Carpentry is not rocket science
The basics of digital programming in carpentry via 3D CAD
This document is specifically intended for designers using woodLAB, who do not yet have experience in carpentry, wood panel layout or using CNC machines. The aim of this guide is to provide a solid foundation to better understand the reality of the workshop, often located just a few meters from the design office. Ideally, designers should spend a few months in the workshop to familiarize themselves with the processes, but since this is not always possible, this document has been designed to fill this gap.
Continuous update
This guide is evolving and will be enriched regularly. We invite you to consult it frequently to discover new sections or additional information.
Understanding the importance of woodLAB CAM in the automation of woodworking
The fundamental precept of woodLAB CAM is simple:
You never make the same project twice, but you always manufacture them in the same way.The vocation of woodLAB CAM is to simplify and automate repetitive and redundant tasks associated with design and production in the workshop. This software aims for optimal automation, covering between 99% and 100% of needs.
For the remaining 1%: these are unique machining operations, too rare or specific to justify complete automation. These can be programmed manually to avoid excessive complexity in the process.
Understanding the Basics of CNC Machines
A CNC (Computer Numerical Control) machine works by reading a program, often written in languages such as G-Code, ISO, or proprietary variants developed by manufacturers. These interfaces allow for more user-friendly programming, but still rely on these fundamental codes.The current challenge:
With the evolution of technologies and simplified interfaces, operators sometimes know little about the geometry or technical details of machining. This poses challenges, but with an automatic CAM like woodLAB CAM, it is possible to:- Interpret geometries and machining directly from CAD (Computer Aided Design).
- Optimize workflow for fast and reliable production.
Automatic CAM software like woodLAB CAM offers several key benefits:
- 1 - Increased efficiency: Geometries drawn in 3D in CAD are automatically translated into precise CNC machining.
- 2 - Reduced human errors: By automating repetitive tasks, the risk of errors is significantly reduced.
- 3 - Simplified training: designers can check directly in woodLAB CAM if the generated machining is correct, without having to master all the technical details of the CNC.
Curiosity and involvement: essential qualities for designers
This document also aims to arouse curiosity among designers. They should feel encouraged to:
- Explore woodLAB CAM to understand the link between their 3D designs and real-world machining.
- Collaborate with the shop floor to better understand technical constraints and production processes.
Anticipate errors: "Prevention is better than cure"
By designing your projects correctly from the start, you avoid costly rework and shop floor interruptions. woodLAB CAM, with its intuitive interface and automation capabilities, is a valuable tool for ensuring a smooth process from design to manufacturing.
A drill bit is a tool that can only move vertically (up and down along the Z axis). Therefore, a DRILL BIT cannot move in X or Y. Never! A drill bit is made to drill a round hole. There are flat and pointed drill bits. A flat drill bit is not supposed to drill to a depth equal to that of the panel because it would make a big chip on the opposite side of the panel when it comes out. A pointed drill bit is made to drill through the thickness of the panel.
A milling cutter is a cutting tool designed to generate a profile (straight or not) when moving. A milling cutter can perform a round hole (with a diameter of the milling cutter) as long as it is equipped with a knife underneath. But this is not its primary purpose. On the other hand, this type of milling cutter (with a cutting edge underneath) is essential for any machining on a face of a panel since it attacks the face perpendicularly.
There are two types of milling cutters. Either with the cutting edge that is integral with the milling cutter, or with disposable knives. For the former, it is obvious that after each sharpening, the diameter of the tool decreases. The operator must therefore, after each sharpening, update the diameter of the tool in the tool table of the machine. Milling cutters with disposable knives have the advantage that their diameter remains constant, since once the cutting edge decreases, the knife is replaced and therefore the diameter does not change.
There are two types of saw blade on a CNC. The blade on the motor block that can only move in X and/or Y. It has a small diameter (+/- 120 mm) and its purpose is to machine straight grooves most often for the back panel of a cabinet. The saw blade on the electro-spindle is intended either to calibrate solid wood or to cut miters in a panel.
When the CNC performs machining on the panel, it is held securely to the machine table by an air vacuum. This is therefore the role of the suction cup. It is imperative not to damage the suction cup. There are systems for automatically moving the suction cups (but this is expensive) or also for laser projection of the shape of the part on the table. The operator can then place the suction cups without risk. Finally, there is the radical solution: never mill through a part. We then leave 1 mm of material and the operator finishes manually with a portable milling cutter.
The CNC table is equipped with several stops around its perimeter. One stop is used to ensure that the panel is correctly positioned at point 0 of the machine.
CNC tables are mainly of two types: pods & rails or flat table (FT – feed through - for Nesting for example). The advantage of working with beams is that it is possible for the machine to work on the edges. On the other hand, this type of table gives an overload of work to the operator. To learn more, consult this article:
Nesting in the layout
Full tables are ideal for nesting parts on a large panel. The advantage is that once the panel is placed on the machine, it performs the machining of "routing" the parts but also all the other machining (or almost because there are limitations) but on the upper face of the panel only. Another advantage is that we do not have to manage the positioning of suction cups. The entire table is a kind of suction cup. The operator, while the program is running, can attend to other tasks. The major disadvantage of this type of table is that we cannot drill horizontally for example. We can discuss endlessly the pros and cons of a full table. To learn more, see this article:
Nesting in the layout
Only applies to milling cutters and saw blades. This is referred to as CENTRAL, RIGHT or LEFT correction.
- CENTRAL: the axis of the cutter is on the path. On woodLAB CAM, the tool then takes on the color green.
- RIGHT: the axis of the cutter is to the right of the path by a distance equal to its diameter divided by two. On woodLAB CAM, the tool then takes on the color blue.
- LEFT: the axis of the cutter is to the left of the path by a distance equal to its diameter divided by two. On woodLAB CAM, the tool then takes on the color red.
In English CW/CCW. If the machining path is clockwise, it is called a clockwise path. Otherwise, it is called an anti-clockwise path.
That is the whole point, my dear Watson. If a milling cutter (whose direction of rotation is also clockwise) moves clockwise, we say that the tool eats the chip. If it moves counterclockwise, we say that it expels the chip. Be aware that there are as many carpenters who will swear that a tool with a right direction of rotation must move clockwise as you will find as many carpenters who will affirm the opposite. In reality, it depends on several factors such as the sharpening of the tool, the type of knives, and especially the material that the tool will attack.
If you look more closely at the CAM, you will see this mysterious term (SCAVO) appear. If we had to translate it into French, we would say excavation. And if you are perceptive, you will notice that the H Block are tools performing excavations. By default, a SCAVO is a closed geometry. This is good, but not always. This is why, when we write the 100% custom post-processor to stick to your way of working, we have a multitude of macros to torture and work the SCAVO to obtain the machining we want. There is in particular a tool that I call guillotine. Example: if you make the SCAVO slightly exceed the edge, you create an overhang that you will cut with the guillotine: result, the geometry is no longer closed but open. It is bliss.
This is a crucial point. The extrusion direction of a SCAVO must always be perpendicular to the face it is going to machine. By analogy, you must understand that the arrow that represents the extrusion direction of the SCAVO represents the axis of the milling cutter on the electrospindle of the machine that is going to perform the machining work. If the extrusion direction of the SCAVO is not perpendicular, the machine will go into error.
This is a very common design mistake.
Refers to milling a closed geometric shape (rectangular, round, etc.) that does not protrude. In English, we call it a pocket. It must therefore be hollowed out. Again, for modern machines, the pocket is managed automatically by the machine's processor by calling a macro. Example in woodWOP: tasche and in bSolid or Biesseworks: tasca. However, this is not always the case. We then do what is called ISO programming, i.e. we manually program the hollowing out of the part (don't worry, woodLAB CAM does this very well for you). For example, we hollow out as much as possible with a large diameter tool with a central correction and then we finish cleanly with a small diameter cutter to have the smallest possible rounding in the corners.
By this term, and as far as woodLAB CAM is concerned, we mean the set of rules (each grouping one or more macros) which represents a sort of internal regulation that the program must follow scrupulously to translate the geometries and machining of the parts drawn in 3D into language understandable by the machine. Here on the left, the programming interface of the post-processor rules in woodLAB CAM.
Or even bogus diameters. Carpentry is a profession with lots of tricks. In PP we also use tricks most often to "cheat" or to make the PP more flexible.
Example: on drawer slides, you will see Single Holes of 5.1, or 5.2 or 5.3 mm depending on where they are. For example, if carpenter A prefers to make just a small hole of 3 x 3 mm to guide his screws, in his PP, we will say that 5.1 x 14 = 3 x 3 mm for example. While carpenter B who uses Euro screws, we write that 5.1 = 5 mm.
Each mill can be programmed with an input and/or output type or not
As you can see in the thumbnail, here on the left, there are many input and output types. This table lists those available in Biesseworks or bSolid. Be careful, not all of these types are necessarily available on all machines of all brands.
The material to be machined plays a major role in choosing the right input or output type.
Here too, like chip expulsion and chip swallowing, each carpenter has his own way of doing things.
In principle, depending on the type of saw used (horizontal or vertical panel saw, and edger or beam saw) we cannot guarantee that the cut piece is square. If this is the case, we have the possibility of sawing the piece for example 4 mm longer and wider and this will trigger machining around the entire perimeter of the piece which will remove 2 mm of material. Thanks to the precision of movement of a CNC, we then have the guarantee of having a perfectly square piece.
Notes: note that this can have perverse effects, such as the lengthening of the time needed to machine a part (time is money, the boss will say) or the presence of peripheral machining which will make it difficult to glue the edges. Fortunately, there are solutions (tricks or machine equipment).
This refers to the depth of passage of a tool. In short, the smaller the diameter of a cutter, the less material you can mill per pass. Otherwise, the cutter will break. Depending on the material, you also sometimes have to go slowly. So there are multiple possibilities. The PP of woodLAB CAM will faithfully reproduce the instructions given by the carpenter.
All the bits arranged in X and Y are grouped on this head. In general, there are more tools in X than in Y, but not always. As luck would have it, the center distance of the bits is... 32 mm to comply with the 32 system used by hardware manufacturers. Consequently, to make bars of all quickly, we will make sure to put several 5 mm bits on chucks that follow one another (of 32 mm). Result, to drill a bar of holes, the CNC processor which knows the location of the 5 bits will optimize the descent of these bits in relation to the number of all to be drilled. For the anecdote, I once had a machine with 125 bits....
In Oikema, you work in 3D. You have also gotten used to the hardware orientation. As a reminder, in Oikema, you start from right to left (X - red arrow), from back to front (Y - green arrow) and from bottom to top (Z - blue arrow). A CNC is the same, at least for the number of axes: 3 axes, X, Y and Z. For the vast majority of machines, the X axis is parallel to the length of the table, the Y axis is parallel to the depth of the table and the Z axis represents the thickness of the table (although it does not actually have one).
But, depending on the origin of the stop you are working with, it can be different. There is also on most machines the possibility of mirroring the parts. We then speak of mirroring in X or Y or XY.
But the good news is, with woodLAB CAM you don't have to worry about that.
Or Spindle in English. This is the milling head of the machine. It is a chuck in which the milling cutter is loaded for the machining to be carried out. On a 3-axis machine, it is fixed. On a 4-axis machine, it can possibly rotate, most of the time at 90°. Finally, on a 5-axis machine, it is free to make these movements.
We speak of 5 positioned axes for a CAM when it is capable of managing only linear movements (straight) while the cutter on the electro-spindle can take any inclination.
We speak of 5 interpolated axes for a CAM when it is capable of managing any type of linear or non-linear movements while the cutter on the electro-spindle can take any inclination. When we make stairs for example, it is interesting. On the other hand, for a panel, it is quite rare.
In carpentry, you can't imagine working with a single tool (here we mean a single cutter). Since you have several tools but the electro-spindle can only have one tool in its chuck, you have to store the other cutters somewhere: in the magazine. The magazine can be either a revolver or comb type. Some revolver type magazines are mounted on the CNC motor block. This is interesting since the time needed to change tools is very short. Don't forget that you have to reduce tool changes as much as possible because they waste time and the boss won't be happy... This also allows me to say that it is important to group all machining on a single face if possible to avoid turning parts which are also a waste of time. For example, in Oikema, you have to try to group all the tools from the inside of the Cabinet to the outside of the Cabinet. This is a golden rule.
By miter, we mean that one edge of the part has a bevel (not a chamfer which is different). In 99% of cases, a miter is at 45°. But not always, especially for furniture under a slope.
Managing miters is tricky and depends on several factors: the number of axes of the machine, the type of cutter I have, etc. The best method for making a miter cut is with a tilting blade (so on a 4 or 5 axis machine).
If you have a 3 axis machine, it is possible to make the miter with a 45° cutter. But, it is, in general not perfect, and precisely a miter must be perfect. It is not always perfect because the suction force of the suction cups can vary. So, you must understand that the 0 point of the part in Z can vary slightly.
Finally, we can cheat and make sure that the parts with a tab will be lengthened by, for example, 25 mm, then will pass on the horizontal panel bender equipped with a tilting blade and finally, will be put on the CNC for execution of the machining operations if there is any.