Breton automatic countersink solution for aerospace and automotive industry

Countersink? No problem!

The use of rivets is one of the most common standards for the permanent assembly of structural parts in aerospace and automotive sectors.
For reference only, the image on the right shows a typical distribution of different rivet types in a famous aircraft with a very recent design.
                                                              

Tratto da: http://www.france-metallurgie.com/2011/04/

Despite some minor limitations, this system offers useful advantages in the assembly process:

• Rivets are cheap
• The procedure is easy and fast
• They are available in many different types covering any need
• There is a long history and experience in their use leading to a good reliability guarantee 
• Compared to other permanent fixations, they can be disassembled quite easily with specific tools 
• They allow a calculated residual flexibility of the assembly 
• They allow easy and fast repair even on the field                   

tratto da: http://www.slideshare.net/hareeshang/riveted-joints-18171530

When rivets are used to assemble the external layers on the supporting structures, they need to fulfill another very important role because the resulting assembly is directly exposed to the airflow: the final surface must be as smooth as possible in order not to affect the aerodynamic performances.

This specific need is very common in the aeronautic and aerospace field and all designers solve it by selecting rivets with countersunk head.

It becomes therefore evident the need of an accurate hole on the surface prepared with a countersink: the rivet head needs to be hidden below or in line with the external surface profile.

Tratto da: https://www.aircraftcompare.com/helicopter-airplane/piaggio-p180-avanti-ii/356

Just to reinforce the importance of the final surface quality the rivet head flush requirement is directly expressed on the assembly  drawing  through specific symbols (like a welded joint) and described in detail through dedicated quality procedures involving, very often, also a source qualification need.

Tratto da: http://www.aslgroup.eu/en/fleet/12/piaggio-p180-avanti-ii

In order to better understand how important is to respect 

the perfect surface continuity we can consider that, on 

some aerodynamic very demanding design, the aircraft  performances are so sensitive that just the surface cleaning has a perceivable impact on the overall performances.

The standard way of performing the rivet assembly is manual with specific tools that allow improving the reliability of the process.

Tratto  da: http://www.northerntool.com/shop/tools/product_200451725_200451725

Generally, the structural parts and the sheet metal pieces are NC machined and prepared with smaller holes in order to guide the manual tools used to create the final hole and countersink prior to assemble the rivet.

Tratto da:  https://i.ytimg.com/vi/ykK37Ms2UiA/maxresdefault.jpg

Sometimes only one of the two element to be assembled is pre-drilled in order to allow compensation of assembly misalignments; in this case, operator’s job become even more complex and sensitive, thus requiring higher manual skills.

There are a few reasons for the aircraft manufacturer to choose this way rather than finishing the hole and the countersink on the NC machine:

• The hole and the countersink must be perfectly perpendicular to the surface
• The countersink depth need to respect quite a tight tolerance in order to avoid rivet head to be above the surface. We must consider that the material  thickness tolerance can be easily equal or even higher than the countersink one
• The position tolerance need to be very tight as well in order to guarantee that the two parts will match during the assembly
• Even if in a modern design all the parts are 3D modelled (it’s not the same in an older aircraft) the production processes of a structural part and a sheet metal one do not guarantee the same level of precision 
• The sheet metal is a flexible piece and it’s  very difficult to create a fixture that maintain the overall surface in the 3D model  theoretical position

All these reasons made the manual rivetting process the more convenient one, leaving to an expert operator the responsibility to recover all the previous processes misalignments.         

Tratto da: http://www.chinadaily.com.cn/bizchina/motoring/2014-09/17/content_18612888.htm

Everything said above is valid even if the sheet metal is classical aluminum or composite based. In this second case, some other points must be considered:

• The dust produced is very dangerous for the operator's health
• The material cut is very critical and need better control of the cutting  parameters
• The material surface control is even more complex

Until the business remains focused on small quantities and the market is ready to reward the “hand-made”, and the consequent high value added, as a “plus”, it’s possible to sustain the manual production process with respect to massive  production competitors.

How does all this match with NC 5 axis machining?

Tratto da: http://www.youtube.com/watch?v=Ih89unYl0-g

When the scenario changes to big numbers (typical of the civil market) with reduced prices and margins, the only solutionthe only solution to stay competitive is the process standardization   and automation, so the aerospace industry needs to find a partner who can help it achieving critical goals.                              

Tratto da: http://www.capmac-industry.it/en/aerospace/

On the market, it is possible to find solutions that substitute the operator job with a quite complex machine that request to introduce the full assembly jig into the machine in order to drill and rivet the components replicating the operator’s gestures.

Tratto da: https://www.youtube.com/watch?v=Ih89unYl0-g

This strategy is very expensive, requesting a huge space allocation and presenting many times issues due to aircraft structures accessibility limitations.

Breton is following a different way, allowing to save the huge amount of money necessary for the previous type of investment and keeping the maximum flexibility to apply the solution to any type of component.

Breton has developed specific machines and several solutions to support this type of challenge and has also a very strong and experienced process development team available to support customers before and after the integration of a fully comprehensive solution.

The only ground condition is the availability of a 3D part model, Breton takes care of anything else.

For each of the previous points supporting the benefits of a manual riveting process, Breton has a specific automatic solution leaving the final fastening to the operator but with the hole and countersink already prepared in the correct position, shape and  depth:

• Position precision is not an issue for any Breton equipment that is designed  to  achieve  the  best  5-axis  tolerance  on  the market.
• A specific automatic probing head is capable to calculate the real surface position in respect to that of the 3D model and calculate the corrections in order to recover depth of cut and surface perpendicularity
• The machine position is automatically modified without any operator assistance before drilling the hole and   countersink
• With this solution the fixture only needs to keep the piece well fixed but it can leave to the machine probing capability the real shape calculation
• The composite dust issue is solved avoiding the operator to be exposed to it during the material cutting
• The composite integrity is guaranteed using a special developed solution that avoids any contamination and completely removes any dust
• All the cutting parameters can be controlled much better than in a manual mode
• The software is also capable to monitor the surface stability during the cutting operation and can be programmed to react in different ways according  to  the material responsiveness.
• The structural part can be machined on the same trimming machine in order  to have the same level of precision. This way is the first step to guarantee a good assembly performance.

The core of Breton automatic countersink solution is the special probing head and compensating software.

They have both been designed at Breton’s and patented due to their specific and unique capabilities on the market.

The special probing head is stored in a specific holding device on the machine, protected and located outside the working area; when necessary, the machine automatically picks it up, while keeping  the tool change capability monitored through a specific application in order to avoid any collision with the device.

The system is composed of three mechanical transducers managed by a specifically developed NC control application in order to acquire the true position and orientation of the piece surface around the hole to be done.

The drilling program is a standard one where the machining cycle is substituted with the Breton routine to activate the countersinking head.

The typical drilling process follows these  steps:

• The machine collects the special probing device
• The machine picks up and measures the cutting tool (using a specific   Breton routine)
• The machine sets up the probing device on a reference gauge integrated in the machine (using a specific     Breton routine)
• The machine probes the surface in the theoretical position and orientation
• The real position and orientation is recalculated by Breton software
• Depending on the surface type and scratch sensibility, the machine position and orientation are corrected by either keeping the probes in contact with the piece or retracting the machine from it (average time of the full probing and position adjustment is 6 seconds)
• The drilling and countersinking cutter proceeds along the real hole axis until the probes detect the correct depth of cut (this time depends on the type of material, layer depth, type of cutter, etc..). The system is capable to respect a depth tolerance of +- 0.03 mm on a stable surface (or +- 0.06 mm if the surface is not perfectly supported and fixed by the fixture)

The machine head is also equipped with a special dust extraction hood in order to collect all the dust generated by the drilling process.

There is no limitation in spindle performances as all the probing systems are static and connected to the head flange without any external   wire.

Depending on the material type, the head can supply compressed air, spray oil mist or pressurized coolant up to 40 Bar as the probing devices are fully sealed.

The following pictures explain the capability of the special head comparing the results of countersinking with and without the Breton solution:

This sequence is useful to understand better how the full process is working:

The system can be installed on any Breton machine giving the customer huge advantages compared to the manual process, spending just a small portion of the investment requested by more sophisticated solutions. 

(Breton is not yet assembling the rivets…).

Summarizing the points of strength of Breton solution:

• One machine to trim, drill and countersinking
• Precise process control
• Small investments in a machine accessory

Since one of Breton’s major points of strength is its capability to hear the customer’s requirements, we are working to further improve this system reviewing the design and testing a contactless   solution.

Test Case: Composite panel

Machine type: Eagle 1500 2T K80 

(5 axis overhead  gantry machine) 

Machine size:  

X=8000 mm

Y=4000 mm

Z=1500 mm

Machine accuracy:  

X=+-0.02 mm 

Y= mm

Z= mm

Number of countersinks on each side of the part: 55

Countersink depth: 0,31 ± 0,08 mm 

Process stability achieved: Cp 1,34

Cpk (lower) 1,14

The following graph shows how the system recovers the hole surface perpendicularity starting from the theoretical one, measuring the real surface orientation (red lines in the graph), correcting the head A and C axis and checking the final result (green lines in the graph).

After this first phase, the system starts monitoring the countersink depth comparing the probes data with the target   values.

The final result, achieved on a composite part not perfectly stable on the fixture, is shown in the process control chart here   below:

Consideration:

The process stability is very nice giving a big safety margin. The customer chose to further increase the safety margin moving the average countersink depth in the lower tolerance direction (as show by the Cpk value).

For more information please write to mail@breton.it.

Thank you for the attention and best regards.

Bye-bye

Sergio Prior

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aerospace industry, automotive industry, Breton automatic countersink solution, structural parts aerospace sector

Launch of the new Renault F1: Breton is a technical partner

Good morning everybody,

Breton, technical partner of Renault Sport Formula One Team, invites you to watch the launch of R.S.17, the new car that will compete in the 2017 Formula 1 World Championship.

Today at 15:30 (14.30 UK).

Here you can follow the live streaming

Good show at all!

Well, that’s all for today. 
Bye-bye
Sergio Prior

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breton, Renault F1, Renault RS17

“We've shifted gear”

The arrival of a Breton Eagle in SCA's workshop in Gessate (Milan) not only solved a host of operational problems, it also allowed the company to approach sectors and materials that were hitherto excluded.
(From: Meccanica&Automazione)

SCA

Founded almost fifty years ago as specialised manufacturer of foundry moulds, SCA is currently headed by the third generation of the proprietor family and, in a sense, it's experiencing the third “revolution” or – more accurately – conscious evolution of its operating activities.
The company was incorporated in 1970 by Domenico Scalzo and is currently headed by his grandson assisted by the second generation of the family.

The Breton Eagle of SCA 

Like many companies set up in the 1970s, the business started in cramped premises and worked with all kinds of industrial sectors: from moulds for motorcycle cylinder heads and interior light fixtures, to the initial production of parts for the Italian bottling industry.

In fact, it was a customer in the bottling sector that provided the basis for SCA's first turning point. With the customer in question, which remains a point of reference for SCA, the company began a journey into the world of industrial automation that enabled it to build its technological expertise until becoming a qualified supplier of parts for bottling plants (glass and plastic).

Rather than resting on its laurels and running the risk of supplying a single customer, over the years SCA maintained or developed a series of opportunities in several sectors that differed widely from the automatic machinery field, until it gradually left its origins in foundry mould-making in the past.

Competing in multiple sectors

This direction change led SCA to work with numerous industrial sectors, especially those calling for the ability to work with different materials with high levels of precision and the maximum operational flexibility.

From food and chemicals to pharmaceuticals and cosmetics, the marine and aeronautical industry, and also construction of large size components for theatrical stage sets. These various different areas of activity called for the ability to work with a large range of different materials, which is why SCA's machining shop today is equipped with machines for plastics, metals, and even, marginally, woodworking machines. The diverse range of applications calls for specific machines for each material type, each capable of producing optimal results.

Alessio Restelli explains “Several years ago we decided to focus our investments on machine tools for metals and alloys. That's why we decided to purchase a large size machining centre for specific work processes on workpieces in aluminium and lightweight alloys. Unfortunately however, we soon discovered that the machine we had identified was unable to cope with the work in our production programme. We were looking for a machining centre with large working dimensions, capable of processing different materials and providing absolute reliability. Above all, we were seeking a definitive solution to the problems we had encountered. And the need was all the more pressing because we were very keen to enter new business sectors and consolidate our capital equipment”.

SCA found the answer by embarking on a series of analyses and checks, trawling through the information available on the various companies and products on the market.

“We soon realised that our requirements in terms of equipment and solutions were a very good fit with the machine tools produced by Breton which, thanks to its long experience in building machines for a range of materials from stone to metal, was the ideal candidate to provide the tranquillity we were looking for. This saw the start of a period of negotiation that went extremely smoothly, especially when we went to visit Breton at the company's headquarters, near Treviso".

Breton Eagle

A paradigm of rationality and organisational efficiency.”
The final choice fell on the Eagle, a gantry-type machining centre offering exceptionally generous working dimensions: 4200 mm (X) x 3000 mm (Y) axis x 1500 mm (Z). We then requested that these characteristics be integrated with a separate lath so we could turn workpieces of up to two metres in length, using the Eagle head (shown in the attached photos) as a turning-milling device.

Restelli explains – “Our Eagle is not merely an extremely efficient machine able to produce work of the utmost quality and with exceptional dimensional precision, it also allowed us to benefit from the positive experience of working with the Breton team that were looking after our interests. Apart from absolute respect of precision and times, we were also impressed by the creation of a valuable collaborative relationship that was built on our combined efforts to find the best possible solution to our needs".

"For sure, the machine tool in question is extremely valuable, but the whole process was also accompanied by a truly exceptional the level of customer care and assistance. We quickly realised that the people at Breton were far more than expert engineers. In some cases the relationships we developed morphed beyond the professional realm and became more akin to actual friendship.

We started to perceive Breton's people as an integral part of our own team - a development that brought substantial value to the whole process. For companies working in our sector it's extremely important to be able to rely on a partner that allows us to focus on our core business, without having to lose sleep about possible breakdowns, problems, or the inability to achieve the quality levels we need. Setting aside the problems and focusing on the job means that we can relax and get on with what we do best. And that's just as important to us as the very air we breathe”.

Breton Eagle, range for resins, composites and alloys

Eagle is fully articulated range of travelling bridge gantry machining centres dedicated to the world of composite materials, resins and aluminium. These machining centres are perfect for fast, high precision 5-axis machining of 5 faces of the workpiece with a single set-up operation.


The various configurations of EAGLE machining centres for composite materials make it possible to perform even the most complex tasks with the maximum flexibility and operating efficiency, with working dimensions from 2,000x2,500x1,000 mm up to 10,500x5,000x2,500 mm and beyond.

The machine offers the maximum production flexibility thanks to the possibility of configuring the work area, which can be optimized for machining single parts or pendulum machining operations. Our job is further facilitated by the optimal visibility of the work area and the double front and rear access doors, allowing easy loading and unloading procedures, tooling set-up and monitoring of machining operations.

Would you like to find out more about the Breton Eagle? For INFO and inquiries write to mail@breton.it.

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5 axis CNC machine tool, 5 axis machining centers, aeronautical industry, breton, breton eagle, breton machine tools, composites, metals, parts, plastics, sca

The 5-axis machining centre of the month: Breton Eagle

High-speed and developed to meet the needs of workshops that deal with materials such as resins, composites, aluminium and carbon, while guaranteeing dimensional accuracy. (From: Tecnologie Meccaniche)

Breton Eagle

In its history as a manufacturer of machine tools, Breton has always stood out for its care and quality in designing and manufacturing solutions for removing metal chips.

High accuracy combined with powers and torques capable of processing new materials have always been the strong points of the company from Castello di Godego (TV), to meet the needs of sectors such as aerospace, automotive and pattern making.

Breton Matrix 1000 Dynamic

For the best results, it has designed models like the Matrix machining centres, also used to process the lighter materials (aluminium, resins and composites), which still require fairly high accuracy and a good degree of chip removal.

However, Matrix is a model that, in some cases, could be overspecified for the real needs of these sectors in terms of power and accuracy and, as we know, users tend to prefer solutions that match their needs perfectly.
Often the market offers lower-performance solutions with inadequate volumetric accuracies. Eagle is Breton’s solution to meet these expectations.

A new application sector

Breton Eagle, the 5-axis machining centre of the month

Breton decided to create a product that is not in direct competition with other manufacturers, nor of course with any of the machines that it was already manufacturing, but to enter a niche that requires good accuracy without the need for large investments.

Not all customers can afford (or need) a high-power machine nor an extremely accurate one. This requirement is typical of those making aluminium moulds or carbon, composite or resin patterns and it became increasingly evident that there was a need to offer a product that could meet this demand. None of these applications requires very high accuracy, but they do need a higher accuracy than can be obtained with low-end machines.

Therefore, Eagle is a high-speed, 5-axis machining centre for milling, drilling and trimming medium and large components made of composites, sandwich structures, light alloys, resins and plastics, all with good dimensional accuracy.

This machine is conceptually simpler and more economical than a Matrix, but at the same time, it is able to guarantee an accuracy that is higher than anything available in the lightweight material machining sector.

Eagle is based on the manufacturing philosophy that has always distinguished Breton’s machines: vertical spindle, high-quality recirculating ball screws, axes drives with backlash recovery to ensure the desired accuracy, thermo-symmetric elements, symmetrical fork head and high-performance cooled motor spindles.

From an economic point of view, Eagle requires a much lower investment than buying a Matrix (about 30% less, depending on the configuration). This is a significant amount for a single machine, but often users need several machining centres dedicated to these tasks, so the economic benefit is even more apparent.

Modular construction

Eagle brings the construction philosophy of other Breton models: in fact, it is a gantry machine with high columns, balanced vertical axis and heads with a symmetrical structure so that thermal dilatation is always limited.

Not all workshops are equipped with air conditioning systems, and thermo-symmetric design reduces structural deformation and makes it easy to correct via software. Naturally, the points where heat is generated (like the head, A-axis and motor spindle) are cooled by a dedicated chiller to reduce heat transfer to other parts of the structure.

Like most of the machines manufactured by Breton, Eagle is also a highly modular design.
It is made entirely of electrowelded steel and is dimensioned using finite element analysis to reduce vibration and limit twisting. This choice allows it to meet the machine users’ need for modular dimensions, allowing Breton to customise the standard product easily to satisfy market demands.

The machine is driven by brushless motors. The bridge on which the gantry moves has racks with two motors and pinions with backlash recovery, which offers a stroke of 2 m and higher thanks to the modularity of the rack solution. Depending on the choice of model, in the Y-axis, the stroke starts from 2.5 m and can reach up to 5 m. Finally, the Z-axis stroke is 1 m for the most compact model and reaches 2.5 m for the largest one.



The streamlined structure can also reach considerable speeds and accelerations: 70 m/min on the X- and Y-axes, 50 m/min on the Z-axis (all the linear axes are equipped with encoders) with accelerations of up to 4 m/s2, 12 rpm on the A-axis and 19 on the C-axis.

The motor spindles are partly inherited from the Matrix, while others have been specially developed to meet the specific needs of users of this type of machine. Breton’s entry-level model offers a torque of 52 Nm, 16,000 rpm, 25 kW of power and is lubricated with grease. This choice was dictated by the typical field of application, namely aerospace, where lubricant leaks onto the composite or carbon parts are strictly forbidden.

Alternatively, there are other spindles developed in co-design with Breton's partners, which offer up to 40 kW and air/oil lubrication.
The machining head was developed to ensure the accuracy and performance required by this type of application sector: a solution that is compact, mechanically driven to achieve the desired performance without using the more expensive direct drive. It also has smaller pivots for improved penetration inside the workpiece, allowing it to perform all the required operations.

It is made from a cast iron block, a solution that effectively damps vibrations directly at the source. Equipped with brakes to work in 3+2 mode with locked axes, it ensures maximum rigidity even with challenging material removal.

The machine received a positive reaction from the pattern makers who make rotational moulds, which typically require heavy aluminium removal. The same goes for pattern makers who make scale Ureol parts, resin products and other prototype components.

Power and control

A requirement related to machining composite materials is that sometimes the structure contains threaded inserts to be drilled or small titanium strips.
Other solutions on the market are not able to cope with this kind of machining, which must therefore be carried out manually by an operator, with the problems of accuracy and productivity that this entails.

On the other hand, Eagle can even handle those workpieces that contain composites, aluminium and various inserts, completing the task directly in the machine.In the civil aerospace sector, Eagle is ideal for all the structural aluminium machining, interior structures, honeycomb panels, aramid fibres, aluminium and composites that required drilling and countersinking.

Obviously, Eagle is also able to machine harder materials, taking into account that its performance will be lower than that of, for example, a Matrix. The choice, therefore, will be dictated by the predominant type of machining to be performed and the materials to be used.

The accessories

Ultrasonic cutting head

In addition to the more traditional optionals, such as video cameras to monitor the machining area and tool magazines of various sizes, Breton has come up with a series of accessories dedicated to the specific application fields for which Eagle is intended.

An ultrasonic cutting head has been developed to prevent tearing or chipping the workpiece when machining composites. It can be managed like a common tool (in fact, it is housed in the magazine).

Also for composites and carbon parts, there is a countersinking control head. This is controlled automatically through simple templates in the numerical control and allows the effective hole position to be verified before countersinking. This procedure is essential, for example, with carbon aircraft doors because the carbon mould geometry is rarely exactly the same as the CAD model.
So, the system carries out a check to establish the effective hole position on the workpiece (using mechanical or laser sensing) at three points to determine its exact coordinates before counterboring. With respect to a sensing cycle, the times, and therefore the costs, are reduced significantly.

The numerical controls that can be installed on the Eagle are the Siemens 840D sl and Heidenhain 640 iTNC, both with full software options. Moreover, at the customer’s request, it is possible to develop applications, cycles and specific interfaces that run on the numerical control to improve machine utilisation.

Finally, there is an accessory with a 6th horizontal positioning axis, to perform turning that requires special workpiece positioning and complete accessibility in any situation.

Safe and productive

Depending on the specific use, the user can choose whether to machine dry or using cooling lubricants, as the machine can do both. Breton has provided for the use of evacuator belts, extraction systems or both. Where there are laminated materials, for which it is necessary to mill the carbon and then thread the aluminium inserts, the carbon dust can be handled by the extraction system and the aluminium chips by the evacuator belts.

Breton puts considerable effort into satisfying the Atex standard. When it comes to safety, especially in industrial systems, nobody wants to run into problems or “surprises”.
The machine is therefore fully closed, with top bellows to avoid dust dispersion within the workplace. There are also extraction systems on the table and spindle nose.

When machining graphite, whose dust is extremely aggressive to both mechanical and electrical parts, Breton offers IP65 cabinets for the electrical panels or, alternatively, located at an appropriate distance from the point where the dust is created.

Would you like to find out more about the Breton Eagle? 
For INFO and inquiries about this 5-axis machining centre write to mail@breton.it.

Well, that’s all for today. 
Bye-bye

Sergio Prior

Read More

5 axis machining centers, 5 axis milling, breton, breton eagle, carbon fiber, Composite materials, honeycomb, large components, trimming