03/01 SHOB BOT

SHOPBOT

DEMO

APPLICATIONS

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WHAT IS A MILLING MACHINE?

A milling machine is a machine tool used to machine solid materials. Milling machines exist in two basic forms: horizontal and vertical, which terms refer to the orientation of the cutting tool spindle. Unlike a drill press, in which the workpiece is held stationary and the drill is moved vertically to penetrate the material, milling also involves movement of the workpiece against the rotating cutter, the latter of which is able to cut on its flanks as well as its tip. Workpiece and cutter movement are precisely controlled to less than 0.001 in (0.025 mm), usually by means of precision ground slides and leadscrews or analogous technology. Milling machines may be manually operated, mechanically automated, or digitally automated via computer numerical control (CNC).

Milling machines can perform a vast number of operations, some very complex, such as slot and keyway cutting, planing, drilling, diesinking, rebating, routing, etc. Cutting fluid is often pumped to the cutting site to cool and lubricate the cut, and to sluice away the resulting swarf.

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HISTORY

In 1861, Frederick W. Howe, while working for the Providence Tool Company, asked Joseph R. Brown of Brown & Sharpe for a solution to the problem of milling spirals, such as the flutes of twist drills. These were filed by hand at the time. Brown designed a “universal milling machine” that, starting from its first sale in March 1862, was wildly successful. It solved the problem of 3-axis (XYZ) travel much more elegantly than had been done in the past, and it allowed for the milling of spirals using an indexing head fed in coordination with the table feed. The term “universal” was applied to it because it was ready for any kind of work and was not as limited in application as previous designs. (Howe had designed a “universal miller” in 1852, but Brown’s of 1861 is the one considered a groundbreaking success.)

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HANDHELD ROUTER

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2D

2.5D

3D

If all we have is a flat outline of something we want to cut out, that would be considered 2D. If we then added straight up and down movements of the cutter into and out of the material, we might now consider the project as 2.5D. This 2.5D work starts off as a 2D design in principle, but during the process of creating the tool path or cutting file you will typically assign a depth or multiple depths for the tool’s motion to cut features like grooves or flat pockets. When the software generates the part file, the instructions will first move the CNC tool to the assigned cutting depth (in the Z axis), then move the cutter through the XY tool path at that depth, and then return to the starting height with a straight pull-up. Thus, when the file is finished, the cutting tool has moved in three dimensions (X, Y and Z), but all the X and Y axis motion is in a single plane and the X and Y axes stop when the Z axis plunges or pulls up. So, for the case of this example, the drawing and design process are fundamentally 2D. Standard cabinetmaking would be a good example of such a 2D or 2.5D project.

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SPINDLE or ROUTER

These tools are similar in principle; basically a motor for turning a cutting bit at high speeds.  A router (we recommend and sell a Porter Cable 3.25 hp router) provides the affordable solution for a CNC tool.  We also sell several high-frequency spindles that are the industrial grade solution for a CNC tool.  Power (usually 3-phase) for a spindle is routed through an inverter that converts it to a higher frequency for powering the spindle/motor.  Spindles have the advantage of being more powerful (note that hp ratings between routers and spindles are not comparable) and will maintain their full torque down to much lower RPMs than a router.  Spindles have precision bearings, which mean less run-out and thus smoother and more accurate cutting. These bearings also stand up to continuous use better than those of a router.  Bearings in a heavily used router might need to be replaced every three-four months, while a similarly used spindle should be good for a year or two between bearing replacements.  A high-frequency spindle is also much quieter in operation than a router.

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ENDMILLS

An endmill is a type of milling cutter, a cutting tool used in industrial milling applications. It is distinguished from the drill bit, in its application, geometry, and manufacture. While a drill bit can only cut in the axial direction, a milling bit can generally cut in all directions, though some cannot cut axially.

Endmills are used in milling applications such as profile milling, tracer milling, face milling, and plunging.

TYPE COMPARISON CHART

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SOFTWARE

TOOL PATHS

FeatureCAM

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G CODE

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TECHNIQUES

Template Cutting

Contour Milling

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SNAP TOGETHER

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MATERIALS

   veneer plywood
   medium density fiberboard (MDF)
   medium density overlay (MDO)
   foam
   High Density Foam

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VENDORS:

BOULTER PLYWOOD

STERRITT LUMBER

HOME DEPOT

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SWARF

advisory on surface milling and excess SWARF

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safety
   cuts, burns, impacts
   glasses, shoes, clothes, hair
   emergency stop, assistance

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OTHER MACHINES
Harrison Alpha Lathe
HURCO 5 Axis

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MACHINES THAT MAKE MACHINES ( Jonathan Ward )

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