MIM Casting vs Machining

Metal Injection Molding Parts: MIM Casting & Machining

What is Metal Injection Molding Parts?

Metal Injection Molding(MIM) parts are high-precision metal parts made using the metal injection molding process, ideal for complex geometries, thin walls, and high-volume production. Using MIM steel, mim aluminum, and injection molded titanium, this micro metal injection molding technique outperforms traditional machining of metal parts, die casting, MIM manufacturing, offered by metal injection molding companies and suppliers, ensures tight tolerances, excellent strength, and minimal waste, making it perfect for medical, automotive, electronics, and industrial applications. When comparing MIM Casting vs Machining, MIM stands out for its ability to produce highly complex, precise parts efficiently and cost-effectively.

What is CNC Machining?

CNC machining uses computer-controlled tools to remove material from solid metal blocks or billets. The process follows precise CAD/CAM instructions, allowing engineers to cut, drill, and shape metal exactly to specifications. CNC machining is ideal for medium to low production volumes, large or heavy parts, and components that require extremely tight tolerances and high strength. In the context of MIM Casting vs Machining, CNC machining is especially useful when a part’s geometry is too complex or delicate for molding, giving designers the precision and control needed for intricate metal parts.

How Does MIM Compare to CNC Machining?

Manufacturing Process

MIM: Additive process using powdered metal mixed with polymer binders, injected into molds and sintered at high temperatures to form solid, precise parts. Ideal for complex geometries and small, intricate components.

CNC Machining: Subtractive process that removes material from a solid metal billet to achieve the desired shape. Works well for simple to moderately complex parts but is less efficient for intricate designs.

Unique Geometry

MIM: Excellent for producing highly complex geometries and intricate features, including undercuts, micro-features, sharp internal corners, and thin walls. Supports part consolidation, combining multiple components into a single part, and offers a cost-effective solution where geometry does not increase overall cost.

CNC Machining: Offers good design flexibility but is limited by cutting tool access and complex internal structures. Producing intricate parts takes more time and increases costs, making it less efficient for highly detailed geometries.

Strength & Performance

MIM: Produces fully dense, high-strength parts with uniform internal structures and minimal stress, thanks to injection molding and sintering. Ideal for intricate or stress-sensitive components, offering a reliable solution for complex designs.

CNC Machining: Cuts parts from solid metal, providing strong and reliable components. However, material removal can introduce minor internal stresses or micro-deformations, which may affect delicate or complex parts.

Matériaux

MIM: Uses powdered metal mixed with binders, molded under high temperature and pressure to make precise, high-strength parts. Supports a wide range of metals—stainless steel, titanium, Inconel, copper, and more—with customizable composition, ideal for complex, high-precision components.

CNC Machining: Uses solid metal stock like steel, aluminum, or titanium. Can handle most metals, but machining harder alloys increases cost and time, making it less efficient for intricate or high-volume parts.

Part Size

MIM: Ideal for high-volume production of small, complex metal parts (typically under 100 g). Achieves 96–99% density, or up to 100% with HIP treatment, producing strong, reliable components. More cost-effective for intricate, miniature parts and offers a good balance of precision, complexity, and efficiency.

CNC Machining: Works well for both very small and much larger components, but generally involves higher material waste and labor costs, making it less efficient for high-volume or highly intricate parts.

Tolerance and Precision

MIM: Typically achieves tolerances from ±0.3% to ±0.5% of part dimensions, depending on feature size. Larger features may have slightly higher tolerances due to 15–18% shrinkage during debinding and sintering, affected by gravity, drag forces, and mold shape. Secondary machining can be added for tighter precision.

CNC Machining: Offers superior precision, often as tight as ±0.005 mm, with very accurate control over milling and turning tools. Ideal for high-precision components where minimal error is critical.

Mold Investment

MIM: Requires upfront tooling investment, which depends on part complexity—more intricate designs need molds with detailed internal cavities. Despite the initial cost, MIM offers lower per-unit costs for high-volume production, making it efficient and cost-effective for complex parts.

CNC Machining: Doesn’t require molds, but producing complex parts takes more time and labor, increasing overall costs. Less efficient than MIM for high-volume or intricate components.

Material Scrap

MIM: Produces minimal material scrap because metal feedstock is injected directly into molds, making efficient use of material. This reduces waste and lowers overall production costs, especially for high-volume or intricate parts.

CNC Machining: Generates significant scrap since metal is removed from solid blocks. Managing this waste requires additional handling, recycling, and disposal efforts, which can increase cost and complexity.

Production Capacity

MIM: Ideal for mass production, especially 10,000+ parts per month. Capacity can be increased without extra machines, offering efficient, high-volume runs with consistent quality. Although tooling costs are high initially, they are quickly recovered, and finishing operations are minimal.

CNC Machining: Slower and better suited for prototypes or low-volume production. Producing complex parts takes more time, and scaling up requires additional equipment, making it less efficient for large-scale runs.

What is the Investment Casting Process?

Moulage à la cire perdue (also called precision or lost-wax casting) is a process where a wax or resin pattern is coated with a ceramic shell. The shell is heated to remove the wax, leaving a cavity that is then filled with molten metal. Once cooled, the shell is removed, revealing the final metal part. In the comparison of MIM Casting vs Machining, investment casting is ideal for producing larger, heavier components with thicker walls compared to MIM, and it excels at creating intricate, detailed shapes with excellent surface finishes. This process is widely used in industries like automotive, aerospace, and art for small to medium-sized complex parts where precision and detail are important.

How Do MIM and Machining Technology Processes Compare?

Metal Injection Molding (MIM)

Moulage par injection de métal(MIM) is an advanced process combining injection molding and powder metallurgy sintering, ideal for small, precise, and complex metal parts in high volumes. In the context of MIM Casting vs Machining, MIM supports nearly any metal or alloy—even those difficult to machine or cast—though stainless steel and low-alloy steels are most common. MIM offers low waste, high production efficiency, and excellent surface finish, making it perfect for intricate components where quality and volume matter.

Machining

CNC Machining: Machining is a traditional metalworking process where material is gradually removed from solid workpieces until the final shape is achieved. In the discussion of MIM Casting vs Machining, it’s ideal for prototypes, low-volume production, or parts requiring tight tolerances, and can create components that die casting, investment casting, or MIM cannot. However, for very small, intricate, or complex parts, machining is often less cost-effective due to longer processing times and higher material waste. Despite this, it remains a reliable choice when precision and flexibility are critical, especially for custom or specialized components.

How Do Materials Compare for MIM and Machining?

Machining can handle almost any metal, but in terms of MIM Casting vs Machining, MIM has expanded its material range and now supports a wide variety of metals, including 17-4PH, 316L, 420 stainless steel, low-alloy steels, cobalt alloys, titanium (for MIM), magnetic alloys, and even high-melting-point metals like tungsten.

Investment casting, on the other hand, is best for metals with lower melting points, such as copper alloys, aluminum alloys, and stainless steel, which limits the material options compared to MIM.

Process	Common Materials	Specialty Materials
MIM	Stainless Steel, Tool Steel, Carbon Steel, Low Alloy Steel	17-4PH, 316L, 420, Cobalt Alloys, Titanium, Magnetic Alloys, Tungsten Alloy, Nickel-Based Alloy
Moulage à la cire perdue	Cast Stainless Steel, Cast Aluminum, Copper Alloy	Cast Titanium, Cobalt Alloys, Nickel-Based Alloy

MIM is great for small, complex, high-precision parts that need strong performance, while investment casting is ideal for parts made from lower-melting-point metals but has more limited material choices.

How Do Complexity and Tolerance Affect MIM Parts?

In terms of MIM Casting vs Machining, MIM is ideal for producing highly intricate parts with fine details. It handles features like undercuts, thin walls, internal channels, and complex geometries that are hard to achieve with other methods. MIM can reach tight tolerances, often ±0.05 mm (±0.002 in), though extremely tight specs may still require post-machining.

Investment casting also creates complex shapes with good surface finish and works well for curved surfaces, thin sections, and detailed designs. Tolerances are typically ±0.5 mm (±0.02 in), but getting tighter tolerances usually requires additional machining.

Feature	Metal Injection Molding (MIM)	Moulage à la cire perdue
Complexity	High, supports intricate parts, miniature features, micro MIM	High, supports intricate shapes and curved surfaces
Thin Walls	0.2–0.4 mm	Can produce thin sections but less precise
Undercuts & Internal Channels	Supported	Limited
Tolerance	±0.05 mm (±0.002 in), post-machining if needed	±0.5 mm (±0.02 in), tighter requires machining
Precision	Superior for high-precision components	Good, but less precise than MIM

MIM generally offers higher precision and is better for extremely detailed parts, while investment casting is strong for complex shapes but with looser tolerances.

What Are the Costs and Production Volumes for MIM?

Material Costs

Metal Injection Molding (MIM) uses fine metal powders mixed with binders, which makes the feedstock more expensive—stainless steel powders can cost around $10/kg. Investment casting uses bulk materials, often much cheaper at about $3/kg. However, MIM generates almost no scrap, so the higher material cost is partially offset.

Tooling Costs

Metal Injection Molding (MIM) needs expensive tooling, like injection and shaping molds, especially for complex or multi-cavity designs. While initial costs are high, molds last longer—up to 50K shots—making MIM cost-effective for mass production. Investment casting molds are cheaper and work well for small or simple parts, making them better for low to medium volumes.

Labor Costs

Metal Injection Molding (MIM) involves several steps—mixing, injection molding, debinding, and sintering—which can make it seem labor-intensive. However, after tooling is set up, the process is highly automated, keeping labor costs low. MIM is best for medium to large production runs, especially for high-precision, complex parts.

Investment casting is simpler and relies mostly on skilled manual labor. It works well for small to medium volumes and moderately complex shapes. Tooling costs are lower, making it a cost-effective choice when high precision isn’t critical.

Production engineers can evaluate project needs—volume, complexity, and budget—to recommend the most efficient method, ensuring the manufacturing process fits the goals without overspending.

How Does Surface Finish Differ Between MIM and Casting?

Surface Finish in Metal Injection Molding (MIM)

Metal Injection Molding (MIM) can produce smooth surfaces, typically Ra 1–3 μm, making it ideal for visible or cosmetic parts with no machining marks. The final finish depends on mold quality, debinding, and sintering, so parts may have a slightly textured look from the metal powders.

MIM also offers high precision, accurately reproducing intricate details and delicate features, often within ±0.02 mm. Some parts may need post-processing like polishing or light machining to achieve a perfect finish or improve dimensional accuracy, but overall, MIM delivers detailed, high-quality surfaces suitable for demanding applications.

Surface Finish in Investment Casting

Investment casting usually produces parts with a rougher surface, typically Ra 6–12 μm, compared to MIM. The process starts with a high-quality wax pattern to make the mold, but minor surface imperfections or parting lines are common.

Precision is good, but investment casting may not match MIM for intricate details. As a result, parts often need secondary finishing like sanding or machining to smooth the surface and meet dimensional requirements. Despite this, investment casting remains a cost-effective choice for small to medium-volume production of moderately complex components.

How Do Thin-Wall Capabilities Compare Between MIM and Casting?

Metal Injection Molding (MIM)

Metal Injection Molding (MIM) is excellent for producing intricate parts with very thin walls. It can achieve wall thicknesses as low as 0.2–0.4 mm, making it perfect for miniaturized and complex components.

The process is stable and repeatable, allowing high precision in replicating fine features and maintaining excellent dimensional accuracy. However, very thin walls require careful control during molding and sintering to manage shrinkage and ensure the part stays strong and intact. This makes MIM ideal for applications where detail, precision, and consistency are critical.

Moulage à la cire perdue

Investment casting can produce parts with thin walls, typically around 1.0–2.5 mm, though extremely thin or intricate walls are more challenging than with MIM. Wall thicknesses as low as 1.5 mm are achievable, making it suitable for many applications.

Care must be taken with fragile or complex thin structures to ensure uniform thickness and avoid defects like shrinkage cavities or surface irregularities. Controlling the casting and cooling process is essential for part integrity. Overall, investment casting works well for moderately thin walls but may need extra attention for very delicate or detailed features.

What Are The Applications Of MIM Parts?

Electronic MIM Parts

MIM parts are widely used in the electronics industry and consumer devices, including connectors, hinges, locking systems, and micro-gears. Their ability to produce complex shapes with high precision makes them ideal for assembling household appliances, laptops, and mobile phones where tight tolerances are crucial.

With minimum wall thicknesses as low as 0.10 mm and excellent surface finish, MIM parts can meet demanding requirements for both functionality and appearance, ensuring precise fitting of delicate components and durable performance in compact electronic assemblies.

Medical MIM Parts

MIM parts are widely used in medical applications, including surgical instruments, orthodontic brackets, implants, forceps, scissors, drug delivery devices, hearing aids, and dental equipment. MIM produces high-strength stainless steel parts with smooth surfaces and tight tolerances, making it ideal for complex, miniaturized components. Compared to investment casting, MIM is more cost-effective for devices like orthodontic appliances and surgical implants, offering precision, durability, and excellent finish.

Industrial MIM Parts

MIM parts are widely used across industrial applications, covering valves, rotors, locking components, precision couplings, and more. Because MIM can create small, detailed shapes with great consistency, it’s also used for custom micro-gears, components in drones, smart wearables, pepper-spray mechanisms, and various machinery parts.

With flexible material options and the ability to handle complex designs, MIM offers a reliable way to produce durable, high-precision components for industries that need compact, lightweight, and repeatable parts.

Automotive MIM Parts

MIM is ideal for small, complex automotive parts like sensors, locks, and actuators, offering precision, compactness, and reliability.

Common MIM automotive parts include vanes, valves, connecting rods, valve guides, and parking brake components. With its ability to deliver precise, durable shapes in high volumes, MIM helps automakers achieve stable quality and efficient production for critical small metal parts.

Why Choose Welleshaft for Your Metal Parts Manufacturing?

For larger or heavier components, MIM casting or investment casting is often the better choice. While casting works well with heat-resistant alloys, it can’t match MIM when it comes to super fine details or complex geometries. At Welleshaft, we help you select the right manufacturing method—MIM, CNC machining, or casting—based on your part’s size, complexity, and production requirements.

Whether you need small, intricate parts, precise prototypes, or larger components, our engineers optimize materials and designs to ensure tight tolerances, reliable performance, and high-quality results.

We combine technical expertise with hands-on support, making complex metal parts easier and more cost-effective. From prototype to full-scale production, we focus on precision, efficiency, and quality—helping your project succeed while reducing waste, saving time, and keeping costs in check.

Pièces MIM FAQ’S

What types of parts are best suited for Metal Injection Molding (MIM)?

MIM is ideal for small, complex, high-precision metal components that would be too costly or impossible to machine. It is commonly used for medical device parts, electronic connectors, precision gears, locks, actuators, and miniaturized mechanisms produced using metal injection molding materials such as stainless steel, low-alloy steel, titanium, and magnetic alloys.

Is MIM more cost-effective than CNC machining?

Yes—when production volume is high. While MIM requires upfront tooling cost, the per-unit cost becomes significantly lower for mass production compared to machining. For low-volume or ultra-tight tolerance parts, CNC machining remains the more economical option.

What is the typical lead time for a new MIM project?

Most MIM projects require 4–6 weeks for tooling and sample development, depending on part complexity. After tooling is complete, production runs are fast and suitable for scaling to tens of thousands of parts per month.

Metal Injection Moulding vs CNC Machining vs MIM Casting

MIM (Metal Injection Molding) is great for producing small, complex metal parts—thin walls, tiny features, hidden channels, anything that’s tough to machine. The process mixes metal powder with a binder, injects it like plastic, then debinds and sinters it into dense metal. It works with MIM steel, aluminum, titanium, magnetic alloys, and more, making it a strong fit for high-volume projects that need consistent accuracy and low material waste.

CNC machining is the better choice when you need extreme precision, tight tolerances, prototypes, or small-batch custom parts. It handles almost any metal, but costs rise with complexity and there’s more scrap. If tolerances are critical, machining still leads.

For larger, thicker, or heavier components, MIM casting or metal investment casting is usually more practical. Casting supports heat-resistant alloys well, but it can’t hit the fine detail or complex geometry that MIM can. In the end, your choice depends on whether the priority is part size, precision, or complexity.

Quick comparison:

1. Complex, miniature, high-volume parts → Choose MIM
2. Ultra-tight tolerance or small runs → Go with CNC machining
3. Bigger, thick-wall shapes → Casting fits best

MIM vs CNC Machining Comparison

Feature	MIM	CNC Machining
Manufacturing Process	Additive	Subtractive
Input Material	Metal powder feedstock	Solid metal billets
Complexity & Geometry	Excellent	Limited by tool access
Strength & Performance	Very high	High
Tolerance & Precision	Moderate	Exceptional
Production Time	Longer setup	Faster turnaround
Cost	Higher tooling	Lower for small runs
Waste Generation	Minimal	More scrap

This blog was provided by the Welleshaft Engineering Team, led by Mr. Xu. Welleshaft specializes in Metal Injection Molding (MIM), CNC machining, and investment casting, delivering high-precision, reliable, and cost-effective solutions for small, complex metal parts across medical, automotive, electronics, and industrial applications.