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.

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.