Troubleshooting DXF Import on DMG NLX 2500 with Mitsubishi M730BM

1. Problem Overview

On a DMG MORI NLX 2500/700 turning center equipped with a Mitsubishi M730BM CNC control (part of the M700/M70 series family), an operator attempts to import a customer-supplied .DXF file from a USB thumb drive via the Punch / Read screen, only to receive an error of the form:

ALARM / MESSAGE
"Can not read file type"
(or localized equivalent: "File type cannot be read.")

The file is a verified, well-formed .DXF produced by AutoCAD or similar CAD package. The error occurs even though the file is reachable from the Punch directory listing. The control will not convert the geometry into a usable punch/nibbling or turning toolpath.

This article documents the three independent failure modes that produce this symptom, the verification steps to isolate them, and the corrective procedures for each. It is written for shop-floor engineers and applications staff working on NLX 2500 / NLX 2500S / NLX 2500 / 700 lathes with the Mitsubishi M730BM (M700 series) control.

2. System Identification

The M730BM belongs to the Mitsubishi 700/70 series covered in the official Mitsubishi Electric CNC handbook (700/70 Series Handbook, document IB1500087). Familiarity with the alarm-code and parameter-numbering conventions in that handbook is assumed throughout the remainder of this article.

3. Root Cause Analysis

The "Can not read file type" alarm is not a single fault. Three independent root causes have been observed in the field:

1. DXF revision incompatibility. The Mitsubishi DXF import filter in the M730BM accepts only AutoCAD Release 12 (DXF format tag AC1009) or a small subset of low-feature R13/R14 output. Any DXF saved as R2000, R2004, R2007, R2010, R2013, R2018, or later contains entity codes (HATCH gradient, SPLINE, 3DSOLID, ACIS entities, etc.) that the importer does not parse, and the importer aborts with the generic "Can not read file type" alarm rather than a specific entity error.
2. Wrong import path used. Two distinct screens on the M730BM deal with .DXF files: Punch / Read (converts DXF geometry into a NC program / conversational toolpath) and Media View (renders the DXF as a static image / document). If the operator is loading a print or a CAD reference drawing into Punch / Read, the import fails because Punch / Read expects geometry intended for toolpath generation, not arbitrary DXF drawings.
3. Optional feature not licensed. On Mitsubishi M700 series controls, the DXF-to-toolpath converter (often referenced as DX-Reader, DXF import option, or bundled into the CAPS conversational package) is a separately licensed option. If the option bit is unset, the Punch / Read screen shows the menu but the underlying parser is absent and any DXF selection returns "Can not read file type." License status is independent of training days or machine age.

4. Solution Path A — Convert the DXF to R12 (AC1009)

This is the most common fix and the first one to attempt, because it requires no control-side changes.

4.1 Why R12

AutoCAD Release 12 shipped in 1992 and uses DXF format identifier $ACADVER = AC1009. The R12 DXF grammar contains only the entities and the limited spline/ellipse representation that the Mitsubishi M700 series DXF parser was designed against. Higher revisions add hundreds of new entity codes (HATCH with gradient pattern, ASSEMBLY, ACIS-based solids, dynamic blocks, etc.) that the parser does not implement. The Mitsubishi parser silently rejects any DXF whose $ACADVER header is greater than AC1012 in most field-tested M730BM firmware versions.

4.2 Procedure

1. Open the DXF in a CAD application that can read your modern file and export R12. Candidates:
   • Autodesk AutoCAD (full product): SAVEAS → AutoCAD R12 DXF (*.dxf).
   • Dassault Système DraftSight: File → Save As → R12 DXF (*.dxf).
   • Open-source: LibreCAD, FreeCAD (use the R12 exporter), QCAD.
2. Before exporting, audit the geometry:
   • Explode all blocks and dynamic blocks.
   • Convert splines to polylines (PEDIT → Spline fit or PEDIT → Decurve).
   • Convert 3D entities to 2D (the importer is 2D only).
   • Remove hatches, dimensions, leaders, and tables — they are not imported as toolpath geometry.
   • Ensure units are inches or millimetres and consistent with the control's setup (G20 / G21).
3. Save as R12 DXF with a new filename so the original is preserved.
4. Verify the export header. Open the resulting file in any text editor and confirm the first header line reads:

     0
   SECTION
     2
   HEADER
     9
   $ACADVER
     1
   AC1009

4.3 Edge cases that still fail after R12 conversion

• Blocks remaining as INSERT entities. The Mitsubishi importer does not expand INSERT references. Explode everything in CAD before export.
• SPLINE / HELIX entities written by even R12 exporters when opened from newer files. Some applications promote the DXF version silently. Always confirm $ACADVER = AC1009.
• UTF-8 / Unicode line drawings. If the source DXF contains extended characters in layer names or text, re-export with ASCII-only layer names (no spaces, no diacritics, no Kanji).

5. Solution Path B — Use the Media View Function

If the operator's actual intent is to view a drawing at the machine — for example to confirm a print matches a part number, or to display a setup sketch — the correct screen is Media View, not Punch / Read. The M730BM distinguishes these as follows:

5.1 Media View load procedure

1. Insert the USB memory stick into the front-panel USB Type-A port.
2. Press the side shortcut key labelled Media View.
3. On the bottom soft-key row, locate the INIT / MEDIA toggle. Press it to switch the active device from User Area (internal memory) to USB.
4. Navigate to the directory containing the DXF or PDF file.
5. Select the file and press the input/enter key to load.
6. The drawing appears as a 2D image. Use the soft keys to pan, zoom, and (on most M730BM firmware revisions) toggle layers.

6. Solution Path C — Verify DXF Option Licensing

If the R12 conversion and the Media View path do not resolve the issue, the DXF import option may not be licensed on the M730BM. Mitsubishi sells DXF import as a separately enabled option bit on the M700 series; it is part of the standard build on some NLX configurations and absent on others.

6.1 How to check option status

1. From the main menu, navigate to Setup → Option (or Parameter → Option list, depending on firmware revision).
2. Look for entries such as DXF import, DXF reader, DX-Reader, or named option fields tied to conversational DXF.
3. If the option is shown as Not provided or absent, the feature is not licensed on this control.

6.2 How to license

The DXF option is enabled via a license key file or via parameter entry by the OEM (DMG MORI service) or the regional Mori Seiki / DMG MORI distributor (in North America, Ellison is the typical channel for DMG MORI machines). The end user does not have permission to enable it directly; request a service visit and supply the machine serial number and the M730BM option ID. Expect:

• Verification of the existing option ledger against the order spec.
• Loading of the option file or parameter modification.
• Test import of a known-good R12 DXF before the technician leaves.

7. USB File Transfer Procedure for the M730BM

The M730BM front-panel USB port is FAT32 / FAT16. Use a USB stick that complies with these limitations to avoid device not recognized errors that can mask the underlying DXF fault:

7.1 Recommended file handling

1. Name the file using alphanumeric characters and underscores only (e.g., PART123.DXF).
2. Place the file in the root directory of the USB stick.
3. Eject the USB stick from the host PC cleanly before unplugging.
4. Insert the stick into the M730BM front-panel USB port. Wait for the device to register (LED on USB slot or on-screen confirmation).
5. Navigate to either Punch / Read (for toolpath generation) or Media View (for static display).

8. Alternative Workflow — CAM Post-Processor

If the DXF import remains unavailable, the supported production path is CAM-based posting. The NLX 2500/700 with M730BM is supported by most mainstream CAM packages through a Mitsubishi M700-series post-processor. Typical workflow:

1. Import the customer DXF into CAM (Fusion 360, Mastercam, GibbsCAM, Esprit, etc.).
2. Apply turning operations (rough, finish, grooving, threading, optional Y-axis milling).
3. Post-process using an M730BM / Mitsubishi M700 turning post-processor. Verify the post outputs G-code matching the control's interpreter (G0/G1/G2/G3, G95 feed-per-rev, G97 spindle mode, M-codes per the Mori ladder).
4. Transfer the resulting .NC / .TAP / .MIN file (Mitsubishi conversational program file) to the control via USB using the same Punch directory or via RS-232C / Ethernet.

9. Verification Checklist

Run through this checklist after applying any corrective action:

10. Troubleshooting Matrix

11. Reference Material — Mitsubishi 700/70 Series Handbook

The Mitsubishi 700/70 Series Handbook (document IB1500087) is the authoritative reference for alarm codes, parameter tables, and option bit assignments on the M730BM. Specific sections relevant to DXF handling and file I/O include:

• Alarm code list — covers file-system and parser-level alarms.
• Parameter tables for USB / I/O device assignment and option enable bits.
• Operator's manual chapter on conversational programming and DXF import (chapter numbering varies by machine revision).

Refer to the latest revision of the handbook at the official Mitsubishi Electric FA document portal: 700/70 Series Handbook (IB1500087). Cross-check any alarm number or parameter number against the version stamped on your control's parameter printout (printed from the Parameter → I/O → Print menu), because the alarm numbering scheme changed at the M700 → M80 transition.

12. Quick Reference — Three-Action Recovery

If time on the floor is limited and the error must be cleared before service arrives, perform these three actions in order:

1. Re-save the DXF as R12 in any CAD tool that can read the source. Verify $ACADVER = AC1009 in a text editor. Test on the control. Many field cases are resolved at this step alone.
2. Switch to Media View if the operator's intent is to display the drawing at the machine, not to generate a toolpath. Press the side shortcut, toggle INIT / MEDIA to USB, and load.
3. Confirm option licensing via Setup → Option. If the DXF option row is missing or marked "Not provided," schedule a service call; the feature cannot be enabled from the operator menu.