CNC Milling
CNCmilling
Workholding, toolpath and measurement strategy for prismatic geometries, with the axis configuration chosen by part geometry. One of Eclipse's target capability areas.
- Focus
- Prismatic parts
- Technology
- Axis strategies · Toolpath
- Files
- PDF · STEP · DXF
- Status
- Capability under development
01Fundamentals
The tool rotates, the part stays clamped
In milling a multi-edge tool removes material from a stationary part; geometry is determined by tool access and the way the part is held.
In milling a rotating multi-edge cutter advances along a toolpath on a clamped workpiece to create faces, pockets, slots and holes. A face can only be machined if the tool can reach it, so how many faces are machined, and from which direction, determines the number of setups.
Every re-clamping adds a small alignment uncertainty. The aim is therefore to produce related features in as few setups as possible and from a common reference.
- Face milling
- Machines wide flat areas and reference surfaces.
- Pocket milling
- Forms enclosed cavities with roughing and finishing passes.
- Slot milling
- Cuts slots of a defined width and depth.
- Contour milling
- Follows the outside or inside profile of the part along a toolpath.
- Drilling
- Makes holes of the specified diameter and depth.
- Tapping
- Cuts internal threads in holes.
- Thread milling
- Forms the thread profile with a rotating tool on a helical path.
- Boring
- Brings holes to a defined size and surface quality.
- Edge breaking
- Creates a chamfer or radius on edges.
- 3D surfacing
- Machines curved surfaces, usually with a ball-nose tool.
02Toolpath explorer
How do tool diameter and stepover change the number of passes?
The diagram below regenerates, live, a real offset computation that clears a sample pocket. Move the sliders.
- Number of passes
- —
- Relative path length
- —
Diagram units; not a real dimension.
- A larger tool diameter clears the same area in fewer passes; but an inside corner radius cannot be smaller than the tool radius.
- Stepover is a percentage of the tool diameter: a small stepover means more passes and a finer surface, a large one fewer passes.
- Real cutting conditions (speed, feed, depth of cut) depend on the material, the tool and the machine; this diagram does not show them.
- Cutting
- Rapid move
- Tool
- Number of passes
- 28
- Relative path length
- 8607
03Axis strategies
Geometry decides, not the axis count
The approaches below explain the strategies used in milling; they do not state equipment owned.
- 01
3-axis machining
The tool moves in X, Y and Z. The natural solution for face, pocket and hole geometry reachable from one direction.
- 02
4th axis (indexing)
The part is positioned about a rotary axis. It reduces the number of setups on cylindrical parts or when several faces must be reached.
- 03
3+2 positional machining
Two rotary axes are positioned and locked first, then 3-axis machining is done. It reaches features on inclined faces in one setup.
- 04
Simultaneous 5-axis
Five axes move together; complex freeform surfaces and hard-to-reach geometries can be machined with continuous tool contact.
Which strategy is applied depends on the part geometry and on the equipment status confirmed per project.
04Workholding and setup
Good workholding is half the dimension
How the part is held directly determines access, vibration and dimensional stability.
- 01
Vices and soft jaws
A common solution for prismatic parts; soft jaws can be adapted to the shape of the part.
- 02
Dedicated fixtures
For repeated jobs, fixtures designed for the part speed up positioning and improve repeatability.
- 03
Zero-point systems
Let clamping elements be swapped with repeatable references, shortening setup time.
- 04
Probing for setup
Measuring the position of the part helps set program references automatically.
Principle: fewer setups, less accumulated error.
05Typical part families
Parts for which milling is the natural route
These families show part types for which milling is commonly used in this field. This list does not imply completed Eclipse references.
Bracket
Supporting parts with mounting holes and seating faces.
Housing
Parts with internal cavities and bearing, sealing and connection surfaces.
Manifold block
Flow-distribution blocks with intersecting holes and channels.
Flange and plate
Connecting parts with hole patterns and flat surfaces.
06Design for milling
Eight practical tips
Principles that reduce cost and risk and do not depend on a particular machine.
- 01
Make inside corner radii larger than the tool radius
A rotating tool cannot make a sharp inside corner. A radius larger than the tool and consistent along the part speeds machining and improves the surface.
- 02
Limit pocket depth relative to width
Narrow, deep pockets need long tool stick-out; the risk of vibration and breakage rises.
- 03
Keep wall thickness adequate
Thin walls flex and vibrate while machining. Increase thickness where possible or support the wall with a rib.
- 04
Avoid deep, small-diameter holes
Once hole depth exceeds a few diameters, chip evacuation and tool deflection get harder; discuss size expectations beforehand.
- 05
Keep thread depth only as long as needed
Very deep threads add cost; set thread length and engagement from the function.
- 06
Think about tool access
Every feature must be reachable by a tool from some direction. Closed internal cavities that cannot be reached call for a different manufacturing method.
- 07
Write tolerance only where it is needed
Rather than a tight tolerance on every dimension, highlight the functional ones; state surface-finish expectations only on the surfaces that need them.
- 08
State the edge break
For burr-free, safe edges, give the edge-break size as a general note on the drawing.
07Quotation preparation
What to send for a milled part
The following makes it easier to prepare a quotation quickly and correctly.
Missing information is not a barrier: what is missing is completed together during the review.
PDF technical drawing
With tolerances, surface expectations, thread details and notes.
STEP geometry
The 3D body geometry; especially needed for complex surfaces.
DXF profile
A 2D profile or plate contour, if any.
Material and grade
Type, grade, blank form (block, plate) and required certificate.
Quantity and call-off plan
Total quantity; state a staged delivery plan if there is one.
Heat treatment and surface treatment
Requirements such as hardening, coating or anodising, and their sequence.
Inspection and document requirements
Inspection report, first-article document, traceability expectations.
Confidentiality
State it if you would like a non-disclosure agreement (NDA).
08FAQ
Questions about milling
What is the difference between 3+2 and simultaneous 5-axis?
In 3+2 two rotary axes are positioned and locked first, then 3-axis machining is done. In simultaneous 5-axis all five axes move together and complex surfaces can be machined with continuous tool contact. Which one is suitable depends on the geometry and the equipment status.
In how many setups is a part completed?
It depends on the number of faces to be reached, the tolerances and the shared datums. The fewest possible setups are aimed for; the decision is made after the drawing has been reviewed.
Can thin-walled parts be machined?
For thin-walled parts, workholding and cutting conditions are planned separately; suitability is confirmed after the drawing has been reviewed.
Is a block or a plate preferred as the blank?
The blank form is chosen by the part's dimensions and the quantity; it is discussed at the request stage and fixed in the quotation.
How should surface finish be stated?
State the surface-finish expectation clearly on the drawing, only on the surfaces that need it. Economical values are preferred on the others.
Related pages
Capability status
Eclipse Engineering is building its precision-manufacturing capabilities step by step. The manufacturing areas described on this page are target capability areas within the company's investment programme; equipment, capacity, material scope, tolerance class and lead time are confirmed separately for each project once the technical drawing has been reviewed.
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