GENERAL

For cases where the horn and tip configuration is such that the tip can not reach far enough into a processing vessel, 5" long "Half Wave" Extender Tips are available.  For even longer-reach applications, 10" (25.4 cm) long "Full Wave" Extender Tips can be furnished.  However, solid extender tips are less expensive than solid horns and thus are also recommended as a lower-cost disposable alternative.

EXTENDER TIPS

Certain protocols, such as older versions of the EPA Contract Laboratory Program for Analysis of Semi-Volatile Wastes and Pesticides and the EPA SW-846 Method 3550 for Analysis of Solid Wastes, required an ultrasonic liquid processor with a ½" (1.91 cm) Standard Solid Horn.  The ¾" Standard Solid Horn gives moderate intensity cavitation, as opposed to the ¾" High Gain ("Q") Disruptor Horn, which gives very high intensity sonication.  Use of the Standard ¾" Tapped or Solid Horns at the same output control knob settings or the ¾" High Gain Q-Horn at half those settings yields identical results.

Further, methylene chloride and other thin solvents, used for extraction in many protocols, were found to wick under replaceable ¾" and 1" flat tips and cause early failure.  For this reason, use of the ¾" Solid Disruptor Horn in lieu of the ¾" Tapped Disruptor Horn was recommended for EPA use.  An alternate would be to use the ¾" Solid High Gain ("Q") Disruptor Horn instead of the ¾" Tapped High Gain Q-Horn.  Since the output at the tip of solid horns is the same as on the replaceable flat tip of tapped horns of like configuration, similar substitutions apply in other disciplines.  Another related problem occurs in sonicating liquids containing suspended abrasive fine particles, such as aluminum oxide or tungsten carbide; such fines are carried between the tip and horn and grind away both mating surfaces.  The result is eventual loss of the horn, as well as the tip.

Many customers like to work in flasks, for which a special ¾" horn and the ¾" Tapped Half Wave Extender Tip were recommended for EPA work.  Again, the output amplitude (and thus intensity) at the ¾" Flat Tip is the same whether it is on the ¾" Standard Tapped Horn or on the ¾" Extender (in turn mounted on the special ¾" horn).  Because of the high cost of the special ¾" horn, the ¾" half wave extender tip system was redesigned.  The original ¾" Solid Horn and Tapped ¾" Half Wave Extender Tips were superseded by newer Tapped ¾" Half Wave Extender Tips which fit the Standard ¾" Tapped Horn.  The latter two newer tips fit directly on either the Standard or the High Gain "Q" ¾" Tapped Disruptor Horns.  To further offset high costs, greatly reduced prices are offered for solid extender tips bought in moderate quantities.

[NOTE - The old {as of 1995} ¾" Extender Tips can NOT be used on the new Standard or High Gain "Q" Tapped Horns.  Similarly, the new Half Wave Extender Tips can NOT be used on the old Special Horn.  For those customers who have already invested in old Extender Tips and the Special Horn and do not wish to change over, the old extenders will continue to be supplied (by Misonix).]

Half and full wave extenders put extremely high stress on the connecting stud, which may not survive extensive use at high output control settings.  Contact the factory for such special applications.  Disclaimers in current processor instruction manuals may be disregarded, provided that three conditions apply.  First, the factory must agree.  Second, the connecting stud MUST be a new stainless steel stud (not an old black alloy steel stud).  Third, the temperature of the horn/extender joint must be routinely monitored (with power OFF!); any temperature more than just comfortably warm requires that power be turned off and the joint disassembled for cleaning and inspection.

(illustration by S. Berliner, III - scope expanded 10 Dec 05 - all rights reserved)
EXTENDER TIP ARRANGEMENT

SAPPHIRE TIPS

To minimize sample contamination by erosion products and further reduce overall project costs, the author developed a bonded sapphire tip for solid horns.  A thin disc of clear, single-crystal, boule-grown, synthetic sapphire is bonded to a solid horn with an epoxy of extremely high shear strength.  Sapphire (corundum, alumina, aluminum oxide) has a hardness of 9 on the Mohs scale where diamond^# is 10.  Tests have shown that sapphire surfaces last approximately 10 times longer than titanium alloy under like conditions.  Although very expensive initially, the sapphire tipped horns avoid the need for some nine changes of tapped tips and associated downtime and labor.  It is suggested that three sapphire tipped horns be rotated in use for critical processes; one on line, one on standby, and the third available for refacing at the factory.  There are three standard sizes of sapphire tipped horns (½", ¾", and 1").

Sapphire discs can not be used on replaceable flat tips because the forces generated in wrenching the tips on and off crack the disc.  Thicker tips can not be used because the joint then moves further toward the highest strain area of the horn (the nodal point) and the joint will fail.  To further reduce overall costs, the author recommends that sapphire tipped extenders be considered.  Sapphire tips can be fitted to solid extenders for the same additional cost as for their fitting to solid horns.

# - Diamond can not be used as a facing because it is pure carbon and will oxidize (burn) away instantly (an expensive mistake!); sapphire, being aluminum oxide, is already reduced (inert).   (10 Dec 05)

SOME TIPS ON TIPS

One of the problems encountered early on in the development of the modern ultrasonic cell disruptor and liquid processor was noted earlier in this work.  There is a tendency for water and certain solvents to wick under replaceable 1" and ¾" (and even ½") flat tips, and of abrasive fines to enter with the liquid, and cause early failure.  The tendency is more marked in the larger diameters because of the "cantilevering" effect; as the tip is pulled back in the deceleration mode, the center moves faster than the rim due to inertia and plastic deformation at 20kHz (or higher).  This leaves the underside of rim slightly pulled away from the circumferential edge of the horn and the contaminants enter the annulus thus opened.  In the acceleration mode, the rim slams back against the horn, trapping and grinding any solid contaminants against both mating faces and cavitating the liquid between the faces.  These two actions rapidly cause deterioration of the tip and horn.

A similar cantilevering effect causes early failure of improperly bonded sapphire disks.  If the epoxy bond line is too thick, the disk "wallows" in the flexible adhesive and fails in a circumferential fracture line, approximately 1/3-radius in from the edge.  On the other hand, a rigid bond will fail because the base metal of the horn (titanium alloy) is elastic.

Coatings such as flame depositions or platings spall off within seconds at high amplitude as the cavitation process unerringly picks the molecular weak spots in the coating and drills through and under.

The author has personally seen the finest technical chromium plating break up while he watched, much as the most highly-touted ceramic facing vanished in moments.  Sintered carbides and sapphire disintegrated in seconds as cavitation occurring at the surface and between the grains broke apart the grain bonds.

To prolong the life of any titanium tip, be it a replaceable flat tip, a microtip, or a solid horn or extender, a reasonable amount of polishing on fine crocus cloth or emery paper may be done.  The limitation is the inability of the unit to be tuned if too much material is removed.  Polishing should be done as soon as the radiating surface becomes roughened (matte finish).  Since the erosion results as cavitation works into the dendritic structure of the base metal, the longer one waits before polishing, the deeper the pitting gets and the less effective any subsequent polishing becomes.  This polishing can not be done well by hand without a jig or fixture to hold the radiating face parallel to the abrasive material.  It can NOT be stressed enough that machining or grinding is too drastic a remedy.

The author recommends always having at least three tips available; one on line, one reserved for replacement, and one being refinished.

S. Berliner, III - © 2005, 1995, 1992, 1988 - (all rights reserved)

[It is my intention to revise the above AL-5 with more illustrations than were present in the last revision or in the original TN-2 and to link appropriate other sections of this website.]

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The original TN-2 (of Oct 1988) also included ordering numbers for Heat Systems (Misonix) horns and tips; it is reproduced here for the convenience of those individuals who can follow the old part numbers; the author makes no representation whatsoever that the numbers are current nor that the items are still available:

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ORDERING NUMBERS:

TIP DIA:		½"		¾"		1" 

SAPPHIRE TIPPED HORN

		201S		208S		209S

TAPPED HORN

		200		207		210 

HALF WAVE EXTENDER TIPS

TAPPED	406HW050T		406HW077T		406HW100T* 

SOLID	406HW050		406HW077		406HW100* 

SAPPHIRE	406HW050S		406HW077S		406HW100S* 
TIPPED 

FULL WAVE EXTENDER TIPS

TAPPED	406FW050T		406FW077T		406FW100T*

SOLID	406FW050		406FW077		406FW100*

SAPPHIRE	406FW050S		406FW077S		406FW100S*
TIPPED

* - Non-standard; special order only

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ULTRASONIC DEBURRING

Ultrasonic energy should, on the face of it (awful pun), be quite useful for deburring machined parts and it has been used successfully in such applications on occasion.  The problem, and the reason such a use is not better known, is that the very action which removes the burrs also degrades the machined surfaces.  Long, narrow burrs, lightly attached, are readily knocked loose and the remanent stub polished over by cavitation impacts but short stubby burrs, wider at the base and strongly attached, are no more affected than the machined surfaces from which they protrude:

(22 Sep 06 illustration by S. Berliner, III - all rights reserved)

Addition of a fine abrasive slurry to the cleaning bath can greatly facilitate burr removal but may also degrade both the work surface and the radiating face of the tip/horn.   (19 Sep 08)

Thus, only very unique situations are amenable to ultrasonic deburring; contact the author for individual solutions.

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You may wish to visit the main ULTRASONICS page, et seq., with more on ultrasonics, as well as the Ultrasonics Cleaning page {in process} and the Ultrasonics Glossary page {also in process}.

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Those persons interested in SONOCHEMISTRY might wish to look at the sonochemistry pages of: