Jump to content
Ultimaker Community of 3D Printing Experts
kasztimate

Holes are smaller than designed

Recommended Posts

Dear all,

I guess I am not the only one mentioning this issue, but i searched for many forums and sites about this problem and cant find the right solution.

My problem is the following. The designed holes are getting smaller when printing. Exactly with 0.4mm no matter what is the diameter. The boundary walls of the model are perfect size. So in my case if i print out a 20x20 box with a 10mm dia hole in the middle i got the following:

- outside dimensions are exactly 20x20 but the hole is 9.6mm dia.

If i try to change the so called "horizontal expansion" setting with -0,4mm than i got the following results

- outside dimensions are 19.2x19.2 and the hole is exactly 10mm dia.

So this setting changed the desired hole size but also ruined the outside dimensions.

Is it a normal thing or its kinda unique.

Is there any other ways than designing it in CAD with extra dimensions like a hole with 10,4mm dia? It is weird because if im going to make some drawings for further CNC than i have to change the whole model again.

I hope someone out there has the clue.

Thanks in advance!

Share this post


Link to post
Share on other sites

This is a normal effect on all similar 3D-printers. The filament is still molten or somewhat flexible when laid down. When the nozzle is printing a corner, as in tight circles around holes, it pulls the molten filament to the inside of the curve.

In small holes this is even more visible: a 3mm hole may come out as a 1.5mm hole. It also depends on printing speed and temp.

Solutions could be: change the dimensions in the design, or go through the hole with a drill.

  • Like 1

Share this post


Link to post
Share on other sites

I noticed exactly the same thing.

5a3340e8d981d_2017-11-1611_55_43-AutodeskFusion360.thumb.png.7b582089367fbc79d64782e7fa202457.png

My 18mm desired outside diameter prints as 17.8mm and my internal desired diameter of 10mm prints as 9.8mm due to material contraction.

I added a horizontal offset of 0.4mm to exaggerate the effect and ended up with 18.6mm outside diameter and an internal diameter of 9mm. It's no coincidence that both dimensions moved exactly 0.8mm as Cura has added an offset edge of 0.4mm to the outside wall but has also added an 0.4mm offset to the inside wall making the hole smaller.

The only way to do it is to perform non-uniform scaling along the X and Y axis in the scale settings rather than use the horizontal offset.

It is clear that Cura is adding an

Share this post


Link to post
Share on other sites

It's not exactly caused by the part shrinking.

It's because as it extrudes, PLA sticks to itself like snot. Like a liquid rubber band. And it is also shrinking rapidly while still liquid so it is pulling inward. and when you go around any corner it pulls inward. It's a little worse on corners. It gets better as you get farther from the heated bed. It seems to help if you have double pass walls (e.g. line width .4mm and shell width .8mm) as the inner wall helps hold the outer wall in place.

  • Like 1

Share this post


Link to post
Share on other sites

if the hole is smaller that designed you need to use a negative number in the horizontal offset.

Depending on the tolerances involved, that could create other issues in your print such as making other areas smaller than they need to be.

An example would be if I have a widget that is printing just fine at the designed width, and it needs to be that width to slot into something else or be accurate, then the hole would be made more proper and the rest would falter.

I think it is better to learn the tolerances, the why of things and then learn to design around that.

Share this post


Link to post
Share on other sites

 

if the hole is smaller that designed you need to use a negative number in the horizontal offset.

 

Depending on the tolerances involved, that could create other issues in your print such as making other areas smaller than they need to be.

An example would be if I have a widget that is printing just fine at the designed width, and it needs to be that width to slot into something else or be accurate, then the hole would be made more proper and the rest would falter.

I think it is better to learn the tolerances, the why of things and then learn to design around that.

 

totally agree, I was just pointing out the fact that DB wondered why the hole got smaller when he applied horizontal offset and he quoted a positive value.

I design all my stuff with a tolerance depending on the feature I am designing.

Share this post


Link to post
Share on other sites
......totally agree, I was just pointing out the fact that DB wondered why the hole got smaller when he applied horizontal offset and he quoted a positive value.

Wow...totally missed that...Duuurrrrhhhhh...:p

Thanks for setting me straight.....

I will go back to me hobbit hole now........

Share this post


Link to post
Share on other sites

 

......totally agree, I was just pointing out the fact that DB wondered why the hole got smaller when he applied horizontal offset and he quoted a positive value.

Wow...totally missed that...Duuurrrrhhhhh...:p

Thanks for setting me straight.....

I will go back to me hobbit hole now........

 

nah don't go to the hobbit hole, there are still more unexpected journeys lol

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

  • 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!