the standard minimill™

Property of Roger Cortesi, MIT Precision Engineering Research Group. DO NOT COPY or TRANSMIT without written permission.

The Standard MiniMill™

Precision Engineering Research GroupMassachusetts Institute of Technology, Mechanical Engineering Department

A small milling machine using ball screws and linear rails

Phone: (617) 253-1953Fax: (617) 258-6427

http://pergatory.mit.edu/

Room 3-47077 Massachusetts Ave.Cambridge, MA 02139

By: Roger Cortesi [email protected] http://pergatory.mit.edu/rcortesi/


The Standard MiniMill™

An Alternate to the original MiniMill™

By Roger CortesiMIT Mechanical Engineering

Precision Engineering Research Group27 FEB 00


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 ScrewsGuided by Air Bearings

orPowered by Linear MotorGuided by Ball Rails


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™.

Why The Standard MiniMill™


The Standard MiniMill™ Features

• The same structural “L” shapes are used by both the Standard and Modified MiniMill™s.

• The same “L” mold can be used for either machine. Only the threaded insert patterns are different.


The Structural “L” for the Standard and Modified MiniMill™s

The Standard MiniMill™ The Modified MiniMill™


More Standard MiniMill™ Features

• All three axis use identical ball screws, ball nuts and ball rails for cost savings.

• Depending on the customer’s 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.


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


Parts to Order From Star Linear™Quantity Description Part

NumberNotes

3 Single Nut 12x5 Rx2/5-3 w/ FlangeFEM-E-S

1532-4-6013

3 Fixed End Bearing ZKILN 1590-1-06003 Fixed End Pillow Block Unit ZKILN 1591-1-0620 May include bearings, need to

check3 Floating End Bearing DIN 625 1590-6-06003 Floating End Pillow Block Unit DIN 625 1590-6-0620 May include bearings, need to

check3 12 x 5 Rx2.5 Rolled Screw, Threaded

Length of 730 mmTBD Need to decide what tolerance

grade (T5, T7, or T9)12 No 15 Trucks TBD Need to decide Super, Steel, or

Al and which accuracy class (Hor N)

6 Size 15 Rails, 750mm Long TBD Need to decide what is theneeded accuracy class (UP,SP, P, H, or N)


A View of the Standard MiniMill™’s X Axis

Linear Position Encoder Not Shown

Motor Mounted HereDetails TBD


Optional Linear Position Encoder

12x5 Ball Screw

Motor Mounted HereDetails TBD

15mm Rails

Fixed Pillow Block

Floating Pillow Block

Ball Nut

A View of the Standard MiniMill™’s Y Axis


The New X and Y CarriagesObviously the X and Y Carriage from the Modified MiniMill™ wouldn’t work so here are the new ones

X Carriage Y Carriage

Y Ball Nut

Z Ball Nut

Z Trucks (4)

Y Trucks (4)

Mounting Point forOptional Linear Encoder

X Trucks (4)

the standard minimill™

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