Benefits of CNC Punching

CNC (Computer Numerically Controlled) punching is a manufacturing process commonly used for sheet metal fabrication. A CNC sheet metal punch is designed to stamp clear and specific shapes into pieces of metal and sheet metal parts. 

CNC punch presses are electromechanical devices that use inputs from computer programming to move tools and create patterns from a software file. The devices are available with one head and a tool rail or a multi-tool turret. 

 

How does CNC programming work? 

Programming the punch press depends on a couple of different factors. The desired pattern is provided in either a 2D DXF or a DWG file format or as a 3D format in the CAD (Computer-Aided Design) file. 

This data is then added to the CAM (Computer-Aided Manufacturing) phase of the cycle with the goal of selecting the best tool for the job and to fabricate the flat sheet metal element. The CNC nest will play a role in this phase when it comes to determining the most effective layout for the size of the sheet metal. 

The CNC machine can then move the sheet metal to accurately position it under the punching arm, so the planned pattern can be punched and generated. Some machines can only move in one or two ways whilst some are able to move along the x, y, and z-axis. 

What can be made using CNC Punching? 

CNC punching is a highly versatile process, meaning the sky is the limit for what is able to be machined, whether its stainless steel, brass, plastic, or even wood, they can all be punched. The thickness that can be successfully machined ranges from 0.5mm to 6.0mm. So, as long as your chosen material falls within this range, it can be used in the machine. 

There are also no restrictions when it comes to design and pattern. You don’t need to stick to the standard circle or rectangle, designs can be cut out to your specifications. CNC punching machines can use single hits, overlapping geometries, and a number of different tools to generate the most complex shapes. 

What are the benefits of CNC Punching? 

Increased productivity 

When a design has been selected and created, it can be used as many times as you need. This easy repeatability improves productivity by taking away technical, intensive, and time-consuming manual processes. 

Speed and accuracy 

The automation and repeatability also make this method much faster than any other similar processes. No matter how complicated the design is, the overall production time is reduced. There is no need to compromise on accuracy either, in fact, CNC machines are often used for some of the most precise and complex shapes and machining. 

Efficiency 

CNC punching machines are fast and accurate whilst reducing the amount of waste being produced. Many machines now have internal quality detectors installed, so when a deficiency is found, the machine will stop punching to avoid any further waste. 

Safe and cost effective 

Thanks to the internal quality detectors, waste in these machines is kept to a minimum. This saves money in the long term because no raw materials will be thrown away. Additionally, as the entire process is automated, there aren’t any risks being posed to the operator, ensuring a hazard-free environment. 

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We are a family-run steel fabrication businesses that has been operating for more than 20 years. As experienced structural steel fabricators, we understand the importance of providing a first-class service to our customers as well as ensuring the highest quality steel products. 

Contact our team today to discuss how our structural steel fabrication service, design fabrication, or any of our other services can help you and your project. 

 

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Can you weld stainless steel?

Yes, you can weld stainless steel. Stainless steel is well known for its resistance to corrosion and use in cases where hygiene is particularly important. Despite its tendency to distort easily when heated, its lower thermal conductivity means the heat energy is not dispersed from the welding zone as quickly, which is helpful during the welding process. It is easy to work with if you want to weld it, but with our tips and advice below, you can gain a greater insight into welding stainless steel. 

Is it difficult to weld stainless steel? 

Welding stainless steel can be done with the MIG welding process, TIG welding, or MMA (stick welding). Like with any weldable metal, stainless steel has its own quirks and behaviours when it is under the arc. Getting the best result from this alloy, when it has a minimum 10.5% chromium content, can take an extremely long time.  

Along with the equally troublesome aluminium, it is, without doubt, one of the more difficult materials to weld. However, it is by no means impossible. 

Which welding method is best for stainless steel? 

Deciding on the right process essentially comes down to the details of the task at hand and the qualities you need from the finished weld. If cost is an important factor in your stainless steel fabrication it could be that MMA is best, but if you are looking for precision with thin materials TIG is likely going to be the preferred approach. 

MIG welding stainless steel 

To start, as with any welding process, your MIG welding machine should be set up in the correct way for stainless steel. It is recommended that you always fit a Teflon wire liner, as you will be able to get good wire feed and it stops the wire from becoming contaminated. Stainless steel fabrication design might mean this alloy is highly resistant to corrosion, but it is still susceptible to contamination. 

When you are welding stainless steel with MIG, any ferrous material (including steel liner contamination) in the weld pool can easily create rust spots on the finished product. You will also want to ensure your MIG torch is in good condition prior to starting your weld. 

Similar to the aluminium welding process, you might want to buy a larger torch size than you would use for normal steel. This is because welding stainless steel generates more heat, a bigger torch will carry higher amperages better. Going back to the issue of contamination, it is essential that you only use stainless steel wire brushes and grinding/cutting discs whenever you are working with this metal. 

As well as the risk of ferrous contamination with stainless steel, you need to check that your working area is clear of iron or steel dust, or any ferrous oxides. This might sound over the top, but it is essential. 

Thoroughly cleaning your materials and workspaces is always a good practice for successful welding. When it comes to stainless steel, avoiding even the smallest of particles is crucial to avoiding contamination and completing the best weld. 

Next is one of the most easily mistaken parts of MIG, having the correct wire type and diameter. This is project specific as with all parts of the welding process so seek advice if you need tailored guidance. More advice shared in relation to aluminium welding is the importance of clamping and tack welding your workpiece to prevent movement and distortion via cracking. 

What gas is used for MIG welding stainless steel? 

The right choice of gas matters when you are MIG welding stainless steel. You might be using pure argon or a combination of argon and some minor gases to improve starting. Alternatively, you might need a specialist gas mix, particularly if you’ve got more unconventional stainless steels like Inconel, Hastelloy, or Monel alloys. With stainless MIG welding, you will use a slightly increased gas-flow rate of about 14-16 LPM. 

TIG welding stainless steel 

If you are TIG welding stainless steel, you can use a DC-only machine or AC/DC TIG welding machines set in DC mode. The most important thing is to make sure your machine has enough power to weld stainless steel. 

For more information about TIG welding check out our TIG welding guide.

MMA welding stainless steel 

MMA is the easiest of the three welding processes to set up (most importantly, select the right electrode for the weld). In addition, it is the least expensive method for welding stainless alloys. 

As long as you have a welding machine that has stick welding capabilities, all you really need to get started are some suitable rods. In this process, there is no gas, torch, foot pedals, or torch consumables, it is welding in its most basic form. 

Stainless steel will move on a welding table, so make sure you clamp or tack weld it your workpiece. Double check you have chosen the right electrode (316, 308, or 312 are standard). 

Keep in mind that you won’t be able to weld thin sheets of stainless steel. A lot of welders will find it difficult with a sheet of stainless steel that is less than 2mm thick. It all comes down to the lower controllability of the MMA arc for these applications. Whilst thin sheets will be a challenge, welding mild steel to stainless steels or high-carbon tool steels will play to MMA’s strengths. 

Pre-heating usually helps with certain stainless steels as it can help to stop cracking. This is most often done with a blow torch, an oxy acetylene, or oxy propane torch. 

 

For more information about our metal fabrication or stainless steel fabrication services contact the team at FEM today. 

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Does stainless steel rust and how could it be prevented?

Stainless steel is constructed with built-in corrosion resistance but in certain conditions it can and will rust, although it won’t be as fast or severe as standard steels. Stainless steels will typically corrode when they are exposed to harmful chemicals, saline, moisture, grease, or heat for extended periods of time. 

The level of protection stainless steel has against corrosion is mostly dependent on how much chromium there is. If there isn’t enough chromium near the surface of the stainless steel, a new chromium oxide layer can’t form when the top layer is scratched off. This leaves the material at risk to multiple different types of corrosion. 

The basics of stainless steel 

To get a better insight into why steel is rust-resistant, and how this resistance can be broken down, it is beneficial to first know how these alloys are different from other steels. 

At the very minimum, stainless steel contains 10.5% of chromium. The chromium quickly reacts with the oxygen that surrounds it and creates a thin oxide layer on the steel’s surface. Unlike iron oxide, which is typically formed in a flaky and corrosive rust, the chromium oxide attaches to the steel. This makes it a better protective barrier. 

Chromium oxide is commonly known as a passive film that covers the iron in the alloy, protecting it from the air and water in the natural environment. It is this film that gives stainless steel its rust-resistance quality. 

Stainless steel is well-known for being low maintenance, and its resistance to oxidation and staining makes it the perfect material for a wide range of applications. 

What types of stainless steel corrosion is there? 

There are four main types of stainless steel corrosion. Each of them presents a different challenge and needs a different approach to effectively deal with it. 

General corrosion 

This is considered to be the safest form of corrosion because it is predictable, manageable, and in most cases, preventable. You will be able to tell it is general corrosion when there is a uniform loss of metal over the entire surface. Stainless steel that has a pH value of less than one is more prone to general corrosion. 

Galvanic corrosion 

Galvanic corrosion mostly affects metal alloys. It usually refers to a situation in which one metal has come into contact with another, resulting in one or both reacting with each other and corroding. 

Pitting corrosion 

This is a localised type of corrosion which leaves holes or cavities. It often occurs when stainless steel is exposed to environments that contain chlorides. 

Crevice corrosion 

Another localised corrosion which forms at the crevice between two joining surfaces. It can happen between two metals or between a metal and a non-metal. 

How to prevent rusting in stainless steel 

When stainless steel begins to rust it can be concerning and not look great either. It is a metal that is specifically designed to resist corrosion so most users will start to worry when they spot stains and rusting on the metal. Fortunately, there are several methods to prevent rusting and improve corrosion resistance at different stages of the stainless steel fabrication process. 

Design 

Taking a proactive stance with stainless steel fabrication design pays off in the long term. Detailed planning in the design phase of stainless steel applications will minimise the risk of water being able to penetrate the material and reduce surface damage potential. In cases where contact with water is unavoidable, drainage holes should be added. The design should allow free air circulation to prevent damage to the alloy. 

Fabrication 

During any stainless steel fabrication work it is important to prevent stainless steel from coming into contact with iron or ordinary steel. This means being extremely careful with work tables, tools, storage units, chains, and steel turning rolls. 

If any cross-contamination occurs with carbon steel dust particles settling onto the stainless steel during the fabrication process, the potential for rust formation increases significantly. Also, any cleaning or grinding tools that have been used with carbon or a low alloy steel should be kept separate from stainless steels. 

Maintenance 

Regular maintenance is an essential part of stainless steel rust prevention, as well as restricting further progression of existing rust. It is important to get rid of any rust that has formed using mechanical or chemical methods. The grime left over can be cleaned using warm water and soap. After the steel has been cleaned, a rust-resistant coating should be added. 

 

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What is TIG welding?

TIG welding (Tungsten inert gas welding) is a sub-type of gas metal arc welding (GMAW). It is a process that uses electricity to both melt and join pieces of metal. This welding method was first invented in the 1940s to tackle the difficulty of welding magnesium and aluminium within the Californian aerospace industry. 

Since then, its popularity has taken off massively and not just in the aerospace industry. This is mostly due to its versatility, cleanliness, minimal finishing requirement, and how efficient it is to use when you want to weld a broad range of different metals. Despite equipment details evolving and adapting from its initial invention, the basic principles of TIG welding remain the same.

How does TIG welding work? 

TIG welding uses electricity to generate an arc (short circuit) between a non-consumable tungsten electrode (positive anode) and the metal being welded (negative cathode). The arc is protected by a stream of inert gas, usually argon. 

A non-consumable tungsten electrode 

Compared to the consumable electrode wire in MIG welding, TIG welding tungsten electrodes have a much higher melting point (c. 6192 degrees Fahrenheit or 3422 degrees Celsius) which means they won’t melt during welding. Instead, the arc that runs between the electrode and the work melts the parent metal. At the same time (unless it is an autogenous weld, like a temporary tack weld), the arc also melts a separate welding rod of filler metal to create the weld bead. 

Inert shielding gas 

The molten weld pool is also covered by an inert shielding gas. Normally, this is argon on its own or an argon mixture, although more experienced TIG welders might opt for helium as it can make for faster welding under specific circumstances. 

The shielding gas is pushed along a supply pipeline from the welding machine to the TIG torch that is holding the tungsten electrode. Like with other types of electric arc welding, when the heat is taken away, the weld pool cools down, solidifies, and creates a new piece of fused metal.  

As a result of this, when you are using a TIG welder for your metal fabrication, you need to co-ordinate the interaction of a hand-held TIG torch with a filler rod on top of varying the electrical current. Ensuring the electrode is the right distance from the weld, holding the filler rod tip in place, keeping both in the shielding gas, and altering the current all contribute to the complexity of TIG welding. 

The versatility of TIG welding 

It is that same complexity that makes the TIG welding process extremely versatile for welding a wide variety of metals. Stainless steel, mild steel, aluminium, copper alloys, magnesium, gold, and titanium can all be welded using the TIG approach. Even metals that are dissimilar can be TIG welded, and all with hardly any mess to clean up at the end. 

Ever since its creation at California’s Northrop Aircraft Corporation, TIG welding has been the top choice amongst welders because of its versatility. In addition to its ability to handle more difficult welds like ‘S’ shapes, corners, and curves. 

What are the benefits of TIG welding? 

  • TIG welding can be used for various metal thicknesses. It is even suitable for particularly thin materials that are challenging (or impossible) to join with other welding techniques. 
  • Good arc and weld pool control will help you get clean, attractive welds when appearances are important. Due to heat input (decided by the electrical current) normally being controlled with a foot pedal, TIG welding enables you to heat or cool the weld pool for precise control of the weld bead. This makes TIG welding perfect for cosmetic welds on sculptures, automotive work, or architectural features. 
  • TIG welding can be done in any position whether it is vertical, horizontal, or overhead. 
  • It’s easy to see your whilst welding as there is minimal smoke and the shielding gas is colourless. 
  • TIG welding only needs minimal cleaning and finishing which will save you time, effort, and money. This is because it creates less spatter, sparks, smoke, and fumes than other welding processes. 
  • TIG welds are much stronger and more resistant to corrosion than other welds. 
  • The best TIG welding machines allow you to do traditional stick welding too. 

Are there any disadvantages to TIG welding? 

  • TIG welding can be quite slow, especially at the beginning. Even when it is carried out by skilled welders the process is typically slower than other welding methods. 
  • Because of how complex it is, TIG welding comes with a steeper learning curve than other types of welding. The rewards you will get when you master it are worth it, but if you’re learning to do it yourself you need time and patience to effectively develop your skills. 
  • TIG welding can be quite dangerous outside the controlled environment of a workshop. This is due to the importance of being able to keep a consistent flow of gas over the weld pool. 

 

As you can see, the benefits of TIG welding far outweigh the drawbacks. 

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If you need help with metal fabrication you should contact an experienced fabrication engineer like our team at FEM. Get in touch to discuss your requirements. 

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