Delrin is DuPont's trade name for acetal homopolymer (POM-H) — a semi-crystalline engineering thermoplastic that combines high stiffness, near-zero moisture absorption and a naturally low coefficient of friction in a material that machines cleanly and efficiently on standard CNC milling and turning equipment. It belongs to the polyoxymethylene (POM) family alongside acetal copolymer (POM-C) and several specialty-filled grades, each optimised for specific mechanical, chemical or tribological requirements.
Where commodity plastics lack the stiffness for precision load-bearing components and metals add unnecessary weight and cost, Delrin occupies a well-established middle ground. It is stiff enough for precision gear teeth, slippery enough to run without grease, dimensionally stable enough to hold tight bore fits in variable humidity, and light enough to replace aluminium in many small-to-medium structural components. Clarwe machines Delrin in four grades: POM-H (Delrin 150), POM-C, Delrin AF and 30% glass-filled Delrin.
Delrin at a Glance
| Common grades | POM-H (Delrin 150), POM-C (Acetal Copolymer), Delrin AF (PTFE-filled), 30% Glass-Filled |
| Density | 1.41–1.56 g/cm³ (grade-dependent) |
| Tensile strength | 53–95 MPa (grade-dependent) |
| Coefficient of friction (dry) | 0.10–0.20 (Delrin AF) · 0.20–0.35 (standard grades) |
| Max continuous service temp. | 100–120 °C (POM-H/POM-C) |
| Moisture absorption (24 hr) | < 0.25% |
| Standard tolerance | ±0.10 mm |
| Tight tolerance | ±0.02–0.05 mm |
| Minimum wall thickness | 0.75 mm (absolute) · 1.0–1.5 mm (preferred) |
| Typical lead time | 1–4 days |
| Certifications | ISO 9001:2015 · ISO 13485:2016 · AS9100D |
| Best for | Gears, bushings, bearings, valve components, precision sliding assemblies |
What Makes Delrin a Strong CNC Machining Material
Delrin's value in CNC machining comes from a combination of properties that few other engineering plastics deliver together: high stiffness, self-lubrication, dimensional stability in moisture, fatigue resistance and efficient machinability. The sections below explain each property and why it matters for part performance.
High Stiffness, Strength and Fatigue Resistance
Delrin POM-H achieves tensile strength of 60–70 MPa with a flexural modulus above 2,600 MPa — high enough for thin-walled parts, gear teeth and precision brackets to hold geometry under operational load without metal reinforcement. Its crystalline molecular structure gives it outstanding resistance to fatigue under repeated loading, separating it from amorphous plastics like polycarbonate or ABS. Gear teeth, snap-fit features and spring tabs subject to millions of load cycles maintain geometry and load capacity without progressive crack growth — making Delrin the preferred choice over nylon or polycarbonate for high-cycle mechanical assemblies.
Natural Self-Lubrication and Low Coefficient of Friction
Delrin's dry sliding coefficient of friction against steel is 0.20–0.35 for standard grades — one of the lowest of any unfilled engineering plastic. Delrin AF (PTFE-filled) reduces this further to 0.10–0.20. This self-lubricating behaviour reduces or eliminates external grease or oil in sliding, rotating and reciprocating assemblies, which is particularly valuable in food contact, medical device and cleanroom applications where lubricant contamination is a concern.
Near-Zero Moisture Absorption and Dimensional Stability
Delrin absorbs less than 0.25% moisture over 24 hours. Nylon absorbs 2–8% and can dimensionally shift 0.2–0.5% in humid conditions, causing bore fits and gear mesh to move out of specification. Delrin holds tight bore fits, gear pitch dimensions and clearance tolerances reliably across variable humidity and light water contact without moisture-compensation allowances — a critical advantage for precision mechanical assemblies in uncontrolled environments.
Chemical Resistance and Operating Temperature
Delrin resists hydrocarbons, fuels, lubricating oils, hydraulic fluids and weak acids across a continuous service range of −40 °C to 100–120 °C (POM-H melting point: 175–178 °C). It is not recommended for prolonged exposure to strong mineral acids, strong alkalis, or hot water and steam above 60 °C. For components regularly exposed to hot water, steam or alkaline cleaning agents, POM-C is the appropriate grade selection.
Delrin Grades for CNC Machining
Clarwe machines Delrin in four grades covering the full range of mechanical, tribological and chemical requirements for precision CNC components. Grade selection at the design stage avoids material substitutions during production and ensures in-service performance matches the application environment.
Delrin 150 / POM-H — Standard Homopolymer
Delrin 150 is DuPont's original acetal homopolymer and the most widely machined Delrin grade. It delivers the highest stiffness and strength within the acetal family, produces clean short chips, and achieves excellent as-machined surface finish with sharp carbide or HSS tooling. It is the default first-choice grade for gears, precision bushings, bearing housings, cams, structural brackets and any part where tight tolerances and high mechanical performance are the primary requirements.
One known characteristic of POM-H is the potential for centreline porosity in large-diameter rod stock — a byproduct of the extrusion process. Parts machined from the core of thick bar stock may encounter this porosity, which can affect structural integrity in critical applications. Clarwe sources rod stock from certified suppliers and can advise on grade selection for large cross-section parts.
Standard colours:Natural (white / off-white), Black
POM-C — Acetal Copolymer
POM-C is the copolymer variant of acetal, produced with a slightly different molecular structure than POM-H that improves resistance to hot water, steam and alkaline environments. It does not exhibit the centreline porosity associated with homopolymer rod stock, making it the more consistent choice for large cross-section parts where core integrity is important, or for components regularly exposed to cleaning agents, moisture or mildly alkaline process fluids.
POM-C has slightly lower tensile strength and stiffness than POM-H but retains excellent machinability and dimensional stability for most engineering applications. In practice, grade selection between POM-H and POM-C is typically driven by stock availability, chemical environment or cross-section size rather than mechanical specification. For medical device and laboratory components requiring steam sterilisation, POM-C is preferable to POM-H; for autoclave-compatible applications, PEEK should be evaluated as an alternative.
Standard colours:Natural (white), Blue, Black
Food Contact and FDA-Compliant Grades
POM-C stock supplied to Clarwe for food-contact and medical applications is sourced from suppliers providing material conforming to FDA 21 CFR 177.2470 (acetal copolymers for food contact use). This covers direct and indirect food contact applications including conveyor components, food processing guides, valve bodies and packaging equipment parts that contact dry, moist and low-acid food products.
Applicable grades:POM-C (Natural). POM-H (Delrin 150) can also be sourced in FDA-compliant stock for specific applications — confirm requirements with Clarwe at the quoting stage.
Not covered:Delrin AF and 30% glass-filled grades are not typically offered in FDA-compliant variants due to PTFE content (Delrin AF) and glass fibre abrasion concerns (30% GF). Consult Clarwe if your application has specific regulatory requirements for these grades.
For medical device components requiring ISO 13485:2016-controlled supply chain documentation, Clarwe can provide full material traceability from certified stock. Autoclave and steam-sterilisation requirements should be assessed against POM-C service limits (90–110 °C continuous) — for sterilisation-compatible components, PEEK is the recommended alternative.
Designing a food-contact or regulated component in Delrin?Share your application details with Clarweand we will confirm grade suitability and certification documentation before production begins.
Delrin AF — PTFE-Filled for Ultra-Low Friction
Delrin AF incorporates PTFE fibres (typically 13–20% by weight) into the acetal homopolymer matrix, producing a variant with a lower coefficient of friction than standard Delrin — typically 0.10–0.20 against steel under dry sliding conditions, compared with 0.20–0.35 for standard grades. This grade is used in tribologically demanding applications where standard Delrin's friction level is insufficient and external lubrication is not feasible or desirable.
Common applications include high-load plain bearings, precision sliding guides, thrust washers, valve seats and sealing faces in medical, food processing and cleanroom equipment. Delrin AF has slightly lower tensile strength than Delrin 150 but maintains good dimensional stability and excellent wear life under sustained contact loads.
Standard colour:Brown (characteristic of PTFE dispersion)
Glass-Filled Delrin (30% GF) — Maximum Stiffness and Creep Resistance
Adding 30% glass fibre reinforcement to Delrin substantially increases flexural modulus and creep resistance — the tendency to deform slowly under sustained load — at the cost of reduced elongation at break and a more abrasive machining chip. This grade is the correct choice when a standard Delrin part would creep or deflect under elevated sustained loads, or when operating temperatures approach the upper service limits of standard grades.
Applications include high-load gear bodies, structural housings, fixturing components for repetitive production environments, and precision brackets operating at elevated temperatures. Glass fibres significantly increase tool wear compared with unfilled Delrin; tooling costs and replacement intervals should be factored into production planning.
Standard colour:Off-white
If you are not certain which Delrin grade fits your application — or if your project has regulatory requirements around food contact, medical certification or chemical compatibility — share the application details with Clarwe and we will confirm grade suitability before production begins.
Delrin Material Properties
| Property | POM-H (Delrin 150) | POM-C | Delrin AF | 30% GF Delrin |
|---|---|---|---|---|
| Density (g/cm³) | 1.42–1.43 | 1.41 | 1.41 | 1.54–1.56 |
| Tensile strength (MPa) | 60–70 | 60–70 | 53–56 | 80–95 |
| Yield strength (MPa) | 60–65 | 55–65 | 50–54 | 75–85 |
| Elongation at break (%) | 25–40 | 20–50 | 8–12 | 3–6 |
| Flexural modulus (MPa) | 2,600–2,800 | 2,400–2,600 | 2,200–2,500 | 6,000–8,000 |
| Hardness | Rockwell M94 / R120 | Shore D 80–82 | Rockwell R115–118 | Rockwell M87–94 |
| Melting point (°C) | 175–178 | 163–167 | 175–178 | 175–178 |
| Max continuous service temp. (°C) | 100–120 | 90–110 | 100–120 | 110–130 |
| Moisture absorption 24 hr (%) | < 0.25 | < 0.25 | < 0.25 | < 0.20 |
| CoF dry vs. steel | 0.20–0.35 | 0.20–0.35 | 0.10–0.20 | 0.25–0.40 |
| Thermal expansion (CTE) µm/m·°C | 110-130 | 110-130 | 100-120 | 40-60 |
Thermal expansion note:Delrin's CTE is approximately 5–7× higher than steel and 3–4× higher than aluminium. For assemblies where a Delrin component is constrained between metal features across a temperature range, calculate the differential expansion at the maximum and minimum service temperature and build in appropriate clearance or compliance. Ignoring CTE mismatch is the most common cause of stress cracking in Delrin parts operating in metal housings under thermal cycling.
Delrin vs. Other Engineering Plastics
Engineers frequently evaluate Delrin against nylon, UHMW, PTFE and acrylic for the same application. The table below summarises the key decision factors, followed by detailed guidance for each comparison.
| Delrin (POM-H) | Nylon (PA6/PA66) | UHMW-PE | PTFE | Acrylic (PMMA) | |
|---|---|---|---|---|---|
| Stiffness | High ✓ | Moderate | Low | Very low | Moderate |
| Moisture absorption | < 0.25% ✓ | 2–8% ✗ | < 0.01% ✓ | < 0.01% ✓ | 0.3% |
| Coefficient of friction | Low (0.20–0.35) | Moderate | Very low | Lowest | High |
| Fatigue resistance | Excellent ✓ | Good | Poor | Poor | Poor |
| Tight tolerance holding | Excellent ✓ | Poor in humidity ✗ | Poor | Poor | Moderate |
| Machinability | Excellent ✓ | Good | Good | Difficult | Moderate |
| Typical cost | $$ | $ | $ | $$$ | $ |
Delrin vs. Nylon (PA6 / PA66)
The critical differentiator is moisture absorption. Nylon absorbs 2–8% moisture by weight and can dimensionally grow 0.2–0.5% in humid or wet conditions, causing bore fits and gear mesh to shift out of specification. Delrin absorbs less than 0.25%, holding dimensional precision reliably in the same environments. Delrin also has a lower friction coefficient than most nylon grades in dry sliding contact.
Choose Delrin:Tight tolerances, humid environments, low friction sliding assemblies.
Choose Nylon:Cost-driven applications, impact absorption, where dimensional variation is acceptable.
Delrin vs. UHMW Polyethylene
UHMW-PE has outstanding abrasion resistance and impact toughness — better than Delrin in both — but its low stiffness and high creep mean it cannot be used for precision bores, gear teeth or close-tolerance fits. Delrin is far stiffer, holds tight tolerances across temperature variation and machines to much finer feature detail.
Choose Delrin:Stiffness, tight tolerances, precision machined features.
Choose UHMW:Abrasion liners, impact buffers, wear pads where precision is not required.
Delrin vs. PTFE (Teflon)
PTFE achieves the lowest friction coefficient of any engineering plastic and offers extraordinary chemical inertness. However, it is extremely soft, creeps significantly under modest loads and cannot hold tight tolerances without substantial bore allowances. Delrin provides comparable self-lubrication in most practical sliding applications while delivering far greater stiffness, strength and dimensional stability. For applications requiring both low friction and structural precision, Delrin AF offers a practical compromise.
Choose Delrin:Structural precision parts requiring low friction and dimensional stability.
Choose PTFE:Maximum chemical inertness, extreme low friction regardless of structural load.
Delrin vs. Acrylic (PMMA)
Acrylic offers optical clarity and UV resistance that Delrin cannot match, but it is brittle, has limited fatigue resistance and is significantly harder to machine to tight tolerances without cracking or chipping. Delrin is tougher, more dimensionally stable and far better suited to functional mechanical components.
Choose Delrin:Any functional mechanical component — gears, guides, brackets, wear parts.
Choose Acrylic:Optical clarity, light transmission, decorative covers and display housings.
CNC Machining Characteristics of Delrin
Delrin — particularly POM-H — is consistently rated as one of the easiest engineering plastics to machine on standard CNC milling and turning centres. Its crystalline structure produces short, brittle chips that evacuate cleanly from the cutting zone, placing low cutting forces on tooling and spindle. Sharp uncoated carbide or HSS tools with positive rake angles of 6°–10° deliver the best surface quality and longest tool life.
Recommended Machining Parameters
Parameters are indicative starting points and will vary with machine condition, fixturing, stock form and specific grade.
| Operation | Cutting speed | Feed rate | Depth of cut | Tool recommendation |
|---|---|---|---|---|
| CNC Milling — Roughing | 200–400 m/min | 0.10–0.25 mm/tooth | 2.0–5.0 mm | Sharp carbide or HSS, positive rake |
| CNC Milling — Finishing | 300–500 m/min | 0.05–0.10 mm/tooth | 0.3–0.8 mm | Uncoated carbide or PCD |
| CNC Turning — Roughing | 200–400 m/min | 0.15–0.30 mm/rev | 1.5–3.0 mm | Carbide insert, positive geometry |
| CNC Turning — Finishing | 300–500 m/min | 0.05–0.12 mm/rev | 0.3–0.8 mm | Uncoated carbide or PCD |
| Drilling | 100–250 m/min | 0.10–0.20 mm/rev | — | HSS or carbide, 118°–135° point |
| Tapping | — | As per thread pitch | — | Spiral-point or spiral-flute, lubricated |
Coolant and Chip Management
Delrin does not require flood coolant in the majority of milling and turning operations. Compressed air blast or light mist cooling is sufficient to manage cutting heat while clearing chips from the cutting zone. Flood coolant can be applied on critical finishing operations or deep-hole drilling but should be water-miscible and verified as compatible with the specific Delrin grade.
The real thermal risk in Delrin machining is insufficient chip load, not insufficient cooling. Rubbing rather than cutting generates localised heat at the tool-material interface, causing surface smearing, dimensional drift and poor surface finish. Maintaining correct feed rates and sharp tooling prevents this more effectively than coolant application alone. For deep pockets and through-holes, periodic tool retraction (pecking) aids chip evacuation and prevents chip packing that can damage bore walls.
Achievable Tolerances
Delrin's machinability and dimensional stability allow tight tolerances comparable to many metals in small and medium-sized parts. The ranges below represent achievable performance under controlled conditions with proper fixturing and temperature-controlled inspection.
| Dimension type | Standard tolerance | Tight tolerance |
|---|---|---|
| Linear dimensions | ±0.10 mm | ±0.02–0.05 mm |
| Bore diameter | ±0.05 mm | ±0.02 mm |
| Flatness | 0.10 mm / 100 mm | 0.05 mm / 100 mm |
| General unspecified | ISO 2768 medium | — |
For tight-tolerance bores and positional features, a two-stage machining approach — rough to within 0.3–0.5 mm, allow stress relief, then finish — is recommended to prevent dimensional drift caused by residual stress release in POM-H rod stock.
Design Guidelines for CNC-Machined Delrin Parts
Good Delrin part design is as important as good machining practice. The guidelines below help engineers avoid the most common DFM issues that cause dimensional non-conformance, stress cracking and unnecessary cost.
Minimum Wall Thickness and Feature Size
Delrin's high stiffness allows thinner walls than most soft plastics, but walls below 0.75 mm are susceptible to vibration during machining, which degrades surface quality and dimensional control. For functional structural walls in assemblies, 1.0–1.5 mm is the practical preferred minimum.
| Feature | Minimum recommended |
|---|---|
| Wall thickness | 0.75 mm (absolute) · 1.0–1.5 mm (preferred) |
| End mill diameter | 0.8 mm |
| Drill diameter | 0.5 mm |
Internal Radii, Fillets and Sharp Corners
Sharp internal corners are among the most common causes of premature fatigue failure in Delrin parts operating under cyclic or impact loading. The stress concentration at a sharp corner is significantly higher than at a filleted corner of even modest radius — in gears, snap fits and spring-loaded latches this can initiate cracking well before nominal design life is reached.
Specify the largest internal radius the design envelope allows. R0.5 mm is the absolute lower limit for any internal corner in a Delrin part; R1.0 mm or larger is recommended for load-bearing fillets. On external edges, chamfering rather than leaving sharp arrises reduces chipping during shipping and assembly handling.
Hole Depth-to-Diameter Ratios
Standard drilling in Delrin is reliably controlled up to approximately 10–12 times the drill diameter before specialised pecking cycles, step drilling or gun drills are needed. End mill plunge depth should not exceed 10 times the tool diameter for reliable chip evacuation and acceptable surface finish on pocket walls. Very deep narrow pockets should be flagged during DFM review — chip trapping in these features can damage bore walls and cause tool deflection or breakage.
Thread Design in Delrin Parts
Delrin machines threads cleanly with standard taps and thread mills. For best performance:
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Coarse threads(M3 and above) are preferred over fine threads — the larger pitch gives greater material cross-section at the thread root, improving pull-out strength.
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Thread engagement lengthshould be at least 1.5× the thread diameter to compensate for Delrin's lower tensile strength compared with metal bosses.
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Threaded inserts(Helicoil or brass press-fit) are recommended for frequently disassembled joints or high-torque fastener locations where the machined thread would wear over service life.
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Allow a small thread run-out clearance at the base of blind tapped holes to prevent tap breakage during production.
Pre-Machining Stress Relief for Tight-Tolerance Parts
Delrin rod and plate stock retains residual internal stress from extrusion. For parts requiring very tight tolerances — particularly those machined from the core of large-diameter POM-H rod — stress releases progressively during machining, causing dimensional drift between rough and finish operations.
Recommended practice:
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Rough-machine to within 0.3–0.5 mm of final dimensions.
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Allow the part to rest at ambient conditions for a minimum of 30–60 minutes (longer for large or complex parts).
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Finish-machine to final tolerance.
This two-stage approach is particularly important for parts with tight bore-to-bore positional tolerances or flat reference surfaces.
Clamping and Workholding
Delrin parts can deform under excessive clamping forces during machining. Thin plates and discs are particularly susceptible to bowing when over-clamped in vices or chucks. Use soft jaws, machinable fixtures or vacuum fixtures for thin workpieces and keep clamping forces to the minimum needed for secure stock holding. Measure parts after fixture release, not while clamped, for accurate dimensional validation.
Surface Finishes for CNC-Machined Delrin Parts
The as-machined condition is the most common and practical finish for Delrin parts. With correct tooling and process parameters, Delrin achieves clean, smooth surfaces directly off the machine suitable for most functional applications including gear flanks, sliding surfaces and sealing faces.
| Finish | Description | Typical Ra | Common use |
|---|---|---|---|
| As-machined | Direct from CNC mill or lathe, no secondary treatment | 0.8–3.2 µm | General functional parts, most Delrin components |
| Light sanding / deburring | Manual edge break and light abrasive pass | 0.8–1.6 µm | Removing sharp edges, improving tactile surfaces |
| Polishing | Fine abrasive or buffing for optical or sealing surfaces | 0.2–0.4 µm | Valve seats, sealing faces, optical windows |
| Bead blasting | Uniform matte texture via glass or ceramic media — removes tool marks; black stock lightens to dark grey | 1.6–3.2 µm | Cosmetic housings, panels, consumer-facing components |
| Laser marking | Permanent high-contrast surface mark (CO₂ laser); no material removal — available on request | N/A | Part identification, serial numbers, traceability markings |
| Anodizing / plating | Not applicable to Delrin | — | Delrin cannot be anodized or electroplated |
| Painting / coating | Generally not applied — adhesion to POM without pre-treatment is poor | — | Specialist adhesion primers required if needed |
Delrin Applications by Industry
Delrin's combination of low friction, dimensional stability, fatigue resistance and machinability makes it one of the most broadly applied engineering plastics for precision moving parts, wear components and lightweight structural elements.
| Industry | Typical CNC-Machined Parts | Recommended Grade |
|---|---|---|
| Automotive and Transportation | Fuel system valve components, door latch mechanisms, window regulator gears, seat adjustment components, steering and pedal bushings | POM-H (Delrin 150); POM-C where alkaline fluid contact is present |
| Industrial Machinery and Automation | Conveyor chain guides, wear strips, pneumatic valve components, linear guide carriages, pump impellers, cams and followers | Delrin 150 (standard); Delrin AF (high-load sliding); 30% GF (sustained high load or elevated temp.) |
| Medical Devices and Laboratory Equipment | Sample handling mechanisms, diagnostic instrument components, drug delivery device parts, laboratory fixture elements | POM-C for cleaning agent / moisture exposure; PEEK for autoclave-compatible applications |
| Consumer Products and Electronics | Snap-fit assemblies, gear trains, structural hinges, hand tool components, PCB guides, component handling fixtures | Delrin 150 (standard); POM-C ESD (electrostatic discharge environments) |
| Aerospace and Defence (Non-Structural) | Instrument panel mechanisms, cable management brackets, seat adjustment gears, ground support equipment fixtures | Delrin 150; AS9100D-controlled projects — confirm grade and certification with Clarwe |
Ready to machine Delrin parts for your application?Upload your design for a manufacturability review and quote.
Frequently Asked Questions
Is Delrin the same as acetal?
Delrin is DuPont’s trade name for acetal homopolymer (POM-H), while “acetal” is the broader material family that also includes acetal copolymer (POM-C) and specialty-filled grades. For CNC machining, Delrin usually refers specifically to POM-H when higher stiffness and strength are required.
What is the difference between Delrin and POM-C?
Delrin (POM-H) generally offers slightly higher stiffness and strength, while POM-C provides better resistance to hot water, steam and alkaline cleaning environments. POM-C is also preferred for larger cross-section parts because it does not show the centreline porosity that can occur in homopolymer rod stock.
Is Delrin a good material for gears, bushings and sliding parts?
Yes. Delrin is one of the best CNC-machined plastics for gears, bushings, bearings, valve components and sliding assemblies because it combines stiffness, fatigue resistance, low friction and good dimensional stability. For lower-friction, higher-wear sliding applications, Delrin AF is usually the better choice
What tolerances can be achieved when machining Delrin?
For most CNC-machined Delrin parts, standard tolerances around ±0.10 mm are practical, while tighter features can often be held in the ±0.02 to ±0.05 mm range under controlled conditions. Bore diameters can be machined to around ±0.02 mm when the part geometry, stock condition and inspection process support it.
Are machined threads reliable in Delrin parts?
Yes, for many applications Delrin machines threads cleanly and performs well, especially with coarse threads and adequate engagement length. For frequently assembled joints or high-torque fastening points, threaded inserts are usually the better long-term solution.
Get a Quote for CNC-Machined Delrin Parts
Upload your CAD file and Clarwe will review the geometry for manufacturability and provide pricing for CNC-machined Delrin parts in POM-H, POM-C, Delrin AF or 30% glass-filled Delrin.