Manufacturing Professional. Prototype Machinist. CNC Programmer. Adjunct Professor. Familiar working with ISO 9001:2015 QMS, AS9100, MIL-SPEC, and ITAR Compliance and Regulations for Manufacturing Environments.
I'm the type of machinist that combs an 11X17" print and clarifies all critical dimensions. I definitely give a nominal or target and include my high and low if I feel it's necessary or can vary quickly with tool wear or thermal conditions. Limit/Unilateral/Bilateral tolerancing can be enough to miss something important let alone interpreting our GD&T characteristics properly and then sprinkling in some MMC or LMC etc. I personally want a specific dimension for a feature whether I'm prototyping, small production, or production. This may take some time on the front end with questions of my engineers, quality, or fellow machinists, but it saves me on the back end when my parts pass inspection without issue.
Acclaim Aerospace ⚙️ Swiss Lathe Ultra Precision Machining ✈️ Aviation 🚀 Space🗽Defense 🔫 Pew Pews 🚑 Medical 📲 Electronics 🤓 Chief Engineer & Machinerer 🏫 STEM Ed Advocate 🐝 GA Tech Yellow Jacket
Quality Inspection requirements planning is just as important as programming and machining - and it really needs to happen FIRST⚙️✅ Why? Because not all customer blueprints are designed as a nominal with + / - tolerances ... such as this sensor housing shell we are #swissmachining here at Acclaim Aerospace in Georgia from 316 Stainless. Many blueprints will have features with a "max" tolerance (ex: .005" max edge break) or especially a diametrical feature like a hole or bore with a +xxx / - 0.000 or opposite to control the assembly fit consistency. If you just send these blueprints as-is to the shop floor with a program... a machinist in a hurry might accidentally make the parts with + / - tolerancence thinking they are good parts. I've made this mistake myself before and it's easier to do than you think, especially in today's "multi-tasking" and thinly staffed world. Additionally some things are toleranced nominal and the usual +/- but it may be more practical to "shoot for the lower end" or similar due to tooling wear, especially if it is a tight range. Meaning if you set up and target the nominal and hit that, as the tools "settle in" or when a little wear occurs, now all of a sudden you are on the razors age of the limit and the normal statistics of variability will probably start throwing out bad parts. When Quality Planning is done up front, especially by a team discussion to get input from shop floor (not just #engineering or in QA) then these risks can be identified and incorporated into CNC programming and instructions (even in the program and setup sheets with comments), visual guides (like a red-lined or marked up inspection blueprint). Especially here with our #swisslathe parts, where we are often dealing with super tight tolerances to begin with... we have to analyze and determine "machining targets" vs "blueprint" for a solid 50%+ customer designs. This avoids accidentally machining parts on the razors edge of tolerance and reduces the need to overinspect parts too... because armed with Process Capability / CpK statistics we know with high confidence our machined parts dimensions will fall tightly well within the blueprint range even with tool wear or thermal changes. How do you perform "Quality Planning"? Do you send Blueprints "as-is" to the shop floor? Do you incorporate notes in a QA inspection plan and/ marked up internal blueprint? Do you include these special instructions on a setup or work instruction guide or perhaps incorporate into the CNC program itself? #manufacturing #aerospace #quality
