Introduction

Mastercam is a cornerstone of modern manufacturing, offering robust CAD/CAM capabilities for generating precise toolpaths across a wide range of machining operations. For production shops that move beyond single-piece runs, setting up multi-part manufacturing jobs is essential to maximize throughput and minimize non-cutting time. Multi-part jobs enable you to machine multiple identical or similar parts in a single setup, reducing cycle time per part, lowering tool change frequency, and improving consistency across the batch. This guide provides a detailed, step-by-step approach to configuring multi-part batch processing in Mastercam, from workspace preparation to final NC code output.

Whether you are a seasoned Mastercam user or new to batch processing, understanding how to efficiently organize and replicate toolpaths across multiple parts is critical. We will cover the fundamental setup, advanced configuration options, simulation verification, and practical tips to avoid common pitfalls. By the end of this article, you will have a production-ready workflow that leverages Mastercam's multi-part job capabilities to their fullest.

For a comprehensive overview of Mastercam's batch processing features, refer to the official Mastercam Documentation. Additionally, the Mastercam Forums are an invaluable community resource for troubleshooting advanced setups.

Preparing Your Workspace for Multi-Part Jobs

Before diving into the multi-part job creation process, a well-organized workspace is the foundation of efficient batch processing. Start by ensuring all individual part files (e.g., SOLIDWORKS, STEP, IGES) are complete, correctly modeled, and saved in a consistent coordinate system. Verify that the geometry is clean—no duplicate surfaces, gaps, or unnecessary entities that could cause toolpath issues when replicated.

Part Alignment and Orientation

All parts in the batch must share a common origin and orientation to ensure seamless toolpath transfer. Use Mastercam's Transform functions to align parts relative to the machine coordinate system (MCS). If parts have different orientations, apply rotations or translations to bring them into a unified frame. For parts that are identical but need to be placed in different locations on the fixture, create a single "master" part and use the multi-part job layout to define the positions.

Machine and Tooling Setup

Define your machine definition (mill, lathe, or mill-turn) and stock model before importing any parts. Set the tool library, speeds, feeds, and coolant settings in the Machine Group Properties. Consistent tooling parameters across the batch prevent mid-job adjustments and ensure uniform surface finish. If your batch includes different materials (e.g., aluminum and steel parts), create separate machine groups or define conditional toolpaths—but for simplicity, this guide assumes uniform material and tooling.

Fixture Planning

A multi-part job often relies on a custom fixture such as a tombstone, subplate, or pallet system. Model the fixture geometry in Mastercam or import it as a separate file. Use stock models to represent each part's material block. This allows Mastercam to simulate collisions between the tool and fixture during batch runs. Invest time in accurately defining the part-to-fixture relationship; errors here can lead to catastrophic crashes.

Once your workspace is prepared, save the entire setup as a Mastercam file (`.mcam`) to capture all groups, tools, and parameters.

Creating a Multi-Part Job in Mastercam

The multi-part job feature streamlines the process of arraying parts across a fixture. Follow these steps to create a new multi-part job:

  1. Open Mastercam and start a new file. Navigate to File > New and select Multi-Part Job from the available templates. If the template is not listed, you can create a multi-part job manually (see alternative method below).
  2. Define the layout. In the dialog box that appears, specify the number of parts in the X, Y, and (if using a tombstone) Z directions. For a flat fixture, you typically set Z count to 1. Enter the spacing (center-to-center distance) between parts. Mastercam will generate a grid of positions.
  3. Import part files. Click Add Part and select the master part file (`.mcam` or imported geometry). Mastercam will insert the part at each grid position. Ensure the part's origin aligns with the grid origin. If necessary, adjust the part's position using the offset parameters in the multi-part job manager.
  4. Verify placement. Use the Fit view to examine the array. Check for overlaps or gaps. Adjust the layout parameters (spacing, rotation, mirroring) as needed. You can also define individual part positions by unchecking "Uniform Layout" and manually entering coordinates for each part.

Alternative: Manual Multi-Part Setup Without the Template

If the multi-part job template is unavailable or if your layout is non-regular, create the array manually using the Transform command:

  • After creating toolpaths for one part, select all operations in the Toolpath Manager.
  • Right-click and choose Transform. In the Transform Operations dialog, select Translate or Rotate.
  • Define the number of instances and the offset distance (X, Y, Z). Mastercam will create copies of all selected toolpaths, each linked to the original part's geometry. This method gives you full control but lacks the automatic stock modeling and simulation integration of the multi-part job template.

Using the Multi-Part Job Manager

Mastercam's Multi-Part Job Manager (available in the Machine Group tab) provides a bird's-eye view of all parts in the batch. From this panel, you can:

  • Add or remove parts
  • Edit individual part positions
  • Assign different stock models to each part
  • Toggle visibility of part geometry

For complex fixture layouts, such as a tombstone with parts on multiple faces, use the Rotary or Index options within the manager. Mastercam will automatically rotate the part geometry for each face, and toolpaths can be chained across faces using a single WCS.

Configuring Toolpaths for Batch Processing

Once the multi-part layout is established, the next critical step is to create and replicate toolpaths. The goal is to achieve identical machining quality across all parts while minimizing programmer effort.

Generating the Master Toolpath

Begin by creating all necessary toolpaths for one part (e.g., facing, pocketing, drilling, contouring). Use the 2D High Speed or 3D HST toolpaths for optimal material removal rates. Pay attention to:

  • Linking parameters: Define clearance planes, retract heights, and entry/exit motions that avoid the fixture. Use Relative heights (e.g., 1 inch above the part top) so that when replicated, the toolpath remains safe for all part positions.
  • Tool selection: Choose tools that can reach all part locations without excessive tool extension. Simulate the longest reach to confirm no interference.
  • Cut order: Mastercam allows you to set the cut order either by operation (finish all pockets on part 1, then move to part 2) or by location (machine all operations on part 1, then part 2). The latter reduces tool travel but may increase tool changes. Experiment to find the optimal balance for your machine.

Replicating Toolpaths Across the Batch

After the master toolpaths are ready, replicate them to all part copies. The method depends on your initial setup:

  • Using the Multi-Part Job Template: Mastercam automatically applies the toolpaths from the master part to all other parts. If you later edit a toolpath on the master part, the changes propagate to all instances—saving huge amounts of rework.
  • Using Transform Operations: For manually created arrays, select the master toolpaths, right-click, and choose Transform. Under Method, select Copy (not Move) and define the translation or rotation vector. Check Update stock to allow simulation to track material removal across multiple parts.
  • Using Toolpath Groups: Organize toolpaths into groups (e.g., "Roughing Group", "Finishing Group") within the Toolpath Manager. Then assign each group to the desired parts using the Part Group feature. This is useful when different parts require different sequences (e.g., some parts need hole drilling, others don't).

Advanced: Associating Parts with Different Operations

In some batch jobs, not all parts are identical. For example, you may have parts A, B, and C that share the same roughing sequence but require different finishing passes. Mastercam supports this through Part Associations:

  1. In the Multi-Part Job Manager, right-click a part and select Part Properties.
  2. Under Operations, uncheck the operations you want to skip for that part.
  3. Alternatively, create a separate Toolpath Group for each part and drag the appropriate operations into that group.
This granularity ensures that batch processing remains efficient without forcing you to create a separate program for each variant.

Simulating and Verifying the Multi-Part Batch

Before outputting NC code, thorough simulation is non-negotiable. A single toolpath error can wreck multiple parts and damage the fixture. Mastercam's Backplot and Verify (simulation) tools are your safeguards.

Backplot for Toolpath Review

Use Backplot (available in the Toolpath Manager) to visually inspect the tool motion for a single part or the entire batch. Check for:

  • Rapid moves that stray too close to clamps or vice jaws
  • Unnecessary tool lifts between parts
  • Incorrect cut order leading to large tool travel distances

Mastercam's Backplot also shows tool arcs and linear moves; verify that toolpath transition moves (e.g., from one pocket to another) are within safe distances. If you spot unsafe rapid moves, adjust linking parameters in the master toolpath and regenerate.

Full Verify with Stock Model

Run Verify (simulation) on the entire batch. For accurate results:

  1. Set the stock model to Stock from the part file or create a custom stock block that encompasses all parts in the fixture.
  2. Enable Toolpath Gouge Check and Collision Detection (including the tool holder and shank).
  3. Simulate the entire job at high speed, then slow down and examine each part after material removal.
  4. Pay special attention to areas where toolpaths from adjacent parts may overlap—Mastercam may attempt to machine air or cause collisions if the stock model isn't properly defined.

If any errors appear—gouges, uncut material, or collisions—go back and adjust the master toolpath or the part layout. Repeat the simulation until no issues remain.

Verifying Machine-Specific Constraints

Beyond the software simulation, consider your actual machine tool:

  • Axis travel limits: Ensure that the toolpath for the farthest part does not exceed the machine's X, Y, Z limits. Mastercam's Machine Simulation (if available in your license) can verify this.
  • Rotary limits: If using a tombstone with rotation, confirm that the rotary axis (e.g., 4th or 5th) can index to all required positions without cable interference or unclamping.
  • Tool changer clearance: If the batch job uses many tools, ensure the tool changer can reach each tool without hitting the fixture or part.

It is wise to run a single-part dry run on the actual machine before committing to the full batch. This validates G code, speeds/feeds, and tooling.

Outputting the Batch Job: Post Processing

After successful simulation, generate the NC code for the entire batch in one shot. Mastercam's post processor will create a single file containing all toolpaths for all parts, with appropriate subprogram or coordinate system calls.

Configuring the Post Processor for Multi-Part

Standard Mastercam posts (e.g., MPFAN, MPLMASTER) support multi-part jobs natively, but you may need to tweak a few parameters:

  • Work offset handling: Most machines use G54, G55, etc., for different part positions. Ensure the post outputs the correct offset for each part. In the multi-part job manager, assign a Work Offset to each part (e.g., part 1 = G54, part 2 = G55). The post will automatically embed the correct G code.
  • Subprogram usage: To save memory, some posts can output a main program that calls subroutines for each part. This is efficient for large batches. Consult your post's documentation or the Mastercam Post Processor Support page for details.
  • Tool change optimization: Choose between By Operation (all part 1 tools, then part 2 tools) and By Tool (all operations using tool 1 on every part, then tool 2). The latter reduces tool changes and is typically faster for large batches. Set this in the Operation Order of the Toolpath Manager.

Generating and Reviewing NC Code

  1. In the Toolpath Manager, select all operations (for all parts).
  2. Click Post (or right-click and choose Post All).
  3. Select the appropriate post processor file (`.pst`).
  4. In the Post dialog, verify that the output file name includes all operations (e.g., `BATCH_NC.NC`).
  5. Click OK to generate the code.

Open the NC file in a text editor and review the first few lines to confirm G54/G55 assignments, program numbers, and that each part's toolpath starts at the correct Z height. Look for any unexpected M codes (like M00 program stops) that could disrupt the batch cycle. If you see issues, adjust the post variables or contact your post provider.

Save the final NC file to your machine's control or to a network drive. Ensure the file is compatible with your machine controller (e.g., Fanuc, Heidenhain, Siemens). For high-volume production, consider using the Mastercam Batch Processing utility (separate from multi-part jobs) to run multiple NC files consecutively.

Tips for Successful Batch Processing

  • Standardize fixtures: Use a modular workholding system with repeatable locations. This allows you to define fixture offsets once and reuse them for every batch. Document the fixture coordinate system for future jobs.
  • Use consistent tooling across the batch. If a tool breaks during the run, replacing it with an identical tool (same diameter, flute count, coating) ensures tolerances stay within spec. Keep spare tools presets.
  • Run a test cycle with a single part first. Before committing to the full batch, machine one part from the fixture using the same program. Measure critical dimensions and surface finish. Adjust offsets or speeds as needed, then update the master file.
  • Regularly update Mastercam to access latest features and improvements. New versions often include better multi-part workflow enhancements, improved simulation speed, and post processor updates.
  • Document your multi-part setup. Create a standard operating procedure (SOP) file in Mastercam's Note or Comment fields. Include part layout images, tool list, and work offset assignments. This helps other programmers replicate the setup.

Advanced Considerations for Complex Batches

Handling Multiple Fixture Setups (Tombstones)

For parts mounted on a tombstone with two or four workholding faces, Mastercam's Rotary Axis feature allows you to program each face as a separate WCS. In the Multi-Part Job Manager, set the Rotary Index angle for each part (e.g., 0°, 90°, 180°, 270°). Then create a single master part for one face and replicate its toolpaths to all faces using Rotary Transform. Mastercam will automatically rotate the geometry and recalculate tool axis. Verify that the post processor outputs the correct axis commands (e.g., B90.0 for a 90° rotation on a horizontal machining center).

Batch Processing with Different Part Variants (Family of Parts)

If your batch contains parts that are geometrically similar but have different features (e.g., a bracket with and without a hole), use Part Groups and conditional operations. Create separate operations for the variant features, and in the multi-part job manager, assign those operations only to the parts that need them. This avoids programming each variant from scratch. Mastercam's Level Management can also help; store variant geometry on different levels and use Masked Toolpaths to select the correct level for each part instance.

Using Macros and Post Processor Customization

For very large batches (50+ parts), consider leveraging Mastercam's C-Hooks or Macros to automate repetitive tasks like part placement and toolpath replication. Custom post processors can also output machine-specific subprogram calls or use variable work offsets (e.g., G54.1 P1-P50). Refer to the Mastercam Developer Tools for scripting capabilities.

Troubleshooting Common Multi-Part Job Issues

Toolpaths Not Updating Across All Parts

If you edit a master toolpath but the changes do not appear on all parts, check that the parts are linked to the master. In the Multi-Part Job Manager, ensure each part has the same toolpath group associated. For transformed operations, verify that the Link to original option is selected in the Transform dialog. If not, delete the old transformed operations and reapply.

Simulation Showing Crashes on Some Parts but Not Others

Often caused by incorrect stock models or part origins. Return to the workspace and confirm that each part's geometry is identical (no dimensional drift). Use the Analyze command to compare part coordinates. Also, ensure the fixture model is accurate—small discrepancies in clamp positions can cause invisible collisions.

Overly Long NC Files

Large batches can produce enormous G-code files that bog down the machine controller. Solutions include using subprograms (as noted above), activating High Speed Machining look-ahead settings on the controller, or reducing the number of small moves by adjusting toolpath tolerance (e.g., from 0.001" to 0.0025" for roughing). Always test with a representative sample.

Inconsistent Surface Finish Across Parts

Variations in finish may stem from tool wear, coolant flow differences, or fixture deflection. Use Mastercam's Toolpath Editor to examine the stepover and cutting angle on each part. If the issue persists, consider adding a finishing pass that runs a semi-finish toolpath before the final pass, ensuring uniform stock removal. Also, verify that your tooling is sharp and that the machine spindle is thermally stable before starting the batch.

Optimizing Batch Processing Workflows

Over time, you can refine your multi-part job setup to be faster and more reliable. Best practices include:

  • Create templates: Save a Mastercam file with the fixture model, machine definition, and default tool library as a template. For each new batch job, open the template, import the part geometry, and update toolpaths. This slashes setup time.
  • Leverage toolpath groups for operation order. Use groups to categorize roughing, semi-finishing, and finishing. Mastercam will optimize the sequence across parts based on the group order.
  • Utilize Mastercam's Batch Processing utility (outside the multi-part job) if you need to run multiple different jobs sequentially (e.g., first job machines all parts on one side, second job machines the opposite side after manual flip). This is not covered in this guide but is documented in Mastercam help files.
  • Monitor machine load during batch runs. Use spindle load meters to detect broken tools or material inconsistencies early. Some shops use a camera or a tool touch probe to verify each part before the next toolpath begins.

By integrating these strategies into your daily workflow, you will achieve consistent, high-quality batch production that maximizes your CNC machine's uptime.

Setting up multi-part manufacturing jobs in Mastercam is a powerful way to boost productivity while maintaining precision. The key steps—workspace preparation, layout creation, toolpath replication, simulation, and post processing—form a repeatable process that, once mastered, can be applied to a wide variety of production scenarios. Always prioritize thorough simulation and a dry run on the actual machine to catch errors early. With the techniques outlined in this guide, you can confidently configure and run multi-part batch jobs, reducing setup time and increasing your shop's output efficiency.