal plates are getting extremely thin. 

Is there any way to setup a rule in ex Cura to control that some dimensions are not scaled below a certain wall thickness?

 

Or any other ideas?

 

I have added an example of a part, where I have scaled it down 1:10

 

Thanks

Christian

30045581.stl 30045581_Scale.stl

[gr5 2,172]

1) The most important new feature in Cura version 5 is that it handles thin walls better.  So make sure you have Cura 5

2) make sure "print thin walls" is checked.  This allows you to print walls twice as thin versus if you don't check that.

3) Look at "horizontal expansion".  If you set that to 0.2mm it should expand each side of a "wall" by 0.2mm to make all walls at least 0.4mm and that should be enough that you get something printable.

4) Fans, propellers I have found to be the most difficult thing to 3d print because of the support issue combined with how delicate each blade is.  I hope you have a dual printer that can print water soluble support.

6) You can print down to 75% of a nozzle size without much (any?) degradation in quality.  So for a 0.4mm nozzle consider setting line width to 0.3mm.  Also then you can set horizontal expansion quite a bit smaller as well but eventually the part is too delicate.

[CCO 0]

Thanks GR5

 

I will try your idea in point 3. I would be great if Cura could extend all too thin walls. 

[gr5 2,172]

4 hours ago, CCO said:

I would be great if Cura could extend all too thin walls. 

Agreed!

[victordriggs 0]

On 6/1/2022 at 6:12 AM, gr5 said:

1) The most important new feature in Cura version 5 is that it handles thin walls better.  So make sure you have Cura 5

2) make sure "print thin walls" is checked.  This allows you to print walls twice as thin versus if you don't check that.

3) Look at "horizontal expansion".  If you set that to 0.2mm it should expand each side of a "wall" by 0.2mm to make all walls at least 0.4mm and that should be enough that you get something printable.

4) Fans, propellers I have found to be the most difficult thing to 3d print because of the support issue combined with how delicate each blade is.  I hope you have a dual printer that can print water soluble support.

6) You can print down to 75% of a nozzle size without much (any?) degradation in quality.  So for a 0.4mm nozzle consider setting line width to 0.3mm.  Also then you can set horizontal expansion quite a bit smaller as well but eventually the part is too delicate.

I'm brand new here, and to avoid creating another post on this topic and at risk of digging up an old thread - I just wanted to add a bit of my challenge here.

 

I'm also struggling with scaling down an stl in Cura, and having it be printable. I will look into the wall thickness and the other points you mention, but something else I see with my situation, is that the brim is also messed up. The lines don't always align properly sometimes are wavy when they shouldn't be. It basically looks like the brim was drawn by hand, if that makes sense. The rest of the print quality is so bad and adhesion is next to none... I sized down from 100% to 91% Anything down to 93% is ok, but beyond that things get bad fast.

I guess I'm asking if wall thickness is enough to deal with the issues I'm seeing or if I need some other kind of adjustment. Getting my PETG to print was hard enough without the scaling problems, lol! Thanks for your help, and sorry to be the newb digging up an old post. I'm wondering if I'd get better results importing the STL into something like blender, sizing down there, then re-exporting to STL. I really only want this to be a last resort, however... Thanks for any tips!

[gr5 2,172]

Please post a project file showing what you mean where you set it at 91%.  do "File" "Save project as" and then post here.

[victordriggs 0]

Sorry, I missed your reply. Yes, duh, forgot the stl file.

 

All I'm doing is using the scale functionality to scale down to 93%. Anything lower than that and the print will not succeed. I'm kind of new to this, so it's probably something related to line width or thickness or something that doesn't work out after scaling down. Even the brim printing is really bad.

 

I'm using PETG, and I've tried tinkering with thickness settings but I'll be honest, i'm out of my element on a lot of these settings but even with PLA and just standard quality, the print is still failing. At 94%, it still prints smooth as butter with my PETG settings.

 

Thanks for your help.

CC_MK_I_Ring.stl

 

FWIW, i have a stock Ender 5 Pro, no mods.

Edited April 26, 2023 by victordriggs

[gr5 2,172]

So if you could provide the project file that would be much better.  Do "file" "save project" and post that file.  It contains your settings which highlight your exact issue.  how you positioned the part, your machine profile and much more.

[gr5 2,172]

At 93% scale (only slight reduction in size) the part seems to slice just fine.  Did you mean 93X?  That would be smaller than 1mm.  I doubt that is what you meant.

 

Again, the project file will include your scaling information.  So get Cura to do "the problem" at the "problem scaling" and then save the project file so I can see exactly what you mean.

 

 

[victordriggs 0]

I agree that it looks fine when sliced - I couldn't see any issues there either. But what I will do is so a simple % reduction from 100 down to 93, then start a print. I'll take a picture of the brim lines, which at 93 start to get all wobbly, which also is a sign that the print quality will be very bad, poor adhesion, etc. Anything above 93 and the brim lines are properly aligned with adhesion, etc. I'll also include the project file.

 

I've attached the project file, and I'll start a print and take some pictures. 

 

Added the pictures of the brim being printed. Based on that, I know that the rest of the print will be very bad quality. It won't adhere, and it will just come apart. At 94 and up, the brim is tight, the print is sold, adhesion is good.

93percent_ring.3mf

Edited April 26, 2023 by victordriggs
Additional Pictures added. The uneven brim lines.

[GregValiant 1,251]

Your setup is showing a .4 line width with a  .4 layer height.  That comes out to almost no squish at the build plate.  I would expect bad adhesion with the line width and layer height at a 1:1 ratio.  Drop your layer height to at most .28mm.  If you feel you really need layer heights that tall you should really go to a larger nozzle that can accomodate it.

You can see here that the Layer Height setting boxes are yellow.  That's a warning that your settings are on the fringe.

[victordriggs 0]

I've gone with that layer height because it's been the only way I can get my PETG to adhere and not stick to the nozzle. It might be the altitude I'm at, or the dry air (~4100 feet, Humidity at ~15%) But I've been all through those settings.

I will try and reduce it and see how that works. And if anyone has a PETG profile that works, I'll gladly give it a try because that was a handful in and of itself and this is where I've landed most of the time because it works.

[victordriggs 0]

Here is a video link to see what the quality is like:

 

Video Here

[GregValiant 1,251]

I print a lot of PETG.  Many models need additional stiction to keep them from warping.  When that's the case I often design my own elephant ears for areas of the model I think will lift.  You can use the "Spoon Anti-Warping" or either of the two "Tab Anti-Warping" plugins that @Cuq (@5axes in the Marketplace) has thoughtfully provided.

This is a case in point.  You can see the added "ears" .  They are robust but I've added a chamfer right at the part so they are pretty easy to remove.  This is silver PETG by the way.

 

I always give the build plate a good bath and then a liberal coat of AquaNet Super-Hold hair spray.  It's necessary as certain types of cross-sections will want to pull up.  Here is the underside of that print.  You can see the dimples caused by the stress the model was imparting to the elephant ears.  That print was pulling hard.

 

But your model is symmetrical on the build plate.  I don't think it even needs a brim but it will likely need some adhesion help (although I would print it with a skirt).  Chemical warfare to aid bed adhesion is mandatory for PETG.  I've settled on hair spray but there are certainly other substances you can use.

I've attached a project file with your model with my PETG settings.  My printer is an Ender 3 Pro about 3 years old.  I did change to an all-metal hot end and I've swapped out all the stock fans for nice ball bearing models.  The mainboard is still the stock 1.1.5 board running Marlin 1.8.  I print PETG at 230 with the retraction at 6.5.  You may want to change those to your preferences.  My printer is dialed in and fully calibrated.  Even so I still print PETG with the flow at 105%.  Experience has proven that to be necessary on my printer.

PETG is different.  It's gooey and sticky and you are likely to pick up boogers on the side of the nozzle.  Don't worry about it so much for this model.  The material that collects on the nozzle is a lot more likely to occur on large skin areas as opposed to the geometry of this model which is mostly walls.

Good Luck!

 

 

 

GV_93percent_ring.3mf

Edited April 27, 2023 by GregValiant

[victordriggs 0]

Thanks for the advice and project file. PETG is likely going to be the filament I need for things I have in mind so that's why I spent so much time trying to get it to print. It is gooey, sticky, etc. All the reading and trying I've done seems to tell me that what works for another, might not work for you. The two things I've noticed so far, go slow, and don't flatten it too much, when I do, it curls back onto the nozzle. I say all this with the caveat of "I'm only a month into 3d printing".

 

I'm going to try your project settings and see how it turns out. That short video I showed of the brim is showing vastly different from a good print. Good prints for me are solid, stuck to the plate, uniform. The 93% print is wispy, feathery... almost dusty. But anyhow.

I appreciate your input, I'll post back with results.

[GregValiant 1,251]

I have the Creality glass build plate.  I don't know how much it varies from the flexible one you are using.  I think the base prep is important though.  I wash it with dish detergent, wipe it down with isopropyl alcohol, and then give it a coating of hair-spray at least in the area the print will be.  Glue stick or Magi-goo(??) are other options for adhesion promoter.  You have to get squish though.  The side of each extrusion needs to weld to the previous extrusion and you can see in your video that didn't happen.  Leveling is a big part of that.  If your initial Z gap is too tall then you won't get the squish you need.

Dropping your print temperature can help the gooeyness, but it isn't going to go away.

 

Here is that print finished.  Along with 4 trapped nuts there is a 3/16" x 9" steel rod running through it (the Florida sun is tough).

There are two of them and they mount to the roof rack on the wife's SUV.  Now she can find it in the Walmart parking lot.  If I print these again I'll put LED's in them.  I need to figure out how to hide the wires that would come up from the taillights.

 

[victordriggs 0]

I think I've strayed away from too much squish because all I've ever gotten is curling back up onto the nozzle. And, this has happened with two brands of PETG now, black and transparent. I've swapped out nozzles a number of times. The layer thickness and some unique bed prep has helped adhesion finally.

I tried a print with no mods based on what you sent. I got zero bed adhesion. Admittedly, I should probably do more with the bed, I do clean it and I've tried hairspray - seemed to make no difference. What I settled on is this - clear packing tape, stuck to the bed, and then I let it heat up. I peel it off before the printing starts. What i've seen is that is does a good job pulling of any debri left behind, and it leaves a super thin layer of tack-ness (I think?) and that's been how I've been able to finally get some bed adhesion.

 

With your settings, based on my experience, the speed was too fast for me, the temp too low. Going to give it another go with a slower speed higher hot end, and higher bed temp.

 

btw, that fin is cool! and the quality looks great. that's how my prints look in my dreams, lol.

Edited April 27, 2023 by victordriggs

[GregValiant 1,251]

Thanks.  I haven't had any problems with bed adhesion in general, but as I mentioned - PETG is one of those materials that really wants to warp and long skinny prints are the worst.  Like the gooeyness, it's part of the deal.

 

[victordriggs 0]

So, I made some adjustments, and then lowered the Z steps as I was watching the brim print (-0.1500) thinking about more squish, and the brim appears to be... uniform and is adhering - which i've achieved before on these 93% scalings, but, the actual object is always a gobbled up mess, not solid at all, usually looks like a bird built it as a nesting experiment.

 

Here are some images of how it's printing right now. Based on doing this... probably 50-100 different times now, I pretty much know this won't succeed. Another spot check and the supports aren't staying in place and the ring itself looks pretty bad so I'll stop the print.

 

EDIT: So you can see in the last two photos after I stopped the print how the infill is spotty, not even up against some of the walls. And the adhesion is quite bad. This is pretty much par for the course for this print scaled to 93%. 94% will be a world of difference for what it's worth. 

I appreciate the help.

 

Edited April 27, 2023 by victordriggs
Added two later photos showing print quality

[DivingDuck 104]

Looking on your last picture, your printer tries to tell you a lot what is going wrong with your printer.

 

Look to the bottom right (1): The lines are squished.

Top right (2): the lines are apart from each other that you can see in the corner paths the bed underneath

Bottom left (3): only a view distance away from (1) the lines are separated.

All this means, that a) your bed is not level correctly and b) the distance of the nozzle is for every point exept (1) fare to much away from the bed.

I wonder how you do your bed leveling. Are you leveling the bed unheated?

Make a manual bed leveling with a piece of paper w/o mesh bed leveling with a hot bed (as you print with PETG, set the bed temp to 80°C (Edit: 240 was obviously wrong), or what ever your bed temperature have to be for your filament).

Then make a test print w/o mesh bed leveling involved with some small squares (e.g. 20x20 mm) part fan of, layer height and initial layer hight: 0.2 mm, speed of 40 mm/s and look how it behaves.

Then make the same with mesh bed leveling.

Alternatively you can install 5axis' plugin called Calibration Shapes and insert the Bed level calibration shape instead of building and placing your own squares. The instructions can be found here: https://github.com/5axes/Calibration-Shapes/wiki/ParametricBedLevel

 

 

Edited May 5, 2023 by DivingDuck
Wrong bed temp. I mixed up bed/filament temperature for PETG

[gr5 2,172]

In above post 240C bed temp is clearly wrong.  You want the bed a bit over the softening temp.  For PETG I think that's around 80C?  It's critical to be over that temp but you have a more serious issue...

 

It looks to me like you have some underextrusion as well.  That is what is causing those inner strings inside the circle and possibly why your brim isn't solid (lots of gaps in the brim).  

 

Test your feeder first - it should be able to pull about 5-10 pounds before slipping (at least 10 pounds for 2.85mm filament - not sure with 1.75mm filament - I assume about 5 pounds).  So heat up the hot end, move the material back to the feeder half way and then move it forwards again and fight the feeder with your hand.  Estimate the force needed to overcome the feeder.  Maybe locate something that weighs 5 pounds (measure with water?  gym weight?).

 

If the feeder seems fine then it could be the hot end.  The nozzle may have some buildup in the nozzle (google about doing cold pulls) or your temp may be off.  What was the recommended print temp?

 

Does your hot end have teflon in it?  Many (most?) do.  Teflon degrades pretty fast at PETG temps (240C?) and needs replacing typically at that temp after only 100-300 hours of printing (if you only print PLA at 200C then teflon can last 500-1000 hours of printing).  The teflon gets soft and when compressed it squeezes the filament.

 

[DivingDuck 104]

@gr5,

Ups, you are absolutely right. I can't believe I wrote that, but reading my post again, I have... shame on me.

Maybe I need to ask S. Freud what was wrong writing this nonsense.

 

For the bed I wanted to write 80°C. 240°C is my filament temperature.

 

[GregValiant 1,251]

This is good.  A duck that can back paddle.