Introduction
Plastic CNC parts show up everywhere in automation: gripper inserts, locating jigs, soft contact pads, and custom fixture spacers. But most designers pick ABS or Delrin blindly without knowing the actual tradeoffs. I’ve seen soft ABS jigs deform under light load and expensive Delrin parts wasted on low-stress static applications. Let’s break down exactly when to use each plastic.
ABS Plastic: Pros & Cons for Tooling
ABS is cheap, easy to machine, and rigid enough for basic static fixtures. It machines cleanly with minimal tool buildup and holds simple dimensions well. The downside is poor wear resistance and low heat tolerance. ABS deforms under sustained clamping load and wears quickly in sliding contact. It’s best for non-critical, low-cycle plastic components.
POM / Delrin Properties
POM, commonly sold as Delrin, is the go-to engineering plastic for functional automation tooling. It has excellent stiffness, low friction, great wear resistance, and superior dimensional stability compared to ABS. It resists creep under sustained load and works perfectly for moving, sliding, contacting parts. The only downsides are higher material cost and slightly trickier machining.
Machinability Differences
ABS is extremely forgiving during machining. It cuts fast, leaves smooth surfaces, and rarely melts or gums up. Delrin requires slightly more careful speed control; excessive heat can melt surface edges. However, Delrin holds tighter tolerances and maintains precision better after machining, especially on thin features.
Wear & Friction Performance
This is the biggest gap between the two materials. ABS has high friction and poor wear resistance. It scratches easily and wears fast in dynamic contact. Delrin is self-lubricating, slides smoothly against metal and other plastics, and maintains surface quality through thousands of cycles.
Dimensional Stability & Creep
ABS creeps noticeably under constant load. A clamped ABS jig will shift dimensionally over weeks of continuous pressure. Delrin resists creep extremely well, keeping fixture alignment consistent long-term. For precision locating tooling, Delrin is always the safer choice.
Cost Comparison
ABS stock is significantly cheaper than Delrin/POM stock. For simple, static, low-wear plastic covers and spacer plates, ABS saves budget. For functional wear parts and precision jigs, Delrin’s performance justifies the small price increase.
When to Use ABS
Static fixture covers, non-wear spacer plates, low-budget prototype tooling, cosmetic plastic components, and parts with zero dynamic contact or clamping load.
When to Use POM/Delrin
Gripper contact pads, sliding plastic guides, precision locating jigs, repeated-cycle tooling, clamped fixture components, and any plastic part that requires long-term dimensional stability.
Frequently Asked Questions
Is Delrin better than ABS for robotic gripper pads?
Yes. Delrin offers better grip stability, lower wear and no creep under sustained clamping force.
Does ABS deform over time in fixture applications?
Yes. ABS creeps under constant load, causing gradual alignment shift in clamped fixtures.
Is Delrin worth the extra cost for plastic tooling?
For functional moving/wear parts absolutely. For static cosmetic parts, ABS is sufficient.
Which plastic holds tighter CNC tolerances?
Delrin/POM is far more dimensionally stable and reliable for tight tolerance precision parts.
Can Delrin slide directly against aluminum?
Yes, it has excellent dry-sliding properties and will not gall or damage mating metal surfaces.