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These are the two main methods of modern production. Additive manufacturing shines in making light weight structures but subtractive has its own advantages in terms of precision. In this article we will examine the differences and pros and cons of each to help you decide which is best for your needs.
What is Additive Manufacturing?
Also called 3D printing, additive manufacturing build objects in a layer by layer fashion. Specialized machines deposit materials based on 3D digital designs in this process. Some broadly used AM technologies are Stereolithography (SLA), Fused Deposition Modeling (FDM) and Direct Metal Laser Sintering (DMLS). Such methods give us the ability to make complicated shapes that can’t be made by old manufacturing methods.
What is Subtractive Manufacturing?
Unlike additive, subtractive manufacturing use machines to literally chip away material off of a solid block to produce parts. A CNC machine is used in this process that follows instructions of G code. It results in very precise parts, to as precise as 0.0001 inches in metal parts.
8 Main Differences: Additive vs. Subtractive
1. Design Intricacy
Additive manufacturing is very good at producing internal cavities and complicated geometries that are difficult to make using conventional techniques. Subtractive manufacturing via multi axis CNC machining can produce complicated designs but is limited with nested structures and internal holes.
2. Manufacturing Process
Additive manufacturing is the process of applying high precision 3D printers to transform virtual CAD data into tangible objects by Stereolithography (SLA), Fused Deposition Modeling (FDM) and Direct-Metal Laser Sintering (DMLS).
On the other hand, subtractive manufacturing carves finished parts from raw material slabs, by performing preprogrammed CNC operations. In order to get to the desired criteria, the machines also use EDM electrodes, turning instruments and end mills.
3. Material Usage
These manufacturing methods differ starkly in terms of material utilization. In this respect additive manufacturing is very material efficient, using only the material needed to build parts layer by layer. This leads to less than 10% of raw material wasted.
On the other hand, subtractive manufacturing carves out large quantities of material from massed blocks, creating massive waste through milling, cutting and drilling. Waste rate is 60–70% of block material in subtractive procedures, while there are some materials that are recyclable. This difference becomes important if you are using materials that are expensive—high titanium for example, or a special alloy.
4. Surface Tolerance and Surface Finish
CNC machining is an exceptional precision form of subtractive manufacturing capable of achieving tolerances of ±0.025mm and surface roughness of Ra 0.2µm. Latest subtractive manufacturing technology provides mirror like finish for aerospace parts.
On the contrary, additive procedures have the layer-line challenges, with metal DMLS setups only achieving tolerances of ±0.1 mm and Ra 4µm. Typically for additive parts requiring high accuracy, some post processing steps such as surface treatment or machining become necessary.
5. Production Speed and Volume
Cutting speeds of subtractive CNC machines are up to 10,000 RPM. Because of this they can make hundreds of identical components every day. So they are perfectly fit for mass manufacturing. In contrast, additive manufacturing works at production rates of 15-150 cm³/ hour of metal components and takes 4-18 hours to complete a production phase.
3D printing is good for low volume runs from 1 to 1000 units, but subtractive machining is good for steady output rates and volumes over 1000.
6. Setup Cost and Tools Cost
There is a great difference in the cost of the equipment for these two methods. Basic FDM 3D-printers start at 399 dollars and go all the way up to $2,883. Metal printers for industries cost a lot more and they can go anywhere between 46,999 and 300,000 dollars.
Opposite to 3d printers, basic CNC machines for subtractive manufacturing cost $2,300 to $3,500. Industrial CNC-systems of the higher end can cost anywhere from $40,000 to $200,000.
Setup costs also vary a lot. Extra tools, fixture and jigs are needed for CNC machines. On the other side, desktop 3D printers are ready to be used right away as there are no setup needs required.
7. Customization Ability
Mass customization is another strength of additive manufacturing which necessitates no tooling changes in between different designs. Using this technology, it’s possible to produce medical implants, particularly designed for special patients, in 24 to 48 hours.
Subtractive CNC operations on the other hand, require new tools, fixtures and programs for each different design. It also takes 4–8 hours per modification to change its setup.
Additive manufacturing is well suited to low volume customized products whereas subtractive methods are right for mass standardized production.
8. Effect on Environment
For low volume (less than 1,000 units), additive manufacturing has higher sustainability with negligible material waste and lower energy consumption. In SLS processes, the technology consumes 10 kW/h and allows local production that significantly reduces transportation emissions. On the opposite, subtractive manufacturing generates more waste by material removal; though it is more efficient (environmentally) for bulk production.
Pros and Cons: Additive vs. Subtractive Manufacturing
Both manufacturing types are two very different approaches. Their pros and cons vary according to application.
Pros of Additive Manufacturing
- AM speeds up production by making it possible to turn a CAD file into a part directly. This reduces prototype and small batch production time down from months to just days.
- Using AM, engineers can produce complicated shapes and lattice structures with much less weight yet significant strength. It is for this reason that AM is great for aerospace parts.
- AM is automatic- requires very little human input. The smart AI systems keep an eye on things and they adjust part settings in real time to keep quality.
- AM can make complicated designs that can’t be done by other milling and cutting methods.
Cons of Additive Manufacturing
- Material options are very limited. Unlike traditional manufacturing methods, AM can only construct parts out of certain photopolymer resins and metal powders which come at a much higher material cost than ‘conventional’ materials.
- To succeed with AM, teams need special skills. It includes CAD-design, finishing expertise and computer modeling.
Pros of Subtractive Manufacturing
- Subtractive manufacturing includes high speed CNC machining, with metal removal rates up to 1500 cm³/min. The result is fast, efficient production for large volumes.
- Subtractive is good at creating massive components especially with outstanding material strength and dimensional tolerance.
- Multi-axis CNC centers using SM can quickly produce complicated parts at high output of 500+ units a day.
- Results from subtractive are mostly good in terms of surface quality, with smooth and accurate finishes often needing little-to-no post treatment.
Cons of Subtractive Manufacturing
- SM produce large amounts of scrap because so much material is removed to create the part.
- In SM there is a requirement for retooling to make custom products or changing shapes, which can be expensive.
Additive vs. Subtractive Manufacturing: Which Is Better?
No one is completely better than the other. This entirely depends on which application requirements they serve.
Complex, custom designs are easy to create by additive manufacturing with very little waste. So it is suitable for small scale, intricate components and prototypes. However, subtractive provides fast production for large volumes and higher precision which makes this process more appropriate for large scale manufacturing of standardized parts. Therefore, the choice between such methods depends on the material kind, how complicated the design is and production cost.
To Sum It Up
Each of the manufacturing methods serves a different industrial need. Prototypes, complex and customized parts are best made via additive manufacturing whereas subtractive manufacturing is used for precision in high volume production.
If you need any kind of manufacturing service- subtractive or additive – then RICHCONN is your best option. You can contact us at any time.
FAQs
Why is it hard to get tight tolerance in subtractive and additive types of manufacturing?
Attaining low tolerance is difficult in additive owing to material properties such as thermal expansion and shrinkage. The main issue in subtractive manufacturing is the need of constant tool replacement and also tool wear.
Is additive and subtractive manufacturing possible in a single process?
Of course, there are hybrid manufacturing systems where additive and subtractive methods are combined together. Additive enables complicated geometries to be made, which can then be finished and fine-tuned by subtractive methods, for precision.
How does computer aided design (CAD) fit into both manufacturing methods?
CAD models are directly used to generate layer by layer prints in additive manufacturing. And in subtractive, CAD models direct CNC machines to remove material with precision
What are the impacts of additive and subtractive manufacturing on product development cycles?
Early prototyping benefit from faster additive methods. Subtractive manufacturing on the other hand, takes longer setup times and tooling preparation but once those things are done, it is much more efficient for mass production.
How does additive and subtractive manufacturing handle multi material parts?
Additive allows for the creation of multi material parts within a single build. Subtractive on the other hand, demands different machining operations and then assembly for each material.
