How to make a car model on a 5-axis CNC machine
Five-axis machining a scale model of an Austin Healey
Austin-Healey was a British sports car, made from 1952 to 1972 as a joint venture between car manufacturer Austin and car engineering and design company Healey. A few great models have been produced, with admirers all over the world.This Gallery page features a video showing five-axis machining with DeskProto, see the link below.
An Austin Healey Sprite, made in 1960. You can see why this model has been nicknamed Frogeye. Picture courtesy of Wikipedia Commons
One of these admirers is DeskProto user Robert Zeinecker, living in Hamburg (Germany). He combines his love for this car with a love for CAD/CAM technology, which resulted a project to model and machine his own scale model of an Austin Healey Sprite.
The Austin Healey car, rendered in 3D CAD.
Modelling the car has been done in Rhino, using the T-Splines plugin (no longer available). As Robert states: "A very useful plugin for Rhino to model organic shapes". Obviously he is a skilled user as well: this is a great job !
For a complete car model many parts needed to be created. This page will show machining the car's main body and the seat, details like the headlights and grille have been created later, as separate parts.
The seat and the car body in DeskProto
The seat and the car body have been exported as separate STL files, to be imported in DeskProto. There for each model a large support block was added in order to clamp the block of material on the machine.
The Isel Euromod 45 machine with DSH-S rotation axis.
Robert uses an Euromod 45 machine made by German machine builder Isel. This is a three-axis flatbed servo machine, made five-axis by adding the DSH-S rotation axis unit (also by Isel). As you can see above the machine also features an Automatic Tool Changer and a tool-length measuring sensor. The Isel servo controller can handle all five axes simultaneously.
Roughing: toolpaths and simulation.
Roughing toolpaths for the top side, made with milling strategy Waterlines. Asking DeskProto to draw a simulation shows these toolpaths more clearly then drawing them as lines only.
Finishing: toolpaths and simulation.
Next came the finishing toolpaths (strategy parallel), done with a ballnose cutter. It can be clearly seen that many undercuts are present: Robert did not even bother to machine the complete block in this orientation of the model.
Roughing the top side
Roughing on the machine: for these topside toolpaths the rotation for both A-axis and B-axis is 0.0 degrees. As you can see a machine vise has been placed on the rotary table, for an easy fixturing of the block.
So far all pictures have shown plain three-axis machining. What makes this project special is that this five-axis machine allows to machine the same model from several sides, without re-fixturing.
Machining the front side (the grille).
The picture above shows machining the front side: the machine will automatically rotate the model to get this front side on top and then machine it. Both the A-axis and the B-axis need to rotate 90 degrees. And the cutter needs to move to a safe retraction point before rotating. All done using one large NC file.
Scale model of an Austin Healey 'Frogeye' classic sportscar being machined in wood: DeskProto five-axis machining in action ! Video created by Robert Zeinecker (Germany) (2:47 min)
Starting at Version 6.0 DeskProto features Five-axis machining (only in the Multi-Axis edition), and this project is a great example.
Extremely important for a good result is that the WorkPiece zero point needs to be set very accurately: with the tip of the cutter on the point where A-axis and B-axis intersect one another. In the DeskProto screenshots this WorkPiece zero point is visible as the small blue "axes cube", which is called the 'Orientator on WP zero point'.
For more information about five-axis machining see Lesson 7 in the DeskProto Tutorial.
Use a special rotation value to remove material below the dashboard.
DeskProto offers indexed machining for five axes, so machining from multiple sides where for each side three-axis toolpaths are used. Easiest setup is to machine a model from five sides (so applying 90 degree rotations). DeskProto also supports any other orientation, which works great when material needs to be removed from an "undercut" area that otherwise would not have been accessible.
Detailing a headlight, and the dashboard undercut- area clearly visible.
Detailing the headlights with a smaller cutter. On the right side the resulting model, showing the undercut area just mentioned. The material used for this model is tooling board, a polyurethane based material that has been developed for model making. For suppliers see the DeskProto Materials links page.
Five-axis milling of the seat
The seat has also been machined at angles different from 90 degrees, in order to achieve a high surface quality.
An important advantage of five-axis machining is that the cutters can be shorter than for three-axis jobs. Shorter cutters are cheaper, will live longer, are more stable and thus produce less vibrations. The results are a smoother resulting surface and less milling noise.
Results
As you can see the final product has been machined in wood: it looks absolutely stunning !
This level of detail would have been very difficult to achieve without using a five-axis machine.