We have a high-mix, low-volume type shop and clean over 50 stencils per day. The wash and rinse cycles in our aqueous stencil cleaner is ok, but the drying time takes too long (15 - 16 minutes per stencil).
You indicate that hot air can damage a stencil. How can I dry my stencils rapidly without elevated temperatures?
If your stencils are going back into inventory rather than into production, expediting the drying process may not be necessary. Just place them on a rack and allow them to air dry naturally. That way you can maximize the throughput of your stencil cleaner by eliminating the drying cycle (and save energy too). There is no need to waste energy on drying stencils if they are just going back to the cabinet.
However, if you do need to expedite drying to meet a production run, the fastest and safest way to dry a stencil is by using handheld LOW-PRESSURE dry compressed air, the same quality air that is used to operate a pick and place machine etc. I stress Low Pressure because the principle is not to �blow� the water off the stencil; it is to simply apply the dry air to the surface of the stencil. The desiccated air is �hungry� for moisture. It�s like seeing alcohol evaporate. A 29-inch (750 mm) stencil can be dried in less than two minutes by using this method (even faster if the stencil is lightly wiped first).
There are several problems associated with stencil cleaners that have integrated drying systems. You have discovered one of them � long cycle times. This usually stems from the fact that the drying is done within the same chamber as the washing and rinsing. This means that the drying system not only needs to dry the stencil, it also needs to dry the chamber walls and manifolds. Couple this with the fact that most stencil cleaner manufacturers are now aware that hot air cannot be used, the drying cycle usually takes longer than washing and rinsing cycles combined. The drying cycle also limits the throughput of the machine. Ideally, a separate chamber should be used for drying so that additional stencils may be processed as others are dying.
High-pressure air knives should also be avoided. Just as high-pressure water sprays can bend delicate land mass areas, so can high-pressure air.
However, if you do prefer automatic drying, there are standalone dryers available. Smart Sonic has one that is capable of drying up to three stencils in approximately 9 minutes (Model LTD-3). It uses low temperature air that is thermostatically controlled not to exceed 110 degrees F. A standalone dryer will allow you to dedicate your machine to washing and rinsing stencils and increase your total throughput significantly.