Parts Manufacturing With Subtractive vs Additive Methods

Samples of stainless steel metal parts

Samples of stainless steel metal parts

Making the right manufacturing choices is crucial for quality products and a successful business.

If you’re involved in designing, building, sourcing, or purchasing metal components, you’ll want to understand the differences between subtractive and additive manufacturing.

You’ll also want to know when it’s better to choose one of these manufacturing methods over the other.

There are a few things you’ll want to know about your finished part when choosing between subtractive and additive manufacturing. For example, the size, the volume, the finish, and the materials used all affect the decision.

Here at United Scientific, we’ll help ensure your parts manufacturing choices meet all your needs. We’ll help you determine what is the best parts manufacture process for your project — subtractive or additive manufacturing.

What’s the difference between subtractive and additive manufacturing?

It’s easy to remember the most significant difference between additive manufacturing and subtractive manufacturing. Here’s why: the two terms mean just what they sound like they say.

Subtractive manufacturing starts with a single piece of material, such as metal, glass, or plastic. There are also some composites and woods that can be used.

Then, the manufacturer removes any part of the material not needed until only the desired manufactured product remains.

Additive manufacturing analyzes the finished product and then builds it “from the ground up,” layer by layer. Once all the layers are assembled, the product is complete. Materials are often plastic composites and may be more flexible.

 Close up of CNC machine at work with coolant streams

More About Subtractive Manufacturing

Here’s an easy way to understand subtractive manufacturing: Visualize a sculptor chiseling away marble to leave behind a beautifully detailed statue made out of one piece of stone.

Subtractive manufacturing is a similar process. You start with one solid piece of material, and sections are removed until you’re left with the finished product you want.

The removal process can be done manually, but most often, it’s done with Computer Numerical Control (CNC) machining. CNC uses computer technology to ensure the removal process is precisely accurate and replicable on a large scale.

Now, you might be wondering: how is the material removed? Lasering, drilling, and boring are just a few of the ways unneeded sections can be removed.

Many different materials can be used with subtractive manufacturing, but aluminum and stainless steel are popular options. Glass, nylon, and composite materials can also be used.

3D printer printing blue wavy shaped part

More About Additive Manufacturing

Additive manufacturing builds a part layer by layer. Often, a computer program like CAD is used to create a 3D model that is then “sliced” into layers that the 3D printer (the most common additive manufacturing tool today) produces.

Parts made from additive manufacturing may need additional work after they are manufactured. For example, the finish may be wrong, or there may be support structures that need to be removed.

There are many different materials that can be used in additive manufacturing, such as nylon or resin. However, material selection is more limited in additive manufacturing than in subtractive manufacturing.

When Should You Choose Subtractive Manufacturing?

You might want to choose subtractive manufacturing if:

  • The part is made of metal. While it is possible to use metal in additive manufacturing, it’s usually cost-prohibitive.
  • Durability is important. Because the item is from one solid piece, there are no seams or weak spots. The durability of subtractive manufactured goods has made them a popular choice for aircraft manufacturing, for example.
  • You want a smooth finish. The lack of lines might mean less work post-manufacturing, depending on your desired outcome.
  • Stringent specifications or sharp angles are required. Using CNC machining results in more consistency and detailed precision.
  • The part is needed in high volume. Subtractive manufacturing with CNC machining is fast and is an excellent choice if you need a large number of identical parts.
  • Industry qualified materials are required. The automobile industry is one industry that relies heavily on subtractive CNC manufacturing.
  • The part is large. Building a large part from “nothing,” as is done with additive manufacturing, can take a long time and diminish the stability and sturdiness of the piece. On the other hand, subtractive manufacturing is a quicker process.
  • There is a near-net-shape part produced by additive manufacturing that needs to be finished. Hybrid manufacturing is an option, and subtractive manufacturing is usually the last step.

CNC machining with sparks shooting out

When Should You Choose Additive Manufacturing?

You might want to choose additive manufacturing if:

  • The design is exceptionally complex geometrically. Intricate models and minor changes are more difficult and costly to make with subtractive manufacturing.
  • Only a few copies of the part are required. Additive manufacturing can be an excellent choice for prototypes or samples.
  • The turnaround time is incredibly short. It is quicker to program a 3D printer than a CNC subtractive machine, so if you need your part in a day, choose additive manufacturing.
  • The material for the part is flexible. Subtractive manufacturing works better with more rigid materials.
  • Limiting waste is crucial for your business. Since the part is built layer by layer, there’s less wasted material to discard when finished, and compostable plastics can even be used. (However, it’s not entirely waste-free and will still require waste-management efforts.)
  • The part has a hollow center. Additive manufacturing is more efficient at creating pieces with hollow interior sections.
  • The part is small. The layered construction method means the finished product isn’t as structurally solid as an item manufactured subtractively.

Can you use both additive and subtractive manufacturing together?

Some clients find that the best way to complete a project is to create a hybrid part, one made using both subtractive and additive manufacturing.

Typically, a hybrid manufacturing process means the geometrically complex pieces are completed using additive manufacturing. Then subtractive manufacturing is used for precision elements.

Need help getting started?

Starting your manufacturing process right is essential. Reach out to United Scientific today to discuss your manufacturing needs and how we can help you fulfill them.

Safety Basics for Machining Companies

gloves, work boots, safety goggles, hard hat on a wood plank background w/ "work safety" written on a framed chalkboard

gloves, work boots, safety goggles, hard hat on a wood plank background w/ "work safety" written on a framed chalkboard

In any industry that utilizes any type of machinery, the absolute number one rule everyone knows is “Safety First.” When machining companies don’t take safety seriously, serious accidents happen.

That’s why we take safety seriously at United Scientific. We serve machining companies that take every precaution to make sure their employees and customers are safe, so we do the same.

If you are looking for a partner that takes safety as seriously as you do, look no further than United Scientific. Not only do we provide the highest quality materials, but we also do so in a manner that surpasses safety standards.

How We Stay Safe

Each one of the employees at United Scientific is well-trained in safety. We know you don’t cut corners in your business, so our employees don’t cut corners in their own safety.

Personal Safety

There are a few basic rules all of our employees follow, and they are likely similar to your safety guidelines.

  • Always wear appropriate clothing.
  • Never wear loose clothing.
  • Steel-toed shoes are STRONGLY encouraged.
  • Secure or cover hair and facial hair.
  • Always be aware of and use proper safety equipment, including safety goggles, respirators, gloves, aprons, or coats.

danger placard held by a clasp held by a safety lock

Machine Safety

When it comes to operating machinery, it is essential everyone operating the machine knows the basic rules.

  • Know and follow the lockout or tag-out procedures.
  • Ensure all tools are in good, working condition with no chips, cracks, or burrs.
  • Only work on a machine you are trained or certified to use.

Workplace Safety

Employers know that a factory or workplace is only as good as its employees and the quality of the machines. If your workplace is not safe, the quality of the product suffers.

At United Scientific, like most other machining companies, we focus on keeping the workplace safe.

  • Keep each work area clean.
  • Return every tool to its proper place.
  • Walk or stand in designated safe areas only.
  • Always know where the first aid and eyewash stations are located.

Why We Stay Safe

It might seem obvious why safety is paramount. However, it is essential to employees why focusing on safety is critical, and why it should happen every day at every station.

  • Focusing on safety minimizes injuries.
  • Focusing on safety ensures equipment is used correctly and eliminates faulty mechanisms or tools.
  • Focusing on safety ensures the highest quality parts for the least amount of dollars.
  • Focusing on safety means no downtime due to not following procedures.

Check out the 10 Commandments of Good Safety Habits here.

man with industrial hand injury

Essential Safety Tips

With all of these safety focuses in mind, it’s time to focus on some safety tips. As a profitable business, you must be able to produce high-quality items customers trust at a reasonable price in the most efficient way possible.

Focusing on safety is the key to all of this and more. Read on for some essential safety tips that are always in place at United Scientific.

Take Extra Steps When Necessary

Most heavy machinery comes with safety mechanisms like safety interlocks. However, some machines don’t, or they aren’t in all parts of the machine. If you have a machine without a built-in safety mechanism, add one.

While we are NOT advocating altering your machine, it is perfectly acceptable to add a sign or a barrier. Furthermore, ensure you thoroughly train all of your operators on which areas need extra consideration.

This rule is especially true with newer operators that don’t have experience with that particular machine. To avoid catastrophic accidents, clearly label all areas with the appropriate precautions.

A simple way to keep your operators safe is to have a sign or warning telling each operator when the machine is back in its home position, or when it is safe to open a compartment.

Finally, allow each new operator to complete a dry run on all new machinery without stock or tools. This step will allow everyone working on the machine to see and understand the process without risk of injury or damage to products.

Clean and Maintain all Machines

Cleaning and maintaining all of your machines has multiple benefits. Obviously, a clean machine runs better, ensuring the operator is safer while working with it. When the machine is up to date on all maintenance and free of debris or residue, there is less chance of malfunction.

Furthermore, a clean and well-maintained machine will extend the life of the machine. Not only will the machine last longer, but it will also produce high-quality parts for longer.

Industry Worker working on cnc machine in metal industry factory

Utilize All Essential Safety Equipment

Ensuring each of your operators uses the correct PPE, personal protective equipment, is vital. It is up to the employer to provide training and equipment, so every employee meets the correct standards set by OSHA.

Proper PPE doesn’t stop at the eyes and feet. Consider protection for ears, hands, faces, and bodies when necessary. Even if the machine has a suitable enclosure and specific protection is not required, it is always wise to utilize appropriate foot, eye, and ear protection.

Along with using the correct personal protective equipment, ensure every employee knows where the first aid and eyewash stations are. To be even more secure, provide regular training to all employees on how to use these stations.

Have a Checklist

Having a checklist all employees must complete before clocking in or out for the day can ensure safety measures are always being met. A few examples might be:

  • Wear all appropriate PPE:
    • Safety Goggles
    • Protective Gloves
    • Respirators
    • Proper Clothing
    • Proper Shoes
  • Inspect your machine and all parts before operating. Ensure there are no loose bolts, screws, or other components.
  • Slow down! Do not rush the machine or feeds. Not only can you get hurt, but you can also damage the machine.
  • Pay attention! Don’t leave your machine unattended. Listen to your machine while it is operating. If something sounds wrong, stop and inspect it.
  • Always follow the appropriate procedures for lockout before doing any work to a machine.
  • Be a professional! Never goof around or play around machines.
  • Clean up after yourself. This includes your machine and your workspace.

Let United Scientific Partner With You

United Scientific is the partner you are looking for that cares about safety and quality of the product. We focus on safety and providing the best parts at the most competitive prices.

What is Overall Equipment Effectiveness (OEE)?

Two workmen operating machines in modern industrial shop standing by control panel and pushing buttons

Two workmen operating machines in modern industrial shop standing by control panel and pushing buttons

Makers of Things, this article is dedicated to you. In any production line, all stakeholders benefit from Overall Equipment Effectiveness (OEE). The ability to produce or receive high-quality parts and products at the lowest price, and the quickest turn-around should be a primary goal for all CNC operators.

From food service to rocket mechanics, your productivity hinges on the achievability of top OEE. At United Scientific, our CNC operators understand the ins and outs of overall equipment effectiveness. OEE is a metric we use to improve our efficiency regularly.

Join us as we break down the components of OEE and show you what to look for in a highly effective parts manufacturer. When only the best CNC collaborator will do for your product or part, United Scientific stands ready. Contact us today to discuss your precision cutting and part production project.

The moving parts of overall equipment effectiveness

One might think that quality or on-time delivery alone signals a high OEE score. In fact, there are three components to achieving top marks for OEE. They are:

  • Availability
  • Performance
  • Quality

Let’s define those terms in depth.

Pale blue mirrored letters OEE on gray gray upturned arrows

Availability

The availability metric of OEE is a product of Planned Production Time, Planned Stops, and Unplanned Stops in production.

In other words, if your factory runs from 8 am to 5 pm Monday through Friday, a 100% Availability score means there are no stops in production during your open hours. A perfect availability score each day is not realistic.

Every production line will encounter equipment breakage or downtime, as well as material shortage from time to time. Other unplanned stops may involve staff shortages or other personnel issues while the line is scheduled to run.

Planned stops include regular equipment maintenance, cleaning, shift change over, process set-up, or something else. Though it would seem that unplanned stops affect the OEE availability the most, the truth is that planned stops have the largest negative impact on availability.

If your shop has inefficient maintenance schedules, long and lingering shift changes, or unclear set-up instructions for your shop floor team, these phenomena can drag down your availability score quickly.

Performance

The performance metric of OEE measures actual cycle time or run rate against ideal cycle time or run rate. In other words, if at our best we could complete a production cycle in 45 minutes, but instead only complete it in one hour, our performance metric would only be 75%.

Slow cycles and small stops contribute to a lower performance score. Whenever your line sits ready-but-idle, constitutes a small stop. Reduced speed on your production line defines a slow cycle.

Old equipment breaks or runs slowly. Machines have their quirks and must be reset. Lubrication runs out, and production materials come in different quality grades. Operators have varying levels of experience and expertise.

All of these “kinks” can slow production or stop it for just a few moments to enact a quick or routine “fix.”

Since production equipment and personnel are fallible from time to time, small repairs or settings adjustments seem like a frustrating but normal part of manufacturing. Many shops become “blind” to these performance-suckers because they happen with such regularity.

However, when slow cycles and small stops pile up, those seemingly “routine” stoppages can have a disastrous effect on performance metrics. It’s smart to periodically evaluate your reasons for slow cycles and small stops so you can proactively reduce their frequency.

Engineer wearing a yellow hard hat and safety glasses inspects a manufactured part while holding a laptop computer

Quality

The quality measure of OEE has everything to do with finished product output. Any imperfect pieces that must be reworked or scrapped will bring down overall OEE.

If you’re striving for a 100% quality score, that means every part you machine must come out to acceptable selling quality. It’s nearly impossible to hit a 100% quality score consistently, as there will always be defective or rejected parts that can be reworked and sold in any project.

Making sense of OEE and setting realistic goals

Of course, any machining or production shop wants a 100% OEE score all the time, right? However, with three independent scoring factors, an A+ in OEE is likely the unicorn you’ll never capture.

A company’s OEE score is a product of Availability x Performance x Quality. Even if each criteria scores 85%, the composite OEE score comes out significantly lower than each individual marker.

On a positive note, improving even one of your OEE component scores will raise your overall OEE. As a company, you’ll likely have one score where you can truly be a rockstar when you apply conscious effort and sound strategy.

As a benchmark, an OEE score of 85% puts you in a world-class category. If you’re not close to that mark yet, consider setting realistic goals for incremental improvement.

For example, if you’ve noticed your shift changes lack a sense of urgency, consider rallying your shop floor team leads. Perhaps you can empower your team to innovate ways to help staff keep production lines running at top speed even as employees change locations on line.

What if the bottleneck in your production is an old and worn out cutter?

A strict budget for the short-term goal of replacing a cantankerous piece of equipment makes sense to increase OEE for long-term productivity.

Two machinists and one supervisor standing around a piece of CNC machining equipment

Increasing OEE is a team effort

When your team knows and understands why OEE is essential to the company’s success and how they benefit from that, OEE scores may be easier to improve.

Gaining valuable input from operators as well as motivation from the top leadership down is essential in achieving and maintaining a high OEE score.

When you get serious about elevating your OEE score, be sure to include all stakeholders in goal setting and benchmarking for success.

Outsource your OEE with United Scientific

At United Scientific, we machine parts with superior precision for each client we serve. We partner with a wide variety of sectors, from automotive to medical devices, and many industries in between.

Contact us today and see how our attention to OEE in our parts production can work for your application.