Looking for some help with an AltMill 4×4 AutoZero issue

[Schurter]

Looking for some help with an AltMill 4×4 AutoZero issue.

I’m commissioning a brand-new Sienci AltMill 4×4 using gSender 1.6.2 and the supplied SLB grblHAL controller.

Everything works correctly:

• Homing

• Jogging

• Spindle

• Z-only AutoZero probing

However, whenever I run an XYZ AutoZero, the machine successfully probes Z, X, and Y, then immediately throws:

ALARM 2 – Soft limit alarm (G-code motion target exceeds machine travel).

I’ve already verified:

• Machine travel settings ($130, $131, $132)

• Probe polarity

• AutoZero settings

• Touch plate placement

• Soft limits and homing are configured correctly

While researching, I found a Sienci forum discussion suggesting the AutoZero routine may require approximately 43 mm of travel during the X/Y probing sequence.

My question is:

Has anyone experienced this on an AltMill? Is there a minimum distance the cutter needs to be from the machine limits before starting an XYZ AutoZero, or is there another workaround I’m missing?

Any advice would be greatly appreciated.

[Chucky_ott]

@Schurter yes, if you’re too close to the machine zero (only tested for x), you’ll get an error while probing, even if there is enough room.

Another user had this issue and I was able to replicate. I forget the minimum distance from x0 you needed to be but 40ish sound about right. It was submitted as a bug but I don’t think it was fixed.

[Schurter]

# AltMill 4x4 – AutoZero Alarm 2 with Soft Limits Enabled (Troubleshooting Summary)

Hi everyone,

I’m commissioning a brand-new AltMill 4x4 and wanted to share my troubleshooting in case anyone has seen this before.

Machine Configuration

• AltMill 4x4

• SLB Controller (grblHAL)

• gSender 1.6.2

• Sienci 1.5 kW spindle/VFD

• Sienci AutoZero touch plate

Machine travel settings:

$130 = 1260

$131 = 1248

$132 = 170

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Problem

When running the combined XY or XYZ AutoZero routines with soft limits enabled ($20=1), the machine completes the probing sequence successfully but immediately throws:

Alarm 2 – Soft limit alarm (G-code motion target exceeds machine travel)

The alarm occurs AFTER the probing sequence is complete, not during probing.

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AutoZero Setup

• Touch plate positioned on the front-left corner of the workpiece.

• Flush against both the front and left edges.

• Correct orientation.

• Probe wiring verified.

• Photos reviewed and confirmed to be correct.

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Testing Performed

With soft limits enabled ($20=1):

Z probe = PASS

X probe = PASS

Y probe = PASS

XY AutoZero = Alarm 2

XYZ AutoZero = Alarm 2

During the XY routine the machine:

1. Successfully probes X.

2. Returns to center.

3. Successfully probes Y.

4. Returns to center.

5. Immediately throws Alarm 2.

The XYZ routine behaves the same way after completing all three probing operations.

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Diagnostic Test

As a troubleshooting step only, I temporarily disabled soft limits:

$20=0

Results:

Z = PASS

X = PASS

Y = PASS

XY = PASS

XYZ = PASS

Every probing routine completed successfully.

This strongly suggests the issue is related to the interaction between the AutoZero routine and soft-limit checking rather than the probe hardware itself.

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Additional Testing

After completing the probing diagnostics, I continued commissioning the machine.

I successfully:

• Homed the machine.

• Verified spindle operation.

• Generated a wasteboard surfacing program using gSender’s built-in surfacing tool.

• Loaded and ran the G-code.

• Set work zero manually.

• Successfully completed a 100 mm × 100 mm surfacing test.

The machine cut perfectly.

This confirms:

• Motion is functioning correctly.

• Homing is functioning correctly.

• Spindle control is functioning correctly.

• G-code execution is functioning correctly.

• Work coordinate system is functioning correctly.

At this point, the ONLY remaining issue is AutoZero triggering Alarm 2 when soft limits are enabled.

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Question

Has anyone else experienced this on an AltMill using the SLB/grblHAL controller?

Is this:

• A known AutoZero/soft-limit issue?

• A configuration issue?

• Something addressed in newer firmware or gSender versions?

Any suggestions would be greatly appreciated.

Thank you!

[Chucky_ott]

@Schurter FYI, the post I was referring to is here: Add soft limit checks on X and Y when probing - #12 by Chucky_ott

I’m guessing it describes your problem. Sienci acknowledged that this is by design but that they might add some logic to not trigger the limit alarm when proving.