Adhesive Bonding

Adhesive Bonding Versus Welding

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When you consider adhesive bonding versus welding for securing your parts, strict specifications must be met while controlling the total cost. Switching over to a new joining process requires addressing many issues, including safety concerns, excessive down time, structural integrity, and structural degradation, as well as your overall manufacturing process.

Adhesive is the new kid on the block for many metal fabricators. The older adhesives weren’t ideal for bonding metal to metal, but newer adhesive types have proven their worth as a viable adhesive bonding option.

Here’s a comparison of the advantages of traditional welding to adhesive bonding’s newest technology:

Welding Advantages

  • No curing time needed in production process
  • Instantaneous procedure
  • Strong bond even at high temperatures
  • Flexibility with attachment location, including large objects with small welding areas
  • No shelf life or monitoring of storage time necessary

Adhesive Advantages

  • May reduce stress concentration points
  • No distorting or discoloring of thin metals
  • Won’t destroy galvanized coatings or cause corrosion
  • Gives a one-step seal and bond process
  • Joins dissimilar materials
  • Minor joint design changes to accommodate surface contact
  • Assembly of different masses and dimensions
  • Joins irregular shaped surfaces with minimal alteration to part dimensions
  • Gives increased fatigue strength by distributing stress across bonded area
  • Improved finished appearance
  • Training of workforce is less costly
  • Ideal for high-volume applications
  • Little or no post-process cleanup

Making the change from welding to adhesive bonding requires a comprehensive view of your bonding needs. Consider how your overall manufacturing time can be reduced with adhesive bonding by analyzing your processes.

Can you switch over to adhesive bonding with only procedural and part-flow changes? Will a change in joint geometry design pay off? If a change in your joining process improves efficiency and quality, and reduces overall manufacturing time, it’s worth the effort to switch from welding to adhesive bonding.

Your goal of cost savings and production efficiency requires choosing the most effective material for your adhesive bonding needs. Consult with your special processes provider for help with the right adhesive technology. PTI Industries offers high-tech adhesive bonding as part of a one-stop experience for all your special processes.

Surface Preparation for Adhesive Bonding

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adhesive-bonding-homeWhen making a quality adhesive bond, the first critical step is selecting the proper adhesive. Once the adhesive type is determined, the second important step is surface preparation.

Adhesive bonds are made to adhere other components to substrate surfaces, but because most surfaces are covered with contaminants, if not removed, bond failure will often result. Even microscopic surface contaminants can obstruct the surface, creating weak boundary layers which drastically reduce adhesion effectiveness.

A typical substrate surface exhibits contaminants in several layers:

  1. Dust, parent material and other loose particles make up the outermost layer.
  2. Oils and grease comprise the next layer.
  3. Oxide films, rust, molds, and additives such as paint and sealants are potential boundaries embedded into the substrate as the innermost layer.

With proper surface preparation, bond failure can be avoided. Pre-Bond treatments vary depending on the type of substrate material as well as the structural bond required.

Depending on the substrate material, surface preparation can include three steps:

  1. Degreasing: Degreasing with a solvent or aqueous detergent removes the outer layer of contaminants such as dust, metal chips, grease and machine coolant. To check for sufficient cleanliness, a water break test is performed, water is sprayed onto the part, if it runs off in a continuous sheet it’s clean, if it beads up like a freshly waxed car it means the surface isn’t clean enough.
  1. Abrading: Abrading eliminates the layer of films, oxides, rust, and paint clinging to the surface. All loose particles from abrading must be removed with degreasing and cleaning.
  1. Surface alteration: Certain materials present the greatest challenge in adhesive bonding, such as rubber, some plastics, and metals such as copper, stainless steel, and aluminum. Changing the surface property of these materials increases the surface energy for best adhesion. PTI uses media blast cabinets as the preferred method of abrasive blasting because it cleans surfaces better and faster than the traditional techniques of sanding and wire brushing.

All surface preparation methods must include a final cleaning and drying before adhesive bonding occurs, this is customarily done by hand wiping with a high purity solvent, the bonding must be done as soon as possible so surfaces do not become recontaminated.

For every material and surface there is a right combination of adhesive material and surface preparation.  We employ our many years of experience to Identifying the best combination that will be the best for your substrate application.

PTI’s special processes includes advanced precision cleaning technology and a dedicated 38,500 SF adhesive bonding facility that maintains two Contamination Controlled Areas for all your one-stop process needs.

Inside PTI’s Adhesive Bonding Department

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BOND Dept. Employee Photo 006

Manufacturers are increasingly choosing adhesive bonding as the preferred method for joining components due to its many advantages over traditional joining methods. Adhesive bonding is a critical process and if done improperly can lead to system failures. Proper bonding techniques start with understanding the process requirements, properly maintaining your bond facility and inventory, and having highly trained operators to carry out the requirements.

PTI Industries Adhesive Bonding Department’s team of experts’ goal is to maintain compliance to all bonding process requirements to ensure your critical adhesive bonding needs.

How the department is organized
PTI’s Adhesive Bonding Department is organized by the different types of adhesive bonding methods and spec requirements for controlled areas. There are two contamination controlled areas that are maintained for temperature, humidity, and positive pressure. One area is for RTV (Room Temperature Vulcanizing) bonding, and the second is for epoxy bonding used in applications such as liner (metal to metal) and Teflon bonding. There are also additional environmentally maintained areas for other methods and specifications, such as magnesium bonding.

Maintaining contamination control areas
Calibrated controls for temperature and humidity are checked twice a day to ensure an acceptable specification range is met. Humidifiers and dehumidifiers maintain the proper humidity levels for effective adhesive bonding.

Approval processing for the right adhesive method
Each adhesive bonding method is specification driven and controlled. Nearly all prime manufacturers require approvals for the type of bonding that is required in the form of an overall approval for processing. They also may require specific approvals in the form of a technical plan or process plan for the parts being processed or the method of processing.

Getting the right fixtures and tooling
PTI determines the appropriate bonding tooling and fixtures required for each specific job. Tooling is designed and created by our bond technical leader, quality department and engineering department. Most tooling or fixtures can be made onsite in our machine shop.

Adhesive storage and quality control
PTI stores adhesives in three ways:
1. Room temperature cabinets
2. Refrigerators
3. Freezer

All storage options are quality controlled. The refrigerators and freezer are monitored with state of the art thermocouple chart recorders. The freezer is set with an alarm indicating variation above or below the acceptable temperature range. When technicians aren’t on site, any deviation is sent to PTI’s security company, who then notifies PTI.

Typical adhesive shelf life can range from six months to one year. Shelf life is monitored with an inventory control system that includes product labels and an online tracking system. All out time of adhesives are tracked and recorded.

Your Certificate of Conformance
PTI provides a certificate of conformance for all jobs and for all special processes in our support services as part of our quality assurance program.

Who works in PTI’s Adhesive Bonding Department?
The Adhesive Bonding Department team includes a Bond Manager, Bond Technical Leader/Expert, two Team Leaders, Expeditor, Quality Engineer, and Bond Operators/Technicians.

All team members undergo on-the-job training on systems, procedures, and processing. Classroom training, special program training, part and job specific training are done by the quality department, bond technical leader, team leaders and high level operators.

For any questions on PTI’s adhesive bonding special processes, please contact Jessica Taylor.

How Can Four Equal One? – A Case Study in Streamlining Multiple Special Processes

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blog-pic-41pti-300x245In a previous post we spoke about streamlining your special processes to improve your bottom line. Now we’ll take a look at how one part would move through our multi-process shop. Four processes can equal one when a part has four sequential special processes done in one shop on one purchase order. To illustrate this, let’s look at a section of the value stream map for a Locking Nut that mates up to an LPT Shaft, which ultimately ends up in a jet engine.

This life limited part starts out as a 410 stainless steel bar. After machining and heat-treating, we receive the part in to perform Magnetic Particle Inspection (MPI) which is a form of Non-Destructive Testing. This special process is done to ensure there are no cracks or voids in the parent material that could result in an in-flight failure.

Having passed MPI, the part travels immediately into our Dry Film Lubricant (DFL) Department, where it has a thin layer of Molybdeum Disulfide (a type of DFL) applied to its threads. This ensures it will rotate smoothly when mated up to an LPT shaft at assembly.

Next, the part moves right into our Bonded Products Division where a special low-friction fabric washer that we laser cut to exacting tolerances is adhered to its bearing surface using our Adhesive Bonding technology.

This special fiber washer acts as a maintenance-free thrust bearing when it mates up to the adjoining surface on the LPT shaft.

The final stop for this part is in our Precision Cleaning Division. Here it will undergo a thorough cleaning and inspection to a microscopic level to ensure there are no particles on it that could damage the part itself or other sensitive components within the engine during use.

It is PTI’s unique Multi-Process capabilities that make it possible for Four to equal One. Streamlining your processes in our shop will result in reduced shipping, handling, paperwork, downtime and all related peripheral activities that will save you money in the long run.

The Benefits of Adhesive Bonding

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Bonding&DFL._cropAdhesives are the number one choice for joining methods. Because of its numerous benefits, adhesive bonding is used in many different industries, and when compared to the alternative of welding and riveting, adhesives win by a landslide.

Loctite’s post “Adhesives are not second best” describes in detail the many benefits of adhesive bonding over mechanical methods of joining substrates. Loctite, a German manufacturer of high-performance industrial adhesives and sealants, explains the difficulties of traditional bonding techniques
and how adhesive bonding gives you improved performance.

Loctite outlines adhesive bonding benefits, including:

  • Less corrosion and material fatigue
  • No heat distortion or warping
  • No weakening
  • Greater flexibility for use with dissimilar materials
  • Increased rigidity and stiffness
  • Decreased weight
  • Cost savings in workforce training and inventory
  • Improved cosmetic appearance

Although there are many circumstances where welding and riveting are appropriate, any limitations are easy to overcome with adhesives. “Adhesives are certainly not second best when it comes to the selection of joining methods. Indeed for many engineers, adhesives are the first – often, the only – choice,” Loctite said.

When choosing the right adhesive for your parts, it is important to understand the different application benefits and adhesion properties. At PTI Industries, we help you find the right adhesive, because, as Loctite says, “there is no such thing as the totally universal glue.”

Adhesive bonding is a high-tech service PTI Industries offers as one of our many specialized processes, giving you a one-stop experience for your critical part processes.

For additional information check out our blog from July 2014; The 10 Top Things to Look for in an Adhesive Bonding Company.

Top 10 Things to Look for in an Adhesive Bonding Company

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PTI Industries bonded the Rulon to the inner diameter of this aluminum bearing then machined the Rulon to dimension as well as blended the ends for a nice radius lead in.

PTI Industries bonded the Rulon to the inner diameter of this aluminum bearing then machined the Rulon to dimension as well as blended the ends for a nice radius lead in.

In our last post we defined adhesive bonding, discussed its advantages, how it’s evolved, and four things you should know about PTI Industries’ adhesive bonding service. In addition, there are other details you need to know prior to choosing adhesive bonding.

What types of materials can be bonded?

The types of materials you can bond are as varied as the production processes used. Adhesive bonding can be used to bond virtually any combination of materials with each other, provided you know how to prep the materials, eliminating the need for traditional joining methods.

Why choose adhesive bonding over traditional joining methods?

Adhesive bonding is the ideal way to join components or materials that don’t always work well with traditional bonding methods, such as welds, rivets, and screws.

Adhesive bonding’s advanced adhesive system gives you significantly stronger joints that are cleaner, lighter, and exhibit greater uniformity in the distribution of stress factors. Adhesive bonding eliminates the need for the high heat input and resulting damage often associated with thermal joining methods.

10 Things to Look for in an Adhesive Bonding Company

  1. Does the company keep adhesives in stock? Are they certified and controlled?
  2. If the adhesive you need is not in stock, what is the lead time for ordering?
  3. What is the shelf life of the adhesive?
  4. Is the company certified to perform the bonding process you need, and can they provide you with the written approval?
  5. Do they make their own fixtures/tooling, or will you need to provide this?
  6. What kind of quality system is in place?
  7. What is the optimal lot size for your part to get the optimal production rate?
  8. Do they issue a certificate of conformance once the job is completed?
  9. Do they need a sample or scrap part to develop the process or bond fixtures/tooling?
  10. Are there any additional testing fees that you will incur, such as for adhesive testing?

Additional Tips

  • Be sure to provide them with a print and all requirements that you will need and get a quote ahead of time…many times the bonding operation cost and lead time is underestimated.
  • What are the details needed for the bonding project? For example if you need a Teflon strip bonded on a metal substrate, many times the bond house will supply the Teflon. Determine in advance if you need to provide materials or if the bond house will supply them.

Before you choose adhesive bonding, you’ll want to understand its benefits, know the materials you can expect to bond and make sure the bonding house can answer the questions above satisfactorily.