Siemens NX Post Builder for DMG Mori MillTap 700 (SINUMERIK 840D sl) and the Brother SPEEDIO Alternative

Selecting a vertical machining center for a prototype job shop forces a converging set of trade-offs: control architecture, post-processor development cost, four-axis indexing support, distributor support depth, and lifecycle reliability. This reference evaluates the DMG Mori MillTap 700 with SINUMERIK 840D sl Operate against the Brother SPEEDIO platform running the Brother CNC-D00 control, with a working workflow for Siemens NX Post Builder development in either direction.

Project Framing: Prototype Shop Constraints

A short-run prototype shop building parts from alloy steel and pre-hardened tool steel up to roughly 400 Brinell has a different calculus than a production cell. The constraints that drive the post-processor and control decision are:

• Taper class. A 30-taper VMC supports the bulk of the part envelope; a 40-taper VMC is reserved for larger workpieces that graduate off the prototype cell once volume rises.
• Workholding density. Most parts are small and nest efficiently on a fourth-axis trunnion, so the control must support 3+1 indexing without forcing five-axis kinematic definitions on every setup.
• CAM environment. NX is the single source for design and manufacturing. A post that does not map cleanly into NX Post Builder is a recurring tax, not a one-off cost.
• Support responsiveness. The shop is isolated; downtime becomes a single point of failure for the prototype schedule.
• Resale optionality. The controller is justified to the budget only if the equipment can be absorbed back into the existing business or liquidated if the project stalls.

Control Platform Comparison: SINUMERIK 840D sl vs Brother CNC-D00

The two controllers are not feature-for-feature substitutes. The table below captures the documented differences relevant to a single-machine prototype shop running NX.

The pragmatic reading: SINUMERIK is a control you can configure deeply, but the configuration effort lives on the post side and on machine data. The Brother control trades configurability for a tightly integrated, single-vendor package where machine and control come from the same engineering team.

NX Post Builder Architecture for SINUMERIK 840D sl

NX Post Builder ships with a library of post templates indexed by control. The SINUMERIK 840D sl family is represented by the siemens_840d_sl template, with sub-variants for mill-turn and three-axis mills. The MillTap 700 ships with a vendor-specific post that DMG Mori maintains, but building a shop-specific post on top of the Siemens template gives the engineer full control over the code that the machine will execute.

Template selection

1. Open NX, then Manufacturing → Post Builder.
2. Select New Post and choose the siemens_840d_sl template closest to the kinematic model. For the MillTap 700 three-axis-plus-indexing configuration, use the three-axis mill template.
3. Set the post name to match the machine label, e.g. MILLTAP_700_840DSL_3X1A.
4. Define machine units (metric), NC mode (3-axis), and the rotary axis as a positioning axis only for 3+1 work.

Critical Program & Tool Path defaults

• sequence_numbering: enabled, increment 5, to leave headroom for hand-edits.
• block_numbering: enable N word for SINUMERIK readability; some operators prefer : for compactness.
• max_circular_radius: 0 to allow full helical interpolation; set non-zero only when commanding line-arc transitions for surface finish quality.
• output_mode: 3-axis + rotary positioning.
• coolant_codes: map NX FLOOD, MIST, THRU to SINUMERIK M-codes M8 / M7 / M71 as appropriate.

Custom command mapping

The MillTap 700 exposes a small set of shop cycles through SINUMERIK. The post can call them as TCL procedures to keep the G-code readable:

tcl
proc MOM_rapid_move { } {
  MOM_output_literal "G0 X\$mom_pos(0) Y\$mom_pos(1) Z\$mom_pos(2)"
}
proc MOM_index_axis { } {
  MOM_output_literal "ROT A\$mom_pos(3)"
}

Where ROT A is the documented SINUMERIK keyword for rotary axis positioning and A matches the MillTap 700 trunnion axis label. Operators verify the axis name against the machine's channel configuration before running the program.

NX Post Builder Architecture for Brother CNC-D00

The Brother SPEEDIO controller accepts a Fanuc-compatible G-code dialect with a set of Brother-specific M-codes. There is no first-party Brother-branded post inside NX Post Builder, which is why shops building for SPEEDIO typically start from the fanuc_3axis template and patch the machine-specific surface area. The two areas that always need attention:

1. Tool change macro. SPEEDIO uses an ATC macro triggered by M6; some older posts emit a Fanuc-style tool preamble that needs to be replaced with the Brother equivalent.
2. Fourth-axis command. SPEEDIO labels the rotary axis A (or B, depending on the trunnion builder) and uses standard G0 A<angle> positioning. This maps cleanly onto the Fanuc template, so 3+1 indexing requires no custom TCL.

Post Builder settings to verify

• rotary_axis_definition: declare the rotary as a positioning (not contouring) axis when the job is 3+1 only.
• tool_change_type: manual call to the Brother ATC macro, not the generic Fanuc four-line preamble.
• program_number: prefix with O as required; SPEEDIO rejects 5-digit program numbers without the O.

The post-development effort for Brother is therefore lower for the 3+1 case but requires the engineer to validate every tool-change and coolant emission against the actual machine, since the template only approximates Brother behaviour.

4-Axis Indexing (3+1) Post Workflow

For parts that nest on a rotary trunnion, the engineer needs a workflow that handles index moves without forcing five-axis kinematics on every operation. The steps below apply to either controller with minor modifications.

Step 1: Operation-level indexing strategy

In NX Manufacturing, mark each operation that should execute at a fixed rotary position as Indexing rather than Multi-axis. This keeps the toolpath evaluator in three-axis mode and prevents unwanted tool-vector commands from being emitted.

Step 2: Index table construction

Build a fixture in NX with a circular pattern of part positions. The post reads the rotary angle from the fixture and emits a single positioning move at the start of each operation:

tcl
proc MOM_index_axis { } {
  global mom_pos
  MOM_output_literal "G53 G0 A\$mom_pos(3)"
  MOM_output_literal "G54"
}

The G53 prefix cancels any active work offsets before the rotary move, which is important for SINUMERIK where a work offset in the rotary axis will fault the move.

Step 3: Tool length compensation across indexes

Tool length compensation is applied along the spindle axis, which does not change with rotary position. The post therefore only needs to apply G43 H# after a tool change, not after an index move.

Step 4: Verify with machine simulation

Use NX machine simulation with the correct kinematics file before any code reaches the shop floor. Confirm:

• Spindle clears the trunnion at every index angle.
• No collision with workholding clamps at any index.
• Tool-change position is reachable from every indexed location without overtravel.

Material and Cutting Parameter Considerations

Tool steel up to ~400 Brinell and alloy steel in the same range impose constraints that flow into the post as comments and operator prompts:

Post-level technique: emit a header comment that lists the tool, the recommended starting cutting speed (vc), and the programmed feed per tooth. Operators in the prototype cell need this because they often set the spindle speed manually when running a part for the first time.

tcl
proc MOM_tool_change { } {
  global mom_tool_name mom_tool_diameter
  MOM_output_literal "(TOOL: \$mom_tool_name DIA=\$mom_tool_diameter)"
}

Side-by-Side Selection Matrix

Post Development Workflow: Step-by-Step

The workflow below is control-agnostic and applies to either machine; the differences are called out in the comments.

1. Define machine kinematics. Export the kinematic model from the builder's official documentation. For the MillTap 700 this is in the SINUMERIK machine data file. For SPEEDIO it is in the parameter sheet shipped with the machine.
2. Open NX Post Builder. Choose the appropriate base template.
3. Map tool change and ATC. Verify against the actual M-code list — do not rely on the template defaults.
4. Map coolant codes. Eight common coolant codes need to be confirmed against the machine builder's reference.
5. Define program header. Include program name, post version, controller, machine serial, date.
6. Define program footer. Safe retract, spindle off, coolant off, M30.
7. Generate test code. Use a known fixture and known tools.
8. Run the program in dry-run on the controller. SINUMERIK: use the program control: dry run feed function. SPEEDIO: use the dry-run switch.
9. Cut air. Run the program above the table with the spindle at zero RPM to verify motion.
10. Cut first part. Operate with reduced feed override (25%) and an operator at the ready stop.

Verification and Acceptance Test

Acceptance is a structured gate, not a single event. Run each item and record the result.

Troubleshooting Matrix

Field-Proven Caveats

Cross-Reference: Standards to Verify Against

For shops that need to align their post with international NC programming conventions, the relevant published standards are:

• ISO 6983-1 — G-code programming language baseline.
• ISO 3592 — NC programming language structure.
• ISO 4343 — APT-style source language elements.

SINUMERIK and Brother both extend ISO 6983 with proprietary cycles; the post should declare its conformance level so that downstream tooling (DNC, ERP integration) can interpret the output consistently.

Recommended Decision Path

1. If the shop already runs multiple Siemens-controlled machines, the MillTap 700 with a properly developed NX post preserves control uniformity and reduces operator-training overhead — provided the specific machine's reliability record is acceptable.
2. If the prototype cell will operate as an isolated island with a single machine, the Brother SPEEDIO lowers post-development overhead, simplifies training, and concentrates support through one distributor channel (Yamazen).
3. For 4-axis (3+1) prototype work with frequent tool changes and short setup windows, the SPEEDIO's faster tool change and integrated conversational cycles translate directly into operator minutes saved per part.
4. For deep configurability, advanced kinematic cycles, and a multi-machine future, SINUMERIK is the more scalable platform — at the cost of higher first-time post effort.