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Case Study: Mirage develops bespoke CNC gantry milling machine for shipbuilding project


Above left: The Gantry Milling Machine under development in Derby (UK). Above right: Ready for testing at Mirage Subsea in Houston (USA).

In 2015 we were asked to provide a solution for an on-site machining project for a client operating in the shipbuilding sector. Our engineers met the challenge by designing a custom built solution which was tested thoroughly before delivering it to the customer. Here’s an overview of the solution our team produced and how it was tested;

The Challenge

The customer, a U.S. based shipbuilder, required a solution to provide some very specific machining requirements:

  • Drilling, threading and counter-boring a selection of alloy steel plate and posts
  • Area being machined 5’ X 10’
  • A planar flatness tolerance of +/- 0.005 inches needed over the entire working area
  • Material specification of items to be machined: SAE-AMS-QQ-S-763
  • Machine to be remotely operated via a computer numerical control (CNC) unit
  • Milling, drilling and tapping, utilizing one spindle motor (speed variable from 0 to 2,000 RPM)
  • Machine capable of being lifted for repositioning without the need for disassembly
  • To be powered by a 480-volt electric supply
  • Working feed rates (per minute): X axis 0 to 30 inches, Y axis 0 to 24 inches, Z axis 0 to 24 inches
  • Installation with replaceable weld-to-deck anchor pads
  • CNC cabinets and motors rated NEMA 4, NEMA 4X or better

The Solution

Mirage has extensive experience in the design and manufacture of portable CNC operated gantry milling equipment.  The design and development team adapted a current three-axis gantry milling machine to meet the client’s needs. The modified design featured enhancements including an automated tool magazine to accommodate no less than seven preloaded machining tools. After investigating various CNC machines available, the Mirage team chose a Siemens Shopmill CNC unit to control the machine. 


Above: The tool magazine with preloaded tools for drilling, counter boring and threading tools.

Here’s a step-by-step description of the machine’s setup and testing process:

  1. Machine assembled and 18 mounting plates attached
  2. Machine lifted and lowered onto the test area
  3. Mounting plates tack-welded onto the work area
  4. Machine levelled and set by adjusting the feet assemblies and laser unit
  5. CNC program must be written to run the machine. All tool lengths must be set before running the machine.
  6. Drilling of holes 7/8” diameter x 3.875” deep
  7. Counter-boring of holes 1.063” x 1.5” deep
  8. Counter-boring of holes 2.25 diameter x ½” deep
  9. Thread mill 2.250” deep from counter drill depth 1” x 8 UNC


Left: Drilling an example stainless steel post. Centre: Counter boring. Right: Finished post example with thread inserted

This custom-built solution was created by the Mirage team and purchased by the customer. The machine was designed as modular construction, but is also robust enough to withstand lifting without the need for disassembly. Each post was drilled, counter-bored and thread milled in approximately 60 minutes. Before using the machine, the customer benefitted from functional demonstrations and hands-on training from Mirage staff. The trials carried out on Mirage premises ensured the machine’s success on-site.

Business Results

  • A custom built solution created by Mirage team and purchased by the customer.
  • The trials carried out on Mirage premises ensured success when on-site.
  • Typical example post drilling, counter boring and thread milling time approximately 20 minutes.
  • Machine designed as modular construction but also capable robust enough to withstand lifting without the need for disassembly.
  • Customer benefitted from functional demonstrations and hands-on training from Mirage staff.

The resulting machine’s specification

The Mirage gantry milling CNC machine is now available for other customers to purchase. Its modular construction makes it suitable for machining areas of up to 3 meters in length and 2 meters wide, with suitable on-site applications including shipbuilding, heat exchangers, nuclear, pump and motor pads, steel mill stands, turbine split lines and more.


 Get in touch to find out more about our range of Gantry milling machines.

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