Assembly / What's Included

Each MG-4 guard includes a 4 x 4 inch four bolt mounting plate with leveling set screws, the articulating arm assembly custom cut to the length you specify at order (CNC billet aluminum, powder coated OSHA Safety Orange), a curved 1/4 inch polycarbonate (Lexan) shield (RMS-1, 15 x 9 inches), mounting hardware, and installation instructions. The mounting plate is drilled and tapped directly to the machine, at least 2 holes with 4 recommended, so unlike PowerSafe's bolt on mill guards, machine modification is required for this product. Interlocked models (MG-4-SK1 or MG-4-SK2) add a pre installed safety interlock switch, but still require a separately purchased motor control device to interface the switch's 2A output with your machine's 3 phase power.

Configuration Options

• MG-4: standard model, left hand mount and opening
• MG-4-RH: standard model, right hand mount and opening
• MG-4-EM: extrusion L-frame mount for radial drills, left hand mount and opening
• Add SK1 for a 120VAC/24VDC magnetically actuated safety interlock switch
• Add SK2 for a 24VDC RFID style safety interlock switch (requires a stable 24VDC supply)
• A machine measurement form (standard or radial drill press specific) must be completed at order time so ATS can cut the arms to the correct length

Shield Options

• Standard: curved RMS-1 shield, 15 x 9 inches, 1/4 inch thick polycarbonate
• Smaller: RDS-1 shield available on request
• Taller: extended height RMS-1 and RDS-1 shields available
• Flat shield sold separately, for setups where the curved profile isn't the best fit
• Custom shield sizes available with a quick turnaround; contact ATS or PowerSafe for non standard geometries

Materials & Construction

• CNC billet aluminum mounting plate and arm assembly, powder coated OSHA Safety Orange
• 1/4 inch thick polycarbonate (Lexan) shield
• Heavy duty steel adjustable handles, splined so they can be repositioned while tight

Applicable Safety Standards

Standards to be confirmed by PowerSafe. See: ATS Safety product documentation for the MG-4 Universal Mount Guard, section to be confirmed.

Installation Instructions

Guard Does Not Stay in Position / Drifts During Operation

Articulating arm moves unexpectedly; shield repositions under vibration or tool loads

• Never adjust the guard while the spindle is running; always reposition with the machine stopped
• Check all arm joint hardware (knobs, bolts, pivot points) for tightness; re-torque as needed
• Verify adjustable handles have been fully tightened after positioning; handles pull out and rotate 360 degrees, and if not locked down they allow unintended movement
• Confirm the four set screws on the mounting plate are still seated correctly against the machine surface

Guard Won't Cover the Spindle / Range of Motion Is Insufficient

Shield doesn't reach the work area, or the arm feels too short or too long

• Confirm the mounting location was chosen with the guard held up to the machine and enough range of motion to cover the spindle before drilling, per the installation instructions
• If the arm length doesn't match the machine, contact ATS or PowerSafe with updated measurements; MG-4 arms are custom cut per the measurement form submitted at order time
• Verify left hand (MG-4) versus right hand (MG-4-RH) opening matches the operator's working side; the wrong hand option can make positioning awkward even when the arm length is correct

Mounting Plate Installation Issues

Holes don't align; plate won't sit flat; guard is unstable after mounting

• Confirm at least 2 holes were drilled and tapped diagonally, or all 4 as ATS recommends, using shallower holes when drilling all 4
• Use the mounting plate's set screws to level it on an uneven machine surface
• Verify the roll pin is facing up when mounting the guard; this is called out specifically in the installation instructions
• Recheck hole placement against the marked layout from the first installation step before drilling if the guard doesn't seat correctly

Shield Installation Issues

Shield won't seat, or mounting holes don't line up

• Confirm you're using a 3/16 inch Allen wrench to install the shield
• The arm has 2 sets of mounting holes; verify the shield is installed in the correct set for your desired position
• Contact ATS if fitment issues persist; longer arms and custom shield sizes are available

Safety Interlock Switch Does Not Signal Correctly (Interlocked Models)

Machine does not stop when guard opens; motor control does not respond to switch state

• Confirm the safety switch output (rated 2A max) is wired to a compatible motor control or safety relay; the switch alone cannot directly interrupt a 3 phase machine motor
• Verify wiring connections are secure at the switch, motor control, and any terminal strips
• For SK1 (magnetic) models: confirm the actuator magnet on the arm is correctly aligned with the switch body when the guard is closed
• For SK2 (RFID) models: confirm a stable 24VDC supply is present; the RFID switch requires DC power and will not operate on AC
• Test the switch in isolation by manually cycling it and verifying the output state changes at the motor control or relay input
• If the switch is suspected damaged, contact PowerSafe for a replacement; the interlock retrofit kit can replace a switch on an existing guard

Machine Compatibility Issues

Guard doesn't seem like the right fit for the machine

• Confirm this is the correct product: Bridgeport pattern and most import copy vertical mills are better served by the bolt on MG-2 or MG-3 guards, which don't require drilling
• MG-4 is intended for large or non standard milling machines, drill presses without a round column, and select radial arm drill presses
• For radial drill press applications, confirm whether the extrusion mount variant (MG-4-EM) is a better fit than the standard bolt on square plate

Preventive Maintenance

To keep the MG-4 performing reliably:

• Inspect all arm joint hardware for tightness at regular intervals, at minimum monthly in high vibration environments
• Clean polycarbonate shield surfaces with a mild soap and water solution; avoid solvent based cleaners (acetone, MEK, lacquer thinner), which will craze and weaken the Lexan
• Inspect the shield for cracks, chips, or stress marks after any heavy chip impact event; replace immediately if damage is found
• For interlocked models, cycle the guard open and closed at each maintenance interval and verify the motor control responds correctly to the switch state
• Check the mounting plate bolts and set screws for looseness; vibration from the machine can back out fasteners over time

Fault Tracking & Continuous Improvement

• Log any guard adjustment, shield replacement, or interlock fault, including the machine and date
• Look for recurring patterns, such as repeated loosening tied to a specific machine's vibration levels
• Use this history to plan hardware re-torque schedules and shield replacement before damage affects protection