CNC ENGINEERING

JBS' engineering philosophy is based on absolute accuracy of measurement and repeatable production. We invest heavily on developing optimised designs.  Computer modelling is used to predict output and dyno testing to verify results. Of course it's all very well producing a beautiful hand crafted prototype but that is not much use if we are unable to replicate that design.

A Computer controlled 3D digitising scanner and CNC machines enable us to replicate ANY design and produce it exactly the way we want.

The result is the customer gets EXACTLY the performance we promise.

  

How it's done:

Scanning - the first stage of replication.

Having made the initial investment of time and expertise in producing a fully gas flowed head, the first stage in re-producing that head is to create an accurate 3-dimensional model of the head.

A Rennishaw Cyclone 2 scanning digitiser is used to digitise the completed, gas flowed head. The Rennishaw scanner is used in many forms of engineering where absolute accuracy is required. These include aerospace airframe and turbine engineering, automotive applications, optics, general engineering, mould and dye manufacture. It is also particularly suited to small volume manufacture, where extreme accuracy and on-demand manufacture is required.

The scan involves mounting the head on a accurately machined jigs using machined dowells to fix the head precisely to the jig. Each jig is selected according to its suitability to scan that particular head. Sometimes a new jig is required and a new one is built. Specific "datum points" are then identified and stored in the computer. Then, the scan process begins.

Scanning is very much an automatic process and takes several hours to do a single head. The scanning itself is done via a spindle probe which physically traces the surface of the head with immense accuracy. It is quite capable of doing a 3-D scan of a fingerprint such is the accuracy. The dimensions of the head are then stored in the computer and can be viewed as a 3D image using the TraceCut CAD/CAM system. This software can then be used to alter the dimensions of any scanned model. We use it to verify the volume of the port and can then modify the port if required.

It is then possible to further manipulate the 3D model using a CAD/CAM system. However, the primary aim here is to replicate the master cylinder head. The Tracecut software then generates the code (XYZ co-ordinates) for the CNC machine. Each port in the head requires approximately 80,000 lines of code to accurately machine the port. The dimensions of the head can then be passed to the CNC engineer to load in to our CNC machine.

Both the scanner and the CNC machine are set up to use the same 'incremental stepover'. This is the movement the scanning probe or the machine head takes on each cycle of its operation. For JBS Spec heads the increment is set at 0.5mm. This may sound like a lot, but when seeking to establish a near mirror finish, the increment is more determined by the size of the piece. A Audi V8 CNC head may use 1mm step over because the port sizes are huge. The result is a near perfect finish to the port. Run your finger inside the port and you will feel how smooth.

A standard cylinder head is then mounted on the same jig, using the same dowels as used in the scanning process. The datum points are again identified, exactly in three dimensions. The CNC machine then begins its machining process, replicating the 3D model of the master head. This can take many hours to complete depending on the complexity of the head and the modifications required.

Once complete, the result is not only visually superb with excellent finish, but also accurate to the original 'master' head. The manufactured heads have been re-measured and found to be accurate to within 0.002mm. Likewise the head have been re-measured on the gas flow bench using the Port flow analyser software and found the result to be less than 1 CFM (< 1%) difference from the original overall and less than 1 CFM difference per cylinder.

If you want the ultimate, a taped head is available where the heads are hand finished (Cost is about £130). These give exactly the same CFM performance to the original master (which proves beyond doubt that our process works). We will also provide the gas flow results for your head via a print out from the Port Flow Analyzer software.

Hand finishing is available at additional cost and provides the last 1 % of gas flow and helps stop and fuel condensing on the port wall.

There are various specs heads available for many popular VAG engine models. For fast road, trackday or race applications, we can supply you with the ultimate cylinder head for your engine either on an exchange basis or we can modify your cylinder head for you.

For what is basically a bolt-on performance modification, these heads are very good value for money considering the performance increase possible.