Hot Plate vs. Other Welding Methods

Hot Plate vs. Infrared Welding

HOT PLATE WELDING

INFRARED WELDING

Accurate part temperature control based on feedback from thermocouples into temperature controllers. Highly accurate part temperature control based on utilization of Phase Angle Control type logic and Power Control (line/load regulation) Transformers
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. 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.
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. Instant on/off design requires no warm-up time (pre-heating) and allows faster tooling changeover (no cool-down required).
Higher power requirement.  Heaters constantly pulsing on/off throughout day to constantly maintain temperature. Lower power requirement.  Higher power drawn only when IR turned on.
Much lower cost system overall.  Constant voltage transformers not required as heat platen incorporates temperature controllers which provide feedback of actual platen 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.
Typically, heat platens are designed for optimal temperature distribution for each application, often requiring an optimized heat platen with each tool. Very cost effective when designing a common emitter platen and change of masks only.
Cartridge heaters also require replacement although the replacement cost is very inexpensive by comparison with Infrared emitters. Emitters last only a few years and are very expensive to replace.
Flash traps may be required for cosmetic applications when welding with contact. Due to limited displaced material, flash traps are often not required.
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. Parts must be molded very precisely as there is no contact based melt step to flatten/parallel joint surfaces.
If required to run at low temperature, Teflon coating on heat platen must be moved (sheet) or replaced (coatings) No need for replacement inserts/coating materials.
Materials such as polyethylene, acetal, nylon and polycarbonate will require release coatings between polymer and heat platen. Greater design flexibility in materials (all non-contact).
Clear materials and polycarbonate are easily weldable without complexity although some may require release coatings between polymer and heat platen. Not ideal for clear materials (particularly polycarbonate).
Heat platen temperature distribution is affected by convection currents. Convection currents not a factor unlike HP welding.
Smoke produced at temperatures above 500ºF only. High amount of smoke created during the process.
Typically standard “off the shelf” parts are used with no leadtime issues on wear-item parts. If Custom emitters are used, customer MUST purchase spares immediately as leadtimes for replacements are up to 6 weeks.

Hot Plate vs. Vibration Welding

HOT PLATE WELDING

VIBRATION WELDING

Slower cycle times:

  • 15 to 45 seconds (high temp) typical.
  • 30 to 60 seconds (low temp) typical.
Faster cycle times:

  • 8 to 15 seconds typical.
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.
Direct control of temperature at weld joint. No direct control of temperature at weld joint.
Process works well for a variety of materials (few limitations). Process works well for a variety of applications (some limitations).
Complex to weld Nylon.  Involves ultra high-temperature heat platen cores which must be scrubbed with metal brushes every cycle to clean off build-up of residual material. Yields the strongest bonds compared to most other welding methods. Easy welding of Nylon.
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.
Fillers in the material can build up on the heat platen requiring periodic cleaning (automatic cleaning systems are available on certain models). Fillers in the material are not a problem.
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.
Less sensitive to molded part variations. More sensitive to molded part variations.
Lower initial capital equipment costs. Higher initial capital equipment costs.
Higher tooling costs (requires heat platen). Lower tooling costs (no heat platen required).
Process requires a heat platen assembly. Less complex tooling.
Heat platen maintenance; replace heaters and Teflon inserts when using low temperature. Lower tooling maintenance.
Slower tooling change-over times; also may have to change heat platen and allow for heat up. Faster tooling change-over times.
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).
Virtually no smoke or fumes during welding process at low temp; will create smoke and fumes when welding at high temp. Virtually no smoke or fumes during welding process.
Higher power consumption (required for heaters). Lower power consumption (no heat platen heaters).

Hot Plate vs. Electromagnetic Welding

 HOT PLATE WELDING

ELECTROMAGNETIC WELDING

Slower cycle times:

  • 15 to 45 seconds (high temp) typical
  • 30 to 60 seconds (low temp) typical
Faster cycle times:

  • 5 to 15 seconds typical
No consumables required. VERY EXPENSIVE consumable required (proprietary ferro-magnetic material).
No additional process steps required. Additional and very critical process step required (installation of consumable ferro-magnetic material).
Melt areas limited to sections where heat platen can contact. Ideal for melt areas that are difficult to weld with any other technique (last resort).
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. Parts must be molded very precisely as there is no contact based melt step to flatten/parallel joint surfaces.
Limited risk of thermal damage to non-weld areas. No risk of thermal damage to non-weld areas. Heat remains in ferro-magnetic component area (joint) only.
Moisture introduced to welded part has no effect on part appearance. Moisture introduced to welded part can result in rust residue on parts.
Accurate failure/problem diagnosis can be performed by virtually any maintenance technician. Accurate failure/problem diagnosis requires extensive knowledge of RF generators.
Replacement parts largely off-the-shelf items. Requires replacement of special expensive RF Oscillator tubes every few years.
Joint line contour limited to 45° from flat plane before weld strength is drastically impacted. Joint line contour almost unlimited (provided RF tooling can remain in roughly equal proximity to other melt areas)
Metallic components can be installed prior to welding. Metallic components should be installed only after welding due to possible magnetic heating in undesirable areas during the electromagnetic welding process.
Defect parts can be recycled easily as no foreign matter exists in the joint area. Defect parts cannot be recycled easily due to ferromagnetic material within the parts.
Process has virtually no effect on surrounding equipment. RF emissions can cause interference in surrounding equipment (particularly low control voltage circuitry…UPS scales, PA Systems, machines with servo motors)
Periodic heat platen maintenance required; replace heaters and Teflon inserts (when using low temperature). Lower tooling maintenance.
Lower initial capital equipment costs. Higher initial capital equipment costs due to requirement of RF Generator.
Higher tooling costs (heat platen). Lower tooling costs (no heat platen required).
Slower tooling change-over times; also may have to change heat platen and allow for heat up. Faster tooling change-over times.