The 4-Axis CNC Router is a completely different machine with different capabilities, restrictions and file set-up process.
Introduction to the 4 Axis Template
Submission for the 4-Axis router will be slightly different from the 3-Axis router. We accept 3D geometry and engrave curves, hence the template file is much less detailed than that of the 3-Axis.
The Template comes with some instructions to reiterate the size restrictions of the router. There are input sections for your basic details, as well as material and any other notes on the job that need to be taken into consideration when milling.
The chuck and center pin has been modelled as well as the maximum material size for your reference as well. Make sure before importing the file to the template, the geometry is scaled to the appropriate size for the stock material.
An easy way to move your geometry to the origin of the template is to put a bounding box around the geometry, draw a rectangle on the end face and move the geometry from the center point of that rectangle to the origin of the template.
Our Machine
Roland MDX540A
For small multi-sided geometries we recommend the Roland 4 Axis router. This will allow for highly detailed and accurate final pieces. The machinable area is much smaller than the Multicam.
The 4 Axis CNC allows the user to create complex objects at a consistency unmatched by human hands. A high-powered router allows a large variety of materials to be processed at many different speeds. Our 4 Axis router works in a similar way to the lathe we have in the workshop here, where material is put in a chuck and a tool then subtracts material as it spins. Controlling the rotation of the lathe component on the router is an advantage we have over the woodworking lathe, this then allows us to mill out extremely complex geometries.
Materials: Timber, Plastics, Foam
Cutting Area: 100mm H x 100mm W x 320mm L
Axis Overview
The router works using X,Y,Z and A Axis to mill out complex geometries. The A Axis is what separates this machine from our Multicam 3 Axis Router.
Materials and Dimensions
We are able to mill a wide range of materials from different grades of foams, hard and soft woods, resin, plywood, etc. At the Fab Lab you are able to bring in your own material if you wish to supply it, otherwise we stock H-Grade Polystyrene and XPS Polystyrene cut to size for the 4 Axis Router. When bringing in materials please consult with the Fab Lab team prior to submitting the job as outside materials need to be approved first.
The main restriction to deal with the 4 Axis router is the material size, the router is able to mill a total material size of 370mm (x) X 150mm (y) X 100mm (z). However this does not mean you will be able to mill the entire stock material size, there are restrictions we put in place to avoid collisions with the machine. The actual millable area is 340mm (x) X (150mm (y) X 100mm (z). The main things to take into consideration is the chuck (vice) on the A-Axis that holds the material, and the center pin opposite.
Drill Bits
There is a wide range of router bits we use when milling with the 4-Axis router. These allow us to increase our level of detail resolution, getting finer and finer.
Restrictions of the tool length and geometry being milled are considerations that should be designed into the model being milled.
The current 4 Axis Router Tool Library is:
6mm Flat Mill Down Cutter (Chippy equivalent)
6mm Ball Nose (Short Flange)
3mm Flat Mill (Short Tool Length)
3mm Flat Mill (Long Flute Length, Foam Bit)
3mm Ball Nose (Short Flange)
2mm Ball Nose Cutter (Short Flange, but Long Tool Length)
V Engrave Cutter (Needle Point)
V Engrave Cutter (45 Point)
File Set-up Basics
The maximum material size that you can place in the 4 Axis router is 100H x 100W x 370L. it is always good practice to ensure the part you want to mill is 10% less than this so it can be milled properly. If your model is too large please split it up over multiple stock materials.
Commands to Know:
_BoundingBox
_Move
_Scale
To avoid milling into the chuck double check the geometry at the origin. The tool holder has a width you need to take into account.
Splitting Over-Size Models and Joint System
When preparing a file for the 4-Axis router, the main thing to take into consideration is the overall size of the geometry you are milling. The model is too long for the stock material, to compensate this the geometry has been split in two with a lap joint as a method to locate the pieces exactly. An alternative to the lap joint is a simple butt joint, this is less accurate but much simpler.
To be able to split the geometry draw in the ‘Front’ viewport a simple ‘S’ shape curve, and ‘lofted’ it across the geometry. Then selecting the lofted polysurface and the geometry I have used the ‘split’ command to split the geometry where the polysurface passes through. Nesting the geometry is no possible over two different stock materials.
Commands to Know:
_Loft
_Split
Generating 4 Axis Engrave Curves
The model has important details that will best be reproduced physically by engraving into the model. The 4 Axis finishing will not produce the level of resolution that is needed for the floor plates to become visible. Engrave curves must be on the surface, the quickest was is to ‘array’ surfaces planes through the building where the rebates are.
Once all the new surfaces are through the geometry, I will select the geometry and the surfaces and use the ‘intersect’ command which will create a curve where the two surfaces meet.
Now we have the intersect curves I will then change them to the engrave layer, clean up any inconsistencies created by the intersect command and define my engrave depth and bit diameter for the job.
It is important to know intersect does not work on meshes so converting to a nurb prior is key.
Placing Geometry in Stock
End Bridges to avoid Breaks or Collisions
End Bridges are additions that can be added to the geometry to compensate and work around tool length issues where the tool holder may collide with the stock material. As the stock rotates on a 45 degree the Z position of the tool must also cope being plunged deeper into the stock material. Collisions are common in this instance, roughing out these potential collisions and using end bridges is recommended.
A truncated cone is an ideal shape to avoid collisions whilst maintaining some stock integrty.
