Jump to content
Ultimaker Community of 3D Printing Experts
Sign in to follow this  
alexanderswo

printing small radii problem

Recommended Posts

Hi together,

I made this model with small radii (r=0,25mm / d=0,5mm) for a locking mechanism:

small radii

I sliced it with cura engine in Repetier and used a DeltaTower with 0.4mm nozzle:

Faulty printed radii

The preview of slicing looks fine, but when the outer contour is actually printed, it makes moves with unregular speeds (I looks like it hangs on some radii, and then more filament is coming out on that spot)

Any suggestions on how to improve this?

Thanks!

 

Share this post


Link to post
Share on other sites

Never seen anything like that on Ultimaker with Cura, so I doubt this is bad slicing.

Good to know, and PERHAPS this might be causing it: a model of a thin walled cylinder is never 100 % round. The cylinder has sides and although it might seem round when there are many sides (120 or more for instance), it actually isn't. Curves don't really exist in a digital system, they are always "steps".... As a result, the thickness of the wall is never exactly the same all over. This is always the case in all curved walls.

So if you have a straight wall that is exactly 0.4 mm thick, when you put a curve in it there will be areas where the wall thickness will be less than 0.4 mm, which usually results in Cura "skipping" these areas.

When this happens, an easy way to solve it is to scale up the model just a tiny bit. 0.5-1% is usually enough. Or you can change the setting for the nozzle size a bit, that also works.

In your case it might be the other way around (so that some bits are just OVER a certain wall thickness) in which case it might help to scale the model DOWN just a bit.

And you only need to scale in x and y direction, no need to scale the height as well.

Again, I doubt whether this is the cause, never seen defects like that, but it can't hurt to try scaling to see if it helps.

Share this post


Link to post
Share on other sites

If these bits are caused by the slicer then you would definitely see it in Cura's layer view. If you don't see anything like that there, it is not caused by Cura or a "faulty" model. In that case the problem is in the printer, mechanical or firmware.

Or perhaps it is caused by cheapo Chinese PLA, but then I would expect to see a lot of other shit in other parts of the model as well. Still, don't use that stuff. Always get good quality PLA if you want good quality prints.

Another tip for delta printers: accuracy of those is worse in the centre of the platform, and better towards the edges...

 

Share this post


Link to post
Share on other sites

Hey guys, thanks for your replies.

I used Repetier Host V1.0.6, what version the Curaengine is, I couldn't find (Anyone knows where too look? In the slicer manager there is nothing said). The PLA is coloufabb and layerheights was 0.3mm which is often good enough for me. I tried other heights for this model, but it didn't make any difference regarding the problem.

I took a closer look to the layer-preview and made out some irregularities at the radii:

Slicing Of small radii (R0,25)

 

could this be the cause?

 

I used a stl with a higher resolution but got the same irregularities:

Slicing Of small radii (R0,25) fine Stl

Any guesses?

 

Share this post


Link to post
Share on other sites

That looks weird. Something is going wrong with the slicing here, so you can rule out printer problems for now. Never seen this happen in Cura (nor in Repetier, but I don't use that a lot). You could download Cura from the Ultimaker site (it's free), and see if the same thing happens when you load the model in Cura.

 

Share this post


Link to post
Share on other sites

What's going wrong then? The toolpath seems to comply with your model.

 

There does occur a problem which you didn't mention: the second perimeters are overlapping, which causes an overflow of material, causing the surface to be ugly.

This bug has been fixed in a new version of Cura.

 

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

  • Our picks

    • How to 3D print with reinforced engineering materials
      Ultimaker is hosting a webinar where we explain how you can achieve and maintain a high print success rate using these new reinforced engineering materials. Learn from Ultimaker's Product Manager of Materials and top chemical engineer Bart van As how you can take your 3D printing to that next level.
      • 0 replies
    • "Back To The Future" using Generative Design & Investment Casting
      Designing for light-weight parts is becoming more important, and I’m a firm believer in the need to produce lighter weight, less over-engineered parts for the future. This is for sustainability reasons because we need to be using less raw materials and, in things like transportation, it impacts the energy usage of the product during it’s service life.
        • Like
      • 12 replies
×

Important Information

Welcome to the Ultimaker Community of 3D printing experts. Visit the following links to read more about our Terms of Use or our Privacy Policy. Thank you!