ISO 14649-11:2004

Industrial automation systems and integration — Physical device control — Data model for computerized numerical controllers — Part 11: Process data for milling

ISO 14649-11:2004 specifies the technology-specific data elements needed as process data for milling. Together with the general process data described in ISO 14649-10, it describes the interface between a computerized numerical controller and the programming system (i.e. CAM system or shop floor programming system) for milling. It can be used for milling operations on all types of machines, be it milling machines, machining centres, or lathes with motorized tools capable of milling. The scope of ISO 14649-11:2004 does not include any other technologies, like turning, grinding, or EDM. These technologies will be described in further parts of ISO 14649. The subject of the milling_schema, which is described in ISO 14649-11:2004, is the definition of technology-specific data types representing the machining process for milling and drilling. This includes both milling of freeform surfaces and milling of prismatic workpieces (also known as 2 1/2-D milling). Not included in this schema are the following: geometric items; representations; manufacturing features; executable objects; base classes which are common for all technologies. They are referenced from ISO 10303's generic resources and ISO 14649-10. The description of process data is done using the EXPRESS language as defined in ISO 10303-11. The encoding of the data is done using ISO 10303-21.

Systèmes d'automatisation industrielle et intégration — Commande des dispositifs physiques — Modèle de données pour les contrôleurs numériques informatisés — Partie 11: Données des procédés relatifs au fraisage

General Information

• Status: Published
• Publication Date: 05-Dec-2004
• ICS: 25.040.20 - Numerically controlled machines
• Technical Committee: ISO/TC 184/SC 1 - Industrial cyber and physical device control
• Drafting Committee: ISO/TC 184/SC 1 - Industrial cyber and physical device control
• Current Stage: 9093 - International Standard confirmed
• Completion Date: 07-Jan-2019

Relations

• Revises: ISO 14649-11:2003 - Industrial automation systems and integration — Physical device control — Data model for computerized numerical controllers — Part 11: Process data for milling
• Effective Date: 15-Apr-2008

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 14649-11
Second edition
2004-12-15
Industrial automation systems and
integration — Physical device control —
Data model for computerized numerical
controllers —
Part 11:
Process data for milling
Systèmes d'automatisation industrielle et intégration — Commande
des dispositifs physiques — Modèle de données pour les contrôleurs
numériques informatisés —
Partie 11: Données des procédés relatifs au fraisage
Reference number
ISO 14649-11:2004(E)
ISO 2004
---------------------- Page: 1 ----------------------
ISO 14649-11:2004(E)
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...

INTERNATIONAL ISO
STANDARD 14649-11
Second edition
2004-12-15
Industrial automation systems and
integration — Physical device control —
Data model for computerized numerical
controllers —
Part 11:
Process data for milling
Systèmes d'automatisation industrielle et intégration — Commande
des dispositifs physiques — Modèle de données pour les contrôleurs
numériques informatisés —
Partie 11: Données des procédés relatifs au fraisage
Reference number
ISO 14649-11:2004(E)
ISO 2004
---------------------- Page: 1 ----------------------
ISO 14649-11:2004(E)
PDF disclaimer

This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but

shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In

downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat

accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.

Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation

parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In

the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.

© ISO 2004

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,

electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or

ISO's member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail [e-mail]
Web www.iso.org
Published in Switzerland
ii © ISO 2004 – All rights reserved
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ISO 14649-11:2004(E)
Contents Page

Foreword ............................................................................................................................................................iv

Introduction.........................................................................................................................................................v

1 Scope......................................................................................................................................................1

2 Normative references............................................................................................................................1

3 Terms and definitions ...........................................................................................................................1

4 General Process data............................................................................................................................2

4.1 Header and references..........................................................................................................................2

4.2 Technology-specific machining operations .......................................................................................2

4.2.1 NC functions for milling........................................................................................................................2

4.2.2 Tool direction for milling ......................................................................................................................3

4.2.3 Milling machining operation.................................................................................................................4

4.2.4 Milling technology.................................................................................................................................5

4.2.5 Milling machine functions ....................................................................................................................6

4.2.6 Milling type operation ...........................................................................................................................7

4.2.7 Freeform operation..............................................................................................................................14

4.2.8 Two5D milling operation.....................................................................................................................18

4.2.9 Plane milling ........................................................................................................................................23

4.2.10 Side milling..........................................................................................................................................24

4.2.11 Bottom and side milling......................................................................................................................24

4.2.12 Drilling type operation ........................................................................................................................25

4.2.13 Drilling operation.................................................................................................................................27

4.2.14 Boring operation..................................................................................................................................29

4.2.15 Back boring..........................................................................................................................................29

4.2.16 Tapping.................................................................................................................................................30

4.2.17 Thread drilling......................................................................................................................................30

4.3 End Schema .........................................................................................................................................31

5 Conformance requirements ...............................................................................................................31

5.1 Conformance class 1 entities.............................................................................................................31

5.2 Conformance class 2 entities.............................................................................................................32

Annex A (normative) EXPRESS listing...........................................................................................................33

Annex B (normative) Short names of entities................................................................................................43

Annex C (normative) Implementation method specific requirements ........................................................45

Annex D (informative) EXPRESS-G diagram..................................................................................................46

Annex E (informative) Sample NC programmes ............................................................................................53

E.1 Example 1.............................................................................................................................................53

E.2 Example 2.............................................................................................................................................56

Index ..................................................................................................................................................................62

© ISO 2004 – All rights reserved iii
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ISO 14649-11:2004(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies

(ISO member bodies). The work of preparing International Standards is normally carried out through ISO

technical committees. Each member body interested in a subject for which a technical committee has been

established has the right to be represented on that committee. International organizations, governmental and

non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the

International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.

International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.

The main task of technical committees is to prepare International Standards. Draft International Standards

adopted by the technical committees are circulated to the member bodies for voting. Publication as an

International Standard requires approval by at least 75 % of the member bodies casting a vote.

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent

rights. ISO shall not be held responsible for identifying any or all such patent rights.

ISO 14649-11 was prepared by Technical Committee ISO/TC 184, Industrial automation systems and

integration, Subcommittee SC 1, Physical device control.

This second edition cancels and replaces the first edition (ISO 14649-11:2003), of which it constitutes a minor

revision.

ISO 14649 consists of the following parts, under the general title Industrial automation systems and

integration — Physical device control — Data model for computerized numerical controllers:

 Part 1: Overview and fundamental principles
 Part 10: General process data
 Part 11: Process data for milling
 Part 12: Process data for turning
 Part 111: Tools for milling machines
 Part 121: Tools for turning

Gaps in the numbering of parts were left to allow further additions. The future Parts 2 and 3 will be for

language bindings according to ISO 10303 methods. Part 10 is the ISO 10303 Application Reference Model

(ARM) for process-independent data. ISO 10303 ARMs for specific technologies are added after Part 10. The

future Part 50 will be the ISO 10303 Application Interpreted Model (AIM) for process-independent data.

ISO 10303 AIMs for specific technologies are added after Part 50.

ISO 14649 is harmonised with ISO 10303 in the common field of Product Data over the whole life cycle.

Figure 1 of ISO 14649-1 shows the different fields of standardisation between ISO 14649, ISO 10303 and CNC

manufacturers with respect to implementation and software development.
iv © ISO 2004 – All rights reserved
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ISO 14649-11:2004(E)
Introduction

Modern manufacturing enterprises are built from facilities spread around the globe, which contain equipment

from hundreds of different manufacturers. Immense volumes of product information must be transferred

between the various facilities and machines. Today’s digital communications standards have solved the

problem of reliably transferring information across global networks. For mechanical parts, the description of

product data has been standardised by ISO 10303. This leads to the possibility of using standard data

throughout the entire process chain in the manufacturing enterprise. Impediments to realising this principle are

the data formats used at the machine level. Most computer numerical control (CNC) machines are

programmed in the ISO 6983 “G and M code” language. Programs are typically generated by computer-aided

manufacturing (CAM) systems that use computer-aided design (CAD) information. However, ISO 6983 limits

program portability for three reasons. First, the language focuses on programming the tool center path with

respect to machine axes, rather than the machining process with respect to the part. Second, the standard

defines the syntax of program statements, but in most cases leaves the semantics ambiguous. Third, vendors

usually supplement the language with extensions that are not covered in the limited scope of ISO 6983.

ISO 14649 is a new model of data transfer between CAD/CAM systems and CNC machines, which replaces

ISO 6983. It remedies the shortcomings of ISO 6983 by specifying machining processes rather than machine

tool motion, using the object-oriented concept of Workingsteps. Workingsteps correspond to high-level

machining features and associated process parameters. CNCs are responsible for translating Workingsteps to

axis motion and tool operation. A major benefit of ISO 14649 is its use of existing data models from ISO

10303. As ISO 14649 provides a comprehensive model of the manufacturing process, it can also be used as

the basis for a bi- and multi-directional data exchange between all other information technology systems.

ISO 14649 represents an object oriented, information and context preserving approach for NC-programming,

that supersedes data reduction to simple switching instructions or linear and circular movements. As it is

object- and feature oriented and describes the machining operations executed on the workpiece, and not

machine dependent axis motions, it will be running on different machine tools or controllers. This compatibility

will spare all data adaptations by postprocessors, if the new data model is correctly implemented on the NC-

controllers. If old NC programs in ISO 6983 are to be used on such controllers, the corresponding interpreters

shall be able to process the different NC program types in parallel.

ISO TC184/SC1/WG7 envisions a gradual evolution from ISO 6983 programming to portable feature-based

programming. Early adopters of ISO 14649 will certainly support data input of legacy “G and M codes”

manually or through programs, just as modern controllers support both command-line interfaces and graphical

user interfaces. This will likely be made easier as open-architecture controllers become more prevalent.

Therefore, ISO 14649 does not include legacy program statements, which would otherwise dilute the

effectiveness of the standard.
© ISO 2004 – All rights reserved v
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INTERNATIONAL STANDARD ISO 14649-11:2004(E)
Industrial automation systems and integration — Physical
device control — Data model for computerized numerical
controllers —
Part 11:
Process data for milling
1 Scope

This part of ISO 14649 specifies the technology-specific data elements needed as process data for milling.

Together with the general process data described in ISO 14649-10, it describes the interface between a

computerised numerical controller and the programming system (i.e. CAM system or shop floor programming

system) for milling. It can be used for milling operations on all types of machines, be it milling machines,

machining centers, or lathes with motorised tools capable of milling. The scope of this part does not include

any other technologies, like turning, grinding, or EDM. These technologies will be described in further parts of

ISO 14649.

The subject of the milling_schema, which is described in this part of ISO 14649, is the definition of technology-

specific data types representing the machining process for milling and drilling. This includes both milling of

freeform surfaces as well as milling of prismatic workpieces (also known as 2½D-milling). Not included in this

schema are geometric items, representations, manufacturing features, executable objects, and base classes

which are common for all technologies. They are referenced from ISO 10303’s generic resources and ISO

14649-10. The description of process data is done using the EXPRESS language as defined in ISO 10303-11.

The encoding of the data is done using ISO 10303-21.
2 Normative references

The following referenced documents are indispensable for the application of this document. For dated

references, only the edition cited applies. For undated references, the latest edition of the referenced

document (including any amendments) applies.

ISO 10303-11, Industrial automation systems and integration — Product data representation and exchange —

Part 11: Description methods: The EXPRESS language reference manual

ISO 10303-21, Industrial automation systems and integration — Product data representation and exchange —

Part 21: Implementation methods: Clear text encoding of the exchange structure
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
Finishing

A milling operation used to cut a part. The finishing operation usually follows a roughing operation. The goal of

finishing is to reach the surface quality required, cf. roughing.
3.2
Roughing

A milling operation used to cut a part. While the aim of roughing is to remove large quantities of material in a

short time, the surface quality is usually not important. The roughing operation is usually followed by a

finishing operation, cf. finishing.
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ISO 14649-11:2004(E)
4 General Process data
4.1 Header and references

The following listing gives the header and the list of entities which are referenced within this schema.

SCHEMA milling_schema;
Version of April 30, 2004
Author: ISO TC184/SC1/WG7
REFERENCE FROM support_resource_schema (*ISO10303-41e3*)
(identifier,
label
);
REFERENCE FROM geometry_schema (*ISO10303-42e3*)
( bounded_curve,
cartesian_point,
direction
);
REFERENCE FROM measure_schema (*ISO10303-41e3*)
( length_measure,
positive_ratio_measure,
time_measure
);
REFERENCE FROM machining_schema (*ISO14649-10*)
( nc_function,
machine_functions,
machining_operation,
machining_tool,
material,
plane_angle_measure,
pressure_measure,
property_parameter,
rot_direction,
rot_speed_measure,
speed_measure,
technology,
toolpath_list,
tool_direction);
REFERENCE FROM milling_machine_tool_schema (*ISO14649-111*)
milling_cutting_tool);
4.2 Technology-specific machining operations
4.2.1 NC functions for milling

The NC functions specific to milling technologies are described in the following subs clauses. These are

subtypes of entity nc_function defined in ISO 14649-10.
4.2.1.1 Exchange pallet
This function is used to execute a pallet exchange.
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ISO 14649-11:2004(E)
ENTITY exchange_pallet (* m0 *)
SUBTYPE OF (nc_function);
END_ENTITY;
4.2.1.2 Index pallet

This function is used to place the pallet to the indicated position by the parameter index.

ENTITY index_pallet (* m0 *)
SUBTYPE OF (nc_function);
its_index: INTEGER;
END_ENTITY;

its_index: The parameter index value by which the destined position of the pallet is

indicated.
4.2.1.3 Index table

This function is used to place the rotation table to the indicated position by the parameter index.

ENTITY index_table (* m0 *)
SUBTYPE OF (nc_function);
its_index: INTEGER;
END_ENTITY;

its_index: The parameter index value by which the destined position of the rotation

table is indicated.
4.2.1.4 Load tool

This function is used to load a tool that can be selected independent from the geometrical information.

ENTITY load_tool (* m0 *)
SUBTYPE OF (nc_function);
its_tool: machining_tool;
END_ENTITY;
its_tool: The tool which has to be loaded.
4.2.1.5 Unload tool
This function is used to unload a tool.
ENTITY unload_tool (* m0 *)
SUBTYPE OF (nc_function);
its_tool: OPTIONAL machining_tool;
END_ENTITY;
its_tool: The tool which has to be exchanged. In case of an operation where more
than one tool is in use at the same time this attribute has to be set.
4.2.2 Tool direction for milling

This is the base class of all tool orientations used for freeform machining. It is subtypes of entity tool_direction

defined in ISO 14649-10.
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ISO 14649-11:2004(E)
ENTITY tool_direction_for_milling (* m0 *)
ABSTRACT SUPERTYPE OF (ONEOF(three_axes_tilted_tool, five_axes_var_tilt_yaw,
five_axes_const_tilt_yaw))
SUBTYPE OF (tool_direction);
END_ENTITY;
4.2.2.1 Three axes tilted tool

In this mode of operation, the tool is tilted, so the tool direction is not parallel to any of the three machine axes.

However, the tool is clamped to fix the tool angle and motion is still only in the three linear axes. Unlike

five_axes_var_tilt_yaw the tilt and/or yaw angles are not variable.
ENTITY three_axes_tilted_tool (* m0 *)
SUBTYPE OF (tool_direction_for_milling);
its_tool_direction: direction;
END_ENTITY;
its_tool_direction: The direction of the tool in absolute machine co-ordinates.
4.2.2.2 Five axes with variable tilt and yaw angles

Simultaneous tool movements in five axes are used for machining. During motion, the tool direction is

adjusted so as to follow the curve given in the toolpath instances.
ENTITY five_axes_var_tilt_yaw (* m1 *)
SUBTYPE OF (tool_direction_for_milling);
END_ENTITY;
4.2.2.3 Five axes with constant tilt and yaw angles

This is a special case of five_axes_var_tilt_yaw. The tool is moved so that the tilt and yaw angles are constant

in each point of the toolpath, relative to the co-ordinate system given by the surface normal in the cutter

contact point and the tangent in feed direction. Tilt and yaw are given as attributes of this entity. Note that

these values may be overridden if an explicit tool direction curve is specified for a toolpath.

ENTITY five_axes_const_tilt_yaw (* m0 *)
SUBTYPE OF (tool_direction_for_milling);
tilt_angle: plane_angle_measure;
yaw_angle: plane_angle_measure;
END_ENTITY;

tilt_angle: The inclination of the tool in feed direction, measured against the surface

normal in the cutter contact point.
yaw_angle: The rotation of the inclined tool around the surface normal, measured
against the surface tangent in feed direction in the cutter contact point.
4.2.3 Milling machining operation

This is the base class of all operations described in this part of ISO 14649. It is a subtype of entity

machining_operation defined in ISO 14649-10. In case that feedrate_per_tooth of its_technology is chosen,

number_of_effective_teeth of its_tool should be given.
ENTITY milling_machining_operation (* m0 *)
ABSTRACT SUPERTYPE OF (ONEOF(milling_type_operation,
drilling_type_operation))
SUBTYPE OF (machining_operation);
overcut_length: OPTIONAL length_measure;
WHERE
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ISO 14649-11:2004(E)
WR1: (EXISTS(SELF.its_technology.feedrate_per_tooth) AND
EXISTS(SELF.its_tool.number_of_effective_teeth))
OR(NOT(EXISTS(SELF.its_technology.feedrate_per_tooth)));
END_ENTITY;

overcut_length: The overcut on the open side(s) of the feature. It is not allowed for manu-

facturing of features which are bounded by material on all sides, i. e. pockets.
In case of round_hole, this attribute is allowed only for through-bottom
holes. If the cutting_depth of drilling_type_operation specifies a conflicting
value, overcut_ length is ignored.
Tool
movement
overcut
Fig. 1: Overcut
4.2.4 Milling technology

This entity defines the technological parameters of the milling operation. It is a subtype of entity technology

defined in ISO 14649-10. Of the four alternatives for specifying speeds, exactly two must be given as

indicated by the WHERE rules. If the attribute adaptive_control s invoked, some or all of these values may be

ignored.
ENTITY milling_technology (* m0 *)
SUBTYPE OF (technology);
cutspeed: OPTIONAL speed_measure;
spindle: OPTIONAL rot_speed_measure;
feedrate_per_tooth: OPTIONAL length_measure;
synchronize_spindle_with_feed: BOOLEAN;
inhibit_feedrate_override: BOOLEAN;
inhibit_spindle_override: BOOLEAN;
its_adaptive_control: OPTIONAL adaptive_control;
WHERE
WR1: (EXISTS(cutspeed) AND NOT EXISTS(spindle))
OR (EXISTS(spindle) AND NOT EXISTS(cutspeed))
OR (EXISTS(its_adaptive_control));
WR2: (EXISTS(SELF.feedrate) AND NOT EXISTS(feedrate_per_tooth))
OR (EXISTS(feedrate_per_tooth) AND NOT EXISTS(SELF.feedrate))
OR (EXISTS(its_adaptive_control));
END_ENTITY;

cutspeed: Cutting speed of the tool, the speed of spindle converted into a linear speed.

spindle: Rotational speed of the tool. As defined for rot_speed_measure, positive

values indicate tool rotation in mathematical positive direction of the c axis,
i. e. counter-clockwise motion if looking from the tool holder to the
workpiece. Note that usual cutting tools require clockwise motion so the
value of this attribute will typically be negative.
© ISO 2004 – All rights reserved 5
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ISO 14649-11:2004(E)
feedrate_per_tooth: Feed of the tool expressed as a distance.
synchronize_spindle_with_feed:
If true, cutting speed and feed of the tool is synchronised. Therefore, the
pitch of tap can be kept constant at the bottom of a hole when cutting speed
is being decelerated and accelerated.

inhibit_feedrate_override: If true, the feedrate override through the operating panel or by adaptive

control systems is not allowed.

inhibit_spindle_override: If true, the spindle speed override through the operating panel or by adaptive

control systems is not allowed.
its_adaptive_control: Any kind of vendor specific adaptive control strategy.
4.2.4.1 Adaptive control

This entity defines the vendor-specific adaptive control strategy. At a later time, the specific nature of the

adaptive control algorithm and further parameters can be specified in appropriate subtypes.

ENTITY adaptive_control; (* m1 *)
END_ENTITY;
4.2.5 Milling machine functions

The entity describes the state of various functions of the machine, like coolant, chip removal, etc. to be applied

during the time span of an operation. It is a subtype of entity machine_functions defined in ISO 14649-10.

ENTITY milling_machine_functions (* m0 *)
SUBTYPE OF (machine_functions);
coolant: BOOLEAN;
coolant_pressure: OPTIONAL pressure_measure;
mist: OPTIONAL BOOLEAN;
through_spindle_coolant: BOOLEAN;
through_pressure: OPTIONAL pressure_measure;
axis_clamping: LIST [0:?] OF identifier;
chip_removal: BOOLEAN;
oriented_spindle_stop: OPTIONAL direction;
its_process_model: OPTIONAL process_model_list;
other_functions: SET [0:?] OF property_parameter;
END_ENTITY;
coolant: If true, the coolant is activated.

coolant_pressure: Optional specification of the pressure of the coolant system. Only valid if

coolant is true.

mist: If true, activate mist coolant. Default is false. Only valid if coolant is true.

through_spindle_coolant: If true, activate coolant through the spindle. Default is false.

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ISO 14649-11:2004(E)
through_pressure: Pressure of coolant through the spindle. Only valid if
through_spindle_coolant is true.

axis_clamping: Describes which axes are to be clamped, e.g. X,Y,A. Note that this

information is machine dependent and should be avoided.
chip_removal: If true, activate chip removal.

oriented_spindle_stop: If specified, the spindle will stop in the given direction relative to the

machine zero position of C-axis in case a spindle stop occurs during or at the
end of the workingstep.
its_process_model: Optional information for process control.
other_functions: Optional list of other functions of generic type.
4.2.5.1 Process model list

For each workingstep, one or more process models may be started. These are modules for process control

like chatter avoidance, thermal compensation, etc.
ENTITY process_model_list; (* m1 *)
its_list: LIST [1:?] OF process_model;
END_ENTITY;
its_list: List of process models for the current workingstep
4.2.5.1.1 Process model

Special machine-specific functions to make the machining process more secure and accurate. (e.g. chatter

avoidance, thermal compensation, ...)
ENTITY process_model; (* m1 *)
ini_data_file: label;
its_type: label;
END_ENTITY;

ini_data_file: A filename including path of the file containing the initialisation data of the

process model.
its_type: The type of process model (e.g. chatter avoidance, thermal
compensation, ...)
4.2.6 Milling type operation

This is the base class of all operations for milling. It includes all necessary attributes to describe technology

and strategy. It is a subtype of entity milling_machining_operation.

In general, there are two types of machining operations: roughing and finishing. The roughing is to remove all

material from the original raw piece surface down to the bottom or side of the feature minus the finishing

allowance in multiple passes. The finishing will then remove the finish allowance to yield the final surface of

the feature. In case of pre-cast features, e.g. pre-cast holes and pockets, roughing operation need to be one

pass. This special condition is considered in the 2½D milling strategy with the attribute allow_multiple_passes.

ENTITY milling_type_operation (* m0 *)
ABSTRACT SUPERTYPE OF (ONEOF(freeform_operation, two5D_milling_operation))
SUBTYPE OF (milling_machining_operation);
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ISO 14649-11:2004(E)
approach: OPTIONAL approach_retract_strategy;
retract: OPTIONAL approach_retract_strategy;
END_ENTITY;

approach: Optional information about approach (plunge) strategy to reach the first cut.

If multiple layers are cut, as specified by all
...