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About Hot Plate Welding
Hot Plate Welding is a thermal welding technique capable of
producing strong, air-tight welds in thermoplastic
parts. When using thermal energy in a tightly controlled manner,
thermoplastic parts can be heated to molten
temperatures very quickly and then joined together.
Thermal heat is introduced to the interface of each part half by
a precision temperature controlled platen consisting
of multiple uniform temperature distribution cartridge
heaters.
Hot Plate Welding Process:
Step One
Part halves are placed into and securely gripped by precision
holding fixtures which insure adequate support and
accurate alignment of the part halves throughout the hot plate
welding process.
Step Two
To heat the part joint area, a thermally heated platen is placed
between the part halves. The holding fixtures close
to compress and melt the part halves to be welded against the
platen, displacing material at the joint area only
Step Three
Compression and material displacement continue until precision
hard-stops built into the tooling are met. Thermal
heat continues to conduct into the material even though
compression and displacement have stopped.
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Step Four
After the joint area reaches molten temperature, the holding
fixtures open and the heat platen is withdrawn.
Step Five
The holding fixtures then close, forcing the two parts together
until hard-stops on the holding fixtures come into
contact with one another.
Step Six
When 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.
Our existing line of hot plate welders is extensive. 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 hot plate 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 the
tooling, ensuring precise, repeatable alignment during welding.
More difficult to manually load both part halves positively as
access to upper tool can be ergonomically challenging.
Not ideal when internal componentry is loose inside the part
halves prior to welding.
Ideal system for part designs where internal components are
loose inside the lower part half prior to welding.
No simple option for operator to load part halves outside the
machine.
Allows option of manually loading part halves outside the
machine (requires drawer load and automatic top-half part
pick-up).
No special location features need be designed into the part
halves or tooling for accurate alignment.
Requires special location features be designed into molded parts
themselves or the tooling (increases tooling cost/complexity) when
using automatic top-half parts pick-up.
Faster tool changeover than most horizontal machines offered
today.
Slower tooling changeover typically.
More complex to automate (often requires roboticaction).
Very easy to automate when optional drawer load and automatic
part drop to conveyor belt is used.
Not ideal for automatic part drop (onto conveyor belt) after
welding.
Allows easy automatic part drop onto conveyor belt after welding
(when equipped with optional drawer load).
Twin motion (left and right) fixturing allows independent
control of force/speed on each part
Single motion (upper only) fixturing allows independent control
of force/speed of upper part half only.
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half, both against heat platen and against each other.
Critical Hot Plate Welder Parameters:
Temperature
Melt Time (parts against heated platen)
Transition (aka: Open) Time between Melt and Weld/Seal Steps
Weld/Seal Time (parts clamped together)
Melt Depth (controlled by stops)
Weld/Seal Depth (controlled by stops)
Melt Force
Weld/Seal Force
Time and Temperature:
The platen temperature to melt the part interface depends on the
type of plastic being joined. Each thermoplastic
has a characteristic melt time/temperature curve, and a weld can
be produced at any temperature on the curve.
Typically the highest possible temperature at the shortest time
is selected to minimize cycle times.The typical hot
plate temperature range is 300 to 950F.
Types of Hot Plate Welds:
Low Temperature
Temperatures less than 500F
Low temperature tools require Teflon coated heat platen inserts
or Teflon cloth.
Typically coating/cloth needs replacement every 1500-8000
cycles.
Used on Medical Applications even with High Temp materials to
eliminate contamination / discoloration / maximize weld
strength.
Typical cycle time is 20-40seconds.
High Temperature
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Temperatures higher than 500F
High temperature tools are typically manufactured using P-20
tool steel.
No melt release coatings typically required
Melt residue smokes away or requires brush cleaning(Nylon)
Smoke/Fumes present: requires exhaust/smoke removal or
aircleaning
Typical cycle time is 10-30 seconds.
Non-contact
Typically temperatures higher than 900F
No residue on platen.
No material discoloration.
Precise molding tolerances required.
Not limited to flat mating surfaces.
Typical cycle time exceeds 40 seconds.
Technique is most complicated and least often used in production
hot plate welding.
High Temp vs. Low Temp Hot Plate Welding:
HIGH TEMP CONTACT WELDING
(above 500F)
LOW TEMP CONTACT WELDING
(500F or less)
Faster cycle times:
15 to 45 seconds typical
Slower cycle times:
30 to 60 seconds typical
No coating required. Residue smokes off through Exhaust Fan.
Lower maintenance.
Teflon coating or Teflon Coated Fiberglass Cloth required on
heat platen or insert surface. Higher maintenance.
Process works well for a variety of materials (some
limitations).
Process works well for a variety of materials (some
limitations).
Process can join certain dissimilar materials (wider range).
Process can join certain dissimilar materials (limited
number).
Not ideal for welding Polyethylene (material excessively sticks
to the heat platen core).
Ideal for welding Polyethylene.
Easy welding of Polypropylene. Can weld Polypropylene (low temp
required in Medical Cleanroom environment).
Highest strength when welding 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.
Lower strength when welding Nylon (temperature too low).
Fillers in the material can build up on the heat platen
requiring periodic cleaning (automatic cleaning systems are
available on several models).
Fillers in the material seldom cause need for increased cleaning
as buildup only occurs when Teflon coating/cloth needs to be
changed.
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Smoke and fumes are common as residue is burned on heat platen
core between cycles (ventilation may be required).
Virtually no smoke or fumes during welding process at low
temp.
Contact vs. Non-Contact Hot Plate Welding:
CONTACT WELDING
(High or Low Temp)
NON-CONTACT WELDING
(Very High Temp above 900F)
Faster cycle times:
15 to 60 seconds typical
Slower cycle times:
30 to 90 seconds typical
Higher Maintenance. Teflon coating or Teflon Coated Fiberglass
Cloth required on heat platen or insert surface with some
materials. Some fillers in high temp materials leave residue on
platen which must be brushed/wiped several times per day.
Lower Maintenance. No coating required regardless of the
material to be welded.
Parts can be welded 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 more precisely as there is no contact based
melt step to flatten/parallel joint surfaces.
Flash traps may be required for cosmetic applications when
welding with contact.
Due to limited displaced material, flash traps are often not
required.
Temperatures typically below 900F. Limited risk of thermal
damage to non-joint areas of parts in close proximity to heat
source.
Temperatures often in excess of 900F. High risk of thermal
damage to non-joint areas of parts in close proximity to heat
source
About Hot Plate WeldingHot Plate Welding Process:Step OneStep
TwoStep ThreeStep FourStep FiveStep Six
Vertical vs. Horizontal Platen Systems:Critical Hot Plate Welder
Parameters:Time and Temperature:Types of Hot Plate Welds:Low
TemperatureHigh TemperatureNon-contact
High Temp vs. Low Temp Hot Plate Welding:Contact vs. Non-Contact
Hot Plate Welding:
