XY Pusher Bar Assembly in Black Delrin, CNC Milled with Press-Fit Dowel Pins

About This Part

This pusher bar is the contact element of an XY handling stage for optical module and photonic device test automation. The bar slides against and positions delicate parts all day, so the material choice is the design: Delrin (POM) is self-lubricating and low friction, it will not scratch aluminum or plated surfaces, and it does not shed the fine debris that softer plastics can. The matte black finish keeps reflectivity down around optical test stations. All of this comes from drawing-specified material, not substitution: the bar is milled from black Delrin rod stock, nothing plated or coated after the fact.

The bar is 34 mm long overall (reference dimension), with a rectangular section that carries two pressed-in dowel pins and two 3.5 mm counterbores for mounting screws. The pins are 1.5 mm diameter by 6 mm long, 18-8 stainless steel (passivated), pressed into reamed holes with a specified minimum axial push-out force of 5 N. That number is not cosmetic: a pin that walks under push loads shifts the location the whole assembly depends on, so retention is verified with a push-out force test rather than assumed from the press fit. Hole position is held to 0.05 against datums A and B, and every edge is broken at 0.3 x 45 degree as drawn.

The route is short and controlled: CNC milling of the outline, slot and counterbores from Delrin rod, pin insertion with force verification, laser marking for revision traceability, then deburring, cleaning and packaging. Plastic machining is its own discipline. Delrin mills cleanly but likes sharp tools and light cuts; dwell or dull edges leave melted smears instead of chips, so tools are changed on a schedule rather than on failure.

Delrin stock is the supply chain story here too. Rod is available in consistent grades, which matters when a pusher family runs year after year: the replacement bar mills the same as the first one. The assembly ships RoHS compliant per 2011/65/EU, with the passivated stainless pins and the unfilled black POM body both inside the scope.

Inspection covers the three things that decide whether the pusher works in its stage: caliper and micrometer checks on the key dimensions, the pin push-out force test at 5 N minimum, and a visual and cleanliness check that includes confirming the laser mark. Dimensional reports are available on request, and replacement bars are matched to the first article so mixed batches stay interchangeable.