Chemical Accelerator Mass Finishing
Can you recommend a vibratory or mass finishing process for smoothing grinding lines on hardened steel gears?
Q. We manufacture hardened steel gears of all types and sizes. We have a vibratory machine, but it’s been ineffective in smoothing our grinding lines. Can you recommend a vibratory or mass finishing process?– H.P.
A. We recommend a chemical accelerator process in your vibratory machine. The machine must have a precise flow-through soap compound system, and coated or stainless drains. Chemical accelerator finishing processes can be accomplished in vibratory, high-energy centrifugal disc, spindle and drag finishing systems. The process produces super surface refinement (in the 2-to-4-Ra finish range) and keeps edge radiusing to a minimum.
Chemical accelerators (oxalic acid, phosphates or citric acids) are metered into and carried by a cutting or non-cutting, high-density (110 to 140 lbs per cu ft), preformed media. The accelerator chemical continuously oxidizes the surface of iron-based and some non-ferrous metal alloys, enabling the high-density ceramic media to remove metals at much higher rates. The accelerator system cuts, refines, and brightens surfaces within the same machine and media.
The vibratory chemical accelerator system has a low initial equipment cost for the amount of material it’s capable of removing . A key component to all chemical accelerator systems is an accurate compound delivery system. This system uses two compound pumps and flow meters to deliver the refinement accelerator chemical, and then a burnishing compound for brightening, if required.
Applications for chemical accelerator systems include refinement and decorative finishes on hand tools, surgical instruments, medical implants, gun parts, knives, pre-plate finishing, air foils, stator rings, gears and bearings.
In particular, the gear industry (within the aerospace, automotive, wind-steam-and-gas turbine industries) has found that accelerator processes improve gear life as much as three times. The process will:
- Reduce gear friction, running temperatures and wear
- Reduce gear noise and vibration
- Increase oil retention
- Remove manufacturing process lines produced by cutting, grinding, hobbing or honing
- Eliminate manufacturing corrosion superior to bead blasting
- Increase fuel economy
- Obtain 2 to 4 Ra finishes in the root fillet areas
- Increase load capacity of gear lubricant.
Chemical accelerator mass finishing is an excellent process for your gear finishing.
Surface finish types for commercially supplied stainless steel sheet are detailed in various standards. ASTM A480-12 and EN10088-2 are two; BS 1449-2 (1983) is still available, although no longer active. These standards are very similar in that they define eight grades of surface finish for stainless steel. Grade 7 is “buff polished,” while the highest polish—the so-called mirror polish—is designated Grade 8
An unclear definition has led to an industry standard for classifying burrs.
Consider these five variables to determine what fits your application.