Machining Factors That Could Affect Lead Times and Price Quotes

Machining Factors That Could Affect Lead Times and Price Quotes

When getting price quotes for CNC machined parts, lead times and pricing can vary dramatically between machine shops. Many complex factors impact the time and cost to manufacture components through machining processes like milling, turning, drilling, and grinding.

In this guide, we’ll examine the key technical elements that affect machining pricing and lead times. Understanding these factors helps designers and engineers work with manufacturers to achieve cost-effective production.

Part Attributes that Influence Machining Costs

Several characteristics specific to the component design greatly influence machining pricing:

-Dimensional Tolerances – Tighter tolerances require more operations and skilled labor, increasing costs. Tolerances looser than 0.005 inches are more economical.

-Surface Finishes – Smoother surface finishes add additional steps like polishing, raising costs. Finishes rougher than 63 Ra are more affordable.

-Complexity – Multiple complex features demand advanced multi-axis machining, affecting pricing. Simpler designs save on programming, fixturing, and operations.

-Size – Larger parts often require expensive fixturing and work holding. Smaller components maximize material yield.

-Machinability – Difficult-to-machine metals like stainless steel and titanium are costlier than aluminum and mild steels.

-Hardness – Harder materials increase cutting tool wear, cycle times, and tooling costs. Softer grades are more economical.

-Quantity – Higher volumes achieve economies of scale. Lower quantities lose savings from repeating setups.

Design Attributes that Impact Machining Lead Times

Several design factors also affect how quickly components can be machined:

• Number of Operations – More machining steps like milling, drilling, and tapping prolong total production time. Simpler parts are faster.
• Setup Requirements – Elaborate fixturing and work holding increases changeover time between operations. Creative cost-effective setups save time.
• Feature Accessibility – Tight pockets and enclosed geometries restrict cutter access, slowing machining. Open-access designs are the most efficient.
• Tool Requirements – Special cutters increase lead time for tool design, grinding, and procurement. Standard tools are readily available.
• Machine Selection – Complex parts may require specialty machines with limited availability, affecting scheduling.
• Batch Size – Larger batches achieve faster production rates once set up. Small batches lose time on repeated changeovers.

With an awareness of how the design particulars influence time and cost, engineers can optimize components for machining efficiency right from the start.

Machine Shop Capabilities that Impact Costs and Lead Times

The production capabilities of the machine shop also significantly affect pricing and lead times:

• Machine Types – Advanced multi-axis CNC machines offer greater flexibility but have higher hourly rates. Basic 3-axis mills cost less.
• Tooling – Shops with larger tool inventories avoid delays for special tool fabrication or procurement.
• Staff Experience – Skilled programmers, setup personnel, and operators prevent mistakes that add time and cost.
• Quality Systems – Robust processes for quality assurance add overhead but ultimately save time and waste.
• Software – Advanced CAM programming software handles complex geometries more efficiently.
• Workload – Available capacity affects scheduling lead time. Less busy shops can start jobs faster.
• Services Offered – One-stop shops with in-house heat treating, plating, etc. simplify the supply chain.
• Plant Automation – Highly automated processes like robotic machines tend to increase throughput.

Thoroughly evaluating a machine shop’s technical capabilities ensures proper alignment with part needs for optimal pricing and lead time performance.

Material Selection Consequences for Machining Cost and Speed

The material specified heavily influences the time and cost equation for machined components:

• Hardness – Harder materials require heavy-duty tooling that wears quickly, increasing cycle times and tooling costs.
• Strength – Strong materials like titanium and Inconel are more difficult to machine, lowering metal removal rates.
• Microstructure – Coarse grain metals machine faster than fine grains. Cast materials are slower than wrought.
• Cuttability – Free-machining alloys with special additives improve tool life and surface finish.
• Chip Formation – Long stringy chips have slow production compared to brittle chips that fragment easily.
• Work Hardening – Metals like stainless steel harden during machining, accelerating tool wear and degrading surface finish.
• Thermal Properties – Metals with higher thermal conductivity like aluminum remove heat better to cut faster.

Engineers should select the easiest-to-machine material that meets functional requirements to minimize manufacturing costs.

Tooling Impacts on Machining Price and Delivery

Cutting tools are a major factor influencing pricing and production speed:

• Tool Types – Specialized tools for difficult geometries or materials are expensive and increase lead times. Standard end mills are the most economical.
• Coatings – Advanced tool coatings like diamond or titanium aluminum nitride improve tool life but add cost. Uncoated carbide is lower cost.
• Tool Geometry – Complex custom tool geometries maximize material removal rates but require longer design and grinding lead times. Standard inserts are ideal.
• Tool Size – Smaller cutters inherently lack stiffness and are prone to breakage, limiting feed rates and increasing cycle times. Larger tools machine faster.
• Tool Cost – Expensive tooling materials like polycrystalline diamond run faster but add overhead. Lower-cost carbide strikes an economical balance.
• Tool Availability – Shops with larger tool inventories avoid downtime waiting for special orders.

Proactive tool selection keeps machining costs under control while avoiding slower lead times from custom tool production.

Optimizing Cutting Parameters for Cost and Lead Time Reduction

Intelligently selecting cutting speeds, feeds, and depths of cut directly impacts cycle time efficiency and tooling cost:

• Speeds/Feeds – Conservative parameters prolong tool life but slow production. Aggressive settings improve productivity but consume tools faster if not balanced properly.
• Axial/Radial Depths – Deeper cuts remove material quicker but also increase forces and potential tool deflection. Shallow passes take longer but are easier on the tool.
• Chipload – Higher chiploads improve material removal rates but also chip thinning and potential tool failure if exceeded. Must find optimal shipload per tool.
• Coolant – Effective coolant selection and application improves cutting performance. Poor coolant increases friction and tool wear.

Achieving the right balance of parameters maximizes metal removal rates without causing premature tool failure. This requires understanding tool capabilities and the machined material’s characteristics.

Quote and Lead Time Implications of Fixturing and Workholding

The fixturing and work holding strategy also impacts cost and manufacturing time:

• Setup Labor – Complex locating schemes require longer hours to precisely align the part, increasing cost. Simple setups are the most economical.
• Changeover Time – Quick change modular vise jaws, pallets, and fixtures accelerate job changeover to reduce lead times.
• Machining Access – Poor access from over-clamping adds additional operations and non-value-added time. Avoid excessive clamping.
• Inventory – Standardized vises, chucks, and tombstones on hand reduce lead times versus custom solutions.
• Tooling Flexibility – Generic tooling plates offer greater flexibility for securing new jobs without re-fixturing.
• Automated Workholding – Robotic or self-centering workholders improve changeover efficiency.

An ideal fixturing solution balances sufficient workpiece securement with quick changeover and machining access to avoid unnecessary cost and delay.

Quote and Lead Time Considerations for Secondary Operations

Beyond the primary machining, any secondary processing also factors into pricing and schedules:

• Heat Treating – Services like case hardening or stress relieving add cost and production time if outsourced. In-house is faster.
• Surface Enhancements – Added steps like plating, blasting, or polishing increase costs and lead times if outsourced.
• Part Marking – Permanent laser marking avoids delays of outsourced stamping or etching processes.
• Quality Assurance – Robust incoming, in-process, and final inspection avoids scrap and ensures schedule adherence but adds overhead. Minimal inspection saves cost.
• Assembly – Sub-assemblies produced in addition to machined components add pricing. Kits simplify external assembly.
• Shipping – Getting parts to suppliers for outside services and delivering final parts impacts delivery schedules.

Secondary operations should be balanced to meet functional needs without excessive production delays and costs.

How Production Batch Size Affects Cost and Lead Time

The quantity of parts required is a major pricing and schedule driver:

• Setup Cost Allocation – Larger batches distribute setup cost over more parts to lower per-piece price. Small runs bear higher per-part setup costs.
• Repeated Processes – Recurring operations like work holding and tool changes constitute proportionally more time on small batches versus high-volume runs.
• Equipment Selection – Large production may use dedicated machining cells versus small batches sharing general machines with scheduling delays.
• Labor Efficiency – Operators develop optimization rhythm over long production runs versus having to continually reset between short runs.
• Material Cost – High volumes benefit from raw material bulk discounts. Low volumes pay small lot premiums.
• Inventory Costs – High WIP and finished goods for large batch sizes incur higher carrying costs. Just-in-time small batches optimize working capital needs.
• Quality Sampling – Large batches require more statistical sampling. Small runs can afford 100% inspection.

Moderately sized production batches typically offer the best economies for machined parts.

Logistical Factors That Impact Delivery Schedules

Several supply chain considerations influence production lead times:

• Raw Material Supply – Readily available standard-size bar, plate, and sheet stock to avoid delays versus long lead specialty sizes or shapes.
• Raw Material Quality – Inconsistent incoming material quality requires sorting or rework and slows production flow. Robust suppliers prevent issues.
• Part Transportation – Local supply chains are faster. Distance to vendors increases lead time risks.
• Customs Clearance – International procurement can encounter unpredictable delays at customs. Domestic sourcing is more reliable.
• Subcontractor Capability – Strong craftsmanship, quality control, and project management at subcontractors prevent errors and delays.
• Communication/Documentation – Regular updates and paperwork issues between parties in the supply chain risk misalignment. Strong IT integration and protocols prevent miscommunication.

A holistic review of the complete procurement and production network is necessary to prevent surprises that hamper on-time delivery.

Conclusion

This overview of the diverse machining factors that influence lead times and pricing shows the importance of cross-functional collaboration. By engineers, designers, and purchasers working closely with manufacturing to align component requirements with shop capabilities, optimal solutions can be achieved balancing cost, schedule, and performance. Considering the total supply chain will result in realistic estimates and high-quality outcomes. With vigilance of key machining elements, manufacturers excel at delivering maximum value for customers.