Friday, November 10, 2006
Scanner drives 5-axis CNC engine porting
Innovative porting technique with digitising routines, gives significant improvement over hand porting and 3-axis machining, allowing exact duplication of optimum IC engine port designs.
For Florida-based CNC Cylinder Heads, certain aspects of engine manufacture just didn't make sense. Why spend thousands of dollars on a precision-machined engine block, crank and pistons, just to bolt on a set of unported cylinder heads with mismatched port volumes and rough wall surfaces inherent to the casting process? For professional engine builders, precisely ported heads mean better engine efficiency and dyno results.
Hand porting is an art form, but from a manufacturing standpoint, it is impossible to identically size each port volume, or to accurately replicate an 'ideal' port design on another head.
It is also time-consuming, often taking a highly skilled person up to 40 hours to complete a set of heads - very inefficient for a high-variety, low-volume porting business.
From a performance standpoint, cleaning up ports by hand does assist flow by reducing restrictions, but the head cannot deliver its full horsepower potential because of mismatched port volumes.
Numerous manufacturers machine heads on 3-axis CNC machine tools, but machining only in 3-axes, leaves tool marks that cross over one another in various directions, requiring hand polishing and blending to smooth surfaces.
Not only does this add time to the process, but it also removes additional material, making the port larger than originally designed.
With these shortcomings in mind, Bob Hudgins, President of CNC Cylinder Heads, developed a system to solve both problems.
Employing a special combination of high-tech equipment, including vertical machining centres (VMCs), custom-built head fixtures with A- and B-axis CNC rotary tables, and specialised CAD/CAM software, he machines aluminum and cast iron heads in five axes simultaneously, producing a mirror-smooth surface finish, without toolmarks, straight off the machine.
But what to do about the duplication dilemma?
For that, Hudgins uses one additional piece of equipment - Renishaw's Cyclone scanning machine A continuous-contact, reverse engineering tool, the Cyclone scans port and combustion chamber wall surfaces collecting dimensional data to produce a 3D wireframe model of the internal features.
A 3-axis system, the Cyclone is fitted with Hudgins own-design thin probe styli and a special fixture that rotates the head in A- (rotation about the X-axis), and B- (rotation about the Y-axis) axes to allow access to hard-to-reach port areas.
From that data, SURFCAM CAD/CAM software creates 5-axis NC code that drives the machine tool through its cutting routines.
After machining and cleaning, heads are ready for immediate assembly.
Hudgins-designed cylinder heads can be found in various enthusiasts' cars, and NASCAR teams, where cars achieve speeds of 200-mph.
CNC Cylinder Heads also sells the 5-axis system as a turnkey package, offering the technology and training for other companies to duplicate and machine heads using this proven method.
The need for duplication comes from two sources - external and internal.
Professional engine builders approach CNC Cylinder Heads to replicate their new port designs and cut them into numerous other castings.
Builders for NASCAR teams may order up to twenty sets at the beginning of each new racing season, but often come back with new designs throughout the season since their R and D is ongoing - requiring a quick turnaround from Hudgins and his team.
CNC Cylinder Heads' in-house engineers are also continuously developing their own port designs on a variety of manufacturers' castings for street performance and racing applications.
After a newly designed head passes various flow bench and swirl meter tests, the Cyclone digitises the finalised design for duplication.
The company has hundreds of port designs and gigabytes of machining programs stored in a DNC workstation, to be downloaded to a machine tool at a moment's notice.
CNC Cylinder Heads sells these heads off-the-shelf, often packaging them with matching cam, intake and computer chip from other vendors, for purpose-built racing or street applications that often raise base horsepower by 40%.
Digitising deep inside a port - in effect, an angled tube - is more difficult than digitising the perimeter of an object.
Hudgins designed a special Cyclone fixture that can be rotated in A- and B-axes manually or by way of servomotors.
This rotation, combined with Hudgins' special thin styli, allows the Cyclone to digitise all areas of the port.
Rotary encoder's register the angular position of the fixture and a digital display shows position to one thousandth of a degree.
Once all port areas that can be accessed from the home position have been digitised, the fixture is rotated by the operator, to allow access to other areas of the head, and the new angular position is noted.
For Florida-based CNC Cylinder Heads, certain aspects of engine manufacture just didn't make sense. Why spend thousands of dollars on a precision-machined engine block, crank and pistons, just to bolt on a set of unported cylinder heads with mismatched port volumes and rough wall surfaces inherent to the casting process? For professional engine builders, precisely ported heads mean better engine efficiency and dyno results.
Hand porting is an art form, but from a manufacturing standpoint, it is impossible to identically size each port volume, or to accurately replicate an 'ideal' port design on another head.
It is also time-consuming, often taking a highly skilled person up to 40 hours to complete a set of heads - very inefficient for a high-variety, low-volume porting business.
From a performance standpoint, cleaning up ports by hand does assist flow by reducing restrictions, but the head cannot deliver its full horsepower potential because of mismatched port volumes.
Numerous manufacturers machine heads on 3-axis CNC machine tools, but machining only in 3-axes, leaves tool marks that cross over one another in various directions, requiring hand polishing and blending to smooth surfaces.
Not only does this add time to the process, but it also removes additional material, making the port larger than originally designed.
With these shortcomings in mind, Bob Hudgins, President of CNC Cylinder Heads, developed a system to solve both problems.
Employing a special combination of high-tech equipment, including vertical machining centres (VMCs), custom-built head fixtures with A- and B-axis CNC rotary tables, and specialised CAD/CAM software, he machines aluminum and cast iron heads in five axes simultaneously, producing a mirror-smooth surface finish, without toolmarks, straight off the machine.
But what to do about the duplication dilemma?
For that, Hudgins uses one additional piece of equipment - Renishaw's Cyclone scanning machine A continuous-contact, reverse engineering tool, the Cyclone scans port and combustion chamber wall surfaces collecting dimensional data to produce a 3D wireframe model of the internal features.
A 3-axis system, the Cyclone is fitted with Hudgins own-design thin probe styli and a special fixture that rotates the head in A- (rotation about the X-axis), and B- (rotation about the Y-axis) axes to allow access to hard-to-reach port areas.
From that data, SURFCAM CAD/CAM software creates 5-axis NC code that drives the machine tool through its cutting routines.
After machining and cleaning, heads are ready for immediate assembly.
Hudgins-designed cylinder heads can be found in various enthusiasts' cars, and NASCAR teams, where cars achieve speeds of 200-mph.
CNC Cylinder Heads also sells the 5-axis system as a turnkey package, offering the technology and training for other companies to duplicate and machine heads using this proven method.
The need for duplication comes from two sources - external and internal.
Professional engine builders approach CNC Cylinder Heads to replicate their new port designs and cut them into numerous other castings.
Builders for NASCAR teams may order up to twenty sets at the beginning of each new racing season, but often come back with new designs throughout the season since their R and D is ongoing - requiring a quick turnaround from Hudgins and his team.
CNC Cylinder Heads' in-house engineers are also continuously developing their own port designs on a variety of manufacturers' castings for street performance and racing applications.
After a newly designed head passes various flow bench and swirl meter tests, the Cyclone digitises the finalised design for duplication.
The company has hundreds of port designs and gigabytes of machining programs stored in a DNC workstation, to be downloaded to a machine tool at a moment's notice.
CNC Cylinder Heads sells these heads off-the-shelf, often packaging them with matching cam, intake and computer chip from other vendors, for purpose-built racing or street applications that often raise base horsepower by 40%.
Digitising deep inside a port - in effect, an angled tube - is more difficult than digitising the perimeter of an object.
Hudgins designed a special Cyclone fixture that can be rotated in A- and B-axes manually or by way of servomotors.
This rotation, combined with Hudgins' special thin styli, allows the Cyclone to digitise all areas of the port.
Rotary encoder's register the angular position of the fixture and a digital display shows position to one thousandth of a degree.
Once all port areas that can be accessed from the home position have been digitised, the fixture is rotated by the operator, to allow access to other areas of the head, and the new angular position is noted.
# posted by Medical Information : 2:37 AM
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