How to Choose a Suitable Hot Plate Welding Technology

by Alex Lee; Email: alexlee2696@163.com; Mobile/Wehcat/Whatsapp: +86-15918523336

Hot platen plastic welding concerned to complex technical factors, normally, before we confirm a hot plate welding technology in detail, we need to consider as below details besing parts material, parts geometric design and welding result requested.

I. The Key Parameters of Hot Plate Welding?

1. Melting Temperature: the temperature of hot platen to melt thermoplastic, which is depends on material. The temperature also effects the time spent in melting, the temperature is higher, the melding time is shorter, ignoring the characteristic of thermoplastic material.

2. Melting Time: the time spent in melting material by hot platen, which depends on thermoplastic material and affected by melting temperature.

3. Melting Pressure: The pressure forced to plastic parts during hot platen melting;

4. Melting Depth: the volume of molten material by hot platen, means the moving distance since hot platen contact plastic parts to moving stop, which affects welding strength deeply and melting follow. It depends on the welding quality requirements, materials and parts designs, etc.

5. Fusing Time: The time spent in keep plastic parts together for fusing, which depends on material mostly and melting volume. It affects welding performance and production capacity critically.

6. Fusing Pressure: The pressure forced to plastic parts to keep them from lose during plastic fusing. It mostly depends on material, variation, stress of plastic parts. I affects welding strength deeply.

7. Fusing Depth: The jigs moving distance since the plastic halves contact each other to the jigs moving stop. It affects welding strength, welding air-tightness and welding flash much.

II. The control of hot plate welding process:

1. Temperature: Means the temperature of hot platen for melting thermoplastic material, requests stable  and even at different area of hot platen;

2. Time: hot plate melding time and fusing time (also called as “cooling time” or “holding time”)

3. Depth: the jigs motion depth when different steps of hot plate welding, including melting depth and fusing depth. Also means material melting volume and fusing flash volume;

4. Action Speed: The hot plate welding tooling motion speed, including jigs motion speed when close and open, jigs motion speed during melting and fusing, hot platen forward and backward motion speed. Normally the speed of jig opening/closing and hot platen motion requests high, and the melting and fusing motion speed requests lower;

5. Pressure: including melting pressure and fusing pressure, normally it requests lower pressure for melting and high pressure for fusing.

III. Low Temperature welding and high temperature welding?

Low temperature hot plate welding normally means hot plate welding applying temperature for the thermoplastic melting is lower than 260℃ (normally 180~230℃), while the thermoplastic melting temperature of high temperature hot plate welding normally is over than 260℃ (normally is 380~430℃). The selection of low temp welding or high temp welding mostly depends on the material. Mostly, low temp welding is good for material which will be carbonized under high temperature, such as nylon, PP with GF, etc. And because of low temperature, material will not be decomposition easily, lower temperature welding can reach higher welding strength comparing high temp welding, while high temp can maximum reduce the volume of molten material sticking on heat tooling. The advantages of both type hot platen welding as below compared:

Factors	Low Temperature Welding	High Temperature welding
For Challenging Material	Good	Not good
Welding Strength	Good for most material	Not goof for some material
Flash Stick on Tooling	More (requests special surface process on hot platen)	Less
Requests Machine Motion Control	Requests much higher closing speed after hot platen move away from parts	No need to high speed
Hot Platen Material	No high requirement	Hot platen material works under high temperature, it requests material with high melting points and good state stability
Better for	Non contact welding	Contacting welding

IV. The force of hot plate welding action?

1. Pneumatic：apply pneumatic cylinders to control jigs and hot platen motion and force pressure during hot plate melting and welding. The advantages of pneumatic hot plate welder is lower machine manufacturing cost, fast motion speed. Pneumatic hot plate welder can meet the most of welding requirement.

1. Hydraulic: apply hydraulic cylinders to control jigs and force pressure during hot plate melting and welding. Its advantages is can provide very high pressure during hot plate welding which is applied to finished hot plate welding requests high strength.

  For the fast motion, normally,machine applies pneumatic system to control the motion of hot platen.

1. Servo Motor: apply servo motor systems to control jigs and hot platen motion and force pressure during hot plate welding & welding. Servo hot plate welding is with advantages of high control precision, fast motion speed, and can realize the steps control of hot plate welding process, meeting hot plate thermoplastic joining to in high requirement, especially perfect to lower temperature welding or non-contact heat welding.

Because the developing of demand, servo hot plate welding machine is more and more welcomed by market.

1. Half Servo (Servo & Pneumatic )Hot Plate Welder: apply servo motor system to control the motion of jigs and apply pneumatic cylinders systems to control the motion of hot platen. Machine apply servo motors to control jigs motion to ensure its fact action, precision control in steps process, and on the other hand, because the speed control accuracy of hot platen is not very important to most of hot plate welding, applying pneumatic system to control hot platen by which ensure fast hot platen motion speed while achieves economical machine manufacturing cost.

	Pneumatic	Hydraulic	Servo Motor	Half Servo Motor
Jig Control	Pneumatic	Hydraulic	Servo Motor	Servo Motor
Hot Plate Control	Pneumatic	Pneumatic	Servo Motor	Pneumatic
Cycle time	fast	slow	Most fast	fast
Control Precision	Low precision, requests extra mechanism design for precision	Low, requests extra mechanism design for precision	High	high
Difficult to realize	Difficult to realize	Difficult to realize	Easy to realize	Easy to realize
Pressure	High	Very high	/	/
Machine Cost	Lowest	High	High	Intermediate
Maintenance Cost	Lowest	High	High	Intermediate