How to Use Tolerance Compensation on CHITUBOX

 


 

Your printed model can't satisfy your requirements when its size doesn't match what was designed and has a significant deviation. Since version V1.8.0 Beta, we have introduced the tolerance compensation feature in CHITUBOX. It helps you adjust the inner and outer diameters of your model, so, when they go beyond the tolerance, you can calibrate them to ensure the model size precision.

 

In this post, you'll know:

  1. Where on the model will tolerance compensation work on
  2. The detailed steps of using tolerance compensation
  3. A simple test case showing its efficacy

 

 

Where on the model will tolerance compensation work on

Tolerance Compensation on CHITUBOX applies to the inner and outer diameters of your models. They are defined as follows:

  • Inner diameter compensation applies to the deviations of the size of closed inner contours (e.g. holes or hollowing) on each layer of the model;
  • Outer diameter compensation applies to the deviations of the size of outer contours on each layer of the model.

 

As you can see from the image below, the red line marks where inner diameter compensation takes effect, while the green lines indicate where outer diameter compensation works on.

 

Note that inner compensation only works on CLOSED inner contours. Inner contours that look like the image below, even though it is almost closed, is counted as an outer contour because it is connected to the outside. So only outer diameter compensation will take effect.

 

CHITUBOX lets you enter two numbers (a and b) to set the inner and outer diameter compensation respectively. These numbers work like below:

 

  • When a is larger, the inner diameter is shorter, and the model body is larger. When a is smaller, the inner diameter is longer, and the model body is smaller. When a is set to positive (to compensate for the model shrinkage), the inner diameter decreases, and the body size increases. When a is set to negative (to compensate for the model expansion), the inner diameter increases, and the body size decreases.
  • When b is larger, the outer diameter is longer, and the model body is larger. When b is smaller, the outer diameter is shorter, and the model body is smaller. When b is set to positive (to compensate for the model shrinkage), the outer diameter increases, and the body size increases. When b is set to negative (to compensate for the model expansion), the outer diameter decreases, and the body size decreases.

 

Notice that the changes of a and b apply to every single side of the inner and outer contours. If you look at the image above, if b increases, all the four sides of the outer contours move out by the value of b, which means the outer diameter goes up by 2*b; if you increase a, the whole circle will shrink by a, and this reduces the inner diameter (here, the diameter of the circle) by 2*a.

 

 

The detailed steps of using tolerance compensation

To use this feature on CHITUBOX:

 

  1. Click Settings button above Slice.


  2. Click Advanced.


  3. According to your requirements, select Tolerance Compensation or Bottom Tolerance Compensation (see its explanation below), and enter your a (inner diameter) and b (outer diameter) values.

 

(Due to the different printing settings for bottom layers, the bottom sizes may have different deviations from the normal layers. For example, the bottom will have longer exposure time, and therefore larger size, so called "elephant's foot". To solve these problems, CHITUBOX has specific settings for the bottom layer compensation, which are "bottom tolerance compensation".)

 

This is how you set up tolerance compensation. Once you finish editing and slicing your model, you can print it and see how this feature works.

 

In normal cases, it is suggested that you print your model first to test and measure it. If you see significant deviations, then you use tolerance compensation to try fixing the issues and printing the model again, until the sizes satisfy you.

 

 

A simple test case

We did a simple test using this feature.

 

We chose a pair of typical hole-shaft models. The shaft is designed as 10 mm in (outer) diameter, and the hole 10.5 mm in inner diameter.

 

When we printed the models the first time, without any compensation, the measured shaft diameter was 10.19 mm, and the hole 10.05 mm.

 

These numbers told us that compared to the design, the diameter of the shaft is larger, and the hole is smaller. So both models swelled up a bit, and they couldn't fit each other.

 

So we used the tolerance compensation feature on CHITUBOX. We set the value for a and b to -0.2 and -0.1 millimeters respectively. Hopefully this could increase the inner diameter by 0.4mm and reduce the outer by 0.2mm (from the explanation above, the changes of the diameter is twice as the compensation values), so they could get close to the designed values.

 

When we printed them the second time, with tolerance compensation, the shaft diameter was 10.00 mm, and the inner diameter for the hole was 10.43 mm.

 

And they fit well.

 

You can see that this feature is working well.

 

 

Last but not least, note that the model body size can be affected by your printing material, hardware, and the environment. So your tolerance settings may not be applicable if you use them with a different printer or resin.

 

This is how you can use tolerance compensation on CHITUBOX. If you still have questions about this feature, contact us at support@chitubox.com, and we will be happy to help you.