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Cross laminated timber machining (CLT)

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Tools for Success by Scott Burton
Scott Burton is the sales and marketing manager for Royce//Ayr Cutting Tools. For more info email: sburton@royceayr.com
Cross laminated timber (CLT) manufacturing facilities are popping up all over North America and new applications for CLT are being explored throughout the building industry. Innovative new machinery and automation designs provide more efficient and accurate ways to manufacturer CLT components.  Innovative cutting tool solutions are required to ensure optimal machine performance, efficiency and safety.  

CHALLENGES:  
Tool size 
CLT designs require large components to be manufactured, which obviously requires large tooling.  Large scale tooling formats do require special consideration to ensure optimal balance and safety. This must be considered in every phase on the operation, from tooling design to final operation of the machine. Tool rigidity and balance is paramount in the design process, as all cutting tools will be performing in extreme conditions at high feed rates on a variety of material compositions.  
Image 1 shows an example of a large-scale carbide insert spiral tool designed to remove material at extreme depth of cuts.  
Machine parameters
Due to the nature of CLT machining, it is critical to consider all the variables to properly assess machine feed rate and RPM, before starting production of these large components. In most cases, the tooling must be extremely large and be designed for high rates of material removal. Extreme material size and density variation makes standard chip load calculations irrelevant in many situations.
For example, Douglas fir or other softwood laminates will machine much easier that high-density composite products. Higher density and greater amounts of adhesive resins will have a dramatic effect on tool performance and optimal feed rate and RPM. Furthermore, the extreme length of tooling will add higher leverage forces on the spindle and holders, which will force programmers to run tooling at slower feedrates. The key is to reduce the RPM of tooling relative to the feedrate reduction. If tooling is making deep cuts at low feed rates on high-density material, it will have a negative effect on tool life.  
Therefore, there must be careful analysis and performance testing of tools before setting up final programs for production. A standard chip-load calculator commonly available in the industry, will likely not include recommendations for this size of tooling and depths of cut. However, there are RPM recommendations available based on tool diameter and weight, so 
that should be the starting point. Once a safe RPM 
is established, then a 
realistic feedrate decision must be made. In most 
cases, this will involve testing tool paths at low feedrates and then increase 
in 10 percent increments while assessing stress on machinery and tooling.    

Tool holder availability
To support larger tool sizes and weights, the tool holders are often made larger on a custom basis or sourced from European markets. These holders are necessary and should not be substituted, but an assessment of tool holder availability should be done before starting full production. Tooling crashes are a reality of this type of machining and back up tooling and holders should be considered, as the lead times for special tool holders will be extended.

TOOLING SOLUTIONS:     
Cross-laminated timber can be difficult to machine with traditional tooling options, depending on the material density and composition; therefore, a variety of tooling options can be explored.
Integrated tool/holder systems (ITHS): 
ITHS solutions are the absolute best way to design tooling for this type of large scale machine application. Tools are manufactured as part of the holding system in one component, which connects directly to the machine interface. ITHS provides unmatched rigidity and balance while performing higher removal rates at high feedrates.   
Image 2 shows an ITHS example with tool built directly onto the holder.

Solid carbide spiral geometry
This option will perform best with smaller diameter tool requirements. Solid carbide tooling will provide optimal feed rates and cut quality on a variety of wood species. The helical nature of this tooling option will allow deep pocketing operations to be performed efficiently with effective chip evacuation.  
The only two limitations are size of tooling and tool life challenges on abrasive material. Solid carbide rod is an excellent material for producing optimal tool geometry; however there are limitations at larger diameters and longer lengths. In most cases, tool diameters over 3/4 of an inch are not cost effective. Solid carbide rod can be produced over 3/4 inch, but the price increase is dramatic and the raw material is susceptible to breakage at longer cutting-edge lengths
Carbide insert geometry
If larger diameters and longer cutting edges are required, solid carbide inserts provide a variety of options. Standard carbide inserts provide a cost-effective tooling solution, which can be designed in several configurations, for a wide variety of materials and applications. 
Image 1 illustrates standard carbide inserts, mounted on a lightweight body for optimal high feed rate machining.
The only limitations associated with solid carbide insert tooling, are tool life limitations and a restriction on smaller diameters. In contrast to solid carbide tooling, carbide insert tooling cannot be made effectively under 1 1/4 diameter. Higher density materials with high resin content, can generate excessive heat and cause premature carbide cutting-edge failure. 
Diamond tooling
If tool longevity becomes an issue, a diamond tooling solution should be explored. Diamond tooling can be produced in a braised to body format, or diamond insert format.
Traditional braised diamond designs can be produced in similar geometry as solid carbide. Smaller diameters are possible and helical geometry will produce equivalent cut quality to solid carbide 
with dramatically extended 
to longevity. Diamond 
tooling can be expected to outlast carbide options by 200 to 300 times in most applications. These tools can be serviced multiple times at a qualified diamond manufacturing facility.
If larger diameters and replaceability is required, there are some new diamond innovations, which provide a great alternative to carbide or brazed diamond.
Image 3 illustrates a diamond replacement insert system. Diamond inserts will provide cut quality results very similar to carbide insert, with dramatic tool life benefits.  Extended tool longevity will reduce requirement for insert changes resulting in labor reduction and less margin for error. Although diamond inserts are much more expensive relative to carbide, they will provide a cost-benefit when machining more abrasive CLT materials.

CONCLUSION:
The market growth in CLT manufacturing has driven machine and tooling innovation forward.
High-efficiency machining processes are required to meet global demand for CLT products. Effective tooling solutions are required to ensure optimal machine performance and safety, during extremely demanding cutting operations. A detailed analysis of material, and machine parameters should be conducted to determine the best tooling options for CLT manufacturing.

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