An ultrasonic cleaning bath does not operate in isolation so getting the best out of your bath means looking at three important and interconnected factors; the bath itself, the cleaning solution used in the bath, and the parts being placed in the bath to clean. Looking at each in turn;
The ultrasonic cleaning bath – Whilst ultrasonic activity is undoubtedly the most important factor, it is worthwhile checking that we are running the ultrasonic cleaning bath at the right temperature; that the parts to be cleaned are being held in the bath by the correct basket and that we are filling the bath to the correct solution level. All of these should be specified in the manufacturer’s operating manual but can generally be determined through a combination of simple testing and common sense. So to the most important factor, the ultrasonic activity that determines how effectively and efficiently we will be cleaning our parts. There are specific (and costly !) pieces of equipment that will measure the level of ultrasonic activity but the simplest and quickest test is the “foil test” – the placing of a small piece of normal aluminium foil vertically in the bath, with the ultrasonics switched on, for 30 seconds. With good ultrasonic activity the foil should emerge evenly covered with tiny pinprick holes or indentations. If areas of the foil are still smooth or you have large holes in certain spots this is a sign of inadequate or excessive ultrasonic activity. Ideally, the test should be performed in various parts of the bath to ensure ultrasonic activity is uniform throughout.
It is important that this test is performed when the bath solution is heated and degassed (removing all air trapped within the solution which impedes ultrasonic activity) so that we get an accurate representation of the ultrasonic activity in normal operating conditions. I would also recommend that the test be performed in four situations (done in the following sequence), with water only, with water and cleaning solution, with the basket alone placed in the bath, with the normal loads of parts placed in the basket in the bath. Comparing the relative results from each of the above should give an indication of where any problems lie. Whilst it is normal for ultrasonic activity to be reduced as we place the basket and then the parts in the solution, the level of reduction will be an indication if there is a real problem in this area.
The cleaning solution – Using the correct cleaning solution is vital. The solution must be right for the removal of the contamination but it must also be right for the transmission of ultrasonic activity within the bath. Viscous and non-water-miscible chemicals will interfere with the ultrasonics. As stated above I would recommend the foil test be performed in straight water and in the chemical solution for the results to be compared. A drastic reduction in ultrasonic activity with the chemical suggests you have the wrong chemistry. Other factors to consider are whether the correct concentration of chemical is being used, whether we are operating at the right temperature, and whether over time the solution is becoming too contaminated to do its job properly. Again we should refer to the instructions of the chemical supplier but observation and common sense should also indicate if there is a problem in this area. If the ultrasonic cleaning bath has been supplied with filtration this should prolong the life of the chemical but the filter cartridge should be checked regularly to ensure it is not blocked.
The parts themselves – This might appear a strange inclusion in the factors to be checked, but performance of the ultrasonic cleaning bath will be significantly affected by the parts being cleaned themselves in three areas. The weight and volume of parts being cleaned should be no more than half of the weight of the bath solution and one-quarter of the bath volume to allow for sufficient ultrasonic activity and removal of the dirt into the solution. The level of contamination on the parts going into the ultrasonic cleaning bath should also be reviewed. ultrasonic cleaning is a very fine detailed cleaning. It is not particularly well suited to high levels of dirt. Where parts are very dirty a pre-cleaning operation to remove the large pieces of contaminant will dramatically improve the cleaning results of the ultrasonic cleaning bath. The positioning of parts within the basket will also affect cleaning performance. Ideally, parts should be evenly spread with sufficient space for the ultrasonics and cleaning solution to access the parts and remove the contaminant.
I hope this short guide to getting the best out of your ultrasonic cleaning bath is helpful. As always feedback and any further questions are much appreciated.
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