The concepts of component interchangeability and dimensional tolerancing have since become an accepted part of manufacturing. Unfortunately, the misapplication of the latter can cause a host of problems. For instance, an overly stringent tolerance might require that parts go to a secondary grinding or EDM operation for completion, unnecessarily increasing costs and lead-time. Tolerances that are too loose or that arent in line with those of mating parts can make assembly impossible, leading to required rework, or in the worst case, making the finished product unusable.
To help avoid these unpleasant situations, this design tip includes some guidelines on how to properly apply part tolerances at Protolabs, along with a few definitions of the more commonly used callouts. Well also explore the industry standard for part tolerancing known as Geometric Dimensioning and Tolerancing (GD&T), a system defined under the American Society of Mechanical Engineers (ASME) Y14.5 specification.
The standard prototype and production machining tolerance at Protolabs is +/- 0.005 in. (0.13mm). This means any part features location, width, length, thickness, or diameter will not deviate by more than this amount from nominal. For example, the 1 in. (25.4mm)-wide bracket you're planning to order will measure between 0.995 and 1.005 in. (25.273 and 25.527mm) across, while the 0.25 in. (6.35mm) hole on one leg of that bracket will come in at 0.245 to 0.255 in. (6.223 to 6.477mm) diameter.
Thats pretty close, but if you need greater accuracy, there's our standard precision or production machining tolerance of +/-0.002 in. (0.051 mm). We're also able to hold +/- 0. in. (0.mm) on reamed holes, and +/- 0.002 (0.051mm) on feature locations, provided those features are machined on the same side of the part. Depending on the part geometry and material, however, we can often achieve even greater accuracy, provided you make us aware of your requirements. For these and other exceptions, please be sure to note them on your part design when you upload the file(s) for quoting.
Also, be aware that these are bilateral tolerances. If expressed in unilateral terms, the standard tolerance would read +0.000/- 0.010 in. (or +0.010/- 0.000 in.) while a limit-based tolerance in our bracket example would be 1.005 / 0.995 in.
All are acceptable, as are metric values, provided that you spell them out on the design. And to avoid confusion, please stick with the "three place" dimensions and tolerances shown, avoiding the extra zero in 1. or 0. in. unless theres an overriding reason to do so.
Theres more to part tolerancing than length, width, hole size, etc. Theres also surface roughness, which in the standard offering is equal to 63 µ in. for flat and perpendicular surfaces, and for curved surfaces, 125 µ in. or better.
With competitive price and timely delivery, JCZ sincerely hope to be your supplier and partner.
This is an adequate finish for most uses, but for cosmetic surfaces on metal parts, were generally able to improve appearance through light bead blasting. Check out our CNC Surface Finish Guide for examples, and if you're in need of something smoother, note it on your design and we'll do our best to accommodate you.
Heres another consideration. As mentioned earlier, we can accept GD&T tolerancing. This provides a deeper level of quality control that includes relationships between various part features as well as form and fit qualifiers. Below are a few of the more common ones:
There are additional considerations to GD&T, including parallelism, straightness, profile, and angularity, all of which are spelled out in ASME Y14.5. As with any other non-standard tolerances, however, they must be called out on the design at the time of upload. Tolerancing with GD&T also means that projects will bypass our automated Protolabs quoting process and be rerouted to our myRapid quoting experience for our CNC machining high-precision/high-quantity option.
So, what is the difference between our machining options? For starters, a quote for high-precision/high-quantity machining is not automated as it is with our automated machining option, so the quote might take a day for human review. With high-precision machining, the finished part lead-time is also a little longer, with seven to 10 days as standard. We require a 3D CAD model, along with a 2D drawing for GD&T tolerances. It could also mean that we go beyond our standard cutting tool set and use machining processes such as wire EDM, EDM hole popping, grinding, and boring to meet your part quality requirements.
Another option that should be mentioned in this context is quality control and documentation. Upon request, well measure parts on one of our CMMs (coordinate measuring machine) and other metrology equipment. We will also work with you on the Production Part Approval Process (PPAP), provide a Certificate of Conformance (CoC) to your specifications, and provide First Article Inspections (FAIs), material certifications, and heat lot numbers.
Ultimately, were here to support your project from prototyping to production, whatever the tolerance requirements. This is because we offer both a fully automated machining option for fast turnaround or a high-precision option with extended milling and post-machining capabilities for the highest complexity parts. We have all of your CNC milling and turning needs covered. Just give us a call or send an if you want to know more. We always have applications engineers available to assist with any questions at [ protected] or 877-479-. Ready to start your next project? Just upload a CAD file to our website.
For more information, please visit Custom Component fine-tuning laser manufacturer.