The Pencil strategy in HSM Performance Pack is highly customizable. It uses a trustworthy center line detection algorithm and is packed with options to help ensure the highest degree of machining quality.
Basic: Overthickness and Bitangent
Overthickness and Bitangent Angle serve to detect the center curves of fillets in the geometry.
The fillets in the geometry are identified by placing a ball mill (virtually) on the geometry and detecting the areas where the ball mill touches the geometry in two points simultaneously. The Overthickness parameter value increases the diameter of the virtual ball mill, in order to detect fillets with a larger diameter than the tool diameter. The Bitangent Angle defines the angle between those two touching points.
Offsets: Normal, Trim and Blend
The Pencil strategy includes three main options to generate offset passes.
The Normal option generates normal scallop passes and with Spiral also enabled, it generates spiral scallop passes.
The Trim option generates fillets using a reference tool at the first step. Offsets start from the center line and are trimmed against these fillets.
The Blend option generates boundary passes using a reference tool at the first step. It only generates blending passes in areas where material is left by the reference tool.
Different machining options for steep areas define the hybrid character of the strategy. The strength of the hybrid pencil strategy is that the user can define a contour-type strategy for steep areas. This is beneficial since the tool does not plunge into the rest material in vertical internal fillets. In a traditional pencil strategy, this plunging was a major reason for excessive tool wear or even breakage.
For steep angles, Pencil allows the user to define a Cutting mode and a slope angle from where this machining approach should be used. Cutting modes include:
Uses Pocket like passes in the Oxy plane to machine steep areas.
Uses Constant Cut like passes in the Oxy plane to machine steep areas.
Uses Pocket like passes in planes which are perpendicular to center lines.
Perpendicular Constant Cut
Uses Constant Cut like passes in planes which are perpendicular to center lines.
In the two images below you can see the difference between Pocket and Perpendicular Pocket cutting modes.
One important option to note is Full part. With this enabled, the entire part is machined using Scallop passes which start from center lines.
Tilt is, of course, also available for the Pencil strategy, but currently only in Beta mode. Please contact our support team for instructions on how to enable Beta mode.