The Pantheon HS3 uses a strain sensing electromechanical system as its means of probing. The probing system on the HS3 is one of the most critical as it responsible for the most difficult part of FDM printing, the first layer. It is essential for the probing system to be functioning well to yield great prints.

This guide will help you check for and maintain good probing performance.

caution Remember to always exercise caution when working with heated components.

How It Works

The system comprises of a strain element near the hot-end of the extruder, when the nozzle comes into contact with anything, the strain element experiences strain, the change in strain is measured and the system detects the change as a “probe” event.

During a probing action, the machine will heat up the extruder to a softening temperature of the material. This ensures that it is the nozzle that causes a trigger event and not cold/hard plastic buildup on the nozzle.

Machine Cleanliness

Machine cleanliness is the first essential part of ensuring a good print. Having a clean print bed print sheet on both side, a clean nozzle, and clean/dry filament is the minimum required to ensure exceptional print quality. Be familiar with the normal operating procedures of the machine.

Basic Function Test

To quickly check that the probing system is functioning at all:

While the machine is powered on and the hotend is cold, tap upwards on the nozzle with a solid object. Flicking it with your fingernail also works well.
There is a green LED on the PCB on the printhead that will flash when tapping upwards on the nozzle.

The LED should only react when a rapid change in force is applied to the nozzle. It should not be flashing randomly or inconsistently to the tapping on the nozzle. 1 tap = 1 flash.
Now preheat the machine to print temperatures and perform the same test. Don’t use your finger to tap on the hot nozzle, use the handle of a stiff screwdriver or other suitably stiff tool. Do not use a hammer or other significantly hard tool. Be sure not to damage the hot-end.

caution Remember to always exercise caution when working with heated components.

If you experience any behaviour that is not as described above as normal, reach out to Pantheon at support@pantheondesign.com.

Probing Accuracy

After confirming that the probing system is functioning, we now want to determine how well it is working. To do so, there is a built-in macro that will generate a small report on the accuracy of the probing system. It will be useful to have a set of feeler gauges for some steps of this procedure.

Ensure the bed is clean, no filament is loaded and a new nozzle is installed. Be sure to have a print sheet installed.
Home the machine and move the axes to X150 Y150 Z2:
G1 X150 Y150 Z2 F1000
Perform the probe accuracy macro using the following command through the console:
PROBE_ACCURACY
The macro will repeatedly probe the same point 10 times and generate a report. Run the macro a few times to verify consistency. Often the first point can be a bit of an outlier on the first attempt.

probe accuracy results:
maximum 0.443750, minimum 0.425000, range 0.018750, average 0.437812, median 0.439844, standard deviation 0.005173
maximum 0.450000, minimum 0.442188, range 0.007813, average 0.445000, median 0.444531, standard deviation 0.002296
maximum 0.453125, minimum 0.443750, range 0.009375, average 0.449375, median 0.448438, standard deviation 0.002539

The important numbers to take note of are the Range and the Standard Deviation.
- For the Range:
  - Less than 0.010mm is great performance.
  - Less than 0.025mm is acceptable performance.
  - Greater than 0.025mm may result in poor first layers.
- For the Standard Deviation:
  - Less than 0.005mm is great performance.
  - Less than 0.010mm is acceptable performance.
  - Greater than 0.010mm may result in poor first layers.
After performing the probing accuracy tests, we need to verify that the probe height reported by the machine is the true height of the nozzle. To do so:
- Home the machine and ensure the relative and absolute coordinates are identical. This is critical to ensure we get accurate measurements.
- Move the machine to X150 Y150 Z2:
- G1 X150 Y150 Z2 F1000
- Perform another probe accuracy macro routine to get the average and range value:
- PROBE_ACCURACY
- average 0.300781 range 0.006250
- Based on the reported range value, we will measure the distance between the nozzle and the bed using feeler gauges. Note that the range value will give you an error band on the feeler gauge measurement.
  - For positive average values such as above of 0.300781mm, the bed is above Z=0, thus to measure the height between the nozzle and the bed, we want to go to a Z position larger than the average. In this case, Z=0.5mm would be a good choice. We can then try to measure the difference between the average probe height of 0.300781mm and the machine bed height of 0.5mm. Ideally we measure it to be 0.5mm - 0.300781mm = 0.199219mm.
    - In this example, 0.2mm fit with little resistance, 0.23mm fit with quite a bit of resistance, and 0.25mm did not fit.
  - For negative average values, the bed is below Z=0, and thus it is easier to measure as we can move the bed to Z=0 and measure the distance. Ideally the reported average value from the probe accuracy routine and the measured value with the feeler gauges are identical.
    - For example, if the average value reported is -0.20mm then the 0.2mm feeler gauge should fit with little resistance, and thicker gauges should be very difficult to insert between the nozzle and the bed or not fit at all.

Bed Leveling

After confirming acceptable probing performance, we can now tram the bed to the X-Y gantry using the probe. To do so, follow the guide here:

Heated Bed | Calibration

Bed Mesh

After tramming the bed, we now will perform a Bed Mesh calibration.

Ensure the bed and nozzle are clean. Be sure to have a print sheet installed.
Preheat the machine to probing temperatures:
- PETG-CF: 220C Nozzle, 80C Bed
- PA-CF and PA-GF: 240C Nozzle, 90C Bed
- TPU: 200C Nozzle, 50C Bed
Let the temperature stabilize for a minute and then perform a bed mesh calibration using the following command or through the web-console:
BED_MESH_CALIBRATE
In the Height Map, we want a flat surface centered around Z=0 with a range as small as possible. A range of 0.3mm and less is normal.
We want to look for suspicious outliers that may reveal damage to the surface of the print sheet or debris on or under the print sheet.

First Layer Test

The last test to ensure good first layer performance is to print a large single layer print. This will quickly show high and low regions on the bed and the performance of probing system.

Below is an STL for a 295mm x 295mm x 0.2mm object suitable for a first layer print test.

Slice the part for the filament you are using and run the print.

Things to look for:

Tiger stripes = too low
Poor line to line adhesion = too high