CNC Plasma Cutter Tool Training

CNC Plasma Cutter Tool Training
Gui Cavalcanti
4/29/2013
Training Goals
1. Introduction to CNC gantries and safety
2. Introduction to plasma cutters and safety
3. Overview of routine plasma cutter maintenance
4. Discussion of sheet metal safety
5. Overview of CNC plasma cutting
6. Mechanical design for plasma cutting
7. Example cutting of mild steel
8. Artisan’s Asylum reservation infrastructure
Introduction to the CNC Gantry
Gantry Control and Height Control Unit
CNC Gantry – X- and Y- Axis
Torch and Z-Axis
Water Accumulator and Drain
Important Notes
• The gantry system mostly does exactly what you
tell it to – execute simple G-code
– “Open Loop” stepper instead of “Closed Loop” servo
– Doesn’t stop at table limits
– Doesn’t stop for fingers/obstructions
– Doesn’t stop for the grounding cord
– Doesn’t stop for torch crashes
• Sometimes, it crashes and does something you
didn’t tell it to do
CNC Gantry Safety
• Clear torch work area of all
obstacles
• Make absolutely sure rails
are clear of obstacles and
cords
• Be aware of the position of
the gantry at all times –
assume it can start moving
at any time
• Keep your hands off and
body away from the machine
at all times while it’s in
motion
Pinch Points
Intro to Plasma Cutters
Intro to Plasma Cutters
Basic Functionality:
• Use electricity to heat a point of metal to melting
• Use compressed air to blow through that superheated point
• Drag the superheated point in a direction to cut a line
Plasma Cutter Safety
• Light
– Arc flash is concentrated enough to cause headaches, dizziness, and
blindness
– For an 85-amp torch, Shade 8 eye protection or better is required
• Electricity
– Plasma cutter cuts with 85 amps at 130 volts DC, or 11,000 watts; 1
watt/second for .5 seconds is enough to stop a heart. GROUNDING
STRAP IS REQUIRED, AND DON’T TOUCH IT WHILE IT’S CUTTING!
– Special bonus: the water table makes everything wet and conductive,
including your skin
• Sparks
– Sparks thrown off by the cutter can burn you, set things on fire, and
destroy nearby equipment
• Heat
– Parts can be very hot when they’re done cutting
Plasma Cutter Safety
• Required Protective Equipment:
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Closed toed shoes
Long pants and long-sleeve shirts (or cape sleeves)
Non-polyester clothing; cotton preferred
Safety glasses and/or welding helmets
Available water for rehydration due to heat, if plasma cutting for
awhile
• Work Area:
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Remove all flammable material (oily rags, solvents)
Clean area of clutter, especially around your feet
Make sure bystanders can’t see arc flash
Identify nearest fire extinguisher
Plasma Cutter Safety
• Operation:
– NEVER LEAVE THE CUTTER UNATTENDED
– DON’T TAKE YOUR EYES OFF THE TORCH
– Don’t touch the metal or the gantry while cutting
– Stay close to the computer to pause or stop the
gantry and cutter in an emergency
– Make sure bystanders are protected and will not
interfere
Plasma Cutter Safety
• Special situations:
– The cutting area needs to be fully screened off from all other
members (including other welding area and shop aisle)
– Auto-darkening helmets are recommended so that you can see if
the torch has crashed during a cut
– Y-axis cuts along supporting rails produce a shower of sparks –
don’t stand to the immediate side of the gantry!
– Make sure water isn’t getting all over the controls or power unit
as you’re cutting
– The MultiCam router and plasma cutter can’t operate at the
same time due to power draw and operator safety concerns
Plasma Cutter Specifications
Example Cut Settings – 85A
Shielded, Mild Steel
Plasma Cutter Maintenance
Maintenance Overview
• Identifying and maintaining consumables
• Debugging error codes on the plasma unit
• Troubleshooting poor cuts
Plasma Cutter Consumables
Consumable Inspection
Consumable Inspection
Consumable Replacement
• ALWAYS TURN POWER UNIT OFF BEFORE SERVICING TORCH
• Artisan’s Asylum provides consumables, but be gentle on their use or
cut costs will go up
• Average nozzle and electrode life = 3 cutting hours
• Replace the nozzle and electrode together for best results
• Inspect nozzles after any crash; do not reuse old nozzles
• Clean shield tip if starting to accumulate crud; replacement is
relatively rare
• Swirl ring replacement rarest of all
• Check O-ring for damage
Plasma Unit Error Codes
Troubleshooting Cut Quality
Special Note: “Parallel” kerf on two sides of a cut-out piece usually means a blown-out nozzle
Sheet Metal Safety
Sheet Metal Safety
• Weight of 4’x8’ mild steel sheets:
– 22 Ga: 31 lb
– 16 Ga: 78 lb
– .125”: 162 lb
– .250”: 324 lb
• Inspect cutting slats for irregularities before putting a sheet down
• Gloves and sheet metal dollies are recommended at all times
• Getting 1 to 3 other people to help lift is essential to position and
remove large sheets
• Gantry crane lifting solution possible, but you will need special
training
Sheet Metal Source
•
Steel:
– Turner Steel Company, Inc.
– 800-521-8881
– www.turnersteelcoinc.com
– $150 minimum for deliveries
– Are happy to cut sheets down into manageable chunks – please take advantage!
•
Other Metals:
– Admiral Metals
– 781-933-8300
– www.admiralmetals.com
– Delivery minimum unknown
•
Special Note: You must be present to accept deliveries, or you must notify
[email protected] if you can’t be present. A fee may be charged
for accepting material deliveries
CNC Plasma Cutting
Tuneable Settings
• Current (Power Unit)
• Cut Feed/Speed (Torchmate Cutting Software)
• Nozzle Type (Consumables)
• Cut Height (Height Control Unit)
• Voltage (Height Control Unit)
• Material Type (You)
Preparing To Cut
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Reserve time for cutting at http://www.artisansasylum.com/reservations
Screen off plasma cutting area with welding curtains
Check slats for high spots and grind down where appropriate
Place sheet on cutting surface
Fill water table to within ¼” of bottom of sheet
Attach grounding clamp to material, or to the closest slat to the power unit
that’s under the material
Put on gloves and carefully check torch consumables for damage, replace if
necessary
Turn on plasma power unit, gantry controller, height controller, and
control computer
Set appropriate amperage on the plasma cutter power unit
Set appropriate pierce delay, pierce height, cut height, and touchdown
torque on height controller
Open Torchmate 4 software and connect to the gantry controller
Plasma Cutting
• Add lead-ins, lead-outs, arrays of parts, and offset cutting paths in
Torchmate CAD software (optional)
• Import a DXF into the Torchmate 4 cutting software, setting cutting
speed and scale in the import dialog box
• Jog the torch head to the desired zero position, and set program
coordinates to zero
• Ensure that all bystanders are aware of your cutting, and are
behind safety screens
• Run the cut, keeping the cursor over the “Hold” command in case
of a crash
• Inspect the first piece for dimensional accuracy and straight edges
• Repeat as needed
Teardown and Cleanup
• Log total cut time rounded to the 5 minute mark on the cutter log
sheet
• Wipe down and dry all rails, gear racks and machine components;
mop floor if necessary
• Jog the head of the machine to the corner closest to the operator
station
• Turn off the gantry controller, height controller, and plasma power
unit
• Disconnect plasma cutter ground clamp and place it next to the
power unit
• Remove the cut sheet from the table and store it or recycle it
• Drain the water into the water accumulator until there’s 1-1.5” of
slat above the water level
• Grind the dross off the slats in the area in which you were cutting
In Case of Crash
• Stop the program with “Hold”
• Turn Cut light off on height controller
• Turn off power unit
• Reset torch head
• Inspect plasma consumables
File Formats
• Torchmate cutting software only reads DXF or Gcode files
• Solidworks can generate DXFs from sketch view
or drawing view
• ALL LINES WILL BE CUT – INCLUDING
ANNOTATIONS, DASHED CENTERLINES AND
CONSTRUCTION LINES
• Inkscape and Gimp have DXF plugins
• Torchmate CAD program can generate DXFs
Mechanical Design for Plasma Cutting
Mechanical Design Considerations
• Plasma cuts start with a pierce that can ruin
straight lines or features
• Torchmate CAD can “lead-in” and “lead-out” to
minimize pierce effects
• Plasma cuts have a beam width that depends on
amperage and material thickness
• That width can be offset by you in the design of
your piece, or by Torchmate’s CAD program
• Repeatability is within .015” across a foot;
accuracy seems to be .02-.03” across a foot
Mechanical Design Considerations
• Very thin features (or material near edges) will
bow, sometimes interfering with the torch
• Thin sheet will warp if heavily cut into,
sometimes interfering with the torch
• Very large features on thin sheets will be
difficult to cut successfully due to sheet warpage
• Dross will build up on the back of your parts,
and will need to be cleaned in some way
Kerf-Width: Mild Steel
Kerf-Width: Stainless Steel
Kerf-Width: Aluminum
Asylum Electronic Infrastructure
Asylum Infrastructure
• All cuts must be reserved and logged on the log sheet; cut time is
$45/hr, rounded to the nearest 5 minutes
• The MultiCam router and CNC plasma cutter CANNOT run at the
same time due to power requirements and operator safety
• Accounts and reservations can be made at:
http://artisansasylum.com/reservations/
• Reservation rules can be found here:
http://wiki.artisansasylum.com/index.php/Making_Reservations
• All operators will be subscribed to [email protected] to report any consumable shortages
or receive new training information
• If the machine breaks down, please email both plasmacutteroperators and [email protected]