As new technologies emerge in the micro hole industry, it can be overwhelming to try and determine which drilling service is best for you and your product’s needs. In this blog post, we will describe each of the following services, mechanical, EDM, and laser, as well as compare the advantages and disadvantages of these three primary drilling techniques.

Mechanical

Mechanical drilling is a process in which holes are cut into solid material using a rotating tool known as a bit. Mechanical drilling uses a “peck” cycle in which the drill is repeatedly inserted and withdrawn from the hole. For this process to work effectively, the bit must have a material hardness greater than that of the workpiece. Failing to acknowledge this will lead to tool breakage during the drilling process. With these basic concepts as a background, let’s review the advantages and disadvantages associated with this technique. 

Advantages: (+)

• Mechanical drilling produces high-quality holes.
• Hole edges and corners have a sharp finish.
• Mechanically drilled holes do not taper off towards the end of the hole (unlike other processes). 
• The quality of all holes is consistent. 

Disadvantages: (-)

• There is always the potential for tool breakage during this process.
• Depending upon the complexity of the project (i.e. number of holes needing to be drilled), this process can be on the longer side.
• Holes drilled mechanically must be deburred.

EDM (Electro-discharge machining)

EDM is a process in which a reoccurring electrical spark erodes at a workpiece’s surface, causing the formation of a hole. There are two types of EDM: wire and die-sinking. As the name suggests, Wire-Cut EDM utilizes a thin piece of wire which is fed through the workpiece while it is submerged in dielectric fluid. Although the wire never touches the workpiece, it is the spark that forms between the wire and material which cuts the piece into the desired shape. Conversely, the Die-Sinking EDM uses an electrode tool (which is connected to an electrical current) that is lowered to the workpiece and submerged in a dielectric liquid. The spark reaction that occurs between these two parts causes the workpiece material to melt away. With these basic concepts as a background, let’s review the advantages and disadvantages associated with this technique. 

Advantages: (+)

• EDM yields good surface quality by way of low material removal rate.
• Holes that are cut using the EDM process do not have to strictly be circles; EDM can cut out complex shapes.
• No burrs are left behind.
• EDM is good for delicate parts that may not be able to endure the stress of traditional machining. 
• Ideal for hard to drill materials.

Disadvantages: (-)

• EDM is a slow machining process.
• While the EDM process can be used to drill deep holes, it jeopardizes quality – producing a tapered shape towards the end of the hole. 
• Only conductive materials (like stainless steel, bronze, copper, graphite, etc.) can be machined. 
• EDM tends to be a more expensive process.

Laser

Lasers are a drilling process in which a stationary laser beam uses high power density to melt or vaporize a workpiece’s material. Four different laser drilling methods can be used depending upon the type of hole required for your workpiece. These methods include single pulse, percussion, trepanning, and helical drilling. Trepanning and helical laser drilling tend to produce larger, high-quality holes with a longer drill time. Percussion and single pulse laser drilling tend to produce smaller, low-quality holes with a higher drill speed. With these basic concepts as a background, let’s review the advantages and disadvantages associated with this technique. 

Advantages: (+)

• Laser drilling is a non-contact technique.
• It can be used on a wide spectrum of materials (from rubber, to wood, to metal). 
• Good for drilling a large number of holes into one workpiece. 
• Laser drilling can have a high manufacturing speed depending on the desired hole quality. 
• Laser holes do not have to be deburred. 

Disadvantages: (-)

• Heat Affected Zone (HAZ) results in poor entrance and exit hole quality including recast layer, micro-cracks, and molten spatter.
• The quality of each hole in a single workpiece may vary greatly (not the most consistent technique).
• Laser drilling holes with a large aspect (depth to width) ratio can experience considerable tapering, which may be unacceptable. 
• Laser drilling lacks accurate depth control. Even when lasering through holes, careful consideration must be made to avoid cutting into any surfaces near the exit hole (i.e. small ID tube). 
• Laser drilled holes can result in a wider hole opening due to constant heat on the workpiece’s surface.
  

[Disclaimer: National Jet does not offer laser services]

After analyzing these three drilling methods, it is evident that there are four key tradeoffs in determining which process is right for you and your product: budget, time frame, the importance of hole quality, and workpiece material. Laser and mechanical drilling methods tend to be more budget-friendly, whereas EDM tends to be a more expensive process. Lasers provide a quicker drilling process, whereas EDM tends to be a slower machining process. The mechanical drilling process seems to lie somewhere in between these two timeframes. Mechanical drilling and EDM tend to produce consistent, higher quality holes, whereas laser drilling is prone to having an inconsistent hole quality. The only exception to this quality statement is that deeper holes drilled through EDM can have a lower quality due to the hole tapering off. And finally, lasers can drill through a wide spectrum of materials, whereas EDM and mechanical drilling have more specific guidelines regarding the material of their workpiece.

Perhaps the ideal drilling solution is one that combines the advantages of multiple processes. Or maybe one process is better than the others at drilling through the material of your desired workpiece. Whatever the ideal solution may be for you and your product, we hope that this information helps guide you through the many drilling processes that occur in the micro hole industry.

This year National Jet Co. has had the opportunity to hire two student interns from Frostburg State University. Typically, utilizing interns can be a challenge for companies within our industry – as machining is not something that is taught in most university curriculums.

In December of 2019, National Jet began interviewing and hiring student interns to fulfill roles within the company that had not existed prior. This year, we hired an engineering student, Hunter Frank, to work as NJC’s Quality Engineer. Hunter’s primary responsibilities revolved around managing and maintaining our company’s ISO 9001 quality management system. We also hired a marketing intern, Rebekah Book, to help promote the business locally and digitally through social media channels and the company blog.

Since having both interns with our company for six months now, we have been very pleased with both their knowledge and performance levels that they have executed on National Jet’s behalf. After having such a positive intern experience, with one of our interns taking on a full-time position, we would encourage other businesses to utilize their local college’s talent within their organization!

“Frostburg State University has always been a great community partner to National Jet Co., hand-feeding us the top student candidates for our various internship positions” – Sam B. Griffith.

As previously mentioned, our company has increased its capacity for melt blown die repairs as well as the production of new dies in response to COVID-19. We are currently drilling long days to keep up with our current demand and welcome additional die production and repair. If you would like to have your melt blown die inspected, have debris or broken tools removed from your dies, or you simply want them to be more consistent, please contact us at 301-729-2300 or visit https://www.najet.com/repair/ today!

For those who may not know, melt blown die tips are used to extrude non-woven materials for filtration and absorbent products. This includes facemasks and the N-95 respirators, which are in high demand during this pandemic.