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Infrared welding is a relatively new welding technique used for the many challenging materials and large part assembly with high strength and hermetic requirements. During the Infrared welding, both part halves are held rigidly in position near an infrared emitting platen to melt the joining surfaces. The platen is removed and the part halves driven together and allowed to re-solidify under pressure. Forward has manufactured infrared systems since 2004 and hot plate welders (the platform for infrared welding) since 1965. Our experience has resulted in the design of equipment based on ultra-rigid construction and detailed melt control to ensure precise repeatability of part quality, year after year of production. Vertical or horizontal platen configurations are available. From manually loaded and unloaded machines to semi and fully automated in-line systems, Forward offers the widest array of standard products designed to accommodate a most product sizes. |
Infrared Welding Process Advantages
About Infrared Welding
Designing for Infrared Welding
Infrared Weld Tooling
Infrared vs. Other Welding Methods
Infrared Welding Process Advantages
- Greater design flexibility in material choice (all applications are non-contact).
- No need for replacement inserts and/or coating materials to prevent adhesion of the material to the platen (no contact with material).
- Instant on/off design requires no warm-up time (pre-heating) prior to starting production.
- Allows faster tooling changeovers as the platen assembly does not need to cool before being safely handled.
- Due to reduced molten material displacement, flash traps and cosmetic flash hiding skirts are often not required in the joint design.
- Convection currents are not a factor as with other thermal techniques such as hot plate welding.
- Contoured melt surfaces are possible with minimal complexity.
- Reduced power consumption. High power is drawn only when infrared energy is needed.
- Highly accurate melt control based on constant incoming voltage.
- Very cost effective when designing a common infrared emitter platen and changing of masks only.
- Recent tests indicate that joint strength of infrared welded glass filled Polyethersulfone exceeded any alternative welding process attempted.
Back to topAbout Infrared Welding
Infrared welding is a non-contact thermal welding technique capable of producing very strong, air-tight welds in thermoplastic parts.
Infrared radiation is most commonly felt in the form of the heat we feel from sunlight. As with any form of light, infrared radiation is electromagnetic radiation which is transmitted at very high power levels at the speed of light.
When using this energy in a tightly controlled manner, thermoplastic parts can be heated to molten temperatures very quickly and then joined together in a manner very closely resembling hot plate welding.
Glass encased infrared emitters (learn more) are the assemblies which generate the infrared energy. Oscillating atoms within the heated conductors inside each emitter or “bulb” emit electromagnetic waves. Typically, the atoms within each conductor produce many different oscillation frequencies (wavelengths) but only some of which are harnessed to perform heating of plastic materials. The infrared wavelengths most often used for plastic welding are those of medium wavelength (approximately 2.0-2.5uM peak) and short wavelength (approximately 1.0-1.2uM peak).
Based on the properties of the plastic to be welded:
- most of the infrared radiation is absorbed within the material
- some of the infrared radiation is reflected off of the surface of the material
- some of the infrared radiation penetrates through the material.
Each infrared system is designed based on the specific wavelength range (medium or short) which will provide optimal absorption based on the material’s spectral analysis.
To heat the material, we utilize an infrared platen assembly consisting of multiple glass encased infrared emitters typically mounted side-side. We are able to target only the joint area of each part half. The targeting is made possible by infrared blocking masks which are used to prevent heating of non-joint areas.
Infrared Welding Process:
 | Step OnePart halves are placed into and securely gripped by precision holding fixtures which insure adequate support and accurate alignment of the part halves throughout the infrared welding process. |
 | Step TwoTo heat the part joint area, an infrared platen is placed between the part halves. The holding fixtures close to make contact with precise mechanical hard-stops on the infrared platen which maintain spacing between the parts and the infrared platen without actual contact. |
 | Step ThreeInfrared energy is initiated, targeting the joint area of each part half only. As the material transitions to a molten state, the molten material remains in the joint area (no material displacement). |
 | Step FourAfter the joint area reaches molten temperature, the holding fixtures open and the infrared platen is withdrawn. |
 | Step FiveThe holding fixtures then close, forcing the two parts together until hard-stops on the holding fixtures come into contact with one another. |
 | Step SixWhen cooling is complete, the gripping mechanism in one of the holding fixtures releases the part, the holding fixtures open and the finished part may be removed. |
This technique is ideal for use in the base equipment platforms of our already extensive line of hot plate welders. Vertical or horizontal platen welder configurations are available (see below). From manually loaded and unloaded machines to semi and fully automated in-line systems, each of our infrared welders is designed to accommodate a specific range of application requirements.
Vertical vs. Horizontal Platen Systems:
Vertical | Horizontal |
| Easy to manually load both part halves positively into thetooling, ensuring precise, repeatable alignment duringwelding. | More difficult to manually load both part halves positivelyas access to upper tool can be ergonomicallychallenging. |
| Not ideal when internal componentry is loose inside the parthalves prior to welding. | Ideal system for part designs where internal components areloose inside the lower part half prior to welding. |
| No simple option for operator to load part halves outside themachine. | Allows option of manually loading part halves outside themachine (requires drawer load and automatic top-half partpick-up). |
| No special location features need be designed into the parthalves or tooling for accurate alignment. | Requires special location features be designed into moldedparts themselves or the tooling (increases tooling cost/complexity)when using automatic top-half parts pick-up. |
| Faster tool changeover than most horizontal machines offeredtoday. | Slower tooling changeover typically. |
| More complex to automate (often requiresroboticaction). | Very easy to automate when optional drawer load and automaticpart drop to conveyor belt is used. |
| Not ideal for automatic part drop (onto conveyor belt) afterwelding. | Allows easy automatic part drop onto conveyor belt afterwelding (when equipped with optional drawerload). |
| Twin motion (left and right) fixturing allows independentcontrol of force/speed on each part half, both against heat platen andagainst each other. | Single motion (upper only) fixturing allows independentcontrol of force/speed of upper part halfonly. |
Critial Infrared Parameters:
- Infrared Intensity
- Melt Time (parts subjected to IR energy)
- Transition (aka: ‘Open’) Time between Melt and Weld/Seal Steps
- Weld/Seal Time (parts clamped together)
- Weld/Seal Depth (controlled by stops)
- Weld/Seal Force
Time & Absorption:
The infrared absorption required to melt the part interface depends on the type, color and polymeric uniformity of the plastic being joined. Each thermoplastic has a characteristic melt time/absorption curve, and a weld can be produced at any point on the curve. Typically the highest possible intensity (without causing burning or unacceptable material degradation) using the shortest time is selected to minimize cycle times.
Factors Affecting Proper Welds:
- Part dimensional stability
- Polymer uniformity
- Incoming line voltage
- Polymer color/translucency
- Mold release agents
- Dissimilar materials
- Infrared intensity
- Fillers
- Moisture
- Transition time between melt and weld steps
Designing for Infrared Welding
Infrared Weld Strength:
As with the hot plate welding process, infrared welding produces a welded joint which, in many cases, yields a weld strength that is consistently equal to or stronger than any other area of the part. As a result, the weld area can most often be exposed to the same strains and stresses as any other area of the part.
Common Infrared Welded Materials:
- Acrylonitrile Butadiene Styrene (ABS-Cycolac)
- PolyOxy-Methylene (POM-Acetal & Delrin)
- PolyAmide (PA-Nylon & Zytel)
- PolyButylene Terephthalate (PBT-Valox & Enduran)
- PolyEthylene (PE)
- PolyEthylene Terephthalate (PET-Polyester)
- PolyMethyl MethAcrylate (PMMA-Acrylic & Lucite)
- PolyPhenylene Oxide (PPO-Noryl)
- PolyPhenylene Sulfide (PPS-Ryton)
- PolyPropylene (PP)
- PolyStyrene (PS)
- PolySulfone (PSO-Udel)
- Thermo-Plastic Elastomers (TPE-Santoprene)
Infrared Welding Joint Designs:
Material displacement is typically 0.030" total. This results only from 0.015" material displacement per side from material fusion during the weld/seal step as there is no displacement during the infrared melt step. This may vary depending on part material and geometry. We strongly recommend discussing your joint design with one of our application engineers before arriving at your final part design.
Infrared Weld Tooling
Advantages of Forward Technology Infrared Tooling:
- Over 95% of all tooling is designed and manufactured for your application by our in-house Tooling Design and Fabrication department in Cokato, MN.
- This in-house capability insures optimal quality and scheduling control as well as reducing time requirements in the event of product design changes.
- No charge/obligation complete application review and joint design assistance.
- Full prototyping capability.
- All tools are designed for ease of maintenance, adjustment, and maximum life.
- Tools provide support and location of joint area as well as accurate alignment throughout the welding process.
- Virtually every tool is thoroughly tested and debugged at our facility on equipment in our laboratory.
- Full start-up service/support at your facility is available.
Standard Infrared Tooling
- Precision CNC cut holding fixtures supports joint area of each part half.
- Holding fixtures can be split if necessary to accommodate part-to-part variations or for welding warm/hot parts.
- Hardened steel fixture top plates (metalized by black oxide, chrome plating or anodizing)
- Steel, aluminum, urethane, or acetal tooling components.
- Lightweight aluminum backing plates
- Heavy-duty slides used for support & part retention in areas where clearance is needed for loading & unloading on lower tooling.
- Custom grippers and vacuum cups used to secure parts in holding fixtures.
- Mechanical positive hard-stops on each fixture and infrared platen.
- Control depth of melt and weld/seal dimensions.
- Provide assembled product consistency
- Eliminate risk of cold joint (all molten material being extruded from joint by excess travel)
- Adjustable for part to part variance
- Precision glass encased emitters contained with platen assembly designed for uniform intensity across all joint surfaces.
- Constant air cooling of all emitter envelopes to insure long life.
Infrared Tooling Options
- Part presence sensors verify part presence/position prior to allowing machine to cycle.
- Part eject eases removal of welded parts from tooling.
- Quick change system for customers using multiple tools in one machine.
- Tool coding utilizes RF Tagging to automatically identify the application and select the correct program/setup.
- Infrared platen & tooling fixture cart with casters for storage and easy relocation of infrared assemblies and tooling.
Advantages of Glass Encased Emitters vs. Ribbon Style Emitters
- Improved safety, no exposed live conductors.
- Air currents can create SIGNIFICANT changes in temperature and wattage when conductor is exposed to air currents.
- As encased conductors are held under tension, they offer much better resistance to sagging as found in ribbons style emitters.
- Conductor is isolated from product – no contact is possible, minimizing risk of damage to the conductor.
Infrared vs. Other Welding Methods
Infrared vs. Hot Plate Welding
INFRARED WELDING | HOT PLATE WELDING |
| Highly accurate part temperature control based on utilization of Phase Angle Control type logic and Power Control (line/load regulation) Transformers | Accurate part temperature control based on feedback from thermocouples into temperature controllers. |
| Temperature control requires constant incoming voltage as system does not allow for readily available feedback from output/tooling. Correction for varying incoming voltage (5% or more) requires costly Power Control Transformer. | Temperature control not easily affected by voltage. Feedback from the thermocouples built into the heat platen allow the system to correct for variable incoming voltage. Power Control Transformer not required even when incoming voltage varies. |
| Instant on/off design requires no warm-up time (pre-heating) and allows faster tooling changeover (no cool-down required). | Warm-up time (Preheating) required for roughly 20-40 minutes prior to start of production. Tool changes often require cooling of the heat platen to tolerable temperatures prior to changing tooling. |
| Lower power requirement. Higher power drawn only when IR turned on. | Higher power requirement. Heaters constantly pulsing on/off throughout day to constantly maintain temperature. |
| Cost increase up to 60% or more dependant on emitter design (custom vs. standard) and whether or not Power Control Transformers are needed. Incoming voltage variances can create IR output density changes which are not readily apparent to the equipment via feedback. | Much lower cost system overall. Constant voltage transformers not required as heat platen incorporates temperature controllers which provide feedback of actual platen temperature. |
| Very cost effective when designing a common emitter platen and change of masks only. | Typically, heat platens are designed for optimal temperature distribution for each application, often requiring an optimized heat platen with each tool. |
| Emitters last only a few years and are very expensive to replace. | Cartridge heaters also require replacement although the replacement cost is very inexpensive by comparison with Infrared emitters. |
| Due to limited displaced material, flash traps are often not required. | Flash traps may be required for cosmetic applications when welding with contact. |
| Parts must be molded very precisely as there is no contact based melt step to flatten/parallel joint surfaces. | Parts can be molded without absolute precision as joint surfaces will be made parallel to one another during melt phase when polymer is making contact with heat platen. |
| No need for replacement inserts/coating materials. | If required to run at low temperature, Teflon coating on heat platen must be moved (sheet) or replaced (coatings) |
| Greater design flexibility in materials (all non-contact). | Materials such as polyethylene, acetal, nylon and polycarbonate will require release coatings between polymer and heat platen. |
| Not ideal for clear materials (particularly polycarbonate). | Clear materials and polycarbonate are easily weldable without complexity although some may require release coatings between polymer and heat platen. |
| Convection currents not a factor unlike HP welding. | Heat platen temperature distribution is affected by convection currents. |
| High amount of smoke created during the process. | Smoke produced at temperatures above 500ºF only. |
| If Custom emitters are used, customer MUST purchase spares immediately as leadtimes for replacements are up to 6 weeks. | Typically standard “off the shelf” parts are used with no leadtime issues on wear-item parts. |
Infrared vs. Vibration Welding
INFRARED WELDING | VIBRATION WELDING |
Slower cycle times:
| Faster cycle times:
|
| Can weld tall, thin, non-supported inside and outside walls. | Cannot weld tall, thin, non-supported either: a) inside walls or b) outside walls perpendicular to the direction of vibration. |
| Process works well for a variety of materials (few limitations). | Process works well for a variety of applications (some limitations). |
| Almost no part size limitations. | Can be difficult to weld VERY large parts. |
| Higher joint strength with Polypropylene and Polyethylene as the process heats the interface without friction. | Lower joint strength with Polypropylene and Polyethylene due to absorption of vibration within the material instead of transfer to the joint area. |
| Process can join certain dissimilar materials (limited number). | Process can join certain dissimilar materials (limited number). |
| Can weld parts with contours in both directions. | Can weld parts with contours in one direction only. |
| Weld plane limited to 45° maximum from flat plane. | Weld plane limited to 10° maximum from flat in the axis parallel to vibration. |
| Higher tooling costs (requires infrared platen). | Lower tooling costs (no infrared platen required). |
| Process requires an infrared platen assembly. | Less complex tooling. |
| Infrared platen maintenance; periodic replacement of infrared emitters required. | Lower tooling maintenance. |
| Slower tooling change-over times; may have to change infrared platen. | Faster tooling change-over times. No platen to change. |
| Process creates solid, smooth flash bead with virtually no particulate. | Process can create flash that can break off causing loose particles (application and material dependant). |
| Process most often will create smoke and fumes. | Virtually no smoke or fumes during welding process. |
Forward Technology is a Crest Group Company