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Foundations of CNC

Tom Dubick

David Taylor

Zack Budzichowski

Vaneza Caycho Ñuflo

Garrett Nelson

Version Updated on March 2026

This presentation is for newbies and beyond.

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Recommend Topic Sections

The following sections have corresponding recommendations for beginner, intermediate, and experienced level users.

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Introduction to CNC

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What is a CNC machine?

A CNC (computer numeric control) tool is used in prototyping and full production for cutting, carving, machining and milling in a variety of materials including wood, mdf, plastics, foams and aluminum.

The term “CNC Machine” is typically used to refer to a device that uses a rotating cutting tool which moves in 3 or more axes (X, Y and Z) to cut-out or carve parts in different types of materials. The information below will focus on what are typically referred to as “CNC Routers” although it would be applicable to most CNC milling and engraving machines too.

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Brief History of CNC

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CNC - What is it?

  • Stands for Computer Numeric Control
  • CNC machines can be mills, lathes, cutters, etc.- the important thing is that the process and the machine itself is controlled by a computer, as opposed to human hands.�
  • CNC machines generally are subtractive processes - that is, they create a design by removing material from a larger chunk.

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CNC - Computer Controlled

Because CNC machines rely entirely on computer control, there is very little in the way of human input during the actual milling/cutting process.

Instead, our input comes at the other end, with CAD programs, but there are ways we can affect the process.

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Bits of Magic

  • CNC Bits and Chip Load

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Bits

CNC routers need bits, and these bits determine the carving type, resolution, and material.

While CNC machines have opened all kinds of creative possibilities, the magic lies in the bit. It determines whether you will end up with a perfect or okay design. Plus, it also makes the difference between cutting down on waste or increasing material costs significantly.

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A Bits Purpose

The bit is used to remove material in a specific way. Initially, routers used to be handheld tools that were guided by templates or ball-bearing pilots, and they were moved manually around the workpiece. But today, routers are controlled using computers that precisely determine the toolpath, and these routers require bits to make intricate cuts.

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CNC Router Terminology

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Flutes

A cutting edge of a bit. Having more flutes increases the strength of the tool, and it means you can have a faster feed rate, but it reduces space for chip flow. Thus, bits with more flutes tend to leave a smoother cut surface and require a faster feed rate to avoid burning. CNC router bits are mostly available in 1-, 2-, and sometimes 3-flute configurations. Generally, bits with fewer flutes remove more material per cut and require a slower feed rate.

  • Straight flute: A straight flute design means the cutting edge is parallel to the body (or shank) of the bit. With this design, the material will not be extracted from the cut. A straight flute is cheaper to make and is mostly for wood and plastic materials. A straight flute produces a clean finish.
  • Spiral flute: A spiral flute is cut in a helix around the body (or shank) of the bit, making them ideal for wood, aluminum, and plastics. The up-spiral flute, for example, is useful for removing chips. There are three major types of spiral bits that we’ll discuss later: up cut, down cut, and compression.

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More about Flutes

Upcut Spiral

The tool’s flutes eject chips upward, out of the gap created between the cut piece and the waste material (kerf).

Upside - Very efficient at dissipating heat and clearing chips

Downside - The chips are forced up on an upcut bit and the material’s top surface can become chipped or frayed (known as a tearout). Thinner material can be lifted up and moved.

Downcut Spiral

A downcut spiral flutes push chips downward towards the machine bed.

Upside - Very good at creating a nice finish on the top face of your material. It’s good for thin material.

Downside - The downwards force created by the chip ejection can cause tearout on the bottom face of the board. Also, you should not drill with this tool due to this reason.

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Flutes

Helical Flutes

Flutes are the helical grooves that wrap around the sides of the end mill. Each flute has a single tooth with a sharp cutting edge (although there can be more than one) that runs along the edge of the flute.

Straight Flutes

Straight flute’s have two flute tools with a zero-degree angle and create a superior finish in natural wood and wood composites. The entire straight flute makes contact with the material when cutting. Chips are not push up or down, creating a good edge quality on most materials.

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Flutes

As the tooth cuts into the wood, each flute whisks away a small section or “chip”. The fewer the flutes, the more material that is ejected with each tool rotation. The overall cutting depth should never exceed the length of the flutes on an end mill. If cutting deeper than the length of the flutes, the tops of the flutes will be blocked and chips won’t clear, building up heat and reducing tool life.

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Chip Load

Chipload is the thickness of a machined chip as cut by a specific tool type. More flutes create a smoother surface finish, while fewer flutes remove material fastest, but make rougher cuts.

Proper chipload is important because chips dissipate heat. Hot cutters can lead to suboptimal results, including burned wood, a poor edge finish and dull tooling.

For example, If you’re machining a material like HDPE plastic, you want to use an “O” or single flute bit to clear the chips away as quickly as possible or heat will build up melting the plastic, which will “reweld” to the tool.

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Chip Load

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Chip Load

The size of the chips or pieces that the CNC bit removes from the material. In other words, it’s the thickness or size of the chip removed per cutting edge (or flute) with every revolution. Chip load is crucial since smaller chips increase heat generation during the cutting process. The smaller chips are not ejected fast enough and are instead re-cut into smaller pieces, which results in heat generation. This can cause premature bit failure when the heat is transferred to the cutting tool. When the chips have the proper size, they will carry away heat and prolong tool life.

Chip load is equal to the feed rate (in inches per minute or IPM) divided by revolutions per minute multiplied by the number of flutes. The chip load value can help you in selecting the right size or diameter of a bit. Some manufacturers give a target chip load.

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Chip Load

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What factors impact cut settings?

Size and type of bit

Hardness of material

Project design detail and desired accuracy

Securing your material

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More Detailed Information of Bits

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Lots of Information on Bits

CNC Bits Guide

The links to the left are interactive.

Table of Contents

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V-bits: Shape versus cut depth/size

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V-bits: Shape versus cut depth/size

Bigger the v-bit deeper the cut. The example was cut at 50 thousand depth.

18*

30*

60*

90* 1 5/8" diameter

90* 1 1/4" diameter

120* 1 1/4" diameter

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V-bits: Shape versus cut depth/size

Finer the lettering, small the v-bit angle. Instructables about V-Bits

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Speeds and Feeds

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Feed Rate and Speed Rate

Feed rate: How fast a bit can move laterally through the material, or vice versa. It’s measured in IPM or inches per minute. Therefore, if your chips are unnecessarily large, reduce the feed rate or you may end up ruining the bit.

Speed rate: The speed of the spindle. It’s represented in revolutions per minute (RPM).

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Speeds and Feeds Calculator

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Feeds and Speeds

The speed at which we move a cutter across the material is called the “feed rate”. The rate of rotation is called the “speed” and is controlled by how fast the router or spindle turns the cutting tool. Both feed rate and spindle speed will vary based on the material being cut. A general rule of thumb is that you want to move the tool through the material as fast as possible, without sacrificing surface finish. The longer the tool rotates in any one place, the more heat that builds up. Heat is your enemy and can burn your material or radically decrease the life or your cutting tool. Feed rate vs spindle speed:

  • Spindle speed that is too fast paired with a slow feed rate can result in burning or melting.
  • Spindle speed that is too slow paired with a faster feed rate can result in dulling of the cutting edge, deflection of the end mill and possibility of breaking the end mill.

A good strategy when selecting a cutter is to attempt to balance feed rate and spindle speed by performing two passes on the work piece. The first pass, called the roughing pass, can be done by using an end mill that will eject a large number of chips at a high feed rate. The second pass, called the finishing pass, then won’t require as aggressive of a cut and can provide a smoother finish at a high speed.

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Spindle Speed and Feed Rate

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Feeds and Speeds

A good strategy when selecting a cutter is to attempt to balance feed rate and spindle speed by performing two passes on the workpiece. The first pass, called the roughing pass, can be done by using an end mill that will eject a large number of chips at a high feed rate. The second pass, called the finishing pass, then won’t require as aggressive of a cut and can provide a smoother finish at a high speed.

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CNC Feed vs Speed

Why it matters:

  • Avoid broken cutters
  • Loss of accuracy
  • Waste time
  • Poor finish

So what is the correct speed and feedrate?

  • Go with the recommended settings on the Makera, Shopbot, and etc.
  • Temper settings with common sense

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Our Tools - Speeds and Feeds

Reference Charts

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Speed vs. Finish

Speed

Speed and thus feed rate will depend on the horsepower of the spindle. While a high RPM will generally result in a higher quality finish, it can also result in higher friction that will, in turn, increase the wear on your bit. Therefore, you are better off referring to the spindle manufacturer’s speed parameters.

If you have to cut a large amount of material in a short time, go for a bit that can go through your material quickly. On the other hand, if you hate sanding hardwood, go for a bit that will leave a smooth finish.

Higher tool RPM produces smaller chips, while higher feed rates produce larger chips. Overall, if the chips are too large, your bit will be likely to break, but if your chips are too small (like fine powder), you will be dulling your bit. It’s all about getting the right balance.

Finish

Bits offer multiple cutting edges for extra flexibility. You have the option of going for 2-, 3-, or 4-flute bits. Having more flutes will give a finer quality of cut, but will go through your material much slower.

Bantam Tools - Speeds and Feeds Information

X-Carve Speeds and Feeds Chart

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Ramping

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CNC Router Bits

  • Drill bits are designed to plunge directly into material, cutting axially and creating cylindrical holes. End mills are typically used for horizontal carving and cut laterally. Additionally, most mills are “center-cutting,” meaning they are able to cut both axially and laterally. This is due to cutting flutes that extend to — and protrude from — the end face and enable plunge cutting. To minimize tool breakage and stress on the material being cut, most CNC software will “ramp” the end mill slowly into lateral cuts.

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Ramping

Ramp moves are a much gentler way to ease the tool into the material. Ramping in at a gradual angle reduces heat buildup and spindle-z axis loads, plus it helps to reduce vibration and keeps parts in place while machining.

Smooth Ramping works well for easing the tool into large parts. This allows for the rotating tool to be gradually and smoothly moved into the material at an incline.

Spiral ramping slowly eass the tool into the material over the full perimeter of a profile toolpath. Spiral ramping is useful for small parts because machining force can push them around as they are being cut.

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Fine Details about the Bits

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CNC Router Bits

  • Even though bits fall into these two main categories, other variables are always at play, like bit material (solid carbide, HSS, carbide-tipped), flute type (straight, up cut, down cut, compression), number of flutes (1-2 flutes, 2+ flutes), and bit end (fishtail, engraving, V-bit, ball nose).

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CNC Router Bits

  • Drill bits: These drive into the material. They are the best choice for tasks that require material to be removed straight down through the workpiece. They are often used for pre-drilling holes for screws.
  • End Milling bits (or cutters, carving bits, and end mills): These cut laterally across your material. They are designed to move across the surface of the workpiece, clearing away chips to achieve 3D designs.

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Bit Materials

  • High-speed steel (HSS): This is a tool steel bit with high heat resistance, wear resistance, and hardness. It’s much better than carbon steel when used for cutting tools and drill bits and is mainly recommended for cutting foams. HSS is processed from raw ore and is heated to its melting point before several elements and minerals are added to enhance the internal structure. HSS tool life is shorter compared to carbide.
  • Solid carbide (SC): A sturdy and wear-resistant steel. SC bits come in different types, ranging from cheap ones to high-quality ones that cost top dollar. When shopping for SC bits, you have to be extra watchful or you will end up with a knock-off. There are many forms of carbide (tungsten carbide, beryllium carbide, silicon carbide, etc.). Note that these bits can be brittle and should be handled with care.
  • Carbide-tipped: Since carbide is costly, large-diameter CNC router bits have chunks of carbide brazed to a steel body. You then get the longevity of carbide with the lower cost of a steel core.

  • Solid tungsten carbide bits: Tungsten carbide bits are made using hard particles of tungsten carbide bound with metallic cobalt. These kinds of bits are super strong and durable, so they remain sharper for a much longer time than HSS bits.
  • Polycrystalline diamond (PCD) bits: These bits are made up of diamond particles sintered with a binder. The diamond is blended onto a carbide substrate to make an extremely hard and abrasive-resistant bit.

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Basic End Mill Anatomy

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Tip Shapes and Application

Ballnose mills produce a rounded pass and are ideal for 3D contour work, while fish tail cutters will produce a flat surface. Ball nose mills are often selected when doing 3D contouring because their rounded edge reduces jagged steps when cutting several stepped layers. Ball nose mills can also be used to cut wide paths with rounded edges by reducing the step over amount (overlapping distance between) between passes.

V-bits produce a “V” shaped pass and are used for engraving, particularly for making signs. V-bit can be 90o or 60o and each depends on the angle of depression that a material needs. Although they often use them to engrave signs on materials, they’re ideal for projects that need excellent sharp edges.

Engraving bits make a shallow cut along a toolpath. They are capable of etching very fine, often decorative, details into surfaces.

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Helical Direction, Chip Ejection, and Surfaces Produced

A CNC router spins a cutter clockwise. The helical direction of the flutes as they wrap around the tool determine if chips are ejected towards the top or bottom of the workpiece.

Upcut mills eject chips towards the top of the workpiece, producing a cleanly cut bottom surface. The downside is possible surface splintering or “tearout” on the top surface as the chips are ejected upwards.

Downcut tools do the opposite, producing a smooth upper surface. They are ideal for pieces that have been previously engraved or v-carved and cannot be flipped to hide tearout. In addition, as downcut mills pack the chips into the cut path, they can be used instead of tabs to hold down a workpiece and keep it from moving.

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Major Cut Types

UP CUT

Up cutting bits pull chips (and the material) up. When using them, your material will need to be securely held down. Upcut bits are preferable if you want to clear chips from your cuts to prevent overheating the bits. They are great for making cuts through the material. An up cut is the most common type of cut.

DOWN CUT

Downcutting bits press the chips and the material back into the cut. Their down shear action is excellent for preserving the top surface of your material. These bits are preferable for cutting thin, flexible material but are not the best for drilling holes because the bottom layer of the workpiece will be pushed away from the bit by chips. Down cut bits leave a clean cut at the top of the workpiece but may fray the bottom edge.

COMPRESSION CUT

Compression bits (up-down bits) offer the benefits of both up and down cut bits. The bit is a standard down cut, but its tip is an up cutter. Therefore, when cutting materials like plywood, you will end up with a clean edge on both sides because the top is pushed down while the bottom is pulled up. Combining both geometries eliminates chipping and reduces the risk of damaging the workpiece.

Note that compression bits should never be used to drill holes. Once the bit goes deep enough beyond the direction change, the chips get compressed because they have no way of escaping, and this creates friction and heat. These bits are a little costly because of their sophisticated nature, but they’re recommended for laminates, composites, and plywood.

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How to Pick a Bit

PROJECT SUITABILITY

What project are you undertaking?

For instance, detailed work like lettering requires a V-bit (sometimes called engraving bits, V-groove bits, or V-carving bits). As the name suggests, V-bits have a cutting profile in the shape of a ‘V’. They come with different “included angles”, and this will determine what they’re used for. A 60° V-bit, for example, will give you smaller details compared to a 90° bit, which is well suited for larger or shallower details or letters.

MATERIAL COMPATIBILITY

What are you cutting? Is it hard or soft wood? Is it stainless steel, fiberglass, MDF, acrylic, or aluminum?

The material matters. It matters so much that you will find different grades of carbides used for different materials. Going for the wrong bit could be detrimental to the bit or even the machine. Plastic will require a specific bit (specifically one that will not melt it) and so will aluminum and plywood.

GO-TO OPTIONS

In case you’re new to CNC routing and you want a multi-purpose bit, go for two-flute spiral bits since they cut a wide range of materials, including plastics, aluminum, foam, and wood. The 2-flute cutting spiral bit is an excellent all-purpose bit if you’re still in the prototyping stage and don’t want to purchase 20 bits right away. The 60° V-bit is also a wise choice for engraving, making signs, and cutting letters.

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Milling

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Our Labs CNCs

CLS Fab Lab Tool Site

  • Please use the link to access workflow and information about our machines.

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ShopBot Reference Tutorials

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X Carve Reference Manual

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Bantam Reference Materials

Bantam CNC Milling

The link above provides access to information on how to use the machine and the softwares, as well as project tutorials.

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Shaper Origin Reference Materials

Shaper Origin Tutorials and Operation

Shaper Origin User Manual and Support

The link above provides access to information on how to use the machine and the softwares, as well as project tutorials.

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Makera Reference Materials

Makera Wiki

User Manual and Support

The link above provides access to information on how to use the machine and the softwares, as well as project tutorials.

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Setup Sheets

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Setup Sheets

Garrett Nelson, Fab Academy graduate ‘22 and CPCC machining instructor, created the following setup sheet to help with CNC file and material preparation.

Setup Sheets play a vital role in the operation of a CNC. They guide the CNC user in setting up the machinery for a specific task. Most Setup Sheets are designed to be simple, making them straightforward to generate and utilize. For more about about setup sheets, please check out the CNC Cookbook.

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Runout

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Runout

What is runout?

Runout is a rotation inaccuracy which occurs when the tool is no longer aligned with the main axis. In drilling applications, this can result in a bore diameter that is actually larger than the drill’s nominal diameter.

Spindle Runout, or Tool Runout, as it can also be called, is the inaccuracies that cause a tool (in a mill) or workpiece (in a lathe) to spin off the ideal axis. It’s very bad for tool life, so it’s good to know more about it.

Runout is the tendency to spin the tool around a centerpoint that is not the tool’s center. It makes the tool wobble instead of spinning cleanly and increases chip loads.

Causes of Runout

A common cause of runout is when machining debris, dirt, chips, etc. enter the spindle and cause interference when the tool is clamped. Furthermore, dirt and damage collets can lead to runout inaccuracy. Lastly, damaged bits and shanks can cause iffuses too. CNC spindle runout can decrease tool life and increase the rate of machining defective parts.

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Measuring Runout

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How to measure runout?

General Overview from CNC Cookbook:

The measurement shown will get you runout from all sources, but it’s important to understand that you may want to measure the individual component sources of spindle-tool runout to find the underlying causes.

This requires several measurements:

1. Clock the inside of the spindle taper to see the spindle’s runout.

2. Clock a precision dowel in the toolholder to see the toolholder’s runout.

3. Clock the taper inside an ER collet chuck with no collet installed to see the runout of just the toolholder rather than the toolholder + collet combination.

There’s even a fourth source that’s very hard to measure which is that the endmill may have been ground with its geometry slightly off-center.

Detailed steps on how to use our labs dial indicator from Precise Bits.

This is our dial indicator at CLS Fab Lab.

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CNC Project Examples

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CAD & CAM

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Toolpath

This is a coded route that the CNC machine follows to cut. Think of it as a guide for the device.

Fab Lab Toolpath Example

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CAD

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Vcarve aspire offsets

In VCarve and Aspire, "offset" refers to creating a new vector or model based on an existing one, either larger or smaller, useful for tasks like puzzle pieces or creating wall thickness in molds.

What are Offsets?

  • Creating New Vectors/Models:�The offset function allows you to create a new vector or 3D model based on an existing one, either expanding or shrinking it by a specified distance.

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CAD

  1. Collect Ideas, External Design work or data
  2. Create 2D & 3D* Designs in Vectric Software
  3. Generate Toolpaths and Simulate in 3D in Vectric Software
  4. Export Toolpaths ready for cutting in Vectric Software
  5. Transfer the Toolpaths to the CNC Control PC
  6. Load Toolpaths into the CNC Control Software
  7. Prepare the Machine with correct Tooling and Material to cut
  8. Run the CNC

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CNC - Software

Creating something with a CNC machine usually requires three kinds of software:

  • CAD (Computer Assisted Design) programs - you should be somewhat familiar!

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CNC - Software

Creating something with a CNC machine usually goes through three steps, software-wise:

  • CAD (Computer Assisted Design) programs
  • CAM (Computer Aided Manufacturing) programs - turns your 3D model into a set of instructions for the CNC machine (usually “g-code”)

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CNC - Software

Creating something with a CNC machine usually goes through three steps, software-wise:

  • CAD (Computer Assisted Design) programs
  • CAM (Computer Aided Manufacturing) programs - turns your 3D model into a set of instructions for the CNC machine (usually “g-code”)
  • Machine Controller - Think of these like drivers for the machine. The machine won’t work otherwise!

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CNC

  • Software
    • Kinds of CAD
      • Free-form
        • Blender
        • 123D Sculpt+

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CNC

  • Software
    • Kinds of CAD
      • Free-form
      • Easy to use with some accuracy
        • TinkerCad
        • 123Design
        • Sketchup
        • Easel

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CNC

  • Software
    • Kinds of CAD
      • Free-form
      • Easy to use with some accuracy
      • Professional
        • Autodesk Fusion
        • Solidworks
        • Alibre

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CNC

  • Software
    • CAD
    • CAM
      • Computer-Aided Manufacturing
        • MeshCam - works across many platforms
        • VCarve - Shopbot
        • Otherplan - Othermill
        • Easel - X Carve

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CNC

  • Software
    • CAD
    • CAM
    • Machine Controller
      • Custom machine specific program
        • Shopbot - Shopbot
        • Othermill - Otherplan
      • Mach 3 (Windows)
      • LinuxCNC

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CNC - Software

Thankfully, most software has at least a couple of these steps integrated directly into it.

For example, most CAD software will export directly to g-code, skipping the CAM step!

However, we’re going to go over the process so we’re familiar with it.

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Workflows

What is a workflow?

Workflow Process refers to a series of activities or tasks that need to be completed sequentially or in parallel to achieve an outcome. In most cases, the process is linear and proceeds in a sequence determined by actions or pre-defined business rules. (Integrify)

Why are checklists important?

When you are working on your projects you are probably multi-tasking and dealing with all sorts of distractions. This can make it easy to forget to do certain tasks or mean having to spend time trying to remember how to complete a specific activity. When you are under pressure or rushing to complete something it is easy to forget a small but important step in your process. This is where checklists can be valuable to help you get things done. (Power of Checklists)

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CAD considerations

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Feed Directions

Material is often fed into machines, such as wood into a table saw. With regards to CNCs, you feed the spinning tool into the stationary material. The feed direction determines which way the tool moves around the material when cutting and how the tool’s clockwise turning flutes create chips when contacting the material.

Climb cutting

In the climb cut, the chip starts thick and ends then. This can result in a smoother cut in materials such as hardwood because it eliminates end-grain splintering. However, the forces created can also mar the finish and push parts around due to the bit trying to “climb” out of the cut. In addition, the forces created can deflect the tool.

Conventional Cutting

With convention cutting, the primary cut is made as the tool exits the material. The chip starts out thin and then gets thicker. This can cause end-grain splintering in hardwoods, but it works with composite sheet goods, like plywood.

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Types of Cuts

Pocketing: Tool routs a defined area to certain depth and does not cut through the material.

Chamfer: Special chamfer tool in the shape of a “v” cuts into material leaving an angled edge.

Fillet: Special fillet tool shaped like a cone cuts into a material leaving a rounded edge.

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Profile

A profile toolpath follows a line of an individual part. A profile cut follows a closed shape to a specified depth. You kerf can impact your cut.

Three types of Profile Cuts:

  • Outside Cut
  • Inside Cut
  • On Cut

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Pockets

Offset

Pockets cut using the offset method start at the center of the pocket indentation move in a spiral pattern until the tools reachers the pocket’s outside edge.

Raster

A raster pocket begins at the one end, and the tool moves side to side from one end of the pocket to the other, clearing out a recessed area.

Stepover

The amount of tool overlap between passes is called the stepover vale. The smaller the stepover percentage, the finer the finish due to the increased toolpath overlap. A stepover of 50%, is usually enough to minimize tool marks and leave a smooth bottom surface.

Pocket cuts have vertical sides and a flat bottom and can be used to create a recessed area for anything you can imagine, from joinery connections to adornments. Pocket tool paths are similar to inside toolpaths; they both cut on the inside of a closed line, but pockets also remove all the material inside the cut line to specified cut depth. It is commonly referred to as clearing a pocket and pocketing.

Ball Bit Stepover Example

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Drill

Drill toolpaths cause a CNC to act like a drill press, plunging the end mill vertically into the material. Drilling creates a hole that correspondence to the diameter of the tool,which it’s not a good choice for creating dimensionally accurate fastener holes - use inside profiles instead.

Peck drilling is when the tool drills to a specified depth, then raises up to clear the chips, and then plunges again, repeating the sequence until the hole is cut.

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Depth of Cut

Depth of cut, also called pass depth or depth per pass, is how deep each individual machine cutting pass should be to reach the cut depth. It often takes several passes to cut all the way through material.

Depth of cut is determined by both the material thickness and end-mill diameter. When cutting with small diameter tooling (⅛” and smaller), it’s best to make shallower passes than when using ¼” and larger diameter tools.

The general rule for determining depth of cut is that one pass should equal the diameter of the end-mill.

Making more passes takes more time, but makes a cleaner cut and puts less stress on your tool. Increasing the ct depth by too much can lead to poor cutting quality, as well as end-mill breakage.

Both depth and tool diameter have an effect on chip load.

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Dog Bones (Fillet slots)

Four different slot fillet solutions:

  • Plain corner
  • Dog Bone
  • T-Bone
  • Sniglet

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Roughing vs. Finishing Cuts

The CNC process can be simply divided into roughing and finishing, and CNC roughing is to make the material into a rough shape, and finishing is to cut the material into fine shape. Rough machining first removes excess parts, followed by precision machining in the second step of finishing. This process can involve multiple toolpaths and tool changes.

Roughing | Finishing

Roughing → Finishing

Your Finishing toolpath will take significantly longer compared to your Roughing toolpath.

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Project Ideas

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CNC Project Ideas

  • Signage & Wall Art
  • Custom Furniture
  • Plaques
  • Molds
  • Toys
  • Lithophanes
  • Clocks & Picture Frames
  • Mantels & Archways
  • Prototypes
  • Chests

Vectric Projects

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Fab Academy CNC Project Examples

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Computer Controlled Machining Student Examples

CLS Fab Academy students’ CNC work.

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Joints

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CNC Wood Joints

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Fab Lab Furniture - 50 Digital Joints

https://www.fablabifurniture.org/

The content discusses Fab Lab iFurniture, a digital fabrication laboratory specializing in furniture. It introduces the team members, including Fab Managers and Instructors, detailing their backgrounds and expertise in digital manufacturing and design. The lab's location in Lima, Peru.

https://www.fablabifurniture.org/50-digital-joints

Fab Lab iFurniture offers an Open Source project focusing on digital wood joints, transitioning from traditional carpentry to precise cuts with two-piece fittings using advanced technology machines. The initiative, developed by C-LAB of Germany, provides accessible manufacturing plans for creating these joints in your own lab. The project, "50 Digital Joints," transforms Japanese traditional carpentry joints into digital formats through CNC router technology. Detailed instructions and steps are provided for implementing these joints, enhancing woodworking techniques with digital precision.

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Living Hinges

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Step-Over

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Step-over

Stepover is defined as the the space between passes of a tool during an operation.

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Scallops

Scallops are the bumps on the surface that require smoothing out

Ball Nose Scallops

V-bit Scallops

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Roughing vs Finishing Tool path

Roughing is about quickly removing large amounts of material but with little finesse. Finishing, on the other hand, is like the artist’s final touch, refining the surface to achieve the desired precision and smoothness.

Roughing tools typically use wavy cutting edges or large rows of cutting flutes with large contact surfaces. Finishing tools usually use sharp cutting edges and high tool strength. The cutting edges are sharp and high in strength, reducing the problem of side milling taper and improving the finish surface quality.

The difference between roughing and finishing is that roughing removes a wide variety of materials, with low cutting speeds, large feeds and tools, less material removal, and high cutting speeds to ensure final dimensional accuracy and surface quality. Roughing is mainly for the purpose of quickly cutting the remaining margins.

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Fixturing

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Fixturing

Fixturing is the process of holding down your material while cutting. Choosing the right hold down method can be challenging, but it is an important part of project planning. Not only does the workpiece need to be held securely, but it is important to know what will happen to parts as they are cut from the surrounding material. Small parts can be caught by the cutter and thrown across the room, causing serious injury or damage.

When using screws, a drill toolpath is used first to create spots for screwing down your materials before cutting.

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More on Fixturing

Composite Brad Nailer

This finish nail system offers a quick and safe clamping method for holding sheet goods down to your machine spoil board. The composite nails hold better than metal nails, but can be machined through without damage to your CNC tooling.

These nails and nailers allow for easy clamping of multiple layers or for small pieces, and save on both set up time and removal down time.

Best of all, they eliminate the potential for router bit damage from accidentally machining into screws or other traditional metal workholding hardware.

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More Fixturing

Adhesives can be more difficult to work with, but they offer some advantages over other methods. This can work well for thin materials that cannot be held by a press-fit jig. More surface area = more holding power, so small projects will require additional hold-downs.

To use tape adhesive, both the table and workpiece must be clean, flat, and dust-free. If planning to cut all the way through the material, keep the tape away from the planned toolpath if possible (it may gum up the cutter, reducing cut quality for the rest of the part).

Vacuum Table

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Tabs

Tabs are small, rectangular sections of uncut material, added to profile toolpaths that keep a part joined to the waste material when making through-cuts. Tabs

Tab length, placement, and thickness are usually user configurable.

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Materials

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CNC - Materials

CNC machines can work with a variety of different materials, including:

  • MDF (Medium Density Fiberboard)
  • Plastics (Delrin, ABS, etc.)
  • Wax (seriously -- but it has to be machinable)
  • Foam
  • Polyurethane Tool Boards (also plastics, but much denser)
  • Metals (aluminum, brass, bronze, etc.)

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Examples

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Examples

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Safety

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General CNC Safety

General overview

  • Safety goggles
  • Hair up
  • No loose clothes
  • Be aware of your surroundings
  • Do not work alone
  • Ear protection
  • Closed toed shoes
  • Be aware of the emergency stop buttons

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SHOPBOT Safety

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X Carve Safety

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Bantam tools safety

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Maker Carvera safety

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Shaper Origin

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References

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Mechanical and manual Milling Machines

horizontal milling machine

universal milling machine

vertical milling machine

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A CNC milling machine

A CNC router is a computer-controlled cutting machine that typically mounts a handheld router as a spindle used to cut various materials:

  • Wood
  • Composites
  • Aluminum
  • Steel
  • Plastics
  • Glass
  • Foams

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Desktop CNC milling machine

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On table CNC milling machine

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DIY milling machine

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Composition

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Why do you think they call it a milling machine?

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Vacuum Table

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Why do you think they call it a milling machine?

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Cutting cool

At first it was similar to a strawberry and it got that name.

Later, the machine was called a “milling machine.”

In other countries they call it “Routeadora” or CNC Router. Or just CNC

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Types of cuts for strawberries

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Types of strawberries

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Types of strawberries

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choose a strawberry

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choose a strawberry

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What is the difference between a milling cutter and a drill bit?

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Difference between milling cutter and drill bit

Axial

Radial

Radial

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Difference between milling cutter and drill bit

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cutting speed

In milling cutters, the most common thing is to have high speed steel or HSS cutters and tungsten carbide cutters. Tungsten carbide cutters are more durable and have a cutting speed of 100m/min (meters per minute) in steel and 300m/min in aluminum.

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Cutting milling cutter

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CNC cutting milling cutter

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Collets for CNC router

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Collets for CNC router

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Drawing smooth motion

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Drawing smooth motion

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Drawing smooth motion

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POST-PROCESSING SOFTWARE

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