The Modified MiniMill

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The Modified MiniMill

• A small milling machine with linear motors and
  air bearing.

By Roger Cortesi rcortesi_at_mit.edu
http//pergatory.mit.edu/rcortesi/
Precision Engineering Research Group Massachusetts
Institute of Technology, Mechanical Engineering
Department
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Using the Axtrusion as a building block, create
a desktop Milling Machine
I will call it MiniMill
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MiniMill Functional Requirements

• A part accuracy of 0.001 (25.4 mm)
• A work volume of 300 x 300 x 300 mm
• A manufacturing cost of 20,000

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MiniMill Prototype Budget
Materials
Assume that the in-production manufacturing cost
between 30 and 50 of the prototype cost.
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MiniMill Production Budget
Estimated Material Costs
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Some Competing Machines
The Compact DMC (left), and the XV Tabletop
(middle) Machining Centers by Defiance. The
Benchman Series (right) by Light Machines.
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Space Efficiency

• Three times the Work Vol / Machine Vol of other
  small machines
• Twice the Work Vol / Floor Space of DMC Compact
  Center
• Four times the Work Vol / Floor Space of the
  Other Machines

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Some Other Initial Concepts
Sawyer Motor for the X Y Directions.
Traditional or Combined Unit for the Z axis and
Spindle
Two Axtrusions on the base (X Y) and an
Axtrusion for the Z axis.
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Two Ls Used to Make Machine
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MiniMill, The Final Concept
One Axtrusion on the Base (X) One on the Gantry
(Y) and one for the Z
This allows for two identical Ls to make the
structure.
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Final Concept Features

• Only Four (4) Major Parts
• Hot Swappable Spindle Interface
• Auto-Tool Changer Easily Accommodated
• More Crash Resilient

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The Model Results(via a MatLab script)
Error at the Tool Tip (microns) vs. Tool Position