In the fabrication world, CNC (computer numerical control) machines have been around for more than 50 years. Over that time, the term “CNC” has been adopted as a shorthand reference to milling or routing, where a spinning end mill removes material to engrave, cut shapes out of flat stock, or carve intricate 3D designs from thick materials.
One of the many reasons CNC mills are so important to Fab Lab is that they provide an easy way to precisely produce complex physical parts for almost every project type imaginable. The CNC moniker means that the instructions that control the machine and toolpath are preprogrammed into code. It ensures that the 100th part produced is identical to the first.
Like 3D printers, which use CNC to control movement of an extruder head, the majority of CNC mills are 3-axis machines that move the toolhead through a piece of stock material. Some function by moving just the spindle, others move the bed, and some move both the spindle and the bed, depending on the axis.
A CNC mill allows you to quickly and accurately work with harder materials that are not normally possible with other technologies. These can vary from hard and soft woods, laminates like plywood, plastics of any kind, and hard and soft metals. The only limitation to what you can cut is the scale and rigidity of the machine and the end mill being used.
The hardness of the material being cut and the size of the end mill makes correct setting of these instructions crucial. Too fast a setting can result in broken bits. Too slow and you risk burning your material.
Due to the wide variety of possible geometries and applications members are required to provide their own end mills and cutting tools.
ShopBot PRS Standard
Cutting Area: 48" x 96"
Spindle Power: 2.2 kW
Maximum RPM: 24,000
Collet Size: 1/8" to 1/4"
Maximum Z Travel: 7"
Please carefully read all the instructions before attempting to operate the CNC routers.
ALWAYS keep the area around the machine clear of obstacles.
ALWAYS check that tools are sharp, free of cracks and set correctly.
ALWAYS check that the correct tool data is entered into the CNC program.
ALWAYS check that the seating surfaces are clean before installing tools.
ALWAYS make sure that all work and fixtures are clamped securely before starting machine.
ALWAYS make sure spindle direction is correct for right-hand or left-hand operation.
ALWAYS keep long hair covered or secured when operating CNC machines.
ALWAYS keep hands clear of moving parts during machining operations.
ALWAYS stand clear of the machine while it is running and warn others of the dangers of being too close.
ALWAYS avoid contact with cutting edges when handling tools or changing tools by hand.
ALWAYS use tools within the limits specified by the manufacturer.
ALWAYS verify that your material is safe for CNC machining.
ALWAYS turn the CNC machine off completely and clean it up when you have finished using it.
NEVER attempt to program a CNC router without proper training.
NEVER wear long sleeves near rotating tools.
NEVER wear gloves.
NEVER wear loose clothing or jewelry.
NEVER reach into a CNC machine while it is running.
NEVER place hands near a revolving spindle.
NEVER leave the machine running unattended.
NEVER leave the machine so that someone else is able to restart it by simply pressing the cycle start button.
NEVER use blunt tools.
NEVER use cracked or chipped tools.
NEVER use tools with damaged tungsten tips.
Use of controls or adjustments or performance of procedures other than those specified herein may result in serious bodily injury.
NEVER disassemble the machine or remove any of its protective covers. The power input to the Variable Frequency Drive (VFD) is potentially lethal.
NEVER remove or handle the spindle power cable while connected to a powered on VFD.
Excessive heat created by dull tools or improper machining methods can create a fire hazard.
ALWAYS use sharp cutting tools.
ALWAYS ramp into cuts rather than plunge unless using a tool specifically designed to plunge.
ALWAYS cut at proper chip-load to avoid heat build-up.
PERSONAL PROTECTIVE EQUIPMENT
EVERYONE in the room while a CNC router is operating must wear the following PPE:
Ear protection. Members are required to provide their own ear protection with a Noise Reduction Rating of at least 25 dB. Disposable ear plugs are available for guests.
Eye protection. Safety glasses/goggles are provided but members may wish to bring their own.
Footwear. Closed toe shoes with non-skid soles.
Respiratory protection. Members are required to provide their own respirator with filters rated at least NIOSH P100. Disposable N95 dust masks are available for guests.
Check wood stock for defects before cutting, such as knots, cracks, and foreign objects.
Check that blast gates leading to points other than the spindle are closed before starting to cut.
Create cutting files that avoid small parts flying out when being cut.