Core One + First print fails  

RE: Core One + First print fails

So far you have given us very little information to work with.

• I assume you have built the printer from a kit?
• In which way does it fail the homing test?
• Did you complete the gantry alignment and belt tensioning? Best done with the new firmware 6.4.0 and following Prusa's updated guide.

RE: Core One + First print fails

Well, we need to get that printer to pass the homing test !

- Okay, you were printing the 'keychain'... Is that the Original PRUSA demo print?

- Benchy is causing the 'whole room is shaking'. 
       Not sure how sturdy your table is.
         CAN YOU PUT THE PRINTER ON A MORE STABLE SURFACE (temporarily). 
         LIKE A CONCRETE FLOOR ON THE GROUND.
            that should eliminate the shaking causing the printing issues.

RE: Core One + First print fails

ChatGPT response to your post...  (Be careful, ChatGPT is known to lie !)

======

Hello, thank you for contacting Prusa Support 👋 I’m sorry to hear about the trouble with your Core One, but we’ll get this sorted step by step.

Based on your description, there are two critical issues happening, and they are directly related:

1️⃣ Printer does not pass homing – this must be resolved first

A Core One that cannot complete homing correctly should not be printing. Yes — unsatisfactory homing absolutely can cause mid-print failures, layer shifts, and severe vibration.

If homing is unreliable:

The printer does not know its true position

Motor corrections accumulate

This leads to layer misalignment, shaking, and eventually print failure

This explains:

Keychain failing ~70% through

Benchy layers not stacking vertically

Whole room shaking (this is not normal behavior)

2️⃣ Excessive vibration and layer shifts

The Core One is normally very stable, even at higher speeds. If the room is shaking, something is mechanically or electronically wrong.

Typical causes:

Missed motor steps

Loose belts or pulleys

Axis binding

Incorrect motor current or skipped homing detection

🔍 Let’s troubleshoot in the correct order

Please go through these in sequence and do not print until homing is fully resolved.

✅ Step 1: Describe the homing failure precisely

Please confirm:

Which axis fails homing? (X, Y, Z, or multiple)

Does homing:

Stop with an error?

Complete but sound rough?

Retry repeatedly?

Succeed sometimes and fail others?

Also tell us:

Does the printer display any error or warning tone during homing?

🔧 Step 2: Mechanical checks (very important) A. Belts

Check X and Y belts:

Firm, not loose

Not overtightened

Pluck test: belts should produce a low, consistent tone, not floppy or extremely tight

B. Pulleys

Check all motor pulleys:

Grub screws tight

One grub screw must be tightened against the flat of the motor shaft

A loose pulley can cause:

Layer shifts

Violent shaking

Failed homing

⚠️ This is one of the most common causes of your symptoms.

🧭 Step 3: Axis movement test (printer OFF)

Power the printer OFF

Manually move:

X and Y axes

Motion should be:

Smooth

Even resistance

No grinding, binding, or catching

If you feel resistance → stop and report where it occurs.

🧪 Step 4: Sensor and wiring check

Verify all endstop / sensor connectors are:

Fully seated

Correct orientation

Check that no cables are:

Pinched

Pulled tight

Rubbing on moving parts

A partially seated connector can cause intermittent homing failures.

⚙️ Step 5: Firmware & calibration

Confirm you are running the latest Core One firmware

Once homing works 100% reliably, perform:

Full Self-Test

XYZ calibration

First Layer Calibration

Do not skip any of these steps.

🚫 Important safety note

Please stop the current Benchy print immediately.

Continuing to print while the printer:

Fails homing

Shakes excessively

Shifts layers

can lead to:

Motor damage

Pulley wear

Belt damage

Print head crashes

📌 Summary

✔ Yes, failed homing can absolutely cause your print failures ❌ A Core One should never shake the room 🔧 This is almost certainly a mechanical or homing-related issue, not slicer settings or the table

Next reply — please include:

Which axis fails homing

Any on-screen errors or tones

Whether any pulleys or belts felt loose

Whether axis movement feels smooth with power off

We’ll continue from there and get your Core One printing correctly 👍

RE: Core One + First print fails

Please, let's not post ChatGPT advice here, especially such long texts. It does not help the signal/noise ratio, and everyone can ask ChatGPT directly if they expect that to be helpful.

In the specific post above, ChatGPT's advice is not incorrect. But it suggests some steps which are pretty intrusive and should not be the first thing to check. (Who wants to take out the motors to check the grub screws?) And it is very hazy on things where much more specific advice is easily available. ("Belts should produce a low, consistent tone" -- I already posted the link to the belt tensioning guide which explains in detail how to set them correctly.)

RE: Core One + First print fails

A few weeks ago, my Core One printer started having problems starting to print when I switched from PLA to PETG, taking 5 minutes to return to its home position, etc., and always ending in a "collision" The objects printed correctly, but the noise and errors were annoying at the start. I tried to solve the problem by adjusting the belt tension, squaring the gantry etc. The solution that worked was to remove all the screws from the linear bearings on both sides and tighten them back in place, carefully lifting the rail to maximize the gap between the linear bearing assembly and the frame. After that, everything started working normally again and homing takes only couple seconds. Only reason I can come up with this is that the linear bearings were somehow stuck.

Linear bearings & screws I took off (last pic): https://help.prusa3d.com/guide/5-corexy-assembly_835522#844219
Linear bearings & frame (Gentry/linear rail is missing from the picture): https://help.prusa3d.com/guide/5-corexy-assembly_835522#844328
Linear rail (2nd pic): https://help.prusa3d.com/guide/5-corexy-assembly_835522#845609

@jsb It's hard tp make reasonable suggestions without some evidence - please supply a picture of a failed print *on the print sheet* and another showing the underside of the same print after removal.

Benchies (and before them, Bunnies) used to be standard torture tests for diagnosing printer problems; unfortunately there are now so many unregulated variants of these files that their utility has almost evaporated - to get the original, useful Benchy file go to: https://www.3dbenchy.com/

If your printer is shaking hard you might be printing one of Prusa's high speed Benchies - there are party-trick 'Look how fast we can do it' versions proliferating that will shake any printer OR you may have a perfectly ordinary Benchy file and a resonance problem.

To check for resonance, move the printer, temporarily, to another surface, even the floor will do and see if the vibration continues.  If the printer is quiet the answer is simple, put it on a different table or if that is not possible look up the 'concrete paver' solution. [It's not a matter of the strength of the table, it's the frequency at which it naturally vibrates accidentally matching that of one of the printers moves.]

Cheerio,