Sizing and Gauging: What Manufacturers Need to Know About Automating Sensitive Process Stages

In the world of rubber-to-metal bonded anti-vibration component assembly, sizing and gauging are arguably the most sensitive process stages.

If you get them wrong, the success of the rest of the manufacturing line sinks like a lead balloon. Even getting it mostly right isn’t good enough in today’s environment of strict quotas and aggressive timelines.

Your profit depends on a process that borders on perfection.

That’s why so many manufacturers turn to automation. And if you’re on the hook for successfully automating an assembly process that includes anti-vibration part sizing and gauging, this is what you need to know.

Considerations for automated sizing

Good automation providers pay close attention to sizing, an obviously essential step in anti-vibration part assembly.

The metal outer shells of a mount are always made over-size prior to mount assembly. This ensures that:

• A strong seal is formed between the rubber and metal when the part is swaged down to size
• The risk of producing an under-sized part is significantly reduced

Servo-driven hydraulic swage dies execute this critical operation. It’s important to understand that this compression of a part changes its dimensions without reducing the amount of material the part contains.

In short, something’s got to give. When a swage squeezes metal, it’s got to go somewhere.

Ideally, part designers will have accounted for the movement of metal during swaging such that a part’s dimensional changes during the process are predictable and benign. But if it’s overlooked, engineers tasked with integrating new assembly equipment should work with providers to understand and mitigate the potential risks associated with how swaging impacts the final dimensions of a part.

In any case, automation makes swaging smarter and more forgiving. The advanced programming that drives modern automation creates a key feedback loop that lets machines account for — and learn from — dimensional variation of raw materials in real time.

For that to work, you need good gauging.

Gauging with LVDT or SMAC? Let your application decide

It’s obviously crucial that sizing via swaging be accurate and reliable. Gauging is how manufacturers verify that it is.

Automated anti-vibration mount assembly systems will gauge parts using either LVDT or SMAC sensors.

Linear variable differential transformer (LVDT) sensors

LVDT sensors are made up of a tube wrapped in three coils of wire with a metal core inside the tube. Movement of the core within the tube is proportional to the movement of the instrument measuring a part’s dimensions. Magnetic fields generated according to the core’s position relative to the coils creates an electrical signal that provides positional information.

By their nature, LVDTs provide very high resolution for position feedback. In fact, it’s practically infinite.

LVDTs are pneumatically driven, so any system in which they’re incorporated must have an air supply. And while they boast essentially infinite resolution, that’s within a comparatively tight window. Accordingly, if you’re gauging a wider variety of parts with varying diameters, you may need to reposition the LVDT frequently.

LVDT gauges are best specified in systems producing at a very high rate with low or no variation in part types.

SMAC sensors

SMAC sensors take their name from a California-based provider of moving coil actuators. They work on the same premise as LVDTs and provide a similar degree of precision.

One difference is that SMAC gauges are electrically driven. If a facility or system lacks air supply infrastructure and the powers that be lack the will or budget to install it, SMAC should be specified.

Another difference is that SMAC gauges are programmable and can measure a wider range of stroke lengths, making them capable of providing position feedback for components of a wider range of diameters without repositioning. For this reason, they’re a good fit for lines producing parts with much wider dimensional variety.

LVDT vs. SMAC cost comparison

Facility or process circumstances notwithstanding, how do LVDT and SMAC sensors compare on cost?

Generally, LVDTs on their own tend to be a bit more costly than SMACs, but the higher costs associated with integrating SMAC gauges within a system evens out the bottom line impact compared to LVDTs.

Each gauging method offers outstanding precision. In our opinion, the suitability of a method to your specific process and facility conditions is a far more important determining factor than price.

The sizing/gauging feedback loop

As noted above, automation technology allows for a feedback loop between the sizing and gauging stages that further enhance the precision and quality of rubber-to-metal bonded anti-vibration part assembly.

Here’s how it works:

• Swaging is designed to bring a part from a theoretical starting diameter down to a theoretical finished diameter
• A servo valve controls the length of the stroke required to achieve this reduction; data from every cycle is recorded
• Next, gauging via either LVDT or SMAC sensors reveals the actual diameter of swaged parts; that data also is recorded
• Using the actual diameter of swaged parts, the automation program “learns” whether the specified swage stroke length is adequate or needs adjusting to account for subtle variations in the diameter of incoming parts
• If the program determines an adjustment is necessary, swage stroke length instructions are modified prior to the next cycle

This cycle-by-cycle automatic compensation leads to a much more precise and predictable process where inspection failures and waste each are greatly reduced.

Automation that meets today’s manufacturing challenges

We know that automotive manufacturers are under intense pressure to meet production quotas from OEMs. And we know how difficult that is to do profitably.

Material costs today are volatile. Transportation and logistics costs have skyrocketed. The costs to hire and maintain skilled workers also continue to balloon — no thanks to a chronic skilled labor shortage in North America that shows no signs of abating.

In practically every way you look at it, integrating a fast, efficient automated assembly system that makes real-time corrections and learns from itself makes more and more sense.

Explore your opportunities with Arnold Machine. Contact us today.