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.