The Standard MiniMill

1
The Standard MiniMill

• A small milling machine using ball screws and
  linear rails

By Roger Cortesi rcortesi_at_mit.edu
http//pergatory.mit.edu/rcortesi/
Precision Engineering Research Group Massachusetts
Institute of Technology, Mechanical Engineering
Department
2
The Standard MiniMill An Alternate to the
original MiniMill

• By Roger Cortesi
• MIT Mechanical Engineering
• Precision Engineering Research Group
• 27 FEB 00

3
The Modified MiniMill Is the original machine
design. It uses linear motors for motive power
and air bearings for the linear guides. The
Standard MiniMill This machine is the same as
the modified machine , but the motive power is
provided by ball screws. Ball Rails are the
linear guides. The transition from the
traditional technology in The Standard MiniMill
to the technology in The Modified MiniMill can
be done incrementally!!! I.E. it is very easy to
have a machine that is Powered by Ball
Screws Guided by Air Bearings or Powered by
Linear Motor Guided by Ball Rails
4
Why The Standard MiniMill
Using the traditional motive components (ball
screws and ball rails) is less of a market risk
than the linear motors and air bearing version of
the MiniMill.
5
The Standard MiniMill Features

• The same structural L shapes are used by both
  the Standard and Modified MiniMills.
• The same L mold can be used for either machine.
  Only the threaded insert patterns are different.

6
The Structural L for the Standard and Modified
MiniMills
The Standard MiniMill
The Modified MiniMill
7
More Standard MiniMill Features

• All three axis use identical ball screws, ball
  nuts and ball rails for cost savings.
• Depending on the customers accuracy and price
  constraints, position sensing on the standard
  MiniMill can be done by a rotary encoder on the
  motor or a linear position encoder on the
  carriages.

8
Design Issues Still In Progress

• Axis motor selection
• Currently Maxon Motor is the most likely.
• Stiffness estimates for the Standard MiniMill
• The Standard MiniMill should be much stiffer
  than the Modified MiniMill
• Determine required accuracy grades on ball screw
  and linear rails and trucks
• Type and mounting locations for limit switches
• Type and mounting locations and type for bumpers
• Mounting hardware and locations for cable carriers

9
Parts to Order From Star Linear
10
A View of the Standard MiniMills X Axis
Motor Mounted Here Details TBD
Linear Position Encoder Not Shown
11
A View of the Standard MiniMills Y Axis
12
The New X and Y Carriages
Obviously the X and Y Carriage from the Modified
MiniMill wouldnt work so here are the new ones
X Carriage
Y Carriage