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.
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.
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
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.
After the joint area reaches molten temperature, the holding fixtures open and the heat platen is withdrawn.
The holding fixtures then close, forcing the two parts together until hard-stops on the holding fixtures come into contact with one another.
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 |
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 half, both against heat platen and against each other. | Single motion (upper only) fixturing allows independent control of force/speed of upper part half only. |
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 950°F.
HIGH TEMP CONTACT WELDING(above 500°F) |
LOW TEMP CONTACT WELDING(500°F or less) |
Faster cycle times:
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Slower cycle times:
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| 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. |
| 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 WELDING(High or Low Temp) |
NON-CONTACT WELDING(Very High Temp above 900ºF) |
Faster cycle times:
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Slower cycle times:
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| 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 900ºF. Limited risk of thermal damage to non-joint areas of parts in close proximity to heat source. | Temperatures often in excess of 900ºF. High risk of thermal damage to non-joint areas of parts in close proximity to heat source. |