By Daniel Austin
Automated and computer numerical control (CNC) cutting systems are not new technologies, but recent improvements in versatility, speed and affordability have made them more attractive to signmakers and other fabricators. Today, many sign shops have integrated these systems into the finishing department of their production workflow.
Simply adding a system, however, is not enough on its own. Many signmakers equipped with one can still find themselves looking around their sign shop, spotting a particular material and wondering how to cut it. With that in mind, it is important to understand how best to use a CNC router to cut a broad array of sign industry substrates.
Signmaking materials tend to be categorized as either soft or rigid substrates. When using a CNC router, a knife blade is typically recommended for cutting a soft substrate, while a router bit is more practical for cutting a rigid one.
Of course, these are very general recommendations for broad categories of materials. Signmakers also work with highly customized composite materials, in which case it is a good idea to speak to the manufacturer or a sales representative to get a specific recommendation with regard to cutting techniques.
Before placing a material down for cutting, there are two important steps to consider. The first is the use of a ‘hold-down’ system to ensure the material does not shift while it is being cut. This is especially important when working with lighter materials, such as vinyl or cardstock, and when a substrate will have many cut-outs, leaving only a thin ‘skeleton’ of material behind.
This step usually involves attaching a vacuum system to the cutting table to create suction on it. A phenolic work surface with air channels can ensure an even distribution and flow of this suction throughout the table.
The second step to consider is incorporating a ‘sacrificial’ material, also known as ‘spoilboard.’ This will be needed underneath any substrate the signmaker plans to cut entirely through, so the cutting tool has somewhere to go without hitting the work table. Such a collision has the potential to damage the tool.
Generally, two kinds of sacrificial materials are recommended. The first, ideal for knife cutting applications, is heavy felt. Felt is very porous, so it allows for plenty of air flow and vacuum suction for hold-down purposes. While it needs to be heavy enough to prevent the knife from piercing all the way through, it also needs to be soft enough not to dull the blade’s sharpness over time.
The second option, for routing,is low-density fibreboard (LDF). Compared to medium-density fibreboard (MDF) that is commonly used in the sign industry, LDF does not incorporate the same type of sealant and its lower density allows for greater air flow.
Some signmakers insist on using MDF as their sacrificial material, but in those cases, it is imperative to table-mill both sides of the material first, to remove all of the sealant. Otherwise, they would not achieve sufficient material hold-down.