Torch Table Intro: Difference between revisions

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=XYZ Table design=
#redirect [[CNC Torch Table]]
 
Please view our development log [http://openfarmtech.org/index.php?title=XYZ here.] The specifications development for a robust and scaleable machine is under development [http://openfarmtech.org/index.php?title=XYZ_Table here]. The prototype specifications for a torch table application will be developed on this page.
 
The basic design follows.
 
Using ball screws and linear bearings appears to be the easiest method. Present research indicates that profile guide rails are twice as cheap for the accuracy required, so this will be redesigned.
 
[[Image:XYZ_Design_rationale2.jpg]]
 
Compare this to [http://www.torchmate.com/industrial/index.htm gear drive and linear rails], which appears to be more complicated in terms of drive components.
 
=Torch Table Implementation=
 
Specifications:
*.01 inch accuracy
*Precision acme rod
*Profile rail guides
Motors: [http://www.xylotex.com/StepperMotor.htm]
*Nema 23 Double Stack/Double Shaft Bipolar Stepper Motor, Flats ground on each end
*269 inch lb holding torque on main axis
*Rated Current - 2.8A/phase
*Shaft width - .25 inch
Controller:
*
 
*Direct coupling to precision acme rod
 
=Bill of Materials for a Simple Prototype=
 
*It appears that the Xylotex drive is applicable to large torch tables. [http://www.kickassmachinesinc.com/ Here is one] that Xylotex told me uses their controllers and motors.
**$425 for motors and controllers
*Ball screw [http://www.mcmaster.com/ 5966K26] at McMaster Carr, $1.26/inch, and $25 for each ball nut - $125 per 6 foot run
**90% mechanical efficiency compared to 30% for acme screw
[[Image:ballscrew.gif]] [[Image:ballnut.gif]]
**$250 for x axis if 2 screws, $125 for y axis (1 screw), $50 for z axis
**End blocks are extra
 
Here is a parts list:
 
 
*Compare [http://www.xylotex.com/425ozin.htm 425 in oz motors] to [269 in oz motors].
*Compare [http://www.xylotex.com/4AxSysKit-425.htm 4 axis kit, $400].
*See [http://www.solsylva.com/cnc/acme.html discussion] on threaded rod vs. acme and precision acme.
*Good discussion on drive options from [http://www.solsylva.com/cnc/beltdrive.html Solsylva]
 
=Instructables References=
Search Instructables.com for CNC projects. There is a load. The people should be tapped for review. Just sign up and send authors an email.
*http://www.instructables.com/id/SDPT6W9F3HY3SLR/
**CNCZone hath lots of DIY implementations - [http://www.cnczone.com/forums/forumdisplay.php?f=48]
*http://www.instructables.com/id/3-Axis-CNC-Router---60x60x5---JunkBot/
**[http://www.solsylva.com/ Solsylva] has plans for 3 axis tables, 2'x5' for the largest
 
=ShopBot=
*[http://www.shopbottools.com/prSalpha.htm ShopBot table]
 
=Rack and Pinion Calculations=
 
An interesting, low cost positioning system for low precision (0.01") machining (such as acetylene torch tables) consists of belt-drive rack and pinion.
 
Calculations:
*Typical motors have 0-1000 RPM and 200 steps
*A drive pinion of 1 inche diameter means 3 inch/200 = 15/1000 of an inch step resolution
*For a 2 inch drive wheel (recommended), this is  3/100 resolution, which is sufficient
**We need only 1/16 resolution, and we have twice that resolution with this system
 
Look for parts to match:
*McMaster Carr part 6486K129 - 20 mm wide, 280 cm long (9+ feet) Power Grip belts - $52.50
**2.2 inch drive wheel - $43, would give 35/1000 step resolution
*McMaster Carr - item 7959K29, 3/4 inch rack-and pinion type belting, $5.69/foot
*Or, part # 7959K26, 1/2 inch belting, high torque applications, $3.59/foot

Latest revision as of 06:43, 25 August 2011

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