Cylinderhead Brush deburring(1)

Many components of the automobile engine are in aluminium .When the aluminium parts are machined it remain on the edges small parts of material that we call burrs.

These burrs have to be removed to avoid problems during the part assembly or for the good mechanical function of the part.

The action to remove these burrs is known as “deburring”. According with the areas where are located these burrs there are several ways to removed it in high production processes: by brush deburring , by abrasive blast , by high water jets, electrolytic, walnut shell, thermal deburring, paste deburring, vibratory bowl abrasive deburring…

The most used in the automotive  industrie for the cylinder heads are the brush deburring and the high pressure water deburring.

There are a lot of suppliers for the deburring equipments but to have a cost productive process the best solution is to include the deburring process on the wash process. Why? . Because the parts after machining or after deburing have to be washed as well and because the brush deburring with aluminum parts has to be made in wet conditions .

The brush deburring and the high pressure deburring have been the two technologies better integrated in the wash lines.

The first integrator of brush deburring in the wash lines was the company AGULLO in the late 70’s. The first machines were supplied to RENAULT in France for the deburring of aluminium cylinder heads at high production (300 p/h). The cylinder head combustion , cam and manifold faces were deburred with automatic brush deburring units located at the entrance of an in line lift and carry transfer washing machine.

The brush deburring units to increase their deburring efficiency have evolved to planetary brushes where several brushes rotated on their shaft at the same time that theirs shafts rotated around the main shaft. These planetary heads have been for many years a reference on the brush deburring having a combined action to remove the burrs of the edges.

In a cylinder head machining line there are normally three wash operations : Primary,intermediate and final . The deburring operations are incorporated generally on the intermediate and the final washers.

 In the  intermediate washer there is the brush deburring of the cylinder head camsahft face , and the complete wash of the cylinder head before the bearing cap assembly .

On the final washer the machine  incorporates the deburring of the remaining faces ( combustion , manifolds, and extremities faces) . According with the production rate and the number of faces to be debured  the final washers became big machines (till  13 mts. long) and the PLC softwares complex. For these reason it was a tendency in late 80’s to separate this last brush deburring operation of the final wash operation in two machines: one machine for deburring with brushes and one for high pressure final wash-deburr.

The cylinder heads had more and more areas to deburr and the final cylinder head deburring became a self transfer complete machine.

 

Late 80’s the high pressure water deburring was also applied in high production cylinder heads . The first high production machine in Europe was supplied by AGULLO in Ford UK with 600 HP power and four high pressure pumps.

The high pressure water deburring can deburr faces but also has the advantage to allow to deburr oil galleries intersections and in the final washers the high pressure wash become also a standard to allow high cleanliness levels . In consequence the high pressure deburr is used in the final washers as a complement of the final wash operation.Having then the high pressure pack on the final washer why not to use the HP water for a complete deburring of the cylinder head? 

Of course this could be an option but the operational cost of a high pressure deburring operation is 2 to 3 times more expensive that for the brush deburring . In consequence anything that can be effectively brush deburred is better to do it with brushes than with high pressure water.

In the present the aluminum cylinderheads or the aluminium cylinder block flat faces are preferably deburred with brushes keeping the high pressure water for the oil galleries intersections , or other small deburring operations (oil galleries , bearing cap intersections, oil feed…)

 For a new part project ( i.e. cylinderhead) is possible to identify areas where the burrs will be present after machining and that have to be removed. But you can not identify 100% of the areas .Some times due to machined areas intersections with cast areas the burrs are present but not  in an predefined position .For this reason is useful on the cylinder head final washers to have a high pressure water jet programable with CNC or robotic  and a reserve of several seconds on the cycle time to can solve these unexpected burrs .

The brush deburring for flat surfaces is the more cost efficient solution compared with the high pressure water , but the high pressure water can reach areas where the brushes can’t.

Now in the market there are several companies proposing the planetary brush deburring heads .

The recommended brushes are the cups with stainless steel wire , but for certain aluminium the abrasive wire is also wellcome.

In  next post we will explain how to manage the brush wire wear compensation.

Parts2clean Stuttgart .High Pressure wash/deburr

I remember when AGULLO supplied the first high production (220p/h) washing machine with high pressure water for wash/debur of cylinder heads in the Automotive industry in Europe . It was early in the 1980’s and the High pressure pumps power were for 600Kw. In this time not many companies in the world were able to supply high production machines and the addition of the high pressure was not frequent.

The high pressure installation engineering was a challenge. Not only the high pressure pump supplier didn’t have experience in the 5.500 hour/year continuous running of the pumps but other circumstances were added : working with recirculated water (filtration engineering) , keeping the water at controlled temperature (cooling engineering), keeping the overall noise of the installation (then at 85 dB )(noise insulation engineering), HP safety valves and HP distribution valves reliability , materials used on the HP jets and lances (mechanical engineering) , materials resistance to the HP impact for the fixtures and clamps, vapour exhaust ,vibrations transmission all along the machine,chemical detergents compatibility,flexible hose life…a lot of engineering and innovation.

For many years the AGULLO experience in the high pressure was on the top . Now , 25 years later there is a lot of companies that they say can offer high pressure wash installations.The HP pumps and accessories suppliers have more experience and the technology is better known but , is really so easy , are they selling with knowledgement of high pressure technique’s?… I don’t thing so.

Who are now the companies in the edge?

In the Parts2clean exhibition in Stuttgart I visited SUGINO , as I wrote in my before post who has a lot of experience in Japan on this Installations mainly in low production.

 In Europe we can find one small specialist: Piller in Baden-Wurttenberg(Germany) who has several HP deburr machines types with manual load or robot load ,like the CNC “Vector Jet”cabinets and dominates the deburring range of 400 to 800 bars with water or oil. Their experience comes mainly from the small mechanical components deburr at low production.They had difficulties to supply the complete process of wash,deburr.blow off , dry in one installation but step by step they are finding sollutions to do it using several machines. In Germany is considered as the main experienced supplier. Their clients are mainly germans. As particularity I can highlight that Piller  uses a CNC gantry robot on the roof of the machine moving the HP jet , keeping the part clamped on the table that can have additional CNC axis.

 

 

Another company present in the exhibition is also the german INDA-Markert of the SCHMID group. Indawas an small company with local activity in the high pressure that met Markert with experience in the German automotive market (Mercedes)and transfer washing machines. Both together are now presenting also CNC cabinets for HP operations with HP automatic tool exchange , or rotary transfers, or in line transfers. Out of Germany there are not too active ( out of Hyunday or Kia projects). They were also presenting a robot for deburring gearboxes , with automatic HP tools changer( rotary lances , V-jet , pin point jet..).

 

Of course we can not forget Dürr Ecoclean as global high pressure supplier despite his presence in the Parts2clean exhibition with only one machine for the general market ,the Cmax that I will talk about in a another post. They have the experience and globality that some others don’t have.

Another big specialist that becomes more global is the Canadian Valiant . This company was for years the competitor of AGULLO , and Centry Spray(after Ingersoll) ,and now for Dürr Ecoclean in America.

Valiant is present at the exhibition trough the Austrian TMS company ( body handling) hat now is part of the Valiant group and that will take the responsibility of the Valiant washers/deburr for Europe. The last 5 years of Valiant in USA have been successful , passing for the transfer in line , Ferris wheel supplier to be a complete partnerfor the Automotive industry ,supplying turn key installations with the handling, robot integration,washers(high pressure or robotics),deburr , leak test ,and special assembling machines and AGV transport . Their Aachen Engineering adventure is now forgotten and they seems determined to attack the European market from their new base in Austria. Is the only manufacturer that can compete with Dür Ecoclean as “global” supplier.

 

Part2clean Stutgart (4) Rotary transfer washers

Out of the already commented rotary transfer machines for small components , in the Parts2clean show I noted other manufacturers that they are active to wash or deburr bigger parts ( main powertrain components as cylinder block, cylinder head, crankshafts, gear box…).

Almost all the manufactures of these machines were German , and only few “foreign”. One of this foreign manufacturers was the Italian Tecnofirma. This company is an “old” company in the business. At the beginning mainly present in Italy . Years ago it started to wash cylinder block and cylinder heads Automobile components but the presence of AGULLO and ICOM in Italy stopped their development in the 1990’s . They were limited to crankshafts transfers or gear box components so long as AGULLO and ICOM had orders for the cylinder block and cylinder heads in line transfer washers for FIAT.

Tecnofirma developed rotary transfer washers for other components related to the motorcycles , tractors or gearbox components in Italy and also for the customer subsidiaries in Latinamerica or East Europe.. Now is improving his sales action in Germany and France , and they presented an interesting rotary transfer wash/deburr machine ( four stations) with an small ABB robot carrying a jet for the flex wash or blow-off.

 

 

 

 

The robot is applied directly inside of the wash chamber and has a jet on his wrist.

The High pressure pack and filter is installed in a separate module with the classic Hamelmann piston pump. The filtration is trough a safety cartridge filters and automatic paper filter

The machine has a robust look and the price announced seems interesting. Tecnofirma has a good experience in mechanical components customers. I hope that they can have a development in the next years if they achieve their export development.

Another of the “foreign” exhibitors was the Japanese SUGINO .This company has also a long history on the wash-deburr business. Their main market is the Japan companies and their transplants to other countries.

SUGINO has the best experience in high pressure applications in the wash and the deburr. Don’t forget that the Japanese automobile companies were the first ,worldwide ,to improve their cleanliness levels using high pressure water in their washers and after using also the high pressure for the deburring.This Market was advanced against the European or American markets.

SUGINOis the sole wash producer in the world, that I know ,that is also producing their high pressure pumps. In fact the division of high pressure pumps and his applications in all the industries is one of the hard points of Sugino. They have several patents and the advantage to produce themselves also the high pressure accessories ( 2ways valves, safety valves, HP jets, lances, distributors…).The use of the high pressure goes till to the jet cutting at 4.000 bars

Surprisingly despite their high experience and acknowledgement in the high pressure they have been not active in Europe. Their competitor KITO at least supplied Toyota in UK but Sugino has been out of this market. In USA they sold some machines 15 years ago in the gear box Ford factories but they din’t push too much the market and remain anecdotal.

Is really a pity because for me Sugino has experience , acknowledgement and inventive. Some tricky devices and original process invented by them ,and not yet discovered by the German suppliers( neither Americans), are fantastic and very efficient.

In the Parts2clean exhibition they presented the “Jet Clean Center”. Is a cell with CNC axis that allows to high pressure wash and high pressure deburr small components . These components can be manually load or robot load.

The must interesting thing of this machine is the Turret tool jet head. The turret has 6 possible different high pressure jets or lances that can be feeded individually trough a HP distributor. This machine is valid for small productions in a cell configuration and has been the first machine on this business to adapt the form of a High pressure cell , idea reproduced now for a lot of manufacturers.

 

SUGINO has also a family of rotary transfer machines for cylinder blocks and cylinder heads . The machine with two , three or four stations is integrated on in line or in cells productions . Recently they have supplied these machines for the new Mazda-Ford factory in China. They have a combination of the machine with a Cartesian 4 axis wash gantry robot located in the roof totally outside the machine as Durr Ecoclean Barcelona had.

The originality of their machine is that the load/unload of the parts can be made automatically without any further device .A vertical movement of the complete rotary table allows the part to be load/unload on a conveyor at the same time that the same vertical movement of the table allows to better wash and blow-off the parts in the other stations.

The application of the gantry robots instead of anthropomorphous robot in the high pressure wash-deburr applications is an interesting debate that I will write about in one further post after also a further robot cells post.

The weak point of these machines is that the indexing driving device with the vertical movement of the table is inside the machine , not easily accessible for maintenance. To do the same process the design of the Dürr Ecoclean Barcelona transfer rotary machine was much better solved with full accessibility to all the mechanics either rotary , lifting or gantry ( but more expensive of course).

In general the SUGINO wash-deburr processes , and high pressure devices are original,tricky and effective. The mechanical concept of the machine and their sizes are really designed for the Japanese Market . The design should be hardly modified to support the European rules and standards and by this reason is very difficult that some European client accept their machines standards. Is not their fault is a question of market demands. Something similar happened on the first machines supplied to Ford America.

But for markets like the Japanese or China, Korea..where the demand for big access for maintainability , and safety rules are not so stringent than in Europe , these machines are valid. But as the price is also important and these solutions are chipper, the client has to balance his decisions.

SUGINO has now a subsidiary in Chekia for his division of machine tools. It would be maybe a good opportunity for them to redesign their machines for the European Market demands.

OK ,that’s all for today. See you soon in my next post.

Parts2clean Stuttgart (3) Rotary transfer washers

One of my former customers , ask me why I have not talk about his Dürr Ecoclean rotary transfer washing machines in my last post.

Sorry¡¡¡ ,  effectively I supplied when I was in Dür Ecoclean an installation with three excellent rotary transfer washers to clean common rail injection pumps components at 2.000/300 bars that are today working 24h a day without problems.

The installation had a previous stage of high pressure deburr with robot at 2.000 bars followed of a rotary transfer machine with medium pressure spray wash,high pressure wash(300bar) with injection in contact and push pull system, spray , blow-off , vacuum dry . These machines are the top range in the field with central filtration and high pressures power units.The machines were designed and engineered by the Barcelona Dürr Ecoclean office team that was closed in 2007 but I’m not sure that these type of machines are still part of the Dürr Ecoclean catalogue. For this reason a I didn’t mention it in my last post that was dedicated mainly to the Parts2clean presentations.

Another innovative advantage of these machines was the flexibility as easy reconversion for new different parts. The pallet support on the rotary transfer table was of a quick change design. The clamping and High Pressure injection devices were of quick reconversion. The high pressure robot deburr( 2.000 bar operation) had automatic gripper change device with automatic grippers storage .

As maintenance features they had: total index driving system accessibility, total open doors for inside accessibility , quick change of internal components. The Centralised tank , filtration ,medium pressure pumps ,high pressure pumps ,very high pressure pumps , water treatment, and safety filters were installed in a remote area allowing to deserve three or more rotary transfer machines. This layout allowed to have a minimum surface layout on the working areas occupied by the machines itself , keeping the bigger floor surface of the tanks and pumps in the remote area . By other side this layout was an advantage for the maintenance people having all the pumps, valves,and filters in the same area for easy control and follow up..   

Neverless there is another type of Rotary transfer machines , the machines for powertrain components like cylinder blocks and cylinder heads by one side , and another simpler machines for gearboxes and crankshaft .

In my next post we will talk of the cylinder block and cylinder head rotary transfer machines.

Parts2clean Stuttgart (2).Rotary transfer washers

Talking with the more important exhibitors I noted some interesting tendencies: Rotary transfer washers, Robotic Cells , High Pressure wash/deburr… We will talk today of the Rotary Transfer Washers

1)Rotary transfer washers: These machines are defined by an horizontal rotary table who transports the parts to be washed step by step ( transfer) trough different stages of the process . Do not confuse with the rotary table washers where the parts are on a rotary table who rotate the parts itself in a vertical axis in front of the spray jets in a single chamber washer.

We can consider that there are two families of “rotary transfer washers” in automotive applications. The small ones dedicated to small parts (diesel injection components, brake components…)  and the bigger one dedicated to the powertrain parts(cylinder blocks, cylinder heads, crankshafts, gear boxes…)

The small ones are dedicated to clean small components of the injection systems or brake components in racks,fixtures or pallets . Bosch and Siemens are some of the Clients in Germany of these machines and several of their suppliers like Strama , Zippel , Silberhorn , Semmelroth etc.. have supplied this machines with several wash, rinse stations according to their specifications.

     

                                                         

                   

 

The special relationship between Bosch and their suppliers (normally not available with other clients) allows to the manufacturer to built a machine according with the Bosch Process specifications. The number of stations of the machine ,the position of the part in the machine, the filtration, the cycle times… all is defined by the Bosch Process. The manufacturer has to warranty the well functioning of the machine as Bosch take the responsibility of the Process .With this way several manufacturers of special machine tool or assembly machines have started to build washing/cleaning machines and now this activity is an important part of their production. After a certain time to work with these special conditions the manufacturers start to take their own responsibilities and to offer the wash equipements to others clients despite their limited experience compared with one specialised washer manufacturers.

These small rotary transfer machines allowes to treat with precision the wash of small parts with conduits with several rinse stations for better quality in a reduced layout. The load/ unload station allows a manual or automated handling . The wash operation if necessary can be in contact with the part due to the well location of the part on the rotary table and the possibility of a permanent clamp. Vacuum dry is also possible. The support of the parts to be washed on the machine can be individual fixture in the machine table itself , or an removable precision pallet.

As weak points we would say : the driving system accessibility , water splash between stations and internal accessibility. Each manufacturer try to improve their design to diminish these problems. For example some manufacturers have developped mobile vertical recipients in each station to contain the splash between stages( like MTM ) , or to have the driving units on the roof.

A well designed rotary transfer washer is a very good tool for the precision cleaning of small components . These machines allows to have the part clamped during all the treatment , and can have a sophisticated process with spray wash , cavitation wash ,high pressure wash, rinse , blow-off,vacuum dry , protection..in a reduced layout , and with energy efficiency.The prices range of these machines is between 150 and 250.000 euro according wit their performances.

The manufactures coming from the special machine tools activity have a tendency to supply a well built mechanical machines , as the manufacturers coming from the wash/cleaning activity tend to supply a more complex process in number of stations.

Parts2clean Stuttgart exhibition(1)

I was on 28th-30th October ”Parts2clean” exhibition in Stuttgart.This show is an specialised exhibition of wash and cleaning suppliers and some auxiliary equipment like filters and cleanliness controls.The exhibitors were mainly German manufacturers( and they were a lot¡).The ambient in the show was surprisingly animated. A lot of visitors ( quality visitors) and exhibitors Staff.

For an end user is easy and fast to visit several potential suppliers and request quotations in the same day.Inconvenient for the visitors: if you are not German , you will have some difficulties . The exhibitors panels and adds are mainly in German , and the staff present in the booth are not all English spoken( neither in french or Italian , of course).

As the exhibition is very specialised on the wash-cleaning and that the exhibitors shows and present their better and last technologies , this exhibition is also a quick way for their competitors to be aware of the new technologies or tendencies in the sector keeping a hard competition between.Around Stuttgart and Munich are located a big number of wash manufactures allowing the cross transfer of engineers between the manufacturers staffs , information , and clients . Another pole is located at the Nord around Aachen and Dusseldorf.A lot of the exhibitors have the engineering and construction in Germany but they also have facilities in the European east countries (Chekia, Hungary , Poland ) and including some of them they are starting also  facilities in China.

       The number of wash/cleaning manufacturers in Germany is a consequence of the big Market for them. Germany has many mechanical Industries. From small , to medium or big companies. All of them working with mechanical quality requests , so with thigth quality (and cleaning) specifications , with strong Tier1 automotive suppliers .This situation is specific to Germany and there is no other Market in Europe like this.By other side due to this competitive and close connection between competitors there is certain uniformity on the machine design and technique. This maybe is the chance that the few foreign suppliers are looking for ?

The ambient in the exhibition was busy . A lot of value visitors . No crisis ambient at all.

In the next days I’ll annalise more in detail this exhibition with other posts.

De-sanding /Lavado de bloques y culatas(o cabezas) de motor de automóvil después de la fundición y pre-mecanizados( cubing o Hypercubing)2/2

(Edición en español)(English versión will be edited later) .

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 Continuo con el examen de los puntos problemáticos indicados en mi anterior Post.

 

3) Acumulación de contaminación en el fondo de la cuba. 

Se produce por el propio efecto que se busca, es decir la eliminación de la contaminación de las piezas, la cual queda depositada en el fondo de la cuba de lavado por ultrasonidos.

La contaminación como la energía, es proporcional a la producción y las dificultades para eliminarla es considerable.

Además hay que tener en cuenta que cuanta más contaminación hay en el baño, mas energía se necesita para el lavado de las piezas ya que parte de la misma se deriva para el “lavado” de la contaminación depositada en la cuba.

Hay también diversos métodos para eliminar la contaminación del fondo de la cuba, pero ninguno de ellos da una satisfacción completa.

La utilización de transportadores dragantes, aumenta la masa a poner en vibración y al mismo tiempo el paso de las palas de la draga provoca distorsiones en las ondas ultrasónicas, lo que crea frecuencias audibles que aparte  de ser muy molestas, pueden fácilmente aumentar el nivel de ruido permitido en el edificio donde se ubica la máquina, creando en consecuencia la necesidad de insonorizar abundantemente la máquina.

El utilizar una bomba para la filtración en derivación del baño, crea además de los problemas expuestos anteriormente para la bomba de refrigeración, la dificultad de que no se puede garantizar la filtración de la totalidad del líquido con lo que siempre queda una contaminación residual en suspensión en el baño, que en determinadas circunstancias puede contaminar una pieza considerada limpia.

Cuando la pieza salga del baño puede volver a ser contaminada con la suciedad en suspensión en el baño.

La filtración no es un filtración en línea sino sólo una filtración en paralelo o derivación.

 

4) Generación de ondas de frecuencia audible.

Debido a que los ultrasonidos utilizan frecuencias próximas al umbral audible, los armónicos de estas frecuencias entran el campo de frecuencias audibles, siendo este fenómeno más acusado a medida que se aumenta la potencia del generador de ultrasonidos.

Este fenómeno que es sobradamente conocido por los especialistas, obliga a insonorizar los equipos con las consiguientes consecuencias de dificultad en la accesibilidad a los equipos.

Si debido a la masa y cantidad de piezas a lavar, la instalación necesita de una alta potencia de ultrasonidos, necesita en consecuencia una insonorización muy completa, con el consiguiente coste de inversión y superficie utilizada.

Hay que construir una “caja insonorizante “ completa alrededor de la maquina.

 5) Fiabilidad de los sistemas de transporte continuo

Las maquinas de lavado de pequeñas piezas trabajan habitualmente con las piezas en cestas y lo que se manipulan son cestas .Para pequeñas producciones se pueden utilizar entonces manipuladores, “gantry” o rodillos  para automatizar las cargas y descargas. pero para altas producciones los sistemas mas utilizados son los de cadena “pater noster” que trasladan y sumergen las piezas en las cubas en continuo . Estos transportadores tienen problemas ya que son de elevada longitud , no son precisos y se estiran con el tiempo 

 

6) Fiabilidad de los sistemas de carga/descarga para producción elevada 

Para las producciónes habituales de unas 100 piezas / hora es necesario cargar como mínimo 2 piezas en cada carga para tener un mínimo mayor a 1 minuto de tratamiento . Como el sistema de transporte no es preciso y la pieza no está totalmente mecanizada, el método de carga y descarga debe ser empujando las piezas en la carga y extrayéndolas en la descarga, guiándolas lateralmente. Este sistema tiene forzosamente juegos mecánicos para que pueda funcionar y ello produce inevitablemente atascos y averías. 

7) Alta energía instalada.

Es evidente que una instalación para el desarenado de piezas de motor a una cadencia de 100 piezas por hora o más necesita una gran cantidad de energía  en una maquina de ultrasonidos teniendo en cuenta la necesidad de potencia para los ultrasonidos , la calefacción necesaria , las bombas de filtración , transportadores y eventual refrigeración de los baños . que aplicada de otra manera, por ejemplo con agua a alta presión, produce los mismos o mejores resultados sin tener que soportar los inconvenientes mencionados anteriormente. 

 

8) Imposibilidad de control automático de la eficiencia de los transductores de ultrasonidos.

Las ondas de ultrasonidos en los baños  de lavado son creadas por unos “Generadores de Ultrasonidos “ o unidades de potencia situadas en el armario eléctrico de la máquina o en un armario aparte , que generan unas ondas eléctricas convertidas en ondas ultrasonoras por unas placas que se sumergen en el baño de lavado . Estas placas se llaman “Transductores” y pueden ser planos o tubulares en función de la potencia a transmitir .

Los transductores sumergidos en el liquido generan las ondas ultrasónicas que van a alcanzar las piezas que se introduzcan en los baños.

Sin embargo para el control del proceso es fácil el controlar eléctricamente que el generador funcione pero no es tan fácil controlar que el transductor en la cuba genere las ondas a pleno rendimiento . Estos transductores pierden eficacia con el tiempo y es necesario el cambiarlos periódicamente .

Para controlar su eficiencia durante los últimos 50 años se ha intentado encontrar algún sistema que permitiera el control en automático de su eficacia del mismo modo que por ejemplo se controla la presión  de una bomba con un manómetro .

Sin embargo hasta ahora no parece que haya sido posible encontrarlo y el único método fiable sigue siendo el de sumergir en el baño una fina hoja de papel metálico que debido al efecto de las ondas de ultrasonidos se produce una cavitación en la superficie de la hoja y la misma se micro perfora .

Comparando el numero de perforaciones en la hoja de metal con un  transductor nuevo con el numero de perforaciones obtenidas en una hoja similar pero con el transductor que queremos controlar podemos evaluar su estado .

Como se entiende este sistema para máquinas de gran producción es muy engorroso y poco práctico. Por ello se considera uno de los problemas típicos de mantenimiento  de estas maquinas al no poderse controlar en automático.

 

CONCLUSIONES

Por todas estas razones consideramos que si bien el sistema de lavado con ultrasonidos es un sistema que funciona bien tanto con agua como con solventes o hidrocarburos para pequeñas piezas o pequeñas producciones es una técnica que en la aplicación de desarenado y alta producción necesita de un gran mantenimiento , superficie ocupada ,potencia instalada y bajo rendimiento ,con una dificultad grave de no poder controlar la calidad del proceso de un modo automático y por lo tanto desaconseja su utilización en el desarenado a alta producción .

 

 

De-sanding / Lavado de bloques y culatas(o cabezas) de motor de automóvil después de la fundición y pre-mecanizados (cubing o Hypercubing). 1/2

Edicion en español ( English edition will be edit later)

 

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Recibo la consulta de un manufacturero de culatas y bloques motor en fundición de aluminio que desea limpiar las piezas de las virutas del mecanizado y de la arena procedente de la fundición.

Tiene dudas sobre la utilización de ultrasonidos en vez de la aspersión y alta presión para el lavado de estas piezas.  

Como este tema, es un tema que resurge repetitivamente en el tiempo entre la Industria de la Fundición de Aluminio he decidido publicar mi parecer en el Blog. Este estudio constará de varias partes que irán saliendo en días sucesivos.

 Voy a intentar ayudar en sus decisiones:

 El lavado de piezas metálicas por ultrasonidos, es un método utilizado industrialmente desde hace unos 50 años y que da buenos resultados especialmente en piezas pequeñas y con cantidades de contaminación reducidas comparadas con el peso de la pieza, asimismo los sistemas están concebidos para tiempos de ciclo de varios minutos. 

En lo que respecta al lavado de piezas de grandes dimensiones y masa tal como es el caso de culatas(cabezas) o bloques de motor, las dificultades aparecen como consecuencia de la industrialización del proceso, es decir el tratar altas producciones del orden de 80 piezas / hora o superiores y con cantidades de contaminación horaria elevadas.

  

Las Instalaciones de Ultrasonidos en estas aplicaciones según mi parecer presentan varios problemas  

 

 

Ø       Calentamiento progresivo del baño de ultrasonidos.

Ø       Necesidad de rotar las piezas en inmersión en la cuba.

Ø       Acumulación de contaminación en el fondo de la cuba

Ø       Generación de ondas de frecuencia audible

Ø       Fiabilidad de los sistemas de transporte continuo.

Ø       Fiabilidad de los sistemas de carga/descarga para producción elevada.

Ø       Alta energía instalada.

Ø       Imposibilidad de control automático de la eficiencia de los transductores

 

Veamos uno a uno estos problemas: 

1) Calentamiento progresivo del baño.

Para el funcionamiento de la limpieza con  ultrasonidos es necesario que el baño de lavado esté caliente y por lo tanto es necesario calentar el baño hasta una temperatura determinada a partir de la cual se tiene el efecto limpiador de la  cavitación.

Sin embargo esta temperatura tiende a aumentar con el funcionamiento de la máquina.

Esto se produce debido a que la energía necesaria para generar los ultrasonidos que hacen entrar en vibración la pieza a lavar se transforma en calor (ley de Joule) y teniendo en cuenta que la energía es proporcional a la masa de las piezas y a la producción, cuanta más masa o producción se tenga más energía se necesitará y más calor se generará en el baño.

Las piezas que se lavan absorben una parte de este calentamiento calentándose ellas mismas pero si la producción es elevada no es suficiente y los baños tienden a aumentar de temperatura.

Evidentemente hay soluciones diversas para resolver este problema pero todas tienen sus inconvenientes.

Si se aumenta el volumen del baño, para tener la misma intensidad de energía ultrasónica (Watios/litro) como hay más liquido, hay más volumen y masa, y por lo tanto es necesario aumentar la potencia de ultrasonidos con lo que el problema subsiste.

Si se instala un intercambiador de calor en el baño, aparte de aumentar la masa del mismo, el intercambiador sufre las consecuencias de los ultrasonidos con lo que su vida es corta.

La solución más simple es la de bombear el líquido a un intercambiador exterior a la cuba, pero con objeto de no distorsionar las ondas ultrasónicas, la bomba de trasvase solo puede funcionar durante el tiempo de transferencia de las piezas, con lo cual hay que hacerlo cíclicamente, perdiendo eficacia. 

 

2) Necesidad de rotar las piezas en inmersión. 

Los ultrasonidos deben tener la energía suficiente para que la energía vibrante llegue al interior de las cámaras de las piezas (cámara de agua y conductos de aceite). Por otra parte es necesario que la suciedad desprendida de las paredes de la pieza sea conducida al exterior de las cámaras y otras cavidades de la pieza, para ello es necesario una rotación de la pieza durante la inmersión en la cuba.

Frecuentemente para extraer esta suciedad desprendida por los ultrasonidos, hacia el exterior de las piezas se utilizan una o dos fases suplementarias en cubas separadas que se pueden llamar enjuagues ( “rinse “ ) y cuya función es con una corriente de liquido en forma de turbulencia o por aspersión el arrastrar la suciedad desprendida por los ultrasonidos pero que continua en el interior de las piezas.

Estas etapas de enjuague están también dotadas de rotación de las piezas.

Estas rotaciones, debido a efectuarse con la pieza en inmersión pueden crear problemas de fiabilidad y mantenimiento si la máquina es de alta producción.

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