Cylinder head brush deburring(2)

The brush deburring units have a wear on the brush wire due to the abrasion with the cylinder heads deburring action.

The first brush deburring units used in the 70’s were not planetary units and the brushes were bolted to a plate .

Each plate had 15 to 20 small brushes and the time to change the brushes was too long and the live short.

 

For this reason it comes the idea to use bigger cup brushes fixed to a planetary system . The first units ( in high production lines of 180 to 300 p/h)  were installed in France in Renault and Peugeot.

Renault had their own research department and they designed a planetary system with internal grease lubrication on a close box. Agullo developed on the same dates their own planetary system but with internal lubrication with oil and compressed air overpressurizing the planetary box.

The internal oil lubricating system was more reliable than the grease system because it avoided the penetration of coolant inside the planetary box and finally was the best in the market.

Now in the market there are several companies proposing the planetary system with different concepts.

The fixation of the brush cup to the shaft of the unit has been also a device that changed with the time. At the beginning it was only a simple bolt on the center of the brush. Some time difficult to change. Then it comes a quick change with individual pressure clutches. Finally now the systems use similar devices as the CNC for their tools.

Another important point in the brush deburring is the brush wear compensation. At the beginning the Renault planetary heads used a sort of touch test to sense that the brush was in “cero” position . A step by step axis moved the planetary head table till the position that the brush was in contact with the leverage.

This leverage had a glass disc with two electrodes. The contact with the brushes gave the signal to stop the brush unit in position. This system has been used for certain  suppliers for long time , but is not reliable. The leverages and the glass disc have a lot of failures and the position is not well controlled.

The Agullo planetary units were using a wear compensation that was controlling the electric power of the unit in empty conditions( no part) and in contact ( deburring the part) . According with the desired deburring action ( soft , medium,hard) the power control had a range were the power of the unit can stay. If the power fell under a predetermined level the machine gave an alarm in order to advise the operator that the brush had to be changed. Managing the ranges and alarms it was also possible to send a pre alarm in order that the operator can prepare the new brushes and stop the machine at the end of the day.

This system with several software evolutions has been used for more than 25 years in high production units. In the last 10 years , with brush deburring machines going to CNC controls the system has also slightly changed but is still the more reliable.

Some suppliers are using the CNC to locate the brush on the “cero” position and they are moving the brush unit according with the number of parts passing trough the machine. Memorizing the positions you can calculate the length of the wire still alive in your brush, but the system is not so reliable and the brushes  become or collapsed or not full wear. The brush length is not precise as a drill tool and his dimmension is not constant.

 

 

Other suppliers ( in america)are using a pneumatic table support for the brush unit that applies a pressure to the brush at each cycle . Is more sophisticated that to use two linear springs but with the same effect : no really control of the brush wearing.

Why is so important the wear control: because a deburring cup rush can last from 5.000 to 30.000 deburred parts and the cost to change the unit has to be the minimum possible , using in the best way the length of the brush wire and keeping the mechanical deburring action force controlled to have always good deburred parts.

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.