VMCsi - ATC Alarms and Overview

How It Works: Siemens Automatic Tool Changer (ATC)

VMCsi - Reference ATC Magazine

VMCsi- Clearing ATC Fault Guide

VMCsi - ATC Arm Manual Movement Guide.

VMCsi - Set Orientation Angle & Tool Change Height

VMCsi - Replace Carousel Disc

VMCsi - BT40 Option - ATC Arm Replacement

VMCsi - ATC Pot Replacement

31577_RotaryJoint

Rotary Joint Wiki

In Expert Deployment v01.01.17 (PLC version 05.04.19), additional alarms were introduced to monitor the tool change process. While the alarms do not follow a strict numerical sequence, they trigger in the following order (from bottom to top in the image):

700940 – Tool Change Active Banner

• This banner is displayed to the user during the tool change process.
• While active, RESET and CYCLE STOP are blocked.

700938 – M81: Pot Down

700934 – M82: Arm Moves from Home to Spindle

700948 – M85: Tool Unclamp

700935 – M83: Arm Swaps Tools

700949 – M86: Tool Clamp

700936 – M84: Arm Moves from Spindle to Home

700937 – M80: Pot Up Active

All alarms are automatically cleared at the end of a successful tool change operation. If the ATC faults during the tool change, the last displayed alarm indicates where the fault occurred. This can help troubleshoot the cause of the fault.

In Update v01.01.23 (PLC version 05.04.36), alarm context help was implemented to provide troubleshooting guidance for some alarms.

Alarm 700938 – M81 Pot Down Failure

The alarm will be cleared when pocket is down, RESET or ESTOP is pressed, or pocket does not go down for more than 2.5 seconds after it is commanded to move. Check pocket down output Q41.4, check the air pressure, and pocket down sensor input I34.7.

Alarm 700948 – Tool Unclamp Input Issue

If the alarm is not cleared, I33.7 (tool unclamp) input to the control may not be set to high. Check whether I33.7 is high when tool is released and low when tool is clamped. If the input is not behaving correctly, check the tool unclamp switch mounting on Z head assembly.

Alarm 700949 – Tool Clamp Input Issue

If the alarm is not cleared, I33.6 (tool clamp) input to the control may not be set to high. Check whether I33.6 is high when tool is clamped and low when the tool is unclamped. If the input is not behaving correctly check tool clamp switch mounting on Z head assembly.

Alarm 700937 – M80 Pot Up Failure

The alarm will be cleared when pocket goes up, or pocket does not go up 1.5 seconds after M80 is issued. Check pocket up output Q41.5, pocket up input I34.6, and air pressure.

If you navigate to [Diagnostics] → [Trak Diagnostics]. At the top, you’ll see the following inputs:

• toolAtClamp-I33.6
• toolAtRelease-I33.7

These inputs correspond to the two sensors monitoring the tool clamp and release states.

When the green unclamp button is pressed (or when the ATC performs a tool change), the pin drops down and engages the bottom sensor. At this point:

I33.6 (Clamp) should transition from True to False.

I33.7 (Release) should transition from False to True.

If the VMCsi encounters tool change issues regarding Error 700949 – M86: Tool Clamp or Error 700948 – M85: Tool Unclamp look into these sensors.

If the clamp/unclamp cylinder lacks sufficient hydraulic oil (SAE 10W / ISO 32), it can cause incomplete operation.

The pneumatic system powers both the clamp/unclamp control as well as ATC pot up and down.

34320-1_PNEUMATIC SYSTEM-VMCSI 7/10

34320-2_PNEUMATIC SYSTEM-VMCSI 12/14

The spindle cage is a critical part of the unclamp mechanism, ensuring tools are properly seated and released from the spindle. The key measurement to check here is the system’s bump-out — the amount the drawtube physically pushes against the tool’s pull stud to break any stiction or taper-lock. A typical bump-out should measure 0.015–0.020 inches (0.50–0.80 mm).

• At the top of the spindle cage is a threaded piston rod connected to the air cylinder (TRAK P/N: 31889).
• The reference nut (Item 004) is threaded onto the piston rod and adjusted to set the home position of the cage assembly.
• When the cage is pushed up against this nut, there should be a 5 mm “unclamp gap” between the bottom of the cage and the top of the spindle unclamp plate.
• Use a 5 mm Allen wrench, drill bit, or gage pin to set this distance.
• After setting the reference gap, rotate the cage slightly to fine-tune the bump-out.
• Hold a tool in the spindle and press the green button — you should see the tool push down slightly, even while resisting it. This confirms bump-out is occurring.
• If the bump-out is insufficient or too much, adjust accordingly before locking the cage.

Below is the 31889 assembly drawing and cross-section view of the top portion of the cage assembly. The cross section is showing the closeup details of the self-aligning connection of the cage assembly’s top plate, to the threaded piston rod of the unclamp cylinder.

• The cage’s top plate has oversized holes (highlighted in yellow in the cross-section) for the 4 locking screws.
• These holes allow the cage to self-align with the spindle unclamp plate when it contacts it.
• After installing, lightly push/pull the cage side-to-side — it should move slightly and return to center.

• Once the bump-out is dialed in, apply Loctite 243 (blue) to the 4 locking screws (Item 007).
• Screws can have light oil residue but must not be dripping — excess oil will prevent the Loctite from curing properly.
• Torque each M5-0.8 x 30 screw to 7.0 Nm (5.2 ft-lb) to lock the cage onto the piston rod.
• The cage should no longer rotate on the threads once secured.

• If the 2 or 4 screws at the top of the spindle cage come loose (especially on older machines), it can cause:
• The tool to stay stuck in the spindle, delaying release.
• The ATC arm to forcefully pull on the tool, creating a loud, aggressive sound.
• Always check these screws for tightness and Loctite during any spindle cage or tool change issues.

Reference Folder: 31577_RotaryJoint

The Rotary Joint 903-140-188-IC (TRAK P/N: 31577), also referenced as Kit 34204, requires tight tolerances to operate safely at high spindle speeds. The critical region is the "Customer Interface" section of the drawing 903-140-188-IC, which defines acceptable concentricity and perpendicularity for the rotary joint mounting surface.

Before installing or replacing the rotary joint, inspect the rear spindle interface for any wear or distortion. Damage from a failed union may push it out of spec.

If any rework is required to the spindle shaft or its rear interface, please provide the spindle serial number to TRAK Technical Support. We will coordinate with Royal Products (spindle OEM) for model-specific repair procedures.

Tighten the rotary joint bolt (24 mm hex) to 35 Nm, equivalent to 25.8 ft-lbs.

18 mm Pin Gauge Fit Check

• Insert an 18mm pin gauge into the spindle’s rear locating bore.
• Diameter Spec: Ø17.995 mm +0.005 mm
• It should seat snugly to confirm the bore diameter is correct and undamaged.

Perpendicularity – Spindle Mounting Face

• Mount a dial indicator to the machine frame.
• Sweep the rear spindle face where the rotary joint will bolt on.
• Max Perpendicularity TIR: 0.005 mm (0.0002")
• This ensures the face is square to the spindle axis.

Concentricity of Locating Bore

• With the pin removed, sweep the inner wall of bore.
• Max Concentricity TIR: 0.007 mm (0.00028")
• This confirms the bore is concentric to the spindle’s rotational axis.

The ATC Service Mode is used to bring the ARM back to its home position when a tool change fails. There are two relevant service mode levels for ARM motion: Service Mode Level 1 and Service Mode Level 2.

To enter ATC Service Mode:

New PLC: Hold [Spindle Stop] and press [Feed Stop] three times.

Old PLC: Hold [Spindle Stop] and press [Feed Start] three times.

In Service Mode Level 1, the ARM respects the normal tool change sequence. When the ARM is positioned below the spindle, you must press the Tool Unclamp (green) button to release the tool before continuing with the tool change process. This ensures the ARM moves according to the expected sequence and prevents damage.

In Service Mode Level 2, the ARM ignores all normal tool change sequences and safety guards. It will move even if the spindle is positioned too low, creating a risk of collision. The Tool Unclamp button does not prevent this; the ARM movement is independent of whether the spindle is clamped or unclamped.

Use extreme caution in Spindle Service Mode Level 2. The ARM will damage anything it collides with.

To enter Service Mode Level 2, repeat the same process used to enter Service Mode Level 1. The light on the MCP will blink faster, indicating the higher service mode level.

For more information about Spindle Service mod and clearing ATC faults, refer to VMCsi- Clearing ATC Fault Guide

The ATC Motor has a brake lever that must be in the down position while running. If the lever is not fully engaged, the arm can drift slightly after each motion. Depending on the motor version, the brake lever may not lift as high as shown in the picture to disable, but fully pressing the lever down always indicates the brake is engaged.

For more information on manually turning the arm via the motor, refer to the VMCsi ATC Arm Manual Movement Guide.

This video shows the arm movement with brake disengaged.

The home sensor on the VMCsi tool magazine detects the metal plate on the magazine to confirm when it moves from the last tool position (e.g., Pot 24, 30, or 40) back to Pot 1.

When the sensor detects the plate (input high), the PLC resets the magazine count to 1.

If the sensor fails to detect the plate, the PLC incorrectly increments the count beyond the intended tool limit (e.g., 41 for a 40-tool ATC), causing an out-of-bounds error.

For more information regarding the home sensor go to Step 8 of VMCsi - Replace Carousel Disc