Hot Plate Welding: Part Sticking & PTFE coming off

[Paolo]

Hello guys,

I'm having problems with my hot plate welding. The wo main issues are part sticking and PTFE coming off from carrier plate made from steel. We weld HDPE 10%GF and HDPE at 240ºC and for both surfaces the PTFE is coming off.
Does it happened with someone and was able to fix the issue? If needed more informations please tell me.

[Jendalf]

Hi,
Check the termocouples at the hot plate - PTFE layer is only to 260°C - 270°C. Its possible that thermocouple doesn´t show right temp and the hotplate is overheated.
Its also possible that it is locally overheated.

If its ok, than change the layer for some high temperature surface.
j

[Paolo]

Jendalf,
I measured the surface temperature with a termocouple and with IR and both gave the same temperature so I supose it's ok. Now what I know is that PTFE is coming off in the same place and I think it's caused by the part (sharp edge).
What other layer surface you suggest?
Thank you!

[Pilot]

Do you have any requirements for welding quality? Also visualy OK, or are the ribs hidden after welding. PTFE is problematic. You can go down with contact speed of part and mirror. Best is move the part as close to PTFE is possible, wait 2 sec. and than continue. Please check and follow strength of welding, You will se the curve of max strength, which will go UP and in this point you have to replace PTFE.
My exp. is to replace PTFE after cca 12 000 cycles. (depending on settings of machine). Next possible way is to use 400°C mirror without of PTFE.

[Paolo]

Pilot,
Thank you for your tips. The quality requirements for welding are low but the weld must resist X Force and cannot let pass water (watertightness) . Waiting 2s in front must be a good idea althought the cycle time will be higher. Shouldn't the strength curve goes DOWN if the welding is weak? I mean , max strenght will be lower with poor PTFE than with good PTFE, or ma I misunderstanding something?
Can you please what brand of mirrors you're talking about?
Once again, thank you!
Paolo

[Pilot]

I am talking about PTFE mirrors. The strength curve will go up with bad sutface and than it will drops down. It is a paradox. please test the parts on daily base and put results into graph. You can also reduce a pressure of melting parts on mirror during melting.