How the Rotary Axis works
The rotary mode works with 2D rhino curve geometry rotated around a 3D rotary axis, based on input settings of the pipe circumference. The chuck spins the tube whilst the laser head moves along the rotary axis.
Machine and material limitations
Each machine and the material you choose have limitations which affect the fabrication process and impact on the design. You will need to understand the following items whilst preparing your file to achieve a desired result.
Machine
The rotary stage can hold a maximum tube length of 700mm while the maximum cut area is 650mm. Clearance zones are necessary so the laser head will not collide with the chuck or support cone.
Materials
The Fab Lab stocks tube that has a thickness of approximately 1.6mm. This can vary slightly due to the way the product is made.
The tube is suspended at each end, multiple cuts across the length of a tube will weaken its structure causing slouching. This can create inaccurate cuts since the material is now off-axis. You may want to consider splitting the geometry into multiple pieces or designing the cuts to maintain the strength of the tube. Smaller diameter tubes suffer from slouching more than larger ones.
Preparing your 3D model
Download the template file - This file includes the appropriate clearances and the unrolled tube stocked by the Fab Lab for reference.
When creating any 3D geometry to be fabricated it is best to work in 1:1 scale. Model the size of the actual tube you will be cutting in rhino, including the correct thickness.
The two examples identify a 3D and 2D working method and display a number of common design strategies to help you understand some of the finer fabrication details when working with rotary cutting.
Example project 3D
You can take the methods used in the example and apply it to achieve many tube cutting outcomes. This project outlines:
Intersecting tube of varying sizes
An angular cut through a tube
Create your tubes
Draw the circles using the _circle diameter tool. See the available diameters. For this example we have chosen 101.6mm and 25.6mm.
Extrude the curves to the desired length. Be sure to toggle _Solid to NO this will ensure the object is tubular.
Arrange the geometry
The tubes have been arbitrarily placed for this example. Your design may require specific placement.
Use the Gumball Tool to arrange geometry.
Use the move ,rotate , Rotate3Dcommands for more precise placement of the geometry.
Subtract the geometry
Using the Split command, you can cut holes in the intersecting geometries.
Select the geometry you want to cut into, in this case it is the larger tube.
Select the 'cutting' geometries, in this case it is the smaller tubes and the plane.
Your geometry is now modified, you can see the holes and slice cut into the tube.
Thickness and tolerance
If making slotted, intersecting or piercing geometry you will need to consider the thickness of the material and the position of the laser head when it cuts the geometry.
The laser is cutting vertically toward the rotary axis, resulting in a slanted cut on the cylindrical surfaces.
You will need to inspect your geometry for collisions. Give your geometry the material thickness, the Fab Lab stocks 1.6mm tube.
Duplicate your geometry so you have a copy (you may come back to this)
Use the OffsetSrf command and toggle _solid to YES, type in an offset distance (1.6mm).
Click the object to change the offset direction.
Measure the intersecting geometries (see diagrams below)
There are multiple ways to edit for tolerance and can be an arduous process.
Go to your original copy of the geometry
Select the smaller tubes and OffsetSrf, use the tolerance measurement from the previous steps.
Split your geometry using the new slightly larger tubes.
Repeat the OffsetSrf to double check your 3D model is free from collisions.
Your geometry is ready to be unrolled.
Unroll your geometry
Using the unrollsrf command you can turn a tube into a flat 2D surface.
Select the tubes outer surface and type unrollsrf
S surface geometry will be generated.
Using theMake2D command, create curve geometry from the surface(s).
Your geometry is now ready to be placed in the template file.
Place the curves inside the cutting zone with the correct unrolled pipe boundary. If you have multiple tubes of varying sizes, keep reading or skip to 3.3 Multiple Pipes Required.
Example project 2D
You can also experiment with creating curve geometry in 2D to develop a rotary project.
Draw 2D geometry
Use the template file's unrolled tube boundaries for reference. Draw your 2D curve geometry within this area.
The Y axis is the outer circumference of the pipe = to one full rotation of the pipe or 360 degrees.
The X axis is the length of the pipe, the max length is 650mm.
Create a tube
Create a tube with your chosen diameter.
Use the UnrollSrf command to get a 2D surface.
Move the surface into the boundary, overlay with the curve geometry.
Project curves onto tube
Use FlowAlongSrf command to project curves onto a tube.
Select your curve geometry and type FlowAlongSrf.
Select an edge (near corner) of the unrolled surface.
Select an edge of the pipe you want to 'project' onto.
Review the model in 3D
Select the tube and Split with the curve geometry.
Move the object and rotate if required - using Gumball tool or Move commands.
Use the OffsetSrf command and set to the desired material thickness.
Clean up the file
Your geometry is ready - delete any surfaces / non-required objects.
Arrange your curves into the cutting zone of the rotary template.
Set your curves to the appropriate cut order layers.
Ensure to update your material, thickness and other details.
Adapting the Rotary Template
Clearance zones
The rotary template includes clearance zones on either side of the cutting zone. This is due to the chuck mechanism that holds the cylindrical stock in place at each end. The laser head can’t move through these clearance zones as it will collide with other parts of the machine. Please place your geometry only in the cutting zone.
Unrolled Pipe Templates
It is important to know the diameter and corresponding circumference of your cylindrical stock before setting up your file. We have provided a number of unrolled pipe templates to the right of the Rotary template. These sizes are based on the diameter of steel tube we stock. Select the correct unrolled pipe layout for your desired material and place it into the cutting zone. You can then proceed to add your unrolled 2D curves onto the template.
If you are supplying your own cylindrical stock and it's diameter does not match one of the templates provided, you must edit the Y-axis dimension of your unrolled pipe so it is equal to the stock circumference.
Multiple Pipes Required
If you require more than one pipe cut just copy and paste the base template for the number of pipes you need. Rename your material type and thickness/ diameter, student name and sheet number/s.
File Setup
CUT Order
When setting up your file You must differentiate between your CUT curves by placing them on the green CUT-Primary or blue CUT-Secondary layers. This places your curves in a cut order, allowing us to cut out any internal geometries first before cutting larger external geometries.
Nesting (for Rotary Mode)
For rotary mode, you should aim to nest (order the cuts) from right to left as the tube is held and secured on the left hand side. For example if you cut all the way through the tube on the left before cutting geometry on the right the tube may fall off the rotary axis, or the structure may be compromised and shift out of line before all cuts have been completed.
Allow a 30mm clearance zone between objects, this area is required when the support cone needs to be moved to re-support the tube.
Don't worry if you can't do this 100% correctly, our technicians are great at navigating through cuts and changing the cut order and nesting if they have to. It's a tricky one to comprehend.
Interlocking Nesting
Some designs may interlock enabling the tube to keep its structure reducing the need for separation and clearance zones. This method can reduce the amount of cuts required and save material. Some interlocking designs may require extra internal cuts to 'unlock' from one another see Internal Cut Wastage for more information.
Internal CUT wastage
In order to remove some unwanted internal cut areas you need to slice up the scrap geometry into multiple cuts, otherwise some internal parts won’t come out due to the curvature of the tube. This part needs to be taken care of when preparing your 3D model otherwise you may have issues later on.
Waste cuts should be made on the Primary cuts layer.
Post Processing
Depending on the material you have cut you may require some post processing work. Metal items will usually need cleaning, polishing and potentially painting/finishing.
For tips on elevating your laser cut project to the next level, read our guide to Post-Processing Metal:
