CNC Engraving Machines

Background

The United States Mint utilizes specialized CNC milling machines (engraving type with high speed air driven spindles) to cut master tooling for coin and medallion production. Currently, the Mint has six (6) high speed CNC milling machines in Philadelphia running approximately 24 hours a day cutting master tooling. The current machining processes produce master tooling with very high quality surface finishes coupled with very accurate and delicate details using finish cutters ranging between 0.006 - 0.012 diameters. Finish cutters are taper ball end mills which were specifically developed for this application & implemented after 5 years of research & testing. Roughing & semi-finishing cutters range between 0.375 - 0.015 diameter depending on the design complexity. Collected tool holders are used for all roughing & semi-finishing operations. Due to the high quality finishing required, heat shrink tool holders are used for all finishing operations. All master tooling is milled in a soft state in both L-6 & A-2 steel. Hard milling is not employed due to excessive cutter wear issues with these micro-ball and mills. Current finish programs can be close to 1,000,000 lines of code.

Requirement

The United States Mint is considering setting up similar CNC milling operations to cut master tooling in the Denver Mint. Should the United States Mint decide to move forward with this effort, the Contractor shall provide all services, resources, and equipment required to design, build, install, and develop machining processes to produce high quality master tooling in accordance with the United States Mint's requirements. The United States Mint uses a proprietary suite of digital design software to produce all 3D coin designs. WorkNC is used for all subsequent CNC cutter path development. The specific cutters used to mill the master tooling in Philadelphia are developed by two different manufacturers: Jabro & Union Tool. These cutters have stood up to the rigors of high speed milling for many hours (fifteen or more) per part over thousands of projects since 2005. The development time spent in Philadelphia to finalize the 3D designs and tool path parameters will produce the digital files (tool paths) that will be shared and utilized in Denver. This sharing of information eliminates duplicate effort and guarantees the same master tooling is produced in both Philadelphia and Denver. To eliminate months or years of tool and fixture development and continuous yearly duplication of efforts the Contractor will need to utilize the same cutting tools and tool paths currently utilized in the production of master tooling in Philadelphia. We understand that a different format file (control based) will be necessary.

The United States Mint is requesting information from sources that may be capable of meeting or exceeding the existing CNC milling (engraving) systems. In order to eliminate any variations in the quality of master tooling for our coin products, the new CNC milling equipment shall be capable of replicating the quality of our current master tool cutting operations in Philadelphia. It is extremely important that the quality & finish of the master tooling produced in Denver matches that of the quality & finish produced in Philadelphia.