User:Benatar.1/WE7406 Article 17

IR Welding

IR welding uses a non-contact heating method to melt and fuse thermoplastic parts together using the energy from infrared radiation and is similar to laser welding. With a decrease in the price of parts in the 1990s, IR welding has become more popular in the industry. The three major steps to the welding process include heating of the parts, change-over (removal of the IR source), and joining and cooling of the parts under pressure. There are many different welding techniques that use IR heating, with the three major modes being Through Transmission IR Welding (TTIr), Surface Heating, and IR Staking.

Advantages / Disadvantages

Advantages

• Fast heating and cycle time
• Non-contact heating on the weld interface prevents plastic parts from sticking to the heat source, as seen in hot plate welding
• Controlled heat affected zone for reduced flash
• Minimal contamination risk with prevention of production of particulate
• Continuous and easily automated process
• Potential for higher joint strengths and lower residual stresses
• Cost-effective in comparison to laser welding
• Direct heat transfer to parts allows for maximum energy efficiency and fast response time with lower weight equipment
• Well suited for welding high temperature thermoplastics

Disadvantages

• IR welding parts and systems are expensive
• IR welding can only weld materials susceptible to IR waves and part interfaces exposed to IR radiation
• Prolonged heating may cause material degradation or vapor oxidation entrapment

IR welding techniques

TTIr Welding Diagram

Through Transmission IR Welding (TTIr)

TTIr welding is the joining of a IR transparent part to a second part such that the IR radiation travels through the transparent part and heat the surface of the second part. IR wavelengths are generally within 800 to 1050 nm in most systems. To make a transparent part absorbent to IR radiation, the addition of dies or colorants such as carbon black can be used. Three methods of heating using TTIr include plunge, scanning, and masked scanning.

Basic steps of the IR surface heating mode

Surface Heating

Surface heating includes heating and melting of the interface between plastic parts with IR radiation and forcing the parts together into a molten joint that solidifies as one part. This process can be split into six individual steps: loading of parts, press actuation (insertion of IR source), IR application, change-over phase (removal of IR source), clamp phase (joining of parts), and unloading.

IR Stacking

IR Staking

IR staking includes the localized welding of a thermoplastic stud from one part into the cavity of a non-weldable part to form a mechanical fastener. The stud can be heated through directed TTIr when pre-placed within the cavity of a IR transparent part, then is melted to deform it into a button shape required to fill the cavity before solidifying. Another method uses surface IR radiation to soften the plastic stud and presses it into a button shaped forming head, forcing the stud to deform into the shape of the forming head before solidifying.

Heating Configurations

Three primary methods for IR systems to heat the surface of a part.

Scanning

Movement of an IR beam across the surface of a part using an automated motion system or galvanic mirrors. Equipment is limited by the speed of movements across the part's surface to maintain uniform temperatures on the surface. In TTIr welding, scanning allows the un-melted portion of the part to act as a mechanical stop to maintain the joint gap between the two parts.

Continuous illumination

More than one IR radiation source is used to heat the entire joint interface at the same time. Part tolerances or fit up is not as important with this method as the entire surface will be melted before welding. This method is also useful when welding parts with complex geometries, employing the multiple IR sources to evenly heat all forms of joint interfaces.

Mask welding

Similar to continuous illumination, multiple IR sources are used to completely illuminate a joint interface, but in this case an IR radiation mask is placed over the parts to control which regions will form a melt layer.

Physics of IR welding

Electromagnetic spectrum

Electromagnetic wave interactions

IR welding typically uses wavelengths from 800 to 11,000 nm on the electromagnetic spectrum. Plastics interact with IR radiation through reflection, transmission, and absorption. Incident IR radiation can either be reflected off the surface of the plastic, transmitted through the plastic, or absorbed into the plastic as other forms of energy including thermal energy. The ratio of these three interactions depends on the wavelength of the IR radiation and the receiving plastic's properties. Amorphous plastics are generally optically clear and can transmit almost all incident IR radiation through it and are commonly used in TTIr. Semi-crystalline plastics can diffuse incident IR radiation between the amorphous and crystalline boundaries, reducing the transmittance and increasing the absorbance of the material. Additives such as clarifying agents can be used increase a plastic's transmittance while dies and pigments can be used increase the absorbance of a material. It should be noted that increasing amounts of these additives can decrease the strength of both the material and the welded joint.

The closer the IR radiation source, the higher incidence efficiency on the material. IR radiation is also most effectively used when indecent radiation is directed perpendicular to the part. Radiation energy effects both the surface and interior of a part with a penetration thickness dependent on the plastic's crystallinity.

Equipment

CO₂ lasers, Nd:YAG lasers, laser diodes, quartz lamps, and ceramic heaters can generate various IR wavelengths. The equipment is selected for each welding process based on the type of radiation it can produce. CO₂ lasers produce wavelengths of 10,600 nm at powers above 10W for high power heating. Nd:YAG and laser diodes generate lower power heating at wavelengths of 1,064 nm and 800 to 950 nm, respectively. Non-laser IR sources such as quartz lamps (1,000 to 5,000 nm) and ceramic heaters (5,000 to 10,000 nm) can produce a wide range of wavelengths.

P-wave technology developed by Kubota Research Associates (KRA) utilizes a IR lamp and a pre-placed focusing device such as a IR transducer or film that can both filter and focus IR radiation at a desired wavelength and increased intensity within a selected area to improve weld penetration with minimal surface damage. This method allows improved IR welding of polymers with higher melting temperatures such as most fluoropolymers and polyketones.

Materials

Below is a list of materials well known for their IR weldability:

• Polycarbonate (PC)
• Poly(methyl methacrylate) (PMMA)
• Ethylene vinyl alcohol (EVOH)
• Acrylic
• Polystyrene (PS)
• Acrylonitrile butadiene stryrene (ABS)
• Polyvinyl chloride (PVC)
• Polyethylene (PE)
• Polypropylene (PP)
• Polyketone (PK)
• Elastomers
• Polyamide (PA)
• Polyoxymethylene (POM or Acetal)
• Polytetrafluoroethylene (PTFE)

• High density polyethylene (HDPE)
• Glass fiber reinforced polyethylene (PPE)
• Polypropylene (PP)
• Polybutylene terephthalate (PBT)
• Glass fiber reinforced polyether sulfone (PES)

Applications

New joining technologies using IR welding are critical for fabricating complex parts and assemblies at high speeds and low costs. Although IR plastic welding has many advantages over other types of plastic welding, limitations such as equipment costs and susceptible materials properties reduce the amount of industrial applications of the method. A few examples of current industrial applications are shown below:

• CO detector filters are IR welded to their plastic housing to prevent damaging the filter with particulate
• Medical IV-bags are IR welded to achieve minimal flash and particulate generation for smooth and clean blood flow
• High-speed cut and seal film (300 m/min) processes allow for minimal fraying at the edges and cauterized seams
• Break fluid reservoirs are IR welded to prevent clogging and contamination of the small fluid transmission channel
• PE pipes in the infrastructure of natural gas transmission can be IR welded using TTIr to improve joint strength with minimal coupling deformation

*This is the end of the final draft for review 2-25-19

Instructor Comments

Viscoelasticity is fairly well covered with multiple articles. I recommend creating a new page on a plastic welding process that is poorly covered in Wikipedia. Another student already selected Spin Welding of Plastics, but you can select another process. Please let me know which process you selected so that I can assign the article to you.

Choosing Possible Topics to Edit:

1) Generalized Maxwell Model:

Many forms of the model and its equations are already posted, but the purpose of the model and its applications are not present. Should contain a link to the Maxwell material page as well as a comparison to the Kelvin-Voigt Material / model page. Could include a derivation of the basic model equation based on the spring and damper equations.

2) Spin Welding:

Contains a short description of the welding process and a video clip demonstration. Suggest name change to Plastic Spin Welding, as not to confuse with friction stir welding of metals. Additional notes on the invention of the process, its applicability, pros/cons, and a general expansion on any other possible knowledge of the process. Could be merged with subtopic spin welding under plastic welding page.

3) Expansion of plastic welding page:

This page is well written and contains a short description of every type of plastic welding process, but some of these processes have external pages for additional information while other do not and have just a few lines of explanation. I could open new pages to fill this gap and place links to them in the plastic welding page, including Non-contact/IR welding, Extrusion welding, and Freehand welding.

After further review, I would like to be assigned to start a new page on Non-contact IR Welding that builds off of the information listed on the plastic welding page and will be linked to it. Similar to other welding process pages, sections will include an introduction, joint configuration, applications, materials, equipment, welding parameters, and advantages/disadvantages sections.

Begin selecting Sources:

Info already posted on Plastic Welding Wiki Page: "Similar to hot plate welding, non-contact welding uses an infrared heat source to melt the weld interface rather than a hot plate. This method avoids the potential for material sticking to the hot plate, but is more expensive and more difficult to achieve consistent welds, particularly on geometrically complex parts."

Notes: This just gives an intro on non-contact welding, but does not identify the differences for IR welding. This will be added on the IR welding page I'm drafting.

Source 1: Grewell, David A., Benatar, Avraham, Park, Joon Bu, "Plastics and Composites Welding Handbook", 2003, ISBN 1-56990-313-1

Notes 1: (paraphrasing used with the exception of process names)

Introduction:

IR welding uses a non-contact heating method to melt and fuse thermoplastic parts together using the energy from infrared radiation and is similar to laser welding. With a decrease in the price of parts in the 1990s, IR welding has become more popular in the industry. There are many different welding techniques that use IR heating, with the three major modes being Through Transmission IR Welding (TTIr), Surface Heating, and IR Staking.

Advantages / Disadvantages:

Advantages: Fast cycle time, no contact heating on the weld interface, controlled heat affected zone, prevention of production of particulate, low residual stresses, easy automation, and smooth flash

Disadvantages: IR heating parts and systems are expensive and can only weld materials susceptible to IR waves and part interfaces exposed to IR radiation

IR welding techniques:

Through Transmission IR Welding (TTIr): TTIr welding is the joining of a IR transparent part to a second part such that the IR radiation travels through the transparent part and heat the surface of the second part. IR wavelengths are generally within 800 to 1050 nm in most systems. To make a transparent part absorbent to IR radiation, the addition of dies or colorants such as carbon black can be used. Three methods of heating using TTIr include plunge, scanning, and masked scanning.

TTIr Welding Diagram

Surface Heating: Surface heating includes heating and melting of the interface between plastic parts with IR radiation and forcing the parts together into a molten joint that solidifies as one part. This process can be split into six individual steps: loading of parts, press actuation (insertion of IR source), IR application, change-over phase (removal of IR source), clamp phase (joining of parts), and unloading.

Basic steps of the IR surface heating mode

IR Staking: IR staking includes the localized welding of a thermoplastic stud from one part into the cavity of a non-weldable part to form a mechanical fastener. The stud can be heated through directed TTIr when pre-placed within the cavity of a IR transparent part, then is melted to deform it into a button shape required to fill the cavity before solidifying. Another method uses surface IR radiation to soften the plastic stud and presses it into a button shaped forming head, forcing the stud to deform into the shape of the forming head before solidifying.

IR Stacking

Heating Configurations:

Three primary methods for IR systems to heat the surface of a part.

Scanning: Movement of an IR beam across the surface of a part using an automated motion system or galvanic mirrors. Equipment is limited by the speed of movements across the part's surface to maintain uniform temperatures on the surface. In TTIr welding, scanning allows the un-melted portion of the part to act as a mechanical stop to maintain the joint gap between the two parts.

Continuous illumination: More than one IR radiation source is used to heat the entire joint interface at the same time. Part tolerances or fit up is not as important with this method as the entire surface will be melted before welding. This method is also useful when welding parts with complex geometries, employing the multiple IR sources to evenly heat all forms of joint interfaces.

Mask welding: Similar to continuous illumination, multiple IR sources are used to completely illuminate a joint interface, but in this case an IR radiation mask is placed over the parts to control which regions will form a melt layer.

Physics of IR welding:

IR welding typically uses wavelengths from 800 to 11,000 nm on the electromagnetic spectrum. Plastics interact with IR radiation through reflection, transmission, and absorption. Incident IR radiation can either be reflected off the surface of the plastic, transmitted through the plastic, or absorbed into the plastic as other forms of energy including thermal energy. The ratio of these three interactions depends on the wavelength of the IR radiation and the receiving plastic's properties. Amorphous plastics are generally optically clear and can transmit almost all incident IR radiation through it and are commonly used in TTIr. Semi-crystalline plastics can diffuse incident IR radiation between the amorphous and crystalline boundaries, reducing the transmittance and increasing the absorbance of the material. Additives such as clarifying agents can be used increase a plastic's transmittance while dies and pigments can be used increase the absorbance of a material. It should be noted that increasing amounts of these additives can decrease the strength of both the material and the welded joint.

Electromagnetic spectrum

Electromagnetic wave interactions

Equipment:

CO₂ lasers, Nd:YAG lasers, laser diodes, quartz lamps, and ceramic heaters can generate various IR wavelengths. The equipment is selected for each welding process based on the type of radiation it can produce. CO₂ lasers produce wavelengths of 10,600 nm at powers above 10W for high power heating. Nd:YAG and laser diodes generate lower power heating at wavelengths of 1,064 nm and 800 to 950 nm, respectively. Non-laser IR sources such as quartz lamps (1,000 to 5,000 nm) and ceramic heaters (5,000 to 10,000 nm) can produce a wide range of wavelengths.

Materials:

Below is a list of materials well known for their IR weldability:

• Polycarbonate (PC)
• Poly(methyl methacrylate) (PMMA)
• Ethylene vinyl alcohol (EVOH)
• Acrylic
• Polystyrene (PS)
• Acrylonitrile butadiene stryrene (ABS)
• Polyvinyl chloride (PVC)
• Polyethylene (PE)
• Polypropylene (PP)
• Polyketone (PK)
• Elastomers
• Polyamide (PA)
• Polyoxymethylene (POM or Acetal)
• Polytetrafluoroethylene (PTFE)

Applications:

Although IR plastic welding has many advantages over other types of plastic welding, limitations such as equipment costs and materials properties reduce the amount of industrial applications of the method. A few examples of current industrial applications are shown below.

• CO detector filters are IR welded to their plastic housing to prevent damaging the filter with particulate
• Medical IV-bags are IR welded to achieve minimal flash and particulate generation for smooth and clean blood flow
• High-speed cut and seal film (300 m/min) processes allow for minimal fraying at the edges and cauterized seams
• Break fluid reservoirs are IR welded to prevent clogging and contamination of the small fluid transmission channel

Source 2: No, D. (2005). A study of the combined socket and butt welding of plastic pipes using through transmission infrared welding. (Electronic Thesis or Dissertation). Retrieved from https://etd-ohiolink-edu.proxy.lib.ohio-state.edu/

Notes 2:

Applications:

• PE pipes in the infrastructure of natural gas transmission can be IR welded using TTIr to improve joint strength with minimal coupling deformation

Source 3: Infrared heating and welding of thermoplastics and composites, Chen, Yang Shiau. The Ohio State University, ProQuest Dissertations Publishing, 1995. 9544534.

Notes 3:

Introduction:

The three major steps to the welding process include heating, change-over, and joining and cooling under pressure. A reduced change over phase time increases the potential for a stronger plastic joint by reducing the amount of cooling that can occur before joining.

Advantages / Disadvantages:

Advantages: Rapid heating, minimal contamination risk, continuous process, higher joint strengths, avoids sticking of the part to the heat source as seen in hot plate welding, more cost-effective than laser welding, better than other non-contact welding methods with direct heat transfer to parts for maximum energy efficiency and fast response time and lower weight equipment, well suited for high temperature thermoplastics,

Disadvantages: Process is still under development as is not fully understood, prolonged heating may cause material degradation or vapor oxidation entrapment,

Physics:

The closer the IR radiation source, the higher incidence efficiency on the material. IR radiation is also most effectively used when indecent radiation is directed perpendicular to the part. Radiation energy effects both the surface and interior of a part with a penetration thickness dependent on the plastic's crystallinity.

Materials:

• High density polyethylene (HDPE)
• Glass fiber reinforced polyethylene (PPE)
• Polypropylene (PP)
• Polybutylene terephthalate (PBT)
• Glass fiber reinforced polyether sulfone (PES)

Applications:

New joining technologies using IR welding are critical for fabricating complex parts and assemblies at high speeds and low costs.

Source 4: New Approach to IR Welding Bonds More Engineering Plastics

Notes 4:

Equipment:

P-wave technology developed by Kubota Research Associates (KRA) utilizes a IR lamp and a pre-placed focusing device such as a IR transducer or film that can both filter and focus IR radiation at a desired wavelength and increased intensity within a selected area to improve weld penetration with minimal surface damage. This method allows improved IR welding of polymers with higher melting temperatures such as most fluoropolymers and polyketones.

Source 5:

Notes 5:

Source 6:

Notes 6: