Tuesday, June 29, 2010

Ultrasonic Welding Effects on Hearing

In air, sound is usually described as variations of pressure above and below atmospheric pressure. These fluctuations, commonly called sound pressure, develop when a vibrating surface forms areas of high and low pressure, which transmit from the source as sound.

Although noise-induced hearing loss is one of the most common occupational illnesses, it is often ignored because there are no visible side effects, it usually develops over a long period of time, and, except in very rare cases, there is no pain. In its early stages (when hearing loss is above 2,000 Hertz (Hz)) it affects the ability to understand or discriminate speech. As it progresses to the lower frequencies, it begins to affect the ability to hear sounds in general.

The upper frequency of audibility of the human ear is approximately 15-20
kilo-Hertz (kHz).
  • This is not a set limit and some individuals may have higher or lower
    (usually lower) limits.

  • The frequency limit normally declines with age.

Most ultrasonic welders have a fundamental operating frequency of 20 kHz. However, a good deal of noise may be present at 10 kHz, the first sub-harmonic frequency of the 20 kHz operating frequency, and is therefore audible to most persons. Ultrasonic welding uses intermittent energy. Only the noise generated during the few seconds of each cycle when the equipment is energized causes exposure to noise. The individual energy cycles are accumulated to equal the duration of exposure. Most of the audible noise associated with ultrasonic sources, such as ultrasonic welders or ultrasonic cleaners, consists of sub-harmonics of the machine's major ultrasonic frequencies.

In extreme cases, this can be disturbing, causing hearing discomfort, occasionally nausea, and sometimes a temporary shift in the threshold of hearing (sound pressure level, or loudness, that can be heard).

Many countries control the amount of audible noise that a worker can receive. In the United States 90 dBA noise level can be maintained continuously for 8 hours. Higher noise levels are permissible for shorter periods of time, typically:

If there is a line operator or other employees in close proximity to an ultrasonic welding system experiencing discomfort, then hearing protection is recommended. Sound enclosures are also available in most cases that would minimize any discomfort to workers near the welding system. For additional information, please read our White Paper titled “Effects of Ultrasonics on Health”.

Myths and Tricks to Successful Thermal Heat Staking

It is a known fact that applying a specific amount of heat to plastic resin using a heated tool will change the characteristics and shape of it, but did you also know that fine tuning the temperature and dwell time it takes to heat that resin can lead to stronger and more cosmetically appealing welded parts?

There are several myths regarding thermal heat staking and tricks to establishing quicker, stronger, and more cosmetically appealing thermal heat welded parts. Here are a few examples:
Myth 1: Post cooling a thermal tip is required on all resins to reduce or eliminate stringing and over welding of a stake or swage.
The Truth: Post cooling only needs to be introduced in a heat welding process when resins, such as Acrylic, are used that require quick cooling.
The Trick: Fine-tune the temperature below the actual resin processing temperature by making very slight changes of 10°F at a time. Each time a temperature change is made, wait 15 to 20 minutes for the changes to take effect in the heated tip. The dwell or (weld time) will need to be adjusted as well to prevent the resin from stringing or burning.

The use of a dual pressure thermal heat staking machine can also eliminate the need for post cool. This feature allows the post to be heated at a lower temperature with a small amount of pressure for a programmed time. After a small amount of time, a greater amount of pressure is applied during the dwell time, collapsing the resin with minimal amount of heat and no post cooling.

Myth 2: Large percentage glass filled or chrome plated studs lack strength and cosmetic appeal after heat staking.
The Truth: Even resins with fillers and coatings can look esthetically pleasing.
The Trick: Use a Pre-Heat to slowly heat up a stud that is to be staked. The resin starts to melt where the glass or chrome plating will not. After the Pre-Heat times out, an appropriate amount of dwell or (weld time) will fully collapse the stud with the correct amount of force applied. This will melt the remaining resin while the glass or chrome plating act as a shell to hold the resin together without melting.

Jerry Downing
Sr. Project Engineer
Dukane Corp. IAS

Wednesday, June 16, 2010

Tony and Paul pull an all-nighter

While it may not be obvious from the picture, this photo was taken at 3:30AM on a Saturday morning. It was a long day that started at 8:30 AM on Friday and would not end until about 8:30 AM on Saturday. This effort was the culmination of what had already been a week of long days which included working through a holiday weekend. However, our customer needed to have their vibration welding machine completed and on a truck by that Saturday afternoon, and Tony and Paul were among a group of individuals who personally lived our Division’s goal of delivering superior customer service and value.

This commitment not only comes from our factory team, it also occurs regularly in our sales team. In the same week that Tony and Paul pulled this all-nighter, two of our sales engineers, Ray and Keith, drove a large vibration welding tool down to a customer to get it installed and running before the next morning, when our customer had to be able to show his end-customer that the tool was in place and ready for production. Ray and Keith left our factory at about 5 PM, drove 5 hours, and then helped install and qualify the vibration welding tool. We got a text message from them at 3:45 AM informing us that the tool was in, and qualified.

While these examples are the exception, the fact that they happen says a lot about the passion and commitment Dukane has when it comes to providing superior customer service. In both cases, it would have been easy to say, “It’s late, let’s finish this tomorrow”, but in both cases that would have meant that the customer would not have been able to meet their commitments. So, Tony, Paul, Ray and Keith went the extra mile to meet the requirements of our customers. Sometimes that means an all-nighter, but is indicative of the heart and soul of our company.

Tuesday, June 1, 2010

Thermal Heat vs Ultrasonics

Thermal heat can provide solutions to many staking, swaging, inserting, and de-gating applications that ultrasonics cannot.

Thermal heat should be considered when working with inserts or stakes that are of various diameters, and/or located on multiple planes and must be processed in a single cycle.

Thermal heat is primarily used when limitations with ultrasonic horns (size, multiple planes, and consistency) are a factor. Other considerations include cosmetic appearance of completed swages or stakes, as well as higher tolerance for glass content and chrome plated parts.

Using thermal heat staking, swaging, and inserting processes can also eliminate particulate that is detrimental to applications such as medical, fluid filters and consumable packaging.

For many customers, the reduction in noise level from ultrasonic inserting or staking of glass filled parts is a significant advantage to switching to a thermal process.

The use of thermal heat also eliminates any vibration concerns that are associated with staking PCB’s to other components. Heat is applied directly to stakes quickly enough that components surrounding the staking post are not damaged.

Overall, when considering heat vs. ultrasonics, review all of the requirements for your application as you may find thermal heat to be the best process.

Jerry Downing
Sr. Project Engineer
Dukane Corporation IAS Division