Problem of Vacuum Coating Machine During Operation
1. Can not reach certain vacuum degree: The same pumping time, but vacuum degree is lower than normal situation. Close main valve, if vacuum meter needle drops quickly, that mostly means vacuum chamber has leakage. So we need to find out where is leaking. If drops slowly, that means pumping ability of vacuum pumps is not good. Then we mainly look for leakage of vacuum pumps and valves, diffusion pump oil was polluted or oxidized, sealing of fore pipes, pump oil is not enough; or pump oil was emulsified, shaft seal has oil leaking, etc. Leaking has internal leaking and out leaking. We can use flame to check bigger leaking point because airflow can deviate flame. Pumping air, use candle or lighter to check around possible point. The point will be found if flame deviate to leaking point. To check little leaking, under high vacuum, sensitive response of ionization tube to some gases. For example, acetone or alcohol, use medical injector to spray. Indicator of ionization tube will swing obviously. This method needs our patience. We have to wait for stable indicator value(pumping ability and leaking rate is balanced) to spray. It is better to check it repeatedly. Internal leaking always happens in the machine with water-cooled jacket. No possible point in out leaking, but has below phenomenon: low mechanical pump pumping speed, low vacuum meter indicator value, easily emulsified mechanical pump oil, iron parts in vacuum chamber is corrosive. Above conditions means internal leaking.
2. Vacuum chamber can not reach vacuum degree: Maybe pumping ability of pump group is not enough, or high air leaking rate, or both. Pumping vacuum chamber to certain vacuum status, close vacuum valve, if vacuum meter value goes up quickly, mostly means vacuum chamber has leaking. Now we need to check leaking point and fix leaking. If vacuum meter value goes up slowly, maybe pumping ability of pump group is not enough. The point is finding leaking of vacuum pump and valve, or vacuum pump oil was polluted or oxidized, or seal of fore pipe is bad, pump oil is not enough, or pump oil was emulsified, shaft seal has oil leaking, etc. This time we need to change pump oil or pump. If vacuum degree goes down within short time quickly, normally it is chamber door, vacuum valve, middle insulated door such dynamic seal parts are ageing, scratched and oxide skin dropped on seal wire. We can clean and change seal parts, inspect and fix manual switch valves. If they are good, then check vacuum chamber and external interface position, such as connected flange, water cooled electrode, pipes and vacuum pipes, etc. Sometimes we can use acetone to check vacuum degree changing to find leaking point. If we can not find the leaking point finally, we disconnect all possible leaking parts, then connect again, or process solid flange to plug up to test.
3. Vacuum coating machine slow pumping: Checking start from rough pumping. If rough pumping time is long, that means rough pumps have problem or fore pipe has leaking. If rough pumping is OK, then it is diffusion pump, we need to clean pump body and change pump oil.
First seen on: http://fsfxzk.blogspot.com/2017/
1. Can not reach certain vacuum degree: The same pumping time, but vacuum degree is lower than normal situation. Close main valve, if vacuum meter needle drops quickly, that mostly means vacuum chamber has leakage. So we need to find out where is leaking. If drops slowly, that means pumping ability of vacuum pumps is not good. Then we mainly look for leakage of vacuum pumps and valves, diffusion pump oil was polluted or oxidized, sealing of fore pipes, pump oil is not enough; or pump oil was emulsified, shaft seal has oil leaking, etc. Leaking has internal leaking and out leaking. We can use flame to check bigger leaking point because airflow can deviate flame. Pumping air, use candle or lighter to check around possible point. The point will be found if flame deviate to leaking point. To check little leaking, under high vacuum, sensitive response of ionization tube to some gases. For example, acetone or alcohol, use medical injector to spray. Indicator of ionization tube will swing obviously. This method needs our patience. We have to wait for stable indicator value(pumping ability and leaking rate is balanced) to spray. It is better to check it repeatedly. Internal leaking always happens in the machine with water-cooled jacket. No possible point in out leaking, but has below phenomenon: low mechanical pump pumping speed, low vacuum meter indicator value, easily emulsified mechanical pump oil, iron parts in vacuum chamber is corrosive. Above conditions means internal leaking.
2. Vacuum chamber can not reach vacuum degree: Maybe pumping ability of pump group is not enough, or high air leaking rate, or both. Pumping vacuum chamber to certain vacuum status, close vacuum valve, if vacuum meter value goes up quickly, mostly means vacuum chamber has leaking. Now we need to check leaking point and fix leaking. If vacuum meter value goes up slowly, maybe pumping ability of pump group is not enough. The point is finding leaking of vacuum pump and valve, or vacuum pump oil was polluted or oxidized, or seal of fore pipe is bad, pump oil is not enough, or pump oil was emulsified, shaft seal has oil leaking, etc. This time we need to change pump oil or pump. If vacuum degree goes down within short time quickly, normally it is chamber door, vacuum valve, middle insulated door such dynamic seal parts are ageing, scratched and oxide skin dropped on seal wire. We can clean and change seal parts, inspect and fix manual switch valves. If they are good, then check vacuum chamber and external interface position, such as connected flange, water cooled electrode, pipes and vacuum pipes, etc. Sometimes we can use acetone to check vacuum degree changing to find leaking point. If we can not find the leaking point finally, we disconnect all possible leaking parts, then connect again, or process solid flange to plug up to test.
3. Vacuum coating machine slow pumping: Checking start from rough pumping. If rough pumping time is long, that means rough pumps have problem or fore pipe has leaking. If rough pumping is OK, then it is diffusion pump, we need to clean pump body and change pump oil.
First seen on: http://fsfxzk.blogspot.com/2017/
Comments
Post a Comment