S.O.S

[luisoliveira05]

Good afternoon everyone once again come here for help.
Last September also gas supplier changed the entire facility.
  to start all well but as I have two systems started to have problems with the oldest past three weeks the problems started in the latest:
1- 73f-ns bond strength test min: 7250psi obtained:5201psi

during the tests we apply 3 test pieces at the same time but the results are very different with two powders is even worse I do not know what is going on, the parameters are the same as always, will the equipment require calibration?


thank you

[loriolo]

Hi Luis
If you do not changed any thing else that gas supplier, try first to check gas purity, and gas distribution net, for leaks or micro pores that can ad air in your gas for ventury effects, the purity of plasma gas must be 99,98 %, and without O2.

[Joris Kraak]

Hi Luis,

Good point mentioned by loriolo, if you changed nothing else than gas supplier first check that. Did the gas supplier specify his gas quality? The higher the purity the better the lifetime of your spare parts and the more reliable your plasma. Equipment manufacturers often recommend a purity of 4.6, >99.996%, for plasma spraying, but the higher the purity the better of course! You can check if you see an increase in electrode wear and a black forming scale on the electrode. What happens with oxygen in the lines is that the tungsten in the electrode will react with the oxygen and become tungsten oxide. The higher the temperature of electrode the more wear you will see!

However I can't believe suddenly the gas quality is that bad it has such a huge effect on the bonding strength. If it has that effect your nozzle and electrode will be eaten away so probably there must be something else. Also coincidence that two systems showing the same problem more or less the same time so I would also not look into direction of calibration at first sight.

Let me summarize some point for you to check:

1. Do you use air jets for cooling or pinching, probably yes so check air quality. Is the oil still removed, filters clean , dryer working properly?

2. Is the air pressure equal and pinched at same point each and every time?

3. Check voltage and parameters at the control module is all within tolerance? If not something else is going on, could be gas (unlikely) check spare parts and water cables, measure voltage at gun and jam-box if drop is too high replace water cables. Perhaps spare parts are worn (insulator ring).

4. What is temperature of test sample, did you change anything in this procedure you follow? (type of glue, curing, temp of sample, thickness,...)

If you still have a problem after these suggestions and in urge this problem needs to be solved you can always send me an e-mail, I will send you my mob nr so we can have a chat.

joris.kraak@czcoating.com

regards,
Joris