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DRO

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on January 18, 2009 at 6:10:44 pm
 

Homemade Digital Readout (DRO)

1940's Atlas MF Horizontal Mill Retrofit

Atlas MF Horizontal Mill (temporarly bolted to my drill press as I refurbish the milling head)

 

As a proof of concept, I constructed a Digital Readout (DRO) for my HorizontalMill using optical encoder modules from discarded ink jet printers. To avoid altering the 1940's aesthetic of the Atlas mill, every attempt was made to conceal encoders and scales within the machine castings.

 

 Most inkjet printers (from the 1990's on) use some version of Agilent's optical encoder modules for positioning.

 

  Datasheet Agilent_Optical_Encoders.pdf

 

 

 

 Using a simple parallel port interface circuit, encoders can be read using DRO software produced by S. Lindsay and A.Eckstein .

 

 

 

Optical encoder and linear scale as installed beneath the X axis

 

 

Y axis encoder module (note tensioning spring at rear of encoder stripe)

 

 Z axis encoder module

 

Resolution

The encoder modules used for this project are capable of acheiving 1"/600 resolution (not amazing by any means, but definately useable for most of my projects). As discussed by Eckstein, it is possible to increase encoder resolution through mechanical gearing. For now, I can simply attach a dial indicator if tollerances closer than 0.0016" are required. By mounting linear scales directly to the X, Y, and Z axes, the effect of lead screw back lash can be completely eliminated

 

Materials:

Encoders

-3 discarded inkjet printers

-Scrap aluminum bits for mounting encoders

 

Interface Board

-6 2n3904 transistors (or equivalent)

-6 4.7k resistors

-6 1k resistors

 

Software

Parallel port DRO software see DRO v4.0 or DRO v4.1 (original) DRO v5.4 (updated). Be sure to set your parallel port to ECP mode (in the BIOS, more on that in the software readme)

 

 

Links

Invaluable starting points for this project: The work of S. Lindsay and A.Eckstein . Both of their websites have excellent information pertaining to inexpensive DRO systems.

  

Elegant PIC interface for reading digital calipers via RS232 http://www.compendiumarcana.com/caliper/

 

Open source DRO http://www.shumatech.com/products/dro-350/index.htm

 

Contact Info

Email

 McKGyver Home

 

 

 

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