CAD of Mobile Bed Design (In Progress)

For Prototype II, define goals based on study of industry standards. Include desired precision + accuracy + speed.
- Minimum step size for each axis plus variance
- Repeatability of motion (drift) (determined by going to certain locations a large number of times)
- Minimum spacing between traces (determined by minimum allowable size of bit + precision)
- Minimum trace size possible
- Goal: repeatability is as good as step size - ie, all inaccuracy is negligible compared to step size, and zero backlash at all practical milling speeds.
- Define practical milling speed range based on substrate

Key Design Specifications

Step Motor Axis Drive

Rotary-to-Linear Motion Converting Stainless Steel Leadscrew and Wear-compensating Leadscrew Nut

Anti-friction Bronze Sleeve Bearings

Precision Stainless Steel Axis-Supporting Shafts

Versatile Holding Platform with Magnets

Brushed DC Motor Spindle Drive

Precision Stainless Steel Spindle Shaft

Computer to Microcontroller to Stepper Driver Electronics Pathway

Gcode Streamer to Gcode Interpreter Software Pathway

Cost

Cost values in USD. In practice, some items must be purchased in greater quantity than necessary; the following values are equalized to the correct quantities. List excludes tools and shipping.

Cube Frame Metal =

Axes Structure Metal =

Metal Shafts = 124

Leadscrews and Leadscrew Nuts = 240

Bearings = 65

Fasteners = 70

Control and Drive Electronics = 130

Power Supply = 35

Software = Open Source

Total =

X-Axis Frame Design Rationale

Start by assuming that the x-axis frame needs to support a pair of precision shafts and allow mounting of the working platform and stepper motor with leadscrew.

The working platform has to be some sort of flat sheet or plate.

Some sort of rectangular support structure seems a good start, with a total part count of 5.

Here is an visual example using 1 plate and 4 rectangular bars:

This is rigid, but bulky and does not easily allow the gantry to be mounted. We notice that a lot of material is still being used despite the low part count. Keep in mind that part count and material volume and ease-of-manufacturing must all be considered separate, though interrelated factors in effective design.

If we use only 2 rectangular bars (for supporting the precision shafts), then we can save on material volume by using 2 angles as structural supports.

Here is an visual example using 1 plate, 2 rectangular bars, and 2 angles:

This is relatively volume-efficient, with plenty of open space at the side for gantry mounting.

Spindle Design Rationale

Sourcing

Spreadsheet File

LINK HERE

Prototyping Spreadsheet

To edit or download the spreadsheet, click on the following link.

https://docs.google.com/spreadsheet/ccc?key=0AlpsBarfpPkzdFk5aDY3dHM0eEhfZHNkWVppdV9EelE

Build Process

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Structure

400mm x 1.5" x 1.5" x 0.125" Steel Angle (14)

140mm x 1.5" x 1.5" x 0.125 Aluminum Angle (12)

35mm x 1.5" x 1.5" x 0.125 Aluminum Angle (3)

Single Point Template

Double Point Template

Frame Template

Axis Template

Mount Template

Electronics

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Soldering Stepper Driver Pins

Insert the short end of the male headers into the stepper driver board from the bottom, then pressfit the headers into the small breadboard for holding.

Apply flux to all header connections

Apply solder to the tip of the soldering iron

Solder header connections at opposite corners of the stepper driver board for stability, reapplying solder to and cleaning the soldering iron tip as necessary; repeat for the remaining header connections.

Soldering Connectors

Wiring

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Software

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Ubuntu 10.04 LTS 32-Bit

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Getting Git

Open Terminal and type:

sudo apt-get install git-core

Getting Arduino Integrated Development Environment

Go to this webpage:

http://arduino.cc/hu/Main/Software

Download the Linux 32-bit version of Arduino IDE to a directory of your choosing

Compatibilizing Arduino IDE

The following steps are a summary of the information in this webpage:

http://www.pluggy.me.uk/arduino-ubuntu/

Open System>Administration>Synaptic Package Manager, then type your password

In Synaptic Package Manager, search for jre, then mark for installation the item with the following name:

Openjdk-6-jre

Note: marking these items will bring up other packages also to be marked. Click "mark" during these times.

In Synaptic Package Manager, search for gcc-avr, then mark for installation the item with the following name:

gcc-avr

In Synaptic Package Manager, search for avr-libc, then mark for installation the item with the following name:

avr-libc

In Synaptic Package Manager, click "Apply"

Restart your computer

Getting RUBY Programming Language

Open Terminal and type:

sudo apt-get install ruby1.9.1

Restart the computer for the changes to take place

Getting GRBL Files

Open Terminal and type:

git clone https://github.com/damellis/grbl.git grbl

Getting Gctrl

Open Terminal and type:

git clone https://github.com/damellis/gctrl.git gctrl

Getting Processing

Go to this webpage:

http://processing.org/download/

Download the latest version of Processing to a directory of your choosing

Moving RXTX files

Navigate to the Arduino IDE folder>lib.

Copy RXTXcomm.jar

Navigate to the Processing folder>modes>java>libraries>serial>library

Paste RXTXcomm.jar, replacing the existing version

Navigate to the Arduino IDE folder>lib

Copy librxtxSerial.so

Navigate to the Processing folder>modes>java>libraries>serial>library>Linux32

Paste librxtxSerial.so, replacing the existing version

Modifying Gctrl

Open the Gctrl folder

Open gctrl.pde in gedit

Change a part of the code as annotated in the following:

Serial port = null; //change starts

String portname = "/dev/ttyACM0"; // Linux, Arduino Uno

//change ends

boolean streaming = false;

Modifying GRBL Files

Navigate to the GRBL folder

Open "Makefile" in gedit

Edit the PROGRAMMER line as:

PROGRAMMER = -c stk500v1 -P /dev/ttyACM0 -b 115200

Flashing GRBL

Open Terminal and navigate to the GRBL folder (ex. by using the "ls" and "cd" commands)

In Terminal, type:

make clean

In Terminal, type:

make

Connect the Arduino Uno to the computer via USB cable

In Terminal, type:

make flash

Disconnect the Arduino Uno

Running Gctrl

Navigate to the Processing folder

Open and run Processing, setting the sketchbook folder as the folder in which the gctrl folder exists

In Processing, open gctrl using File>Sketchbook>

Connect the Arduino Uno to the computer via USB cable

In Processing, run gctrl using Sketch>Run

Now the Gctrl GUI window should pop up

Note: For certain functions of gctrl, press and hold down the key for the popup windows to populate.

Determining GRBL Configuration Changes Required

Go to the following webpage:

http://dank.bengler.no/-/page/show/5474_configuringgrbl?ref=mst

Modifying GRBL Settings

Navigate to the Arduino IDE folder

Double-click "Arduino" then click "run" in the popup window

Note: you may want to create a quick launcher for the Arduino IDE

Connect the Arduino Uno to the computer via USB cable

In Arduino IDE, open Tools>Serial Monitor

Note: the Serial Monitor window should pop up and you should see the following:

Grbl 0.6b

'$' to dump current settings

In the Serial Monitor, change the left drop-down setting to the following:

Both NL & CR

In the Serial Monitor, type the following in the command line:

$

Note: you should now see the following:

$0 = 157.480 (steps/mm x)

$1 = 157.480 (steps/mm y)

$2 = 157.480 (steps/mm z)

$3 = 10 (microseconds step pulse)

$4 = 500.0 (mm/min default feed rate)

$5 = 600.0 (mm/min default seek rate)

$6 = 0.100 (mm/arc segment)

$7 = 0 (step port invert mask. binary = 0)

$8 = 25.0 (acceleration in mm/sec^2)

$9 = 225.0 (max instant cornering speed change in delta mm/min)

'$x=value' to set parameter or just '$' to dump current settings

In the Serial Monitor, type commands as necessary in the following format, where "X" and "Y" are numbers:

$X = Y

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Design Modifications

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Modularity

Different step motors and drive mechanisms can be mounted onto the axis support angles via mounting holes

Different frames can be used, provided they have precise mounting holes for the axis support angles

Different holding platforms can be used, provided they have mounting holes for the X axis moving angles

Different spindle setups can be used, provided they have mounting holes for the Z axis moving angles

Different stepper driver boards and power supplies can be used, provided they have compatible performance specifications within the electronics system

Scaling

Scaling mainly consists of changing the size of the frame (to affect travel ranges) and the type of step motors (to affect travel rates)

Other discrete components such as fasteners, leadscrews, and shafts need only be scaled if necessary for functionality or certain desired performance specifications

The travel range calculation for the X axis:

(X Travel Range) = (Distance Between 2 Parallel Frame Angles Along Horizontal Plane) - (Length of Platform Along Axis)

The travel range calculation for the Y axis:

(Y Travel Range) = (Distance Between 2 Parallel Frame Angles Along Vertical Plane) - (Length of Z Support Angles Along Axis)

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Usage

Circuit Schematic to Gcode File Toolchain

See following link for list of electronic design suites:

http://en.wikipedia.org/wiki/Comparison_of_EDA_software

PCB-Gcode Optimizer

http://cnc.goodbits.net/wiki/index.php5/Pcb-gcode_optimizer

http://www.millpcbs.com/index.php?option=com_content&view=article&id=10&Itemid=44

Maintenance

Distributive Enterprise

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GVCS Product Ecology

CNC Circuit Mill Product Ecology

Uses

Induction Furnace - Steel

Aluminum Extractor - Aluminum

Metal Roller - Fasteners, Metal Angles, and Flats

Rod and Wire Mill - Wires, Shafts

CNC Multimachine - Bearings, Leadscrews, Leadscrew Nuts

Motors - XYZ Movement

CNC Circuit Mill - Control Circuit Boards

Universal Power Supply - Power

Creates

Milled Circuit Boards

See Product Ecologies for more information.

CNCCMV2