This article introduces and explores the new Prusa Core One printer. It includes a number of methods to increase this printer's accuracy and usefulness. Some printable 3D resources are included, including a Web camera mount to provide a local-network, full color, video frame rate printing monitor, to replace the Prusa Buddy3D camera.

This article describes the Prusa Core One from a user perspective. I have no connection with Prusa, no editorial constraints, and some personal preferences having to do with privacy and independence.

This article assumes you have a working Prusa Core One, either a factory-built machine or a completed kit. This article goes beyond the instructions provided by Prusa and offers some configuration and tuning advice not found elsewhere.

Although this article's focus is the Prusa Core One, many of its methods apply to other Prusa printers.

This article is intended as a resource archive for a video yet to be released.

Let's get started!

As delivered, either factory-built or user-assembled, this printer needs certain alignments for best performance, some of which aren't very well documented. This section provides a Z-axis (vertical) alignment method to level the print bed.

Figure 1: Pathologically Misaligned Print Bed

Figure 1 shows a print bed with greatly exaggerated misalignment, just to make a point — if the print bed isn't properly aligned or "leveled", many other things will go wrong. On delivery, many Prusa printers, especially those assembled by the recipient, will have misaligned print beds.

Here's the remedy: the Prusa Core One print bed is supported by three threaded shafts, each connected to a stepper motor. The stepper motors operate synchronously, rotating the threaded shafts during printing, so that the bed remains level at all vertical positions — but this is only true if the bed has been properly leveled in advance. In this section we'll make sure the bed is level.

Here are the steps to align the print bed:

• Move the print bed to its lowest position. This is accomplished using the Prusa Core One control menu:
• Start at the main menu control icon
• Move Axis
• Move Z
• Press the control knob to activate motion, so the current position is printed in red
• Rotate the control knob to move the print bed to its lowest position.
• As the print bed arrives at its lowest position, this will likely be accompanied by a grinding or clicking sound — this is harmless but at that point, stop the motion inputs.
• Either activate the "Disable motors" command, or turn off the printer. The latter choice is simpler and safer.
• Manually rotate each of the three threaded shafts counterclockwise (as seen from above) to move the print bed to its lowest position:
  
  Figure 2: Shaft Rotation to Level Print Bed

• This procedure should level the print surface:
  

  Figure 3: Level Print Bed (click for full-size)

  The Prusa Core One is designed so that, when the three shafts have been rotated counterclockwise to the degree possible with power off, the print bed will be level. Then, during printing, because the print bed motors are synchronized with each other, the print bed will remain level at all other positions.

The Prusa Core One uses the so-called "Core XY" scheme, in which the print head's X (left/right) and Y (toward/away) positions are controlled by stationary motors and a system of belts and pulleys. For accurate motions and printing, this scheme requires that the X and Y axes be separated by exactly 90°, so that X motions have no effect on the Y dimension and vice versa.

One clue that the X and Y dimensions aren't properly aligned is something called "Print skew":

Figure 4: Print Skew (greatly exaggerated)

The effect seen in Figure 4 results from the fact that the printer's X and Y axes aren't separated by exactly 90°. This can have many undesirable effects on 3D printing, as well as cause the Prusa Core One to fail its Y axis motion test:

Figure 5: Prusa Core One Y-axis motion test failure

The remedy for this issue is to tune the relationship between the X and Y axes so they are "orthogonal," meaning separated by exactly 90°. Unlike the Z axis adjustment explained above, correcting this misalignment requires applying a small amount of force to the Core XY mechanism — very carefully, minimal necessary force, and with intermediate tests after each adjustment. Here is the procedure:

• Turn off the printer — no power is needed for this procedure, and removing power will reduce the possibility of unintended control activation.
• Move the X axis rail fully to the back of the printer and center the print head:
  

  Figure 6: X axis rail and print head correctly positioned (click for full-size)

• Now press the left and right ends of the X axis rail against the provided stops, toward the back of the printer, as shown:
  
  Figure 7: X Carriage Clearance Test

• In a properly adjusted Core XY carriage, the amount of movement, and the required force, on each end of the X axis carriage should be equal, without a larger amount of motion at one end or the other. And if this is already true, go no further, don't make any more adjustments.
• If instead there is a larger gap at one end of the X carriage than the other, and if you feel confident in your technical skills, you may choose to adjust the X carriage rail so the two ends of the carriage have the same gap at the motion stops.
• NOTE: If you have never done this sort of thing before, or if you don't feel confident in your ability to carry out this procedure, you can always hire a professional to perform this adjustment for you. Don't forge ahead without an understanding of the process and the possible outcomes.
• The purpose of the next step is to gently and carefully bend the X carriage mounting brackets so the angle between the X and Y dimensions is exactly 90°.
• First, cover the printer's fragile bed heater with a print surface or cardboard sheet to protect it from dropped tools and other accidents.
• Make note of the end of the X carriage that has the largest gap, and create a gap with any convenient tool behind the opposite end, as shown here:
  

  Figure 8: X axis carriage adjustment setup (click for full-size)

• Gently apply some force to the free end of the X axis carriage as shown in Figure 8. Don't apply too much force. And remember that your printer's X carriage might need an adjustment opposite that shown in Figure 8, in which case the adjustment and tool ends of the X carriage as shown in Figure 8 should be reversed.
• Remove the tool shown in Figure 8 and repeat the clearance test shown above in Figure 7 to see whether the two ends of the X carriage have the same gap between themselves and the stops. The goal is to give the ends of the X carriage the same clearance from the stops, or in other words, to assure that the X carriage is at exactly 90° with respect to the Y axis rails at each side.
• Repeat the adjustment shown in Figure 8, and the test from Figure 7, as required to make the right and left X carriage gaps equal.
• A successful adjustment will result in the same amount of Y-axis clearance at each end of the X carriage, and when this is so, the printer should pass its Y motion test, and X/Y axis test prints should look like this:
  

  Figure 9: Successful Core XY alignment test print (compare to Figure 4 above)

Figure 10: Core XY Belt Layout (click for full-size)

Overview

The Prusa Core One relies on a system of belts and pulleys to move the print head in the X (left/right) and Y (near/far) axes. The belts are visible at the right and left sides of Figure 10 above.

As it turns out, the tension of these belts is critical to the successful operation of this printer. Here's an outline of the belt tensioning method:

• Turn off the printer.
• Move the print head to the position shown in Figure 10 — all the way to the rear, and centered between left and right.
• Gently pluck the belts like guitar strings, at the center of their long spans at the left and right, while measuring their frequency.
• While monitoring the belts' frequencies (see below), with an Allen wrench carefully adjust the belt tensions using the tensioners marked in Figure 11:
  

  Figure 11: Core XY Belt Tensioner Locations (click for full-size)

• Use a frequency meter (see below) to measure the frequency of the plucked belts.
• Interactively pluck the belts and adjust their tensions as explained above, until both belts are tuned as close to 85 Hz as is practical.
• It's important that both belts be tuned to the same frequency, in any case within a few Hz of each other, and as near to 85 Hz as practical.

At this point my readers will ask, "Wait ... how do I measure 85 Hz?" Here are some available methods:

• The cellphone-compatible Prusa Mobile App, which includes a marginally functional frequency measuring method (Android link | IPhone link). This is the least usable method.
• An Android app called "Spectroid" (download link), much superior to the Prusa method, only available on the Android platform.
• Other frequency measuring utilities are available for the IPhone platform, which unfortunately I cannot test.

But wait ... I provide a:

Test Signal Generator

To evaluate a cellphone frequency-detecting app in advance of trying to tune your printer's Core XY belts, here is a signal generator that provides a reliable 85 Hz signal for testing:

| | Gain: 50

• Press the Start/Stop button at the left and move your cellphone near your computer's speakers to pick up the signal.
• Adjust the speaker gain as required to make the signal audible, but without overloading your computer's audio system.
• Use this test signal to learn how to use your chosen frequency-measuring app in advance of actually trying to tune your printer's belts.

Frequency Measuring App Evaluation

Again, the Prusa Mobile app includes a way to measure the belt frequency, but it's not very good. It may take an unconscionably long time to respond to signals, meanwhile telling you that:

Figure 12: Prusa Mobile App Typical Display

A warning — don't assume that the Prusa Mobile app is providing correct information. If you assume it's accurate and expect it to respond in a timely way, you may overtighten a belt, with numerous consequences, all of them bad.

By contrast, here is the Spectroid app display under the same circumstances, which responds instantly:

Figure 13: Spectroid (Android) Typical Display

Much better.

A Traditional Method

Let me suggest one more method, which won't be practical for everyone. If your computer has a quality sound system with the ability to play low-frequency sounds and is able to play 85 Hz clearly, without distortion and with enough volume, it should be possible to play the above test signal near the printer and match its frequency "by ear" while tuning the printer's belts. This is how an orchestra tunes its instruments, how a piano technician tunes a piano, and how groups of people sang the same note before modern times.

Okay, this is somewhat out of date, but in the right circumstances it would work.

Prusa offers a camera named "Buddy3D" for the Core One, but it has a number of drawbacks:

• Unless there is more light available than is typical for the Core One print volume, the camera provides monochrome images.
• The camera updates its image only once every ten seconds.
• Without an Internet connection, the camera stops working.
• Use of the camera requires a Prusa Connect account.

I think Prusa is a terrific company that has made many contributions to 3D printing over the years, but when I hear they require a Prusa account to use their camera, I want to consider a different one — and this section provides it.

The Basics

This project uses a 3D printed camera mount, some magnets, and an inexpensive color camera.

The 3D printed mount looks like this:

Figure 14: 3D printable camera mount as rendered by Blender: without camera | with camera

Here's a list of resources / links for the camera mount:

• A SolveSpace design file for the mount, for those who need to customize the design, perhaps for a different camera.
• A printable STL file of the mount, suitable for the Yi camera listed below.
• A Prusa Slicer file containing the mount, with appropriate settings for ABS printing on the Prusa Core One.
• NOTE: If you create your own Prusa Slicer profile for this project, be sure to enable supports, like this:
  
  Figure 15: Prusa Slicer print configration with organic supports (click for full-size)

• Neodymium magnets, length 27mm, diameter 6mm, Amazon link, need 6.
• A small inexpensive camera, manufacturer Yi, Amazon link.
• A micro-USB to USB-C adaptor cable to power the camera from the printer, Amazon link.

NOTE: All these links will become invalid over time. I hope I have provided enough detail so the items can be located anyway.

Using Spring 2025 prices, this camera setup costs about US$42.00 altogether, only because one cannot buy just six magnets. This is slightly more expensive than Prusa's Buddy3D camera.

The Yi camera has a micro-USB connector, but the Prusa Core One has a USB-C power connector, so an adaptor cable is included in the above list, to use printer power for the camera.

Use of ABS filament is probably not required. I normally use ABS for durable parts that need to tolerate elevated temperatures, but I haven't tested other filament types, some of which may work correctly in this project.

Setup Instructions

When the above parts list is complete and the mount has been printed, take these steps:

• Slide six neodymium magnets into the slots provided in the 3D printed mount. Make sure all the magnets are inserted with the same polarity, i.e. the magnets should have either their North or South poles all pointing toward the center of the mount.

Figure 16: Mount with installed magnets
• Remove the Yi camera from its tabletop support.
• Snap the Yi camera into the gripping fingers on the front face of the mount.

Figure 17: Mount with magnets and Yi camera
• Using these instructions, route the USB adaptor cable from the Prusa Core One's USB-C power outlet to the upper left inside location where the Buddy3D camera would normally go.
• Connect the USB-C end of the adaptor cable to the Prusa Core One USB-C power connector.
• Connect the Micro-USB end of the adaptor cable to the Yi camera.
• Check for clearance and cable routing, then position the camera mount near the printer's upper left inside corner and release it.
• Make sure the mount is located symmetrically in its corner and firmly gripped by the magnets. Rotate the mount to be sure.
• With printer power off, move the print head to position Y = 0, X = 0 (the position nearest the camera) to make sure there is no collision possibility between the camera and the print head.
• Power up the printer and test the camera's wireless network connection. Make sure you have a clear picture of the print bed.
• To maximize the camera's usefulness, set the chamber light brightness to 100% and disable dimming. Use this command sequence from the printer's main menu:
  • Settings
  • User Interface
  • Chamber Lights 100%
  • Chamber Dimming Off

Third Party Camera Firmware

Without any changes and like every modern TV camera, the above-described Yi camera is over-reliant on company resources and connections. But a first-rate, open-source, third-party project solves this issue for this very popular camera, so it no longer phones home — here's a link. If you acquire the same camera model as that listed in the Amazon ad, its firmware prefix should be y211ga, usable as a search string at the linked firmware site.

Or perhaps you have located some other small, inexpensive security camera that, with no changes, doesn't try to phone home. If you have, please tell me about it at my message page. This isn't likely, but anything is possible.

Here are some recommendations for 3D design software and the best slicer to use with the Prusa Core One.

CAD/CAM Design

Some of my readers know I've created a few videos about SolveSpace (example), a free, open-source, multi-platform computer design program. I recommend it for students and for those who prefer open-source programs over the alternatives. Here's the camera mount described above, as shown by SolveSpace, where it was designed:

Figure 18: Camera Mount design in SolveSpace (click for full-size)

Many alternatives to SolveSpace exist, but most are either too buggy and hard to use (FreeCAD), or they own both you and your projects (Fusion 360). SolveSpace has a rather steep learning curve and is missing some features many people regard as important (like the ability to create numeric dimensioning variables), but it's both free and pretty good. It's more than adequate for projects like those in this article.

Best Slicer Program

In my opinion, for the Prusa Core One the best slicer program is the one created by Prusa, named PrusaSlicer. The big advantage of PrusaSlicer is that it knows about the Prusa Core One and includes profiles for many filament types, with parameters tuned specifically for the Prusa Core One. This is a huge advantage over the common practice of tuning a slicer program to accommodate an unknown printer and a 3D printing filament of uncertain properties.

Another PrusaSlicer advantage has to do with print speed. Without inside knowledge of a printer's mechanical properties, a slicer program isn't likely to know how to balance print speed and quality. But PrusaSlicer understands the Prusa Core One intimately and has been extensively tested in order to maximize performance and print quality.