Stock-Aware Toolpath Accelerates CAM Programming
An important technology in advanced CAM systems is “stock awareness.” As subtractive machining
operations are applied to a piece of raw stock, the shape of that stock is continually changing with each pass
of the cutting tool. If a CAM system has no awareness of these progressive changes to the stock, toolpath
will be created for material that no longer exists. To truly optimize the calculation of toolpath, a CAM system
must be digitally synchronized with the real-world process of material removal.
Simulating toolpaths is another vital step for CNC programmers to ensure they have created safe,
collision-free toolpaths. But as the number of operations increases, it is imperative that a programmer can
immediately view the state of the stock at any point in the process without wasting time watching the entire
simulation. This is particularly true for complex 3D surface machining, which can take a long time to simulate.
To optimize toolpath and speed simulations, ESPRIT® CAM utilizes an advanced stock automation engine
to calculate and update stock models as operations are applied. This “stock awareness” allows for dynamic
toolpath adjustments as the stock shape changes during machining. It also allows for simulations to start
from any point in the programming process since the system is constantly aware of what is happening to the
The benefits of the stock automation engine are twofold.
1. Optimize the calculation of toolpath to only those areas where material remains to be removed.
2. Optimize simulation time by allowing a simulation to start at any step in the machining process.
Since stock models are always available and up-to-date, there is no need to simulate all operations from the
beginning or for the user to manually save previous simulation states. A simulation can be started any time
with the previous operation stock.
Stock automation is an option of the application. The software user has full control over whether the engine
is enabled or disabled.
Accelerating the calculation of in-process stock models
To minimize the impact on document file size, ESPRIT® does not store stock models in the document.
Instead, all stock models are recalculated in the background as soon as a document is reopened.
For many documents, the recalculation of stock upon opening of the document goes unnoticed. However, as
one operation after another is applied to the digital stock model, the model becomes more and more complex
until adding even a simple operation can result in long calculation times.
The code behind the stock automation engine was refactored in ESPRIT® 2017 to drastically reduce
computation time. The new refactoring takes advantage of the raw processing power of modern computers
to compute in-process stock in dramatically less time, even on complex parts.
-Pocketing: up to 25 times faster
-Contouring: up to 3 times faster
-3-Axis mold roughing: up to 12 times faster
This refactoring is paying big dividends in computation speed, often reducing calculation time from minutes
Stock Awareness Leads to Optimized Toolpath
ESPRIT® utilizes the stock automation engine to continuously calculate the condition of the stock for
toolpath calculation as well as simulation.
To imitate real-world machining as closely as possible, a CAM system starts with an accurate digital
representation of the raw stock. The starting stock model can replicate any number of real-world stock types
such as castings, purchased blocks or bars, extrusions, turned profiles, or any other type of stock that can be
represented by a solid model from a CAD system.
To help automate the process of estimating the size of standard stock, the system can automatically size a
block or bar to the external limits of the CAD model to ensure the part model is fully encompassed by the
The goal of machining, then, is to transform the shape of the stock as effectively as possible into the shape
of the CAD model by progressively removing material.
When the CAM system has accurate knowledge of the starting stock, the system can consider the stock
height and shape to calculate the optimal start height for the cutter and the optimal distance for tool lead-ins
and lead-outs at each incremental depth of cut for safer, more reliable roughing operations.
Knowledge of the stock facilitates the calculation of improved types of toolpath like “bottom-up” toolpath for
faster roughing. Bottom-up machining uses upward, rather than downward, incremental steps to not only
remove material faster but to also attain a smaller residual stock height on the part surface for better finishing
Since ESPRIT® tracks the actual stock condition during all phases of machining, the system reliably
calculates toolpath that does not waste movement on areas where material has already been removed.
When the CAM system is stock-aware, it has precise knowledge of the in-process stock for more accurate
positioning of the cutter. This knowledge allows the system to calculate optimal tool positions more quickly
and accurately than manual programming.
Stock-aware toolpath calculation knows the perfect start height for the cutter, knows where to position the
bottom of the cutter along edges for a clean finish, and can calculate the optimal distance for tool lead-in and
lead-out at each incremental depth of cut.
To make programming faster and more reliable, ESPRIT® offers programmers the option of letting the
system handle the calculation of certain parameters internally for prismatic machining operations such as
facing, rough pocketing, and rough contouring.
-Automatic calculation of safe start height to avoid collisions
-Optimal tool overhang along edges for a clean finish
-Optimal lead-in and lead-out distances to save cycle time
-Optimal cutting angle at all incremental depths for fewer retract moves
All these calculations can be handled internally by the system through accurate measurement of the stock
model and cutter profiles.
With stock automation, the number of options displayed in the interface is reduced so that only key
parameters are presented to speed the decision-making process.
Figure 8. The system always calculates a safe start height for the tool based on the shape and
orientation of the stock — even when the workpiece is rotated.
Figure 9. Approach and exit moves are optimized by the system to safely avoid stock while
minimizing cycle time.
Figure 10. Optimal positioning along edges guarantees a clean finish.
Saving Stock for Other Setups
Although the stock automation engine does not save calculated stock models with the document, any stock
model for any operation can be saved to a separate file.
ESPRIT® supports the export of two file formats: STL or SIM. The SIM format is native to an ESPRIT®
simulation. An STL file is a triangulated representation of the simulation stock.
When saving the stock in SIM format, the stock retains the same quality and cutting colors of the tools as the
current ESPRIT® simulation. However, a SIM file can only be used in ESPRIT®. If you want to use the stock
model for purposes other than simulation in ESPRIT®, save it as an STL.
An STL model of the stock can be used for multiple purposes in multiple systems. For example, a stock
model saved as an STL file could be used as the basis for other machining methods such as wire EDM, or in
work setups on other machines.
As we synchronize the virtual and physical worlds, stock awareness brings significant advancements to the
way a CAM system interacts with subtractive machining processes. CNC programmers have many options
for transforming a piece of raw stock into a desired part shape. A CAM system with stock awareness lets
programmers focus their effort on getting the best results, while the system constantly monitors the
stock-in-process to ensure collisions are avoided and time is not wasted on “air cutting.” Stock-aware
toolpath accelerates the programming process to make the most effective use of human time and machine
ESPRIT is a global leader in high-performance computer-aided manufacturing (CAM) software. ESPRIT is a
cloud-enabled CAD/CAM software compatible with a full range of machine tool applications in a wide array of
industries. ESPRIT delivers powerful full-spectrum programming for 2-5 axis milling, 2-22 axis turning, wire
EDM, multitasking, mill-turn, Swiss-turn and B-axis machine tools, and high-speed 3 and 5-axis machining.
Offering factory certified post processors, accurate G-code, and world-class customer support ESPRIT is the
ultimate machine tool solution.
About DP Technology Corp.
DP Technology Corp., maker of ESPRIT CAD/CAM software, maintains its worldwide headquarters in
Camarillo, California, and product development teams in California, Florence, Italy, and Berlin, Germany.
Sales and support operations are located in Europe, Asia, and North and South America.
For additional information about DP Technology and ESPRIT, call +1 805 388 6000, send an email to
firstname.lastname@example.org, or visit the company website at www.espritcam.com.