Troubleshooting Prints

As much as I appreciate being asked for advice on 3D printing issues, I must clarify that I’m not an expert in this field. My experience is limited to the Prusa printer family. In this chapter, I won’t delve into specific printer problems. Instead, I’ll guide you on how to effectively verify your prints, which should help you identify the reasons behind any print failures.

Essential Tool: Calipers for Accurate Measurements

Accurate measurements are crucial in 3D printing, and for this, you need calipers. High-quality measuring tools come with a cost. It’s important to note that calipers capable of measuring with 1/100 mm precision usually start at around $50. While there are less expensive digital calipers available, they often offer lower precision, sometimes only up to 1/10 mm. Surprisingly, you might find that analog calipers (those with no digital display, just marked lines) can provide more accurate readings than cheaper digital alternatives.

For those serious about precision in 3D printing, investing in a high-quality caliper is essential. Recommended brands include Mitutoyo (Japanese), Starrett (US), Fowler, and VINCA. The most common type measures between 0 - 150mm (0-6 inches). Ensure that the caliper’s accuracy (not just resolution) is at least 1/100 mm (0.0005 inches).

Examining a Reference Print

Here is a reference print of the LR2052-112C model. This was printed using an Original Prusa i3 MK3S+ printer, with a fast 0.2mm profile and a 0.4mm nozzle. This setup is my standard for testing all my models.

A reference print

The surface quality is noteworthy, exhibiting minimal defects. The box sides are straight, and using a set square, you can verify that the angles are a perfect 90 degrees.

Let’s examine the bottom of the box:

The bottom of the reference print

Notice how the box’s bottom is flat and features an even pattern of lines.

Now, take a closer look at the back side of the reference print where the part number is engraved:

The backside of the reference print

When inspecting the side under bright light, you’ll see the printed layers and may notice minor defects. These can include slight ringing – vertical wave patterns, as shown on the left side. While these ringing artifacts might be visible, they should be smooth enough that you don’t feel them when running your finger across the surface.

Additionally, on the outer sides, corresponding to where ribs are on the inside, you might observe small bumps. These should be almost imperceptible to the touch.

Precise Measurements: Starting with Side Thickness

Measuring the wall thickness of your box is an essential first step. It provides insight into whether your printer tends to under- or over-extrude filament.

Measuring the wall thickness

The stacking tolerance for wall thickness is 0.2mm. A good tolerance is within +/-0.08mm, while +/-0.15mm is acceptable.

The tolerances for the wall measurement

A well-calibrated printer should fall within the “Good” tolerance range, ensuring that objects print correctly. If your measurements are in the “Ok” range, the boxes might stack, but the fit could be loose or tight. Measurements outside these ranges indicate a problem with your printer setup.

Common causes for out-of-tolerance prints include:

  1. Temperature: Printing at too high a temperature can hinder precise control of plastic flow.
  2. Incorrect Printer Profile: A mismatched printer profile in the slicer can lead to over or under-extrusion.
  3. Inconsistent Filament Quality: As 3D printers rely on the filament’s length to deposit material, the filament’s diameter must be precise. A slight deviation in diameter can lead to significant discrepancies in extruded material.

Assessing the Stacking Bottom Width

Next, measure the bottom width at its narrowest point, where one box stacks on another.

Measuring the stacking bottom width

This measurement should adhere to the same tolerances as the wall thickness: +/-0.08mm is good, and +/-0.15mm is acceptable. However, consider the cumulative effect of tolerances. For example, if the length is +0.15mm and the wall thickness is also +0.15mm, this could result in a total deviation of +0.15mm, exceeding the stacking gap of 0.1mm on each side, leading to stacking issues.

The tolerances for the wall measurement

A well-calibrated printer should easily stay within the “Good” tolerance range. Deviations could be due to:

  1. Over-extrusion: Refer to the previous section.
  2. Loose Hardware: Loose belts can cause slight inaccuracies in movement, affecting dimensions.
  3. Uncalibrated Printer: Inaccurate movement calibration can lead to dimensional inaccuracies. This is particularly evident in prints where dimensions are critical, like in storage boxes.
  4. Quality of Printer: Precision in prints requires precision in printer components. Lower-cost printers, particularly those under $100, may struggle with producing accurate prints, especially for functional parts.

Accurate Dimensions: Width and Depth of the Box

It’s crucial to measure the total width and depth of your box accurately.

Measuring the width and depth

To calculate the target dimensions, use the formula: units x 60mm - 0.5mm. Aim for a tolerance of +/-0.08mm for best results, while +/-0.15mm is still acceptable.

Next, measure the top rim of the box. Remember to handle the calipers gently, as the sides of the box are flexible. Avoid applying pressure which might distort the measurement. During this process, use a set square on all four sides to ensure the layers are perfectly perpendicular at 90 degrees.

Measuring the top rim width and depth

Additionally, measure the inside dimensions of the box. Ideally, these should match the outside dimensions minus twice the wall thickness, which is 1.67mm.

Measuring the inside width and depth

If the top rim doesn’t align with the sides below, it may indicate an issue with your printer’s calibration. This misalignment can be caused by belts that are too loose or too tight, leading to stepper motors skipping steps. Inexpensive 3D printers often struggle to print perfectly vertical walls due to cumulative minor imprecisions, especially in taller prints.

Final Measurement: Box Height

The height of the box is also important, though it does not require the same level of precision as the width and depth. A variation in height may affect the boxes’ alignment when stacked, but they will still be functional and stack well.

Measuring the box height

Refer to the model description for the target height of each box. For instance, regular boxes have a target height of 44mm. A good tolerance here is about +/-0.2mm, approximately one layer. Remember, the height of the first layer can vary depending on the printer bed used and is often slightly less than the standard 0.2mm layer height. This variation can impact the overall height of your model.

Conclusion

In this guide, we’ve walked through several critical measurements for troubleshooting 3D prints of storage boxes. From assessing wall thickness and stackability to ensuring precise width, depth, and height, each step plays a vital role in achieving a successful print.

Remember, 3D printing is as much an art as it is a science. Variations in printer calibration, filament quality, and environmental factors can all influence the outcome. Consistent testing and calibration are key to maintaining print quality. Use this guide as a reference to identify and rectify common issues, ensuring your prints meet the desired specifications and quality.

Happy printing, and remember: patience and precision are your best tools in the world of 3D printing!