In nested manufacturing a complete sheet of material is placed on a flat bed CNC and parts are machined and cut in one automatic operation.
The benefits are :
- A completely automatic machining and cutting with no machine operator.
- Material savings.
- It’s possible to add automatic labeling and load and unload to create a completely automatic process for high volume processing.
However two of the disadvantages of nested manufacturing are:
- That during the initial machine operation parts can only be machine on one face. Parts requiring machining on both faces will have the face on the machine bed still unmachined. The second face of these double sided parts must be machined in a secondary machining operation.
- Flat bed processing doesn’t enable parts to be machined on their edges. Parts requiring edged processing also require secondary machine processing.
There are two ways to manage machining the second face of double sided parts. Each method has its advantages and disadvantages.
For edge processing the parts have to be put back onto the CNC or similar processing machine.
Let’s look at the different ways of adapting nested manufacturing to overcome these limitations.
1. Second face part by part
In this method, once cut the parts requiring double sided machining are placed back on a CNC or another processing machine and a separate program is run to machine the second face.
Here is the Polyboard, OptiNest and CAM workflow.
- Export first face output for nesting
- Export separate second face machining file
- Nest first face output
In CAM software:
- Import nesting maps and create machine programs
- Import second face and create machine programs
On CNC machine:
- Place and cut sheet
- Separate double sided parts
- Replace double sided parts on CNC
- Run the second face machine program
The individual parts are easy to manipulate.
If parts need edge processing their second face and edges can be processed in one operation if the secondary CNC processing machine has edge drilling capacity.
Because the part has been precisely calibrated by the nest, precise 2nd face positioning is easy.
Workflow is divided into 2 phases and second face machining can be done on a separate machine while the nesting CNC continues to process a new sheet.
This makes it possible to create a continuous automatic or semi automatic panel processing system with automatic labelling, load/unload and a secondary face and eventually edge machining process.
Requires sorting the doubled sided parts and manually replacing them back on the machine and running a specific program per part.
The extra work and organisation required can add extra production time and be more error prone.
2. Second face by sheet flip
In this method the nest is separated into 2 operations: the sheet of material is placed on the machine and the first face is machined without cutting the parts. The sheet is then flipped and the second face machined and the individual parts cut.
Here’s the Polyboard, OptiNest and CAM workflow.
- Set up face sort coding
- Export OptiNest machining files
- Set priority management
- Nest output
In CAM software:
- Import OptiNest nesting maps and create double sided machine code
- Export machine program for first face without cutting
- Export machine program for second face with cutting
On CNC machine:
- Place sheet
- Run the first face machine program
- Flip sheet
- Run the second face machine program
Only one nesting map.
No sorting of individual parts.
Big sheets of material are heavy and flipping without special equipment is difficult.
Both sides of the sheet must be placed very precisely on the machine bed, not always easy if the raw sheet materials are not perfectly cut to size and square.
Without special equipment, it requires 2 people to flip the sheets.
Workflow on CNC requires manual intervention and is not continuous, making auto load /unload only semi automatic.
If parts require edge processing they have to be sorted and put back onto a CNC or another drilling machine for further processing.
Using Polyboard and OptiNest for second face part by part and edge drilling
In this process it’s necessary to produce files for nesting and separate files for the second face machining and eventually edge drilling.
Polyboard version 7.05b and later has a multi-post processor export function that enables us to export separately the faces to be nested and the second face machining.
In our example we are going to export two sets of machine files.
Imagine that we have a nesting machine for automatically cutting the parts but that we also have a drilling machine running MPR files.
In this case we will need to export a set of DXF files for nesting in OptiNest and a set of MPR files for machining the second face and the edge drilling.
Here is an example of the type of cabinet requiring this type of production:
In this example we can see that the uprights 9 and 10 require drilling on both faces as well as edge drilling for the dowels.
To set up Polyboard for this type of processing go to File > Multiple Post Processor Options.
The dialogue box shows 3 lists. The far left list is the list of Super post processors you have set up, the middle and right hand side list are named “Post Processor and associated Filters”.
These enable us to set up the features of the Super post processor that’s selected in the left hand list. For the moment the left hand list is empty.
Let’s see how to use these lists to export our manufacturing data.
We need to set up a new super post processor for exporting our project.
Click the green cross to set up a new Multi PP:
This will add a new post processor called Super PP you can rename it to reflect what this post processor will do, for example “nest 2 faced parts”.
We are now going to set up two separate post processor outputs by filtering the parts and the machining types required.
To set up the MPR (woodWOP / Homag machine files) we need to filter all parts requiring second face and edge drilling.
The middle Post-Processors and associated Filters list now shows 3 items:
Select a Post-Processor
– Filter (All Panels)
Select a Post-Processor
Select the first “Select a Post-Processor” and in the right hand side drop down list select WoodWOP MPR.
We now need to set up the type of panel and/or machining that we want to send to the MPR post processor.
In the middle list we select “Filter (all Panels)”, the left hand list now shows the different data we can filter.
There are 4 types of data we can filter. The drop down list or secondary window will enable us to select the options needed.
Here are the different options per data type:
Selection in a drop down list:
To export only the second face machining to the MPR files we select “Second Face”.
Clicking the Edit button opens a secondary dialogue box that enables us to select the different Polyboard panel types.
For this export we require that all panels be processed that have second face machining and edge drilling. For this we must leave “All Panels” ticked.
Click the Edit button to open a secondary dialogue box to select the different types of machining that Polyboard can produce.
For our example the tooling types we need to export to the MPR files are Horizontal Drilling, Inner Toolings (Blind), Vertical Drilling, Regular Drilling, Groove, Chamfer and Macro.
The unticked options, Profiling and Inner Toolings (Through) will be exported in the DXF post processor for the nesting CNC.
This filter can send to the post processor only panels within specific size limits.
Selecting the “+” button will add a dimension filter or the “X” sign will delete any existing filter.
In our example we don’t need to have a Dimensions filter, so select the “X” to the right of any existing filters.
We have just set up the first Post Processor output to write a MPR file to CNC process any panels requiring second face and edge processing.
The last line in the middle Post-Processor and associated Filters list has no filter options below because all the parts that have not been exported in the previous post processors will be exported to this last post processor.
In our example we want all remaining machine files to go to the nesting machine.
To do this we select the second “Select a Post Processor” and in the drop down list select an OptiNest DXF post processor. In our example we have selected “Optinest-Vcarve-en”:
Clicking OK will save this “nest 2 faced parts” Multiple Post Processor.
Exporting a Multiple Post Processor
To export the manufacturing data go to File>Multiple Post Processor Export and select “nest 2 faced parts”:
Polyboard will open a window asking where to save the first post processor MPR files.
It will then open a second window to save the OptiNest DXF files and open OptiNest to start the nesting process.
In the nested result we can see that OptiNest has only processed the first face machining of the vertical division and no edge drilling is present.
The second face of the vertical divisions and the edge drillings are exported to the MPR post processor:
Using Polyboard and OptiNest for second face by sheet flip
In this process we need to export a single file to be nested. But we must know what face of the sheet machining operations are applied to.
If we use a standard Polyboard to OptiNest export, parts are flipped with the machined face up before nesting. This is great for nesting parts with only one face machined, but when both faces are machined it’s difficult to know which face is up and which is down.
To cope with this problem, in Polyboard v7.05B and later we have a face code converter that will enable us to know which face a machine operation is applied to by attaching a face code. Export also includes a priority feature that will enable us to separate double sided parts from single sided parts and therefore enable us to minimise the number of sheets that will need flipping.
To set up the Polyboard export for double sided nesting with sheet flip we must first set up an OptiNest post processor with the correct face code conversion.
To do this we go to File > Post processor options and choose an OptiNest post processor.
An OptiNest post processor is in fact a DXF post processor with a couple of added functions, it will automatically open OptiNest and send edging and additional reference information to OptiNest.
As we are actually working with a DXF post processor we will be setting up the DXF layer names to contain the information required by CAM programs to apply the tool path information and produce a machine program file.
In the following example we’ll explain how to set up the layer names for use with VCarve but you can adapt the set up to the coding requirements of the DXF import of any other CAM program e.g. Aphacam, Enroute, EasyWood, WoodWop, BiesseWorks, etc.
Using the same example as before, the cabinet has 2 internal uprights, parts 9 and 10, that are drilled on both sides. If we replace the dowel assembly with a nesting connector all parts can be processed directly on a nesting CNC without the secondary processing required for edge drilling.
In the following example the dowel assemblies are replaced with Wood Designer’s Nest-fix adapters that only require face machining while using Minifix cam connectors.
To set up Polyboard to export DXF files for nesting double sided panels we need to code the machined faces in the DXF layer names.
To do this, in Post-Processor Properties we open the OptiNest post processor that we are using to export.
We will have to add a face code in the layer name for each face specific machining operation.
In general this will include Chamfer, Inner tooling, Groove and Vertical drilling. In general cutting operations and horizontal machining will not need face codes.
Clicking the “+” sign to the left of a tooling operation will open the tooling parameters.
In the following example a specific layer name has already been set up to allow automatic processing by VCarve. In this case it’s necessary to keep the coded layer name and add the face code.
To add the face code we click the “…” button and in the drop down list choose “Format”.
The format table will open with the existing Format options list:
Drag and drop the field to the Format list.
Select the field and click Options.
Polyboard will open a Face Code conversion table with 2 lists.
The first list “1 Face Exported” contains the codes to be applied to parts with only one faced machined. In this list we must type in the code 1 for both face 1 and face 2 of these parts.
The second list “2 Faces Exported” contains the codes to be applied to parts that require double sided machining. In this list we must type in 1 for face 1 and 2 for face 2.
When both widows are closed the layer name will receive a specific coding and look like this:
The OptiNest DXF output will now have a layer name per machine type with face code “f1” for the sheet upper face and “f2” for the sheet lower face.
Loaded into a VCarve double faced machine set up, the file will look like this:
Using a VCarve layer select it’s now possible to move all “f2” coded layer machining to the opposite face and produce a separate machine file for each face.
Select all the objects on the f2 layer, right click and in the menu choose “Move to Other Side”.
Nested sheet flip optimisation
As well as adding the face code it’s also possible to optimise the number of sheets that require flipping.
Polyboard’s export contains a priority code according to whether they require single or double sided machining. Single sided parts have a code 1 and double sided parts a code 2.
Using priority management, this code can be used to separate the nesting maps into maps with single and double sided machining.
In Optimisation > Optimisation Parameters, using the Algorithm Parameters tab, the nesting order can be set using the Priority management slider:
The Placement Order can be set to Increasing or Decreasing.
If the slider is set to a minimum all parts will be treated equally and mixed on the nesting maps:
This means that there is no optimization of the number of sheets to be flipped, but the number of sheets is optimum.
If the slider is set to maximum, the single sided and double sided parts will be completely separated onto different sheets.
Separating completely the parts can result in increased off cut surface as in this example:
Whereas mixed priority optimisation will yield better material optimisation:
An intermediate position of the Priority slider will give different off cut results while trying to mix a minimum number of single and double sided parts.