Posted May 6, 2021

Choosing Custom Milling Services for Parts and Projects

A CNC milling machine cutting a metal part

To precisely build custom components, product engineers rely on machine shops with advanced computer numerical controlled (CNC) milling and turning services. In a 2013 survey of its readers, Machine Design reported that 85% of engineers relied on custom-built parts. These components range from small specialty washers to structural parts and machined subassemblies. CNC mills form many of the more geometrically complex components used in multiple industries. Here’s a closer look at custom milling services for parts and how engineers should carefully consider the machine shops that they partner with for the best results.

CNC Milling; What it is, and How it Differs from Other Machining Processes

Today’s manufacturers produce parts in many ways, including 3D printing, injection molding, and CNC machining, among others. While the first two are additive processes, CNC machining, which includes turning and milling, is considered a subtractive process. Subtractive manufacturing processes use computerized controls and tools to remove material sequentially from a raw block. Material options can range anywhere from plastic to hardened steel.

The CNC manufacturing process begins with the customer’s data in a CAD model of a prospective part. Machine shops use CAM software to help determine the toolpaths that will manufacture the part. G-code governs toolpathing, a set of instructions for the mill based on tool selection. This G-code data is what drives the CNC lathes and mills during the fabrication of the part.

CNC lathes turn the workpiece on a spindle at high speed, while cutting tools are used to remove material in layers. Lathes can also remove material from the center of the workpiece using a drill. Using CNC lathes for turning parts provides a more cost-effective option than milling, but it can only produce cylindrical parts. For more complex cylindrical components, a machine shop will use a CNC lathe with live tooling. Live tooling involves a milling attachment, which will cut a path in the workpiece once the lathe’s spindle stops rotating.

CNC mills use a cutting tool similar to a drill bit which spins at high speeds to cut paths in the workpiece. This workpiece can range in size and shape up to the limitations of the machine and holds firmly in place by the mill's “workholding.” Ideally, a machine shop will support continuous 5-axis, 5-axis-indexed, and 3-axis machining on mills, accommodating approach vectors for complex geometry from most angles. If a job requires additional angles, a machinist will re-position the workpiece manually. 

A CNC mill can automatically form the complex contours and shapes needed for custom parts. Those parts, used across numerous industries, have many different applications.

From Prototyping to Production: Custom Milling Services for Parts in Every Industry

CNC milling suits the manufacturing of complex custom parts due to the following capabilities:

  • Minimal setup: Machinists can set up CNC mills very quickly to produce a new part. Once a customer places an order and an engineer programs the G-code, the shop can quickly load the material, workholding, and necessary tools into a CNC mill.
  • Fast processing: Mills can quickly fabricate individual parts. Depending on the part’s complexity or production volume, machine shops can often turn an order around in as little as three days.
  • Precision fabrication: CNC mills can reproduce exact measurements in the parts they fabricate, with standard tolerances as tight as +/- 0.08mm.
  • High-quality manufacturing: The milling process will produce the same level of quality in prototype parts that it does in regular production runs. This repeatability means that full-scale production parts match the quality of a prototype exactly.

The capabilities listed above, along with the different materials available for fabrication, make CNC milling the ideal choice for manufacturing custom parts for these industries:

  • Food processing: Processing gears, mixers, conveyor components, and support structures
  • Automotive: Engine blocks, transmission cases, engine parts such as flywheels, and dashboards
  • Energy: Wind turbine blades, control valves, hydroelectric impellers, and gearbox housings
  • Aerospace: Landing gear components, seat frames, hydraulic manifolds, and control panels

The above is only a handful of the industries and applications that utilize CNC milling, but the list goes on ad-infinitum. The next step involves finding the right machine shop to produce a particular product efficiently.

What to Look for in a Machine Shop for Custom Milling Services

When looking for a machine shop, it is essential to ensure that the shop has the equipment, processes, and certifications to produce a particular part. After that, focus on primary business details such as their years of service, facilities, and price. The shop’s location might also be an essential consideration, as overseas facilities may pose communication difficulties and take longer to deliver the finished product.

Next, you will want to start looking into the finer details of their milling capabilities, including the following:

  • Do they have experience with your industry to mill your parts?
  • What is their commitment to quality, and are they ISO 9001 certified?
  • Do they have a good supply chain set up with their materials vendors? What materials do they keep in stock?
  • What type of CNC milling equipment do they use, and is it sufficient to build your parts?
  • Do they have the capacity to produce both prototypes and production parts depending on your needs?
  • How long does it generally take them to program G-code or toolpaths for your part?

Another vital part of choosing the right machine shop for custom CNC milling services includes the initial quoting process. Using a shop with an online ordering system can expedite a production schedule instead of waiting for the more traditional engineering analysis and paper quote. Online quoting tools will first analyze an uploaded CAD model for manufacturability and instantly advise on any problems before presenting the quote. Once a customer specifies the quantities and materials for an order, the machine shop will immediately begin queuing up the project for manufacturing.

At Plethora, we can offer assistance and advice with custom milling services for your parts and projects. We are a certified ISO 9001 machine shop with state-of-the-art equipment and proprietary software tools and systems. Our online part analysis and the quoting system will get your project started immediately, and our staff will collaborate with you through the entire production process. Call us at 415-726-2256 for more information or, to get started today, upload your design files through Quote My Part.

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Topics: materials, processes, Manufacturing, finishing, CNC machining, Quality, Prototyping, threading, Custom Milling