When a tool path is first created, it is a series of XYZ positions that the tool moves along; in order to complete the pass, a matching series of orientation angles must be assigned for every XYZ point on the tool path sequence. SculptPrint has many helpful features to make it as simple as possible to generate these orientations. In the last blog post, the concept of an access map was introduced; in this post, this concept is extending to an access space.
When the sequence of access maps for each step of an entire tool pass are placed in order, the access space is created. Each access map is a digital image and the series of maps forms a video sequence. The access space shows the accessible and inaccessible orientations of the tool from the start to finish of the tool pass.
To create orientations, the goal is to find a series of rotations in which the tool remains in accessible positions. The proper orientations on the tool pass can be thought of as a path through a tunnel in the access space, depicted in white on the model below.
SculptPrint uses computer vision algorithms to create a path through these tunnels. These paths are called “access paths”. When one tunnel comes to an end, SculptPrint knows to switch to a new tunnel. The green paths show examples of this “tunnel switching”. When a tunnel is changed, the tool path is split and the tool is directed to retract to a safe distance in order to reorient.
In SculptPrint, access maps are generated to show which orientations and positions can be used so that the tool does not collide with the part. Each point on an access map corresponds with a possible orientation of the tool at a specific point in the tool pass. Regions in black represent orientations that would result in the tool colliding with the part, while regions in white represent accessible orientations for the tool. The images above depict four accessible orientations for the same point in a pass, and the corresponding access map.
The access map corresponds with the spherical end of the tool similar to the way a world map represents a globe.
The point selected on the map represents the direction the length of the tool extends directly from. The direction the tool is rotated from top to bottom corresponds to a phi (Φ) value. This is analogous to latitude on a world map.
The direction from left to right corresponds to a theta (ϴ) value for rotation about the Z axis, as with longitude.
Using a combination of theta and phi values, any possible orientation can be generated. Access maps make it easy for SculptPrint users to generate proper orientations and retractions for successful tool passes.
When manufacturing a part on a mill, several passes are typically required to achieve the final product: first, a roughing pass to cut away the bulk of the unnecessary material, followed by more detailed finishing passes. Larger tools are used in the roughing pass so that a lot of material can be removed quickly. Then smaller tools which take longer to remove the same amount of material can be used on the finished passes to incorporate detail and sculpt the specific shape of the part.
The image above shows the path of a roughing pass, as well as its starting and ending volumes. Below, a sequence of finishing passes sculpt out the final part (head) from the volume created in the roughing pass.
To further increase efficiency, SculptPrint allows users to create cross section passes for the roughing. A cross section pass is much quicker than a typical pass because it’s movements are less specific to the part, making it more effective for removing material.
In a finishing pass, the tool’s movements are specific to the part, as shown below.
In a cross section roughing pass, the tool either moves in a raster or radial pattern, both of which are much easier and faster for the tool to cut.
Raster: A raster pattern moves the tool across only the x or y axis. This technique is most effective when cutting from block stock.
Radial: A radial pattern consists of concentric circles; the tool begins cutting large circles that get progressively smaller. This technique is ideal when cutting from cylinder stock.
SculptPrint’s features are designed as easy and efficient tools for creating the most effective tool paths.
Last month, Georgia Tech students used SculptPrint to produce a complete centrifugal compressor. A housing for the impeller featured in the last blog post was sculptprinted on an Okuma Multus B-300 5-axis millturn machine. SculptPrint features supporting boring operations were used extensively to produce the inner diameter geometry of the housing.
The voxel model of the compressor housing in the SculptPrint software is shown below.
The millturn machine allows a mixture of turning and milling pass to produce the asymmetric geometry of the housing.
A boring pass on the inner diameter is shown below.
A milling pass to produce the asymmetric outlet port geometry is shown next.
A turning pass as modeled in SculptPrint is shown below.
A collision free milling pass on the inner diameter modeled in SculptPrint is shown next.
Finally, the test rig for the assembled compressor is shown. The compressors was tested up to around 2800 rpm with good results.
Georgia Tech students used SculptPrint to generate CNC paths for a turbocharger impeller. The impeller was produced on an Okuma Multus B-300 5-axis millturn machine. The tool paths were automatically assigned collision free orientations using SculptPrint’s access map technology. The students are also working on a housing for the impeller to complete the turbocharger.
The part modeled in SculptPrint using voxel modeling and access map technology shown below.
The image above show the “Candle Holder” geometry produced at Georgia Tech on their Mazak VCU 500 5-axis mill. The aluminum part has difficult to access spirals. SculptPrint’s advanced GPU technologies such as voxel modeling and access maps made producing this shape possible.
The image of the voxel model in SculptPrint is shown below.
In April of 2016, SculptPrint was featured at nVidia’s GPU Technology Conference. Demos of the software were given in our booth as well as in nVidia’s Design and Manufacturing section of their booth. The slides from the talk given at the conference are now available on nVidia’s website and can be found here.