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.

Gantry wash robots vs. articulated wash Robots

The utilisation of robots in the washing machines began for the need to wash different parts in the same machine or the need to high pressure deburr of some areas of the parts .

The german Dürr Ecoclean starts to use the robots in their in-line transfer DGI machines as a complementary high pressure wash of  cylinder blocks or cylinder heads. The parts were transferred in a lift and carry transfer trough the machine an in one station it was the robot with the high pressure jet in the wrist that  works on the part. The robot was located vertical with base at the floor outside the machine with a complete glove on the arm to protect the robot arm inside the machine.

The same philosophy was applied by Stic-Hafroy (now Dürr Ecoclean) ,  ICOM , Valiant , ITF and others. But it happen also the application of deburring small parts like ABS distributors or injectors components where the robot ( or robots) were picking the parts from a pallet and presenting the parts in front of HP jets or lances . In this case the wrist of the robot had grippers for the part and no jets as before.

The”flexibility” of the machine in this case is coming from the possibility to have several wash/deburr programs inside the same machine , but the gripper of the robot need to have at least common points in the component to be washed in order to pick the parts.

Here is appearing the two different concepts on the robotic wash/deburr applications : a robotic wash/deburr operation with a jet moved by the robot against a part transferred by a mechanical system or a robot with a gripper picking the part and moving the part against HP wash/deburr fixed location jets.

In the first case( robot moving the jet) the robot is less exposed to the direct splash of water and there is no mechanical-pneumatic-electric components on the wrist.

 

In the second case (the robot moving the part) the robot wrist is exposed to receive direct high pressure splash , and it has mechanical-pneumatic-electric components on the part gripper risking to be wet .

Some people with experience in robot automation have plunge in the wash/deburr applications with robots gripping the parts without evaluating the additional risk on the wrist. The robot suppliers are working hard to protect the articulated robot but the maximum protection proposed is a IP65 for the arm , with stainless steel covers , and IP68 for the wrist( see my before “post” concerning the IP validity’s). Some of them they are also adding  air over pressure for the wrist. In any case in these applications there is much more risk than in the case of the robot moving the jet.

 In the before post I mentioned the advantages of the Agullo gantry moving the jet at the end of the vertical arm with all the mechanical outside the machine.

 

 

 

The same disposition is adapted by the japanese SUGINO . Sugino is living in the country with more robot suppliers of the world . Why Sugino is not using the articulated robot in their machines? : Because they are more confident with the gantry on the top of the machine than with a robot.

 

 

 

Other manufacturers like the german Arau has presented in the Parts2clean Stuttgart exhibition his robot cell using also a gantry in the roof of the machine. (years before it was using articulated robots inside the machine).Another example is the german Piller that is using the gantry on top of the machine for the HP deburr jet in his cells.

Another advantage of the gantry robot utilisation is that the machine has only one electric control: a CNC known by the users and easy to run. In the case of the articulated robots inside machines , the machine needs a PLC and the robot has his own electronic control( two controls units in one machine).

But the articulated robot has also good points :It can load/unload the part in the machine by himself  when the gantry robot moving the jet , needs of  another transfer device for the parts, it can be produced in advance and customised in the last moment (gripper and programme) ..

So , what a dilemma ¡¡… Yes , and there is another interesting point : the total investment for the machine.

The Robot cells with articulated robots carrying the part are as single  cell an “economic” machine compared with a transfer-robotic  in line machine , or a rotary transfer-robotic machine. But the throughput is not the same.

In a robotic cell loading and unloading the part with the articulated robot you have dead time( load/unload) that penalize the complete cycle of the machine . More big is the part to be washed ( heavier) more time you will spend on the load/unload( lower speed on the movements due to the inertia). The wash time and the blow-off /dry times can not be fully reduced and then there is a need to use several robotic cells according with the requested throughput production .That’s means that you will need two,four.. or five robotic cells versus one equivalent transfer in line or rotary transfer robotic machines.

As a general rule we can say that in the majority of the automotive cylinder blocks and cylinder heads applications the investment is higher with the robotic cells . But is also an strategic choice: you can have one robotic cell as spare , in case of a shutdown in another, or you can increase the production step by step buying the cells in several years … Interesting comparison.

Robot cells : wash / deburr

In the STUTTGART Parts2clean exhibition , a lot of WASHER manufacturers were claiming their ability to supply robot applications for the wash and deburr process.

The application of robots in the wash/deburr is not new. Late in the 1980’s AGULLO was one of the first companies in the world to look for the application of these technologies. In this time the robots were mainly hydraulics or pneumatics and the main robot suppliers were the Americans UNIMATION ( Polar-articulated) and PRABB( cartesian) .

 To look closely to this applications I remember that I visited these two companies in USA , and both were proclives to decline any warranty of the robot working in the wet and dirt conditions of a washing machine.

Why? : The conditions inside a wash chamber are very inconvenient for the robot : water splash, possible direct contact with high pressure jet( 150 to 800 bars), hot ambient ( 50 to 70ºC), high humidity air , vapours , condensations ,  solids dirt , mechanical chock due to the chips removed from the part that can crash against the robot arms as bullets…

For the part gripper at the end of the robot wrist the same problems that for the robot : water , humidity, condensations, temperature, mechanical bullets… and additionally : problems for the electric switches and wiring , and pneumatic hoses ,controlling the open/close positions of the gripper. 

So de-couraging was the result of these visit to USA that in the AGULLO company it was decided to design a specific robot to respond to the difficult conditions of the wash/deburr operations. The Market was requesting machines able to wash different parts, in the same machine, and at low production and the robot could help for that. The classic washing machines had then wash box fixtures with pin point jets adapted to each part to be washed . If the parts to be washed were different , then it was necessary to change the wash boxes of the machine at each time that the new part arrived to the machine.

For certain machines like crankshaft washers , or cylinder head washers , it was possible to create one fixture that was carrying he wash boxes and then the operator could change the complete package for each new part. With the cylinder block washers the wash fixture becomes heavy and requested a lot of time and hand labour to be changed. A robot (despite his high price) could simplify the work with only a wash robot program to be stetted for each part.  

The result in 1983 was the design of a Cartesian robot , five axis ,with all their mechanics and servos on the opposite end of the arms( patented) .The payload was 350Kg and a prototype for validation was build in the Barcelona Agullo factory. Some of the customers robot experienced people visited the robot and gave some feedback. The most important  was coming from a Mercedes robot engineer suggesting to switch from the hydraulic servos( American Moog) of the prototype to the electric drive system as it was the future for the robots at least in Europe. The robotic electronic command was also another concern . Too much electronic companies offered robotic commands in the shows but they didn’t have experience in the field. By other side the customers didn’t like to train their people to each robotic command of the suppliers .

Another concern was also to consider if instead to grip the part to be washed to the robot arm , if it would be faster and agile to move the jet with the gantry robot and leave the part static. Then instead to need a 300Kg payload to move a cylinder block to wash and his gripper , we would need only a 50 or 70 Kg payload for the high pressure applications. Finally the decision was to re-convert the design to a Cartesian gantry robot with electric drive and servos with CNC controls ( Siemens or Allan Bradley the more popular then in the field ) and to move the jet. Totally a four axis gantry robot CNC controlled , working against the part to be washed presented in a fixture , or an in line transfer or a rotary table transfer. The fixture could have a supplementary CNC axis giving a total of five axis , enough for the wash/deburr process.

With this gantry robot located in the roof of the machine , with folded bellows to close the gap on the roof , all the mechanical an electrics of the gantry were outside the machine well protected against any water splash , or condensations. No mechanics neither electrics were on the wet area of the machine but all was outside the machine in the roof for easy access.The CNC command was controlling the gantry robot and the machine itself.

This AGULLO gantry robot was build for more than 17 years , around 100 units , and a derivative of it is still supplied by Dürr Ecoclean on some Rotary transfer washers for cylinder blocks and cylinder heads applications. There is one of these gantry robot 14 years old that is still working in his washer.

Why I have explained all these past experiences?  Because the alternative to the gantry robot using the articulated robots in the machines was difficult years ago. The first that I know were used the Smart-COMAU(Fiat) for the Borg Warner USA compressor applications but with the articulated robot outside the machine , vertical, on the floor, and with a complete vertical circular bellow wall to protect the robot. This bellow last normally no more than one year in normal conditions but with accidents or bad manual movements it has to be replaced very often. The english manufacturer CERA was also trying to use the same robot layout but with ABB robot.

In France Renault developed also one small vertical Cartesian robot that was used by the french company Brochot on the machines supplied to Renault to clean / deburr gear boxes but with many problems on the belows and mechanics, because the complete robot was inside the machine.

Fanuc was also marketing his small articulated robots for small wash applications ( first in japan and later in USA), but with frequent disassembling for maintenance.

Then ABB pushed also his robots . They were applied in the high pressure jet cutting located in the roof of the water-jet cabinets , and this application inspired to certain washer manufacturers to use the articulated robots inside the washing machines. 

 

Manufacturers like STIC_Hafroy in France and ICOM in Italy , Eurowide in England used the ABB in the roof with a big textile wrap ( moving the water jet).

Today the articulated robot suppliers have improved their robots and now they start to propose a better water protection to the end wrist and to the robot body . (As is the case of ABB and in a second place Fanuc,may be we could also add Staubli if his last robot runs well). In consequence there are more and more manufacturers that they propose “robotic washers” using standard robots of the market.

A lot of robot  suppliers assure IP67 protection for the robot ,but maybe we have to remember that IP67 protection in the robot is not enough for a wash deburr application . You would have to go to the “electrics standards” and see what means “IP67″ . The first digit”6″ means solids protection :”power dirt protection” .The second digit (“7″) is a water protection but “7″ means protection to the water inmersion without pressure for 30 minutes¡¡ Inside a wash/deburr cell , there is high pressure water ¡¡

Some robot suppliers claim higher protection :”IP68″ , but again please note that the digit ”8″ means “harder conditions (to be defined by the supplier) of immersion than the IP67″ but still immersion , not protection to the high pressure jets.

What means all that ?, that the washer manufacturer who is proposing to a client a “robot cell” with an articulated robot of the market needs to add some additional engineering to his machine for additional protection of the robot . If not, the client is taking a big risk ordering a machine to this washer  manufacturer. 

But there is still a confusion using the term “robotic washer”. What is better to move the jet with the robot or the part against the wash/deburr jet?. We will see in a next post…