Here is a closer look at five options for choosing a CNC machining supplier:
1. Service Bureaus
Service bureaus typically have a wide choice of manufacturing technologies, with the best offering a full suite of services such as injection molding, CNC machining or 3D printing. In addition, these bureaus often provide online automated quoting, and valuable design-for-manufacturability analysis. Higher-value service bureaus will have the ability to work with you throughout the design and development process as well as the entire life of your product. Service bureaus typically have a deep knowledge of how to make the best use of their processes and materials.
Quality control: Consistency is a strong suit. They typically have better control plans, inspection reports, and processes to ensure repeatability and reliability.
Turnaround time: Should be extremely responsive, with better results from those with the ability to respond immediately to your order.
Volume: Varies, depending on capacity. A small service bureau may hold little volume advantage over an internal shop.
Production cost: Varies but may be higher than some internal shops. Service bureaus, however, know the competitive landscape and price accordingly. Prices at larger bureaus fluctuate less than at smaller ones, which tend to drop prices when they need work and raise them when they’re busy.
2. Service Brokers
A broker can help companies, especially smaller ones, that don’t have the resources to evaluate suppliers. Brokers have an incentive to find the right fit between their client and the outsourcing partner in terms of manufacturing capabilities, quality control or certifications. Find out a broker’s sweet spot and determine whether it aligns with your project. A broker specializing in automotive prototypes, for example, might not be the right choice for your ISO 13485 medical device.
Quality control: Consistency is a potential problem because subsequent orders may go to different service bureaus. You may get exactly what you want one time but not the next.
Turnaround time: Varies based on the size of the broker’s network and the capacity of the suppliers within it. Delays are inherent as the broker bids out the project.
Volume: Also depends on the size of the broker’s network. If their usual bureaus are busy, your project may go to a lesser-known supplier.
Production cost: The broker’s practice of bidding jobs out may offer some savings. But using a broker adds cost.
3. Independent Machine Shops
These suppliers typically are smaller and more specialized. Some may be good at working with challenging materials like Inconel, but may be more expensive for basic aluminum parts. Machine shops may be among the best at their core expertise but not in others.
Quality control: Ranges across suppliers and usually depends on their niche or expertise. Quality control at machine shop specializing in aerospace or ISO 13485 medical devices should be excellent and should still be good but less formalized at “garage shops.”
Turnaround time: Should be fast and competitive when they have capacity but subject to backups when busy.
Volume: Because they tend to be smaller, machine shops may have capacity constraints. If your project is in the shop’s core service, it should have greater capacity for that than for other jobs.
Production cost: Shops specializing in parts for the aerospace industry, for example, or those working with exotic materials or parts with tight tolerance typically will be more expensive because of the higher-end machines required.
4. High-Volume Production Houses
High-volume production houses, typically focused on injection molding and CNC machining, reduce piece part price when running thousands or millions of parts. Their niche is shaving seconds and pennies off of projects through high-speed repetition, especially when running “lights out” or in a factory that’s fully automated. Upfront engineering expenses may be high. These suppliers typically don’t like doing prototypes because they’re not cost effective at it.
Quality control: Typically very good. Production houses specializing in highly regulated industries typically will meet the required standard. Quality control for commodity-type parts will be at a lower but appropriate level.
Turnaround time: Typically good and predictable for high volumes. Delays may result if the supplier has to acquire equipment to produce your part, which many will do.
Volume: Large orders are their bread and butter. Will dedicate equipment to a project, such as a molding cell that would run parts for years at a time.
Production cost: The higher the volume, the better the cost because of the focus on operating efficiently. If you need just a few dozen or a couple hundred parts, however, they’re more expensive.
5. In-House Production
In-house production offers the prospect of convenience—just walk down the hall to get a part made. A desktop or industrial-grade 3D printer can make a concept model of a product or parts for form and fit testing. An in-house shop with an industrial 3D printer, CNC machine, or molding press can provide engineering-grade parts that are production representatives. That convenience comes at a cost, however, from the upfront capital investment in equipment and acquiring and storing materials to having skilled who can operate the machines effectively. And that convenience is available only when an internal shophas capacity. They regularly partner with service bureaus for quicker, simpler production parts or functional prototypes.
Quality control: Typically very good but likely sporadic in an early R&D shop and better when a part is transitioning to production.
Turnaround time: In-house shops often operate at or near capacity, leading to long lead times that force development teams to outsource to get parts made quickly.
Volume: Typically work in lower volume because of limited capacity and specialization.
Production cost: Larger OEMs often have a friendly cost structure that doesn’t apply costs to individual projects. OEMs and in-house shops can be more expensive when manufacturing parts outside their forte.
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