If your design calls for a plastic that handles heat, chemicals, and electrical insulation without losing precision, PEI is the right material for your part. PEI (Ultem) CNC machining is a core part of what VMT does. We hold tight tolerances and keep parts dimensionally stable from prototype to full production.
For 16 years, VMT has produced precision plastic components for the electrical, fluid handling, chemical processing, and medical industries, sectors where PEI is often the only material that meets both thermal and insulation requirements. Our CNC machining of Ultem parts is always custom to your drawing, so feel free to send yours over. Below are some of the parts we’ve machined for our customers.
Multiple threaded ports machined into a single block, reducing assembly points for compact fluid or gas distribution systems.
Precision-milled pocket holds components securely in place, with clean edges and consistent depth across every unit produced.
Machined with a stepped inner bore for O-ring seating, delivering a tight, repeatable fit in rotating assemblies.
Outer keyway slots machined for precise alignment, holding tight tolerances across every unit in a production batch.
Spiral channel milled directly into the plate, machined to consistent depth for reliable thermal or routing performance.
Multiple bore diameters machined into a single body, holding tight tolerances across ports for reliable assembly fit.
Precision milled pocket and mounting holes machined to consistent depth, ready for direct assembly straight off the machine.
Multiple bore sizes and outer notches machined around a central hub, holding position accuracy across every rotation point.
Contoured inner profile machined to hold mating components securely, with clean edges and repeatable fit across the batch.
Moisture absorption is a material property you cannot machine away, but you can design and prepare around it. Here is how we handle it:
| Capability | Specification |
|---|---|
| Machining Process | CNC Milling / CNC Turning / 5-Axis Machining |
| Material Grades | Ultem 1000 (Natural/Black), Ultem 2300 (Glass-Filled), Ultem 1010 |
| Tolerance | ±0.005″ (with drawing) |
| Minimum Wall Thickness | 0.5mm |
| Maximum Part Size | 1200 × 500 × 150mm |
| Post Machining | Drilling & Tapping, Laser Marking, Ultrasonic Welding/Bonding |
| Lead Time | 7–14 business days |
| Color | Natural amber (translucent), Black |
| Surface Finish | As-machined (matte), Bead Blasting, Polishing |
| Minimum Order Quantity | No MOQ |
Choosing the right grade affects both machining behavior and how your part performs in the field. Below is a quick comparison to help with your ultem CNC parts machining project, whether you need general precision, added rigidity, or extra chemical resistance.
| Ultem 1000 (Unfilled) | Ultem 2300 (30% Glass-Filled) | Ultem 1010 | |
|---|---|---|---|
| Image |  |  |  |
| Tensile Strength | 16,500 psi | 17,000 psi | ~15,900 psi |
| Flexural Modulus | 500,000 psi | 850,000 psi | ~480,000 psi |
| HDT @ 264 psi | 204°C | 210°C | ~200°C |
| Flame Rating | UL94 V-0 | UL94 V-0 | UL94 V-0 |
| Best For | General precision parts and electrical insulators needing high dielectric strength | Structural brackets and housings needing extra rigidity under load | High-temperature parts needing extra chemical resistance or sterilization |
| Advantages | Best dielectric properties and easiest to machine cleanly | Higher strength and dimensional stability, low thermal expansion close to aluminum | Highest chemical resistance among PEI grades, autoclave-sterilizable |
| Trade-offs | Lower stiffness than glass-filled grades under sustained load | More abrasive on tooling and opaque in appearance | Slightly higher cost than standard Ultem 1000 |
Most PEI parts leave the machine with a clean, functional finish, but certain applications call for additional surface treatment. Our CNC machining PEI service supports the following options depending on your part’s function and appearance requirements:
A customer manufacturing internal components for switchgear equipment needed 300 insulating bushings machined from Ultem 1000, with a flanged design and a critical bore tolerance of ±0.005″. The bushings needed to hold their dimensions precisely to maintain proper insulation clearance once assembled, and any batch-to-batch variation risked misalignment during final assembly.
What We Did
Our CNC machining ULTEM process combined these steps to keep every bushing within tolerance across the full run.All 300 units passed final inspection with zero rework, and the customer confirmed consistent fit across the full batch during assembly.
Every PEI part is different, and small design choices can affect both machinability and cost. A few general starting points:
These are general guidelines, but every project has its own geometry, tolerances, and application requirements. Send us your drawing, and our custom ULTEM CNC machining service includes a DFM review specific to your part, not a generic checklist.
Our custom ULTEM CNC machining service factory is backed by a rigorous inspection workflow and internationally recognized certifications, so every part that leaves our facility is documented and verified.
PEI’s sensitivity to moisture and heat means standard inspection alone isn’t enough to catch dimensional issues before they reach you. Our quality process is built specifically around these risks:
Our PEI CNC machining operations are backed by internationally recognized certifications and material-specific compliance documentation:
Is PEI a good insulator for electrical applications?
Yes, PEI has one of the highest dielectric strengths among commercial thermoplastics, making it a common choice for connector housings, insulating bushings, and other electrical components where ultem cnc machining is used to hold tight tolerances around conductive parts.
Can PEI withstand repeated steam sterilization?
Yes, PEI holds up well under repeated autoclave cycles without significant loss of strength, which is why it’s often chosen for reusable medical device components that need to survive sterilization over their service life.
What’s the natural color of PEI, and can it be dyed other colors?
PEI’s natural color is amber and translucent. Glass-filled grades like Ultem 2300 are opaque. Custom colors are possible in some cases, but PEI isn’t typically available in a wide color range compared to standard plastics like ABS or nylon.
Can PEI parts be drilled and tapped for assembly?
Yes, drilling and tapping are common post-machining steps for PEI parts used in assemblies. Our pei cnc machining process accounts for PEI’s brittleness around thread features, helping to avoid cracking at the tapped hole during assembly.
What are the downsides of using PEI compared to other engineering plastics?
PEI costs more than standard plastics, has limited color options, and is more brittle than tougher materials like nylon, meaning it’s less forgiving under sudden impact. It’s also more sensitive to moisture during machining, which requires extra process control on our end.
Why is PEI more expensive than materials like nylon or ABS?
PEI is a high-performance resin with a more complex manufacturing process than commodity plastics, and it requires tighter process control during ultem cnc machining to avoid warping or moisture-related defects, both of which add to material and processing cost.
Upon receiving your 3D CAD file, our dedicated customer service engineer will thoroughly review your design for manufacturability, ensuring it meets your precise specifications and budget requirements. Contact us today for a free quote!
