Machining

A list of subtractive manufacturing tools commonly used in Formula for any material. Theory, safety, pros/cons, photos, cost, etc... When this gets too large we can consider separating it into other pages.

Safety

Main page: Health_and_Safety

Health and safety in the workshop environment and on track is a crucial priority for Formula Student teams and must be treated as such. If significant injury or death occurs related to work in a Formula Student team, there will be a risk of the university or faculty (governing body) to shut down the team permanently. Safety is not to be underestimated and a set of workplace safety policies never guarantees personal safety unless practiced. Lead members, or designated HSE responsible members should be proactive in making internal guidelines for PPE inventory, changing respiratory filters in masks etc. All members have a personal responsibility to follow safety guidelines set forth by the university and the team itself. HSE policies should reflect the principle of ALARP .

Personal Protective Equipment (PPE)

If your team is going to be using any of the tools below, please wear the correct Personal Protective Equipment (PPE) for the work being done.

Safety goggles are most common to use for any workshop activities. Goggles should be worn for most activities, primarily when working with moving machinery, or labor that can have projectiles/ dust going into eyes.

Hearing protection such as ear muffs or ear plugs are highly useful for loud activities. It should be noted that hearing protection is useful for impulse noises (i.e hammering) and for constant loud noises over long periods of time, like machine humming under operation. Both types of noises can accelerate noise-induced hearing loss.

Typical shop dress code is: cotton short sleeve shirt, jeans, close-toed shoes, no jewelry, and hair tied out of the way.

Recommended PPE includes safety glasses and hearing protection. Occasionally additional PPE is required such as a full face shield, respirator, or gloves.

NOTE: Using rotating machines with gloves or a long sleeve shirt might seem safer, but it is actually more dangerous due to the risk of getting sucked in.'

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Presses

Vice

A vice uses two jaws to compress a part and come in a variety of sizes. These are traditionally used to hold a workpiece while machining. Vices are often used as a makeshift press by attaching a cheater bar.

Die Press

A shaped die is used to punch a shaped hole into a sheet of material. For example, a die press can be used to quickly punch multiple holes into sheet metal for rivets.

Arbor Press

A simple mechanical press for press fits or broaching.

Hydraulic Press

Hydraulic presses can exert much more force than an arbor press using hydraulics. A cheap hydraulic press can easilly press bearings.

Grinders

Grinder Safety

• Always wear safety glasses.
• Do not remove any safety devices/shields.
• Make sure your sparks are not aimed at anyone.
• Do not use cutting wheels to grind - they WILL explode in your face.
• Do not use abrasive wheels to grind aluminum - it WILL explode in your face.

Rotary Tools are also known by the trade name Dremel®. The rotary tool is ideal for small and delicate work. Depending on the bit installed, the tool can grind, sand, cut, or polish. Die grinders are typically more powerful than a rotary tool, but are used simillarly.

Angle grinders are even more powerful than a die grinder but also larger, less precise, and more dangerous. Different disks can be installed on the tool for different types of work. A grinder wheel can quickly remove material. Flap disks are convenient for finishing or cleaning.

Bench Grinders are powerful table mounted grinders. Common wheels include abrasive, wire-wheels, polishing, and deburring. These wheels are long lasting and must be occasionally dressed. Have a bench grinder set up for each major alloy you will be using to reduce cross-contamination, keep a small bucket of water on hand for cooling off parts, and make sure the tool rest has a small gap of 2 to 3 mm of the wheel (1⁄16" to 1⁄8").

Drill

Drills use drill bits to remove material and create a hole. Other attachments can be installed such as: burs, sanders, grinders, and polishing wheels.

Hand Drill

Hand drills are portable and can be corded or battery powered. The RPM is controlled by the trigger pull and sometimes uses a gearbox; feed rate is controlled by the pressure applied. Straight holes are more difficult to achieve with hand drills, and it is recommended to use a center punch to reduce walking.

Drill Press

Drill presses are more stable than hand drills. They have a movable table to attach a vice and a spindle with a chuck. The RPM is typically controlled by a gearbox and sometimes with a VFD; feed rate is controlled by pressure applied to the spindle lever. Walking the drill bit is less likely, but a center punch is still recommended.

A drill press is not a vertical mill. They may look similar but (1) a mill is designed to take side loads and (2) mills can usually place the head of the machine more precisely.

Cutting

Water Jetting

Water Jet cutting is performed by a high pressure jet of water containing an abrasive grit.Therefore, it is usually higher quality than laser or plasma because it doesn't use heat and won't warp the part. The workpiece can also be non-metallic such as carbon fiber or plastic, and also good for very hard or very soft materials. Water Jet can hold good ~±0.1mm (~±0.005") tolerances depending on the machine used. Before welding a water jet part, the surface needs to be prepared more than usual to remove abrasive imbedded in the surface. Quotes for water jet jobs are very budget friendly and have a faster turn around time than conventional machining.

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EDM

Electric Discharge Machining works by slowly removing metal between and electrode and the workpiece using electricity. This process is often called "burning". EDM only works with metallic parts and will not work with most coatings. With the right operator and enough passes, EDM can hold very tight tolerances <±0.025mm (<±0.001).

While EDMing, material will weld back onto the workpiece. This is called recast and can initiate cracking. Recast must be removed from critical parts. It must also be removed before welding.

Wire EDM

For Wire EDM, a thin wire is used as the electrode. These are good for facing material or making thru-holes (provided there is a pilot hole). Wire EDMs can also cut through very thick material.

Sinker EDM

If the electrode is slowly lowered into the workpiece, it is called sinker EDM. Custom electrodes are machined then used in the EDM to get special shapes. For example, a blind square hole.

Hole Popper

Hole poppers are similar to sinker EDMs but are made specifically for holes. These are ideal for making tiny holes in hardened parts. Probably very uncommon for FSAE.

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Wire EDM

Sinker EDM====

Mills and Lathes

A vertical milling machine with a vice and DRO installed

Mills and lathes vary from small bench top tools to large floor models. They are more precise and universal than something like a drill press, although these machines can take longer to setup.

Machining technique varies depending on tool type/material and workpiece material/size. Topics such as speeds and feeds, heat generated, and lubrication should be considered.

Dimensions can be confirmed by either using the hand wheel markings, scribing and measuring, or using a Digital Read Out (DRO) if installed.

There are CNC versions of both mills and lathes.

Mills

The most typical milling machine is the vertical milling machine. In this configuration, the workpiece held to the table typically within a vice and elevated with parallels. The table is controlled in the XYZ axes. The tool is held with a collet or drill chuck and spun by the spindle. The spindle speed and plunge axis is also controlled by the user.

Tools such as end mills, drill bits, reamers, fly cutters, and saws can be installed.

Lathes

The metal lathe rotates a spindle with a chuck to hold the workpiece. If the workpiece extends far past the chuck, a tailstock with a livecenter or other support can be used. Lathe tools are attached to a carriage and controlled in multiple axes with hand wheels.

Tools are commonly used for facing, turning, boring, drilling, reaming, and threading.

Lathes are also one of the most dangerous tools in a workshop. Large lathes won't even flinch while sucking in the user! Be careful and take a class if your university has one. Formula students have died using lathes!

CNC Machining

Not all teams may have access to a CNC. You do not need CNC to make a formula car but it is recommended for complex, high tolerance, or high quantity parts. Talk to local machine shops and trade schools, they may be willing to sponsor your team with CNC services.

Computer Numerically Controlled (CNC) machining is a process which takes programmed tool paths via user input in order to machine a part. Programming the tool paths is done in a Computer Aided Manufacturing (CAM) software, which allows the programmer to choose the tools used for machining and visually simulate the machining if the part. The program is then transferred to the machine to do the work.

• Complex shapes can be made with CNC compared to manual machining
• Parts, tools, and software can be more expensive than manual machining
• Involves additional programming time and testing
• Precision and finish is generally higher with CNC parts as everything is controlled by a computer and the ability to climb mill.

2 Axis

2 Axis machining generally the X and Y axis

2.5 axis machining

With 2.5 axis machining, you have fine control in the x and y axes but rudimentary control in the z axis. 2.5 axis mills are simpler and cheaper, while still being able to manufacture many parts.

Multi-axis

Multi-axis CNC Machining is any CNC machining performed on a machine with greater than 3 axis (degrees of freedom) control. Different variations

Further Reading

• MIT Machine Shop Videos (Youtube Playlist)