Dimensional accuracy tips

 


                                                          

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tips for improving dimensional quality

The accuracy of printed parts is of course very important, especially for projects that require an exact fit between other components. 

There are a number of common causes that can affect accuracy, such as under-extrusion or over-extrusion, filament properties, and the quality of the first layer. Additionally, the intricacy of the print model’s design can play a role in obtaining satisfactory results. 

First things first, be sure to check the actual print quality of your printer.  You can do this by running a test with a calibration cube.

Our calibration cube measures 50mm on all axis directions. The dimensional accuracy is the difference between the digital model and the printed model.

 

3d printer calibration cube

Download it here: Calibration Cube

On FDM machines the accuracy values are:

  • Less than +/- 0.1mm = excellent accuracy
  • Less than +/- 0.2mm = good accuracy
  • Less than +/- 0.5mm = regular accuracy
  • More than +/- 0.5mm = bad accuracy

In most cases, positive dimensional errors are better because you can fix them during post-processing of the model.

After conducting this test, you can continue to improve the accuracy of your 3D printed models by implementing the following steps.

 

Model units

size of the model on BCN3D stratos

If your slicing software uses one unit and the model is designed in another, you will notice an obvious difference between the two. Although this issue can go unnoticed, it can cause a lot of problems when measuring 3D models. 

Therefore, make sure that you are using the same unit to design and slice your model.

Note: The BCN3D Stratos works with millimeters (mm)

 

Clean and lubricate the axis

3d printer axis lubrication

A common problem for accuracy is a lack of maintenance, specifically the cleaning and lubrication of the axis. If the printing head, carriage, and printing platform have problems moving smoothly, the accuracy is affected. 

We recommend carrying out maintenance on the printer every week, and protecting the printer from the dust and leftovers of filament in the linear guides and the Z-axis structure.

For more information, read these guides that detail how to ensure that the axis is in good shape:

How to clean and lubricate the axis (BCN3D Sigma)

How to clean and lubricate the axis (BCN3D Sigmax)

How to clean and lubricate the axis (Epsilon Series)

How to clean and lubricate the axis (Sigma Series)

Note: Lubricating the pulley's shaft and the bearing pillows helps a lot - you only need to add some mechanical oil over these components.

 

Belt tension

3d printer belt tension check

The movement transmission is of the utmost importance when you want accurate measures.

If the belts are loose or too tight, the movement could result in dimensional inaccuracies.  

Check out our guides to adjusting the belt tension for all of our printer models:

How to check and adjust the belt's tension (BCN3D Sigma)

How to check and adjust the belt's tension (BCN3D Sigmax)

How to check and adjust the belt's tension (Epsilon Series)

How to check and adjust the belt's tension (Sigma Series)

Note: Our guides have a printable tool for checking belt tension.

 

Hotends size

3d printer hotend size comparison

Different hotend sizes produce different results for the same model. For example, hotends with big diameters need less time to complete the print but sometimes lose accuracy on details.

In this article, you can find more information about the difference between hotend sizes and how to choose them according to your needs: How to choose the right hotend size for each 3D printing application

Print temperature and flow rate

3d printer printing temperature and flow rate

In order to further increase the accuracy of your print, you can lower the print temperature by 5ºC and the flow by 5%, until the excess of material disappears. 

Be cautious when doing so, as this can lead to under-extrusion and clogging in the hotend. The best way of performing this adjustment is to use small steps on repeated prints.

Print speed

3d printer axis movement velocity

The speed at which you print also affects accuracy. High speeds can cause a tiny layer shifting in some areas of the model, which can be eliminated by reducing the speed by 50%.

If you want to print faster than the recommended speed from our BCN3D Stratos profile, follow the steps in this article: How to speed up your prints

Cooling between layers

3d printer cooling fan cooling between layers

When the nozzle is continuously moving in the same area, this can cause an excess of temperature that softens the material and creates small irregularities, leading to accuracy issues.

This can happen when printing thin pieces that are also tall e.g. a small diameter cylinder. Another typical deformation occurs in inclined cantilevers: the material which is still-hot is deformed when suspended in the air until it solidifies.

These problems can be solved by making adjustments to the layer fan. If you notice that the walls of your model are irregular, similar to over-extrusion, check the cooling configuration of your profile and try to increase the fan speed and minimum layer time.

First layer's quality

3d printing first layer quality importance

The first layer is the most important layer of a print, as the rest of the piece will be built on top of it.

One problem that can arise in the first layer is called "elephant's foot"; this issue is caused by a bad calibration that squishes the first layer, making it spread out more horizontally compared to the rest of the model.

To solve this and other problems that could affect the first layer, such as warping, have a look at the following article: How to fix first layer issues

Constant dimensional error

horizontal-expansion-landing

The BCN3D Stratos offers the option to offset the edges of your model. This setting is called the "Horizontal Expansion", which works perfectly when the measurement error is constant. For example, if you check the size of your model and you notice that it is 0.2mm bigger in the X and Y directions, you can apply -0.2mm of horizontal expansion to remove this difference.

Designing to compensate for the tolerance

design-for-3dprinting-03

Although these aforementioned steps can help you to improve the dimensional accuracy of your 3D models, we cannot expect perfect accuracy from the printed versions everytime. 

Subsequently, it is important to take this inaccuracy into account when designing your own models. For example, if you are creating a hole in a model to fit another part into and your printer consistently makes the error of holes being 0.1mm too small, you should design the hole 0.1mm bigger.

 

Conclusions

If you still experience accuracy issues, get in contact with our support team by filling this form.

Forum community 

The repair didn’t go as planned? Check out our forum community for troubleshooting help.

 

It's important to keep your printer in good shape to make the most out of it. In this chart, you can find a list of the extruder maintenance procedures and how frequently these should be done. 

Maintenance Plan (BCN3D Sigma)

Maintenance Plan (BCN3D Sigmax)

Maintenance Plan (Epsilon Series)

Maintenance Plan (Sigma Series)

 

bcn3d-recycle  Take your e-waste to a certified recycler. Check how we do it in BCN3D

 


RELATED ARTICLES

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