Offshoring turned part manufacturing may save a few hours and operating costs while opening up access to new equipment and capabilities not available in-house. But selecting the wrong supplier can create its own challenges. Lead times, variability in part size, expensive rework, and scrap come to mind. Before discussing a rapid supply chain for machined components, an engineer needs to understand the component's requirements in the first place. This means digging a little deeper than the part drawing and discovering how that component needs to perform in the field. How much fatigue will it need to tolerate? Will it be exposed to vibrations, heat, or even movement? Those little things can make a big difference in the manufacturing process. A reliable
CNC turned parts manufacturer can listen to those details and explain how the product will be produced to meet the application's requirements. And if the only thing the supplier talks about is price, then they are still missing the bigger picture.
Evaluating Manufacturing Capabilities and Available Equipment
Some, but not all, machine shops can make every type of precision part. Some make simple turned parts; some make complex geometry, tight tolerances, and multi-pass, multi-machine turned parts. As a designer or engineer, see what equipment the shops have to offer: CNC lathes, multi-axis turning centers, automatic bar feed systems, machining system support equipment. Machine tool capacity has a lot to do with repeatability, speed, and the ability to produce a lot of components for a given supplier. Does it accommodate the diameter, length, material, and features required? Can secondary operations, such as drilling, threading, and milling, be performed in-house, or will this be sent out to another shop? Just because one shop says they can do a project does not mean they can do it in-house, without subcontracting. Find this out beforehand.
Verifying Dimensional Accuracy and QC Processes
Precision manufacturing doesn't leave any margin for error. It is tempting to think that if a component appears fine during a quick visual check and then gets rejected when it's sent to the assembly line, the problem is with the end product. But an engineer should pay attention to the supplier's quality systems and know how parts are measured for dimensional precision and variation during production. Inquire about inspection equipment such as coordinate measuring machines, bore gauges, micrometers, optical comparators, and other precision measurement and quality-checking systems. But more interesting is when the inspection takes place. Large-volume production runs of minute parts require first-piece inspection, in-process measurement, and final quality assurance checks to avoid quality issues for the entire batch. Inspection reports, material certificates, and other documentation matter as well. An articulate, confident supplier who understands what happens during the manufacturing process is better equipped to produce quality parts.Material Knowledge and Its Effect on Production
Material choice can have a greater impact on manufacturing than some buyers initially realize. Now, the buyer knows the material and spec, but that was not always the case when the component design was being developed. Understanding the machinability of stainless, aluminum, brass, carbon steel, and specialty alloys is quite important. Materials have varying amounts of cutting temperature and either create little or excessive tool wear or finishing and machining performance issues. The engineering professional should look to see if the supplier has readily available experience working with the material being used on the part, particularly if the part has ultimate strength, corrosion, temperature, or wear considerations. The machinist should be aware of how different materials react to certain cutting speeds, feeds, tooling, and final size tolerances, so that potential machining challenges can be identified before production starts. For example, some materials deform during machining when under pressure. Not major problems when assembled tightly and accurately, but not always desirable.Reviewing Industry Experience and Technical Expertise
Experience helps, but not necessarily in every field. What you really want is someone who has machining experience in parts with similar complexities, same tight tolerances, similar materials, and similar quantities. Take a company experienced in machining shafts as an example; it probably won't be the right company for every miniature threaded part or complex turn part that you require. When interviewing a Wilsonville CNC turned parts manufacturer, or any other local machining partner, ask to see some examples of comparable parts and what difficulties they faced in machining them. Good suppliers should be able to explain how they overcame difficult machining requirements, maintained tight tolerances, and kept costs down. Technical communication skills are also important. Can their engineers review drawings and point out problems in the design? Do they ask questions about tolerances and functional criteria? Those sorts of interactions can be very telling. Look for a supplier that verifies that a part is possible to machine before accepting the job.Production Capacity, Lead Times, and Scalability
The supplier may make great prototypes and be ill-equipped to go into production. A common mistake: production issues can mess up an entire schedule. While outsourcing, engineers should find out if the supplier has sufficient capacity, machines, staffing, and flexibility. Ask how long it takes to develop prototypes and whether production can be done on the same setup. Will the process hold several hundred or thousand parts? Is there any repeat work – such as from a monthly need or post new product release? Is there enough capacity to keep to schedule? Lead times comprise more than turning time, as materials have to be ordered, programming time allowed for, setup established, inspection carried out, parts finished, and packing done. Beware, the supplier willing to give a short lead-time is perhaps prepared to cut down on one or more aspects of work. The trick is to give realistic promises based on a clear production plan rather than promising short lead times but no confidence the process will deliver.Understanding Pricing, Communication, and Project Management
Cost is obviously part of your decision, but the lowest quote is rarely the most informative. Consider the actual contents of each quote. Is this a bidding process with no detailed specifications, or has each supplier measured and priced the exact amount of material, secondary machining, inspection, finishing, packaging, and other services? Will the low-cost solution one day cost more as new specifications are added? So much for price. Engineering considerations need to be taken into account as well. Whether it's getting a drawing revised or getting an answer about the hold time of a certain batch of metal, communication is just as important as price. Do you know who will be keeping you informed throughout the process, and who will be watching out for your best interests? Is there a defined process for dealing with engineering changes, unplanned material shortages, and manufacturing defects? When things go wrong, everyone notices. The question is who is watching you when the first problem strikes.Assessment of Compliance, Traceability and Long-Term Trustworthiness
Depending on your industry, you may require your outsourced part to meet certain quality requirements, documentation, or your own regulatory standards. Manufacturers of aerospace, automotive, medical equipment, and industrial machinery may demand a more rigorous qualification process from their suppliers. When working with engineers, ask if the supplier has certifications or documented inspection procedures, material traceability, and records of production. However, certifications do not automatically translate to quality; the supplier's quality system needs to actually work on the shop floor. Inquire how they handle nonconforming components, including identification and separation, investigation, and correction. Intellectual property protection is another important factor, as detailed drawings, product specifications, and design files may contain sensitive commercial information; confidentiality agreements and limited access to files are worth discussion. While they were good on one order, will they deliver quality on many? In the case of
screw nut & bolt manufacturing, threading, fit, strength, and dimensional accuracy must carry through to subsequent production runs.
Conclusion: Choosing a Supplier That Supports the Entire Project
Outsourcing precision component manufacturing has to be an engineering decision and not just a purchasing decision. Consider the machine equipment, dimensional tolerances, material knowledge, production capacity, quality systems, and communication flow when you are looking at a finished product. An engineer needs to understand how a supplier operates, not just the information provided on a website or the feel of the pricing proposal. Ask for sample components, inspect inspection reports, discuss technical issues, and be certain that you are aligned on expectations before you're in the process of larger volume production. The ideal manufacturer will be there from the first round of design changes through repeat production. And if they're able to get ahead of a problem, that can be a bonus. That's the type of working relationship that's worth establishing. More analysis in the beginning can save a lot of headaches during production.
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