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Month: August 2024

GD&T Tip: Turning Plus/Minus To Profile Tolerance

Posted on by Ido Turg

In the realm of precision machining, even minor ambiguities in design can lead to significant quality and functionality risks. This GD&T tip demonstrates how a seemingly straightforward plus/minus tolerancing scheme can mask potential problems, and how a well-implemented profile tolerance, aligned with ISO GPS and ASME GD&T standards, safeguards both product function and manufacturing efficiency.

Original drawing

While quoting the following part, we found that the customer drawing is ambiguous and parts produced to specification may not meet the customer’s design intent. Original drawing is seen in figure 1.

Original drawing showing the part with plus/minus tolerance

Possible interpretation

Since the drawing is a Plus\Minus drawing:

  • It is impossible to tell the primary features of the part (what feature dictates the primary directions)
  • The conic surface is indirectly toleranced, which may yield to a situation where parts that pass geometric verification may not be functional.

Figure 2 shows a possible interpretation of variation limits. A part that will be within these boundaries will pass geometric inspection, and be at functional risk. the conic taper appears to be a critical feature

Drawing showing the possible interpretation of the original drawing
Figure 2

Functional constraints

A request for clarification from the customer brought up the functional constraints documented in Figure 3:

  • The part lies tangent to an opposite planar surface (marked in purple)
  • The part is centered by the outer cylindrical diameter 9 (the axis line of the orange surface)
  • Original drawing no direct specification to the conic surface (the area marked in red in Figure 3 between marker A and marker B), the conic and flat are critical features of the part
  • The red area should not exceed a symmetrical offset of 0.015mm (In the original drawing, this area could reach the limits of 0.057 – 0.071).
Drawing showing the functional constraints
Figure 3

Correct GD&T implementation using profile tolerance

Considering this, Machinx’s recommendation (Figure 4) was to update the drawing,

  • Specify purple and orange surfaces as datum features.
  • Add direct specification to the critical surface (red) with a profile (instead of plus minus).

(Profile directly specifies a zone that limits size, position, position, and shape variation of the critical features (marked by the red zone in figure 4, and is simpler to control)

Drawing showing the correct GD&T implementation
Figure 4

A better way to communicate technical feedback

Machinix’s digital platform streamlines the quoting and ordering process of precision machining parts. Using its technical feedback feature it facilitates clear communication between engineers and Machinix technical solutions team. It ensures that any technical issues, including correct implementation of GD&T, are promptly addressed and resolved before production begins. This proactive approach minimizes risks and guarantees a smooth manufacturing experience.

Screenshot showing Mahcinix digital technical feedback feature

Conclusion

GD&T serves as a critical communication tool in the world of precision parts, seamlessly transferring design intent from the engineer’s mind to the production floor and quality control. By clearly defining tolerances and features, GD&T significantly reduces the risk of quality issues and ensures the part’s functionality.

If you’re looking for expert guidance on implementing GD&T into your precision manufacturing processes – create a quote request and upload your drawings today. Our technical solutions engineers will review and give you valuable feedback within 48 hrs.

The following tip was written in cooperation with TES-TECH. Our technical solution engineers are constantly learning and enriching their knowledge, one way to do that is by attending TES-TEC GD&T technical courses and learn more from Gili Omri and the team.

Aluminum low thermal expansion super-alloys for precision machined parts

Posted on by Onix Admin

Slavik Marinovski, Machinix technical solution engineer, talks with Roger Senden from RSP Technology about the aluminum super-alloys they produce and its uses in precision equipment manufacturing, including:

  • How it’s made
  • Their usage in the semiconductor and other precision equipment industries
  • Slavik’s experience machining it
  • Tool wear and cost effects

Q&A

When does low thermal expansion material needed?

Thermal expansion is the tendency of matter to increase in length, or volume, changing its size and density in response to an increase or decrease in temperature.

Low thermal expansion alloys are essential in applications requiring high dimensional stability across temperature changes, in order to achieve a part or a system’s stability, reduce potential stress or damage, so that temperature fluctuations are of little concern to consistent performance.

Thermal expansion and stiffness compare tables between RS Alloys and conventional alloys like AL6061 and Stainless steel 403

What is RSP technology?

RSP Technology produces and develops aluminum superalloys.

The company specializes in producing and developing aluminum superalloys using an ultra-rapid cooling technology that solidifies liquid metal at over 1,000,000ºC per second. This process creates super-strong alloys with a fine, homogeneous microstructure. Their melt-spinning method results in unique materials ideal for high-end applications in aerospace, optics, precision equipment, racing, electronics, medical, and automotive industries. The Rapid Solidification Process (RSP) allows for extensive alloying possibilities and efficient production cycles.

Melt spinning - a process used by RSP Technology to produce aluminum superalloy

RSA443 Vs. AL 6061 Vs SS 304

Mechanical properties compare table between RSA 443 AL6061 AL7075 and SS403

Which industries can benefit from using RSP Alloys?

In the below specified industries, several systems require low thermal expansion alloys to maintain high performance and reliability:

  1. Semiconductor industry: In semiconductor metrology, components like baseplates, frames, stages, optical mounts, and probe arms benefit from low CTE, high stiffness, and low weight materials, which ensure stability, precision, and minimal thermal drift. they can benefit from reduced vibrations and support fast, precise positioning in critical measurement tools. These properties are essential for minimizing errors caused by thermal expansion, and ensuring consistent performance across varying conditions.
  2. Medical Devices: MRI machines, CT scanners, and high-precision surgical tools. These systems depend on low thermal expansion materials to prevent deformation and maintain accuracy across temperature variations.
  3. Aerospace: Satellite components, mirrors, and support structures for telescopes.
  4. Precision Instruments: Telescope mounts, precision measurement equipment, and high-accuracy scales.
  5. Fine Motion Systems: These systems, such as those used in robotics and automated manufacturing, require materials that maintain their dimensions under varying temperatures to ensure accurate movement and positioning.
  6. Lasers: Optical components in laser systems, like mirrors and lenses, need to retain their precise shapes to maintain beam quality and focus. Any thermal expansion could lead to misalignment and degraded performance, affecting tasks like cutting, engraving, or communication.

What are the Is there any limitation on material shape availability?

  • RSP alloys can be produced in the following standard dimensions:
  • Bars: diameters 18, 22, 26, 35, 45, 60, 65, 85, 105 mm
  • Billets: diameters 165, 200, 290, 360, 420, 500, 600, 800, 1.000 mm
  • Custom made (near net) forgings and rectangular blocks
  • Any other size can be custom made in round, rectangular or any other shape up to approximately 1000mm (39.37”)

What are the different alloys produced by RSP?

These are some of the alloys produced by RSP, their characteristics and use cases:

  1. RSA-443 (Al Si40): This alloy offers high dynamic and thermal stability (high conductivity, low expansion), and high damping. Its fine microstructure makes it ideal for precision equipment and diamond-machined/polished mirrors.
  2. RSA-461 and RSA-611: These alloys possess high-temperature strength, making them suitable for piston applications. Their low thermal expansion allows for tighter piston-cylinder fits, resulting in a CO2 emission reduction of at least 20%. Additionally, the increased combustion temperature possible in high-performance diesel engines further saves energy and reduces CO2 emissions.
  3. RSA-905: This alloy boasts particularly high strength and stiffness (about twice that of aluminum alloy 6061). It’s useful for structural components in machine building, medical equipment (as a titanium replacement), measuring equipment, hydraulic systems, and more.

When is stress release recommended?

It is recommended to apply stress release after rough machining, when the machined part requires tight tolerances in the range of 0.01-0.03mm, and when there is substantial material removal from the raw material.

for example RSA-443 alloy can be artificially aged using the following process:

  1. Rough machine to within 0.2-0.5mm of final dimensions.
  2. Put the part in a cooled furnace, at room temperature (20 – 25 ºC).
  3. Heat the part gradually to 380±5 ºC, at a rate of 100ºC per hour.
  4. Keep the part at a stabilized temperature of 380±5 ºC, for 2 hours.
  5. Cool the part to room temperature (20 – 25 ºC) slowly, in a closed furnace.

Following this process, a final finish machining can be performed.