Torch Table Intro
This is the open source development page for an industrial duty acetylene or plasma torch table. The table is readily adaptable to industrial duty routing. Accuracy is not sufficient for circuit fabrication. Cost of the table is about $1500 for materials, and we aim to produce these tables for an additional $500-1000 in labor costs for a total of $2000-2500. Present motivation behind this is rapid fabrication of The Liberator CEB Press.
Contributors
From Appropedia:
- Arnar Mar Sigurðsson - hardware design, electronics
- Smári McCarthy - controller software, GTP language
- Mel Chua - firmware
- Marcin Jakubowski - hardware design, open enterprise model, fabrication of turnkey XYZ Tables
Others:
- CAD_CAM_EDM_DRO Yahoo group
- DIY CNC Yahoo group
- Xylotex Yahoo group
Torch Table Design
Our development log is here.
Here is a design that is based on review from the CAD_CAM and DIY CNC Yahoo groups as well as feedback from other sources. The drive is obtained with stepper motors and rack-and-pinion style direct drive with a 1" pinion gear. Using 425 in oz stepper motors, this allows for direct coupling and ~50 pounds of force delivered to move the gantry. Linear bearings and ball screws were replaced with rack-and-pinion drive due to cost considerations. Using direct rack and pinion drive, good accuracy is possible: theoretical 2/1000 of an inch for a 1 inch pinion gear with 1/8 stepping. The limiting factors will be straightness of the guide rail (1 1/4" cold rolled steel rod) and resolution of the pinion gear.
Notable design goals:
- 1/32" accuracy is sought for general acetylene torch cutting (or plasma cutter) applications
- Ball bearings ride directly on guide rail on the drive side
- Bearings ride directly on structural metal on the non-driven side
- Direct coupling of stepper motor to metal rack via a single pinion gear; no gearing involved
- Stepper motor speed: 10 RPM for ~30 inch per minute (IPM) motion with ~1 inch diameter pulley
- Fast rapid motion should be possible, 100 RPM for 300 IPM
- Traction of rack-and-pinion drive is obtained via the weight of the gantry
- Gantry weight: ~40 lb
- Frame is 6" wide U-channel, 5/16" thick
- 4'x8'x1' maximum working object dimensions
Design Details
The initial concepts above have been refined to the following detail for the main precision rail. The red part is a rectangular tube 4"x4"x1/8".
Design rationale:
- Traction for the rack and pinion is obtained by gravity through the weight of the gantry and drive system
- Long-axis alignment is secured by the main guide rail, with 4 guiding ball bearings in the long direction (x)
- The shaft for the pinion gear is supported on both ends
- Direct coupling of motor to gear is utilized
- 10 rpm of stepper motor yields 30 inches per minute travel - the max desired speed for cutting with an acetylene torch
- Rapid travel of torch ~300-600 inches per minute
- Pinion gear radius = 1 inch; circumference ~3 inches
- Driving torque is 425 in oz yields about 50 pounds of force for a gear radius = 1/2 inch
- Gantry weight ~40 lbs, so approximately 1 g acceleration is possible
- Pitch of rack and pinion is 20 teeth per inch
- 200 step stepper motor is driven with 1/8th steps for theoretical 2 thousandths of an inch resolution in the x direction
- Straightness of guide rail will be the limiting factor
Frame
Initial 3D views:
3D Views
Frame
X Rail
Gantry
The Gantry assembly bill of materials falls out of this:
- X Rails
Z Axis
2D Views
X Rail Detail, Front View
Pinion gear bearing: File:Pinion gear bearing.jpg
Stepper Motor to Pinion Gear Coupling via Flexible Shaft Coupler
X Rail Detail, Top View
The assembly on the bottom left is the guide rail system detailed in the above 2 pictures. The gantry that carries the torch head consists mainly of the same type of guide rail as found for the long exis (x axis).
Gantry Front View
Gantry Top View
Y Axis Drive Detail
The y rail is the blue part of the above 2 diagrams. The detail of the y-direction drive is shown below:
Y Rail End View
Z Axis Detail
Initial Designs
see Torch Table Initial Designs
Design Reviews
Dave from Xylotex user group Gene Haskett
Bill of Materials
Details:
- Rack from Standard Steel Specialties. Quick response, great price on the rack.
- Pinion from McMaster.com, item 5172T12
- Pinion holder - square tube 2" x 2" gauge 12 .109" x 2ft - weight: 2.802 lb/ft * 2ft = 5.604 lbs
- rectangular tube 4" x 2" x gauge 11 .120" x 2' - weight: 4.75 lb/ft * 2ft = 9.5 lbs
- Xylotex motors and controller - [1]
- Bearings from vxb.com - [2]
- Small bolt prices at boltdepot.com - [3]
Sourcing Research
- http://cgi.ebay.com/---CNC-Track-Roller--V-Groove-Bearing_W0QQitemZ270349417490QQcmdZViewItem
- http://cgi.ebay.com/MCGILL-VCF3-1%2f2-TRAKROL-BEARING-W%2fV-GROOVE-ON-OD-NEW_W0QQitemZ250310140048QQcmdZViewItem
- http://www.vxb.com/page/bearings/PROD/V-Groove-Bearings/Kit8408
- http://www.google.com/products?hl=en&as_q=v+groove&num=10&scoring=r&as_epq=&as_oq=cam+follower+bearing+wheel&as_eq=&price1=&price2=&as_occt=any&show=dd&safe=off
Fixed bushing for #2 V wheel V-groove wheel #2 Item Number: 302010 Wheel bushings: Add one eccentric bushing per wheel Edit this product $15.02
- whole number
$60.08 V-track for #2 V wheel V-track for #2 V-groove wheel Item Number: 302040 G dimension from left or Right?: Left Over all length of each piece - Enter L dimension in inches. ie. 23.62. Tolerance is +/- .05 inch.: Answer: 18 Enter number of pieces ( order each length seperately ): Answer: 8 Edit this product $0.96
- whole number
$7.68 Remove Update Subtotal: $67.76
License
This design is placed explicitly in the public domain and under a Copyleft License.