How to Add More CNC Machines to Mastercam
This guide is for programmers and manufacturing engineers who need to bring a new mill, lathe or 5-axis center into Mastercam without breaking existing programs. It covers machine definitions, post processors, control files and the checks that catch collisions before the first cut. Read it once and you can judge whether your machine is ready to post or still needs a custom build.
In this article
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Key takeaways
Why you add more CNC machines to Mastercam at all
A shop adds machines to Mastercam for one reason: the programming side has to match the floor. When you buy a second 5-axis center or bring in a mill-turn, every new spindle is a new set of kinematics, travel limits and tool-change positions. If the software still thinks it is posting to the old machine, the programmer becomes the collision-detection system. That does not scale.
The practical benefit is speed of response. When a customer sends a 6061-T6 bracket on Monday and wants parts by Friday, the programmer needs the right machine group available immediately. Adding the machine properly once means the next job posts in minutes, not hours of hand-editing.
There is also a safety argument. Mastercam stores travel limits, rotary table position and machine home in the definition. Post a program that exceeds Z travel and the control may still accept it, then alarm mid-cut or, worse, drive the tool into the table. A correct definition stops that at the simulation stage.
This is not a one-time task. Shops that grow from 3-axis work into 4-axis and 5-axis work revisit their machine library every year. Treat the library as a living asset, not a setup chore.
- 1New spindle, new groupEach physical machine gets its own machine group in the operation tree.
- 2One post per controlTwo machines with the same control can share a post if the kinematics match.
- 3Library hygieneArchive old definitions instead of deleting them. Legacy jobs may still reference them.
The three files that make a machine work
A working machine in Mastercam is a stack of three files. The machine definition (.machine) describes the physical hardware: axis configuration, travel limits, spindle orientation, tool change position and the model geometry used for simulation. The control definition (.control) describes the CNC control behavior: G-code format, arc output, canned cycles and coolant codes. The post processor (.pst) translates toolpath into that control's dialect.
Mixing them is the most common failure. A programmer downloads a generic 3-axis post, points it at a 4-axis machine definition and gets rotary output that the control rejects. The post does not know about the fourth axis because the control file never declared it. Check all three before you blame the post.
File locations matter too. Mastercam keeps machine and control files under a shared folder structure, usually under the Shared mcam directory. If you drop files in a personal folder, the next programmer on the seat will not see them. Put shared assets in the shared path.
Version control is worth a mention. Keep a copy of every definition and post that has produced good parts. When a new Mastercam release changes the file format, you can rebuild from a known-good baseline instead of guessing.
- 1.machineHardware model: axes, travels, spindle, tool change position.
- 2.controlControl dialect: G-code format, arcs, cycles, coolant.
- 3.pstOutput translator that writes the NC file.
When a stock post is enough and when it is not
A generic post is usually fine for a 3-axis vertical mill running simple profiles and drilling. The output is predictable and the control dialect is well documented. If your parts are prismatic and the tightest tolerance is ±0.005 mm on a bore, a stock post plus a correct control definition will get you there.
A generic post is not enough when the machine has non-standard kinematics. Mill-turn centers, twin-spindle lathes, and 5-axis machines with a tilting head and rotary table are all cases where the post must understand the machine structure. The toolpath is correct; the output is wrong. That is a post problem, not a programming problem.
Custom macros are the other trigger. If your control uses a probing cycle or a custom G-code for pallet changes, the post has to emit it. A stock post will not invent a macro it has never seen.
The decision rule is simple. If two machines share the same control and the same kinematic layout, one post serves both. If either differs, build a separate post. Post processors are cheaper than crashed spindles.
- 1Stock post OK3-axis mill, standard Fanuc control, prismatic parts.
- 2Custom post neededMill-turn, twin spindle, tilting head, probing macros.
- 3Separate groupAny machine with a second spindle or a second turret.
How GreatLight keeps its machine library aligned
GreatLight runs 127 high-precision CNC machines across three wholly-owned plants, including 16 simultaneous 5-axis machining centers, 12 four-axis mills, 27 three-axis machines and 16 mill-turn centers. Every one of those machines has a matching definition, control file and post in the programming library. That is the only way a job can move from quote to chips without rework on the software side.
The travel range is wide, so the definitions are not interchangeable. Large gantry work goes up to 4,000 mm, while compact cells run envelopes like 500 × 500 × 450 mm. A programmer selecting the wrong machine group sees a simulation that fits and a real setup that does not. We tag each group with the machine name and travel so the mistake is visible before posting.
Inspection data feeds back into the library. With ±0.005 mm tolerance work and 100 percent inspection before shipment, a post that produces consistent output is valuable. When a new machine is commissioned, we run a test part with known dimensions, compare the report and only then release the post to the programming team.
This matters to customers because it shortens the gap between quotation and production. A quotation and free DFM analysis come back within 12 hours, and production can start within 24 hours, but only if the machine that will run the part is already defined correctly.
- 1Tagged machine groupsMachine name and travel range visible in the operation tree.
- 2Test part on commissioningKnown dimensions verified before the post goes live.
- 3Shared libraryAll programmers work from the same definitions, not local copies.
Mistakes that cost a shift or a part
The first mistake is importing a definition from a different Mastercam version and assuming it works. Axis data can be dropped silently. Open the definition, walk through every axis and confirm the travel values against the spec sheet.
The second is leaving the default home position. If the machine definition still points to a generic home and your machine's tool change position is 150 mm away, the first rapid will alarm or crash. Set the home and tool change position to the real values from the machine manual.
The third is testing with an empty stock model. Simulation without the fixture and holder looks clean and proves nothing. Load the vise, the chuck or the tombstone and let the software check clearance.
The fourth is letting two programmers maintain separate copies of the same post. Within a month the outputs differ. Keep one shared post, and version it when it changes.
- 1Version mismatchAxis data can be lost on import from older releases.
- 2Default homeGeneric tool change position causes alarms or crashes.
- 3Empty simulationNo fixture model means no real collision check.
- 4Forked postsTwo copies drift apart. Keep one shared file.
Step by step: add more CNC machines to Mastercam
Follow the order. Skipping step 2 is the most common cause of bad output.
- 11. Collect the machine data sheetGet the exact model number, control make and version, axis count, travel limits in X, Y and Z, spindle taper, and maximum spindle speed. For a 4,000 mm gantry, record travel as 4,000 × 400 × 150 mm. Missing a single travel value forces a manual definition build later.
- 22. Load the machine definitionIn the Machine Group setup, choose Machine Definition and browse to the .machine file. If the builder or reseller supplied a file, use theirs first. Only build a definition manually when no file exists, and expect to spend a full day on a 5-axis model.
- 33. Attach the control definitionOpen the machine definition and set the Control Definition to the file that matches the control, for example a Fanuc 31i or a Siemens 840D. Confirm the arc output setting: most Fanuc controls want absolute arc centers, many Heidenhain controls do not.
- 44. Assign the post processorPoint the machine group at the correct .pst. If you are editing an existing post, work on a copy. Test with a simple facing pass and a drilling cycle before running a full 3D program. A single misplaced G28 can ruin a fixture.
- 55. Set up the machine group and WCSCreate a machine group, set the work coordinate system to match the datum on the drawing, and define the stock and fixture. For 5-axis work, confirm the rotary table center. A Ø400 mm rotary table has a small setup window; a 2 mm error in the pivot offset shows up as taper on the part.
- 66. Run stock-based simulationSimulate with the real holder and fixture geometry, not just the tool. Check for holder-to-fixture clearance on deep pockets and confirm retract moves clear the vise. Fix collision warnings here, not on the machine.
- 77. Post a dry-run program and prove itPost the NC file, run it in single block with rapids at 25 percent and the tool 100 mm above the part. Verify the first tool change position and the rotary orientation before cutting. Then release the program to production.
Machine definition source: which route to take
Pick the route that matches how common your machine is.
| Source | Best for | Time to set up | Risk |
|---|---|---|---|
| Machine builder file | Common production machines | 1–2 hours | Low if version matches |
| Reseller or integrator file | New or uncommon models | 2–4 hours | Medium, depends on support |
| Mastercam library file | Standard 3-axis mills | Under 1 hour | Low for simple kinematics |
| Manual build | Prototype or custom machines | 1–2 days for 5-axis | High, needs careful checking |
| Copy from similar machine | Identical control and layout | 1 hour plus edits | Medium, travel limits must match |
Get the definition right once
A correct machine definition, control file and post turn a new spindle into a production asset. A shortcut turns it into a crash waiting for a Friday shift. If you would rather send the part out than build the post, we run 127 machines with matched definitions and can quote from your STEP file within 12 hours.
Frequently asked questions
Can I add any CNC machine to Mastercam?
Yes, in principle. Mastercam supports a wide range of mill, lathe, mill-turn and router configurations, and you can build a definition from scratch if no file exists. The practical limit is not the software but the data. You need accurate travel limits, axis layout and control details.
If the machine builder cannot supply a definition and the control is uncommon, budget more time. A manual 5-axis build is a full-day task for an experienced programmer.
Do I need a new post processor for every CNC machine?
Not always. If two machines share the same control and the same kinematic layout, one post can serve both. The machine definition still needs to be separate so travel limits and simulation geometry stay correct.
You do need a separate post when the kinematics differ, when a second spindle or turret is involved, or when the control uses custom macros that the post must emit.
How do I find the right machine definition file?
Start with the machine builder or the local reseller. Most mainstream builders supply a definition and a matched post for their current models. If that fails, check the Mastercam machine library for a close match.
Match on control make and version first, then on axis configuration and travel. A definition with the right control but the wrong travels is more dangerous than no definition, because simulation will pass and the machine will not.
Is it difficult to set up a 5-axis machine in Mastercam?
It takes longer than a 3-axis setup because the kinematic chain has to be correct. You define the rotary axes, their pivot points and the relationship to the spindle. On a machine with a Ø400 mm rotary table, a small error in the pivot offset shows up as taper across the part.
Use the builder file whenever possible. If you build it manually, verify with a test part before running production work.
Can I use the same machine definition for different projects?
Yes. A machine definition describes hardware, not a job. The same definition serves every part that runs on that machine. What changes between projects is the machine group, the work coordinate system, the stock and the tool list.
Archive definitions rather than deleting them. Old programs may still reference a machine that has been sold or retired.
What should I check before releasing a new post to production?
Post a simple test program and run it in single block with rapids reduced. Check the tool change position, the rotary orientation and the retract plane. Confirm the arc output matches the control.
Then run a test part with known dimensions and compare the inspection report. Only after that should the post be used for customer work.
Send the part, not the setup problem
Upload a STEP file and we will return a quotation with free DFM analysis within 12 hours, then start production within 24 hours. No minimum order quantity, from one prototype to 10,000+ part runs.
12-hour quote100% inspection±0.005 mm tolerance
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