Milling Depth Research Articles

Peat Compressibility: a Parameter for Automatic Depth Control of Milling Machines

The primary object of the peat milling operation is to mill a layer of peat on the surface of the bog such that all of this layer (throughout the bog) dries to the required moisture content in the same time interval, so that it can all be harvested simultaneously. Peat type (and hence drying characteristics) vary considerably throughout a given bog, hence the depth of this milled layer should at any given location in the bog match the drying characteristics of the peat at this location. In order to do this, it is necessary to determine some measurable characteristic of peat, representative of the drying time, so this can be used to determine the milling depth. Field and laboratory experiments revealed that compressibility of milled peat is a good depth control characteristic because of its high correlation with the relative drying time of milled peat. For example a typical high density peat (compressibility of 12%) has a milling depth requirement of 21 mm compared with 9 mm for a low density peat (compressibility of 25%). Results indicate that the application of this method within the peat industry would give a 27% increase in dry matter yields per hectare and the variation of the moisture content of the harvested milled peat would be reduced from a standard deviation of 0·55 kg/kg to one of 0·22 kg/kg.

ＬＳＩのオンチップ配線修正システムにおける集束イオンビーム加工技術の開発

During debugging logic LSIs, a period to reproduce LSI in order to change the logic design is becoming longer. To reduce the period from several weeks down to one day, an on-chip direct wiring modification system, using the focused ion beam (FIB) milling and the laser CVD, has been developed.This paper describes a precise FIB milling technique for cutting the wirings and making the via holes to the wirings of the LSI. Milling depth control by monitoring the ion induced photo-emissions and the milling strategy to overcome the surface steps of the LSI resulted in the milling depth accuracy of ±0.25μm. The system, consist of the FIB milling described in this paper and the laser CVD, has been applied to the logic modification of the LSIs of Hitachi M880 mainframe computer. Several tens of cuts, vias on an LSI chip were made by FIB, and the several jumper wirings were made by laser CVD. The average yield of modified LSI chips of 91.8% was achieved.

Two‐Dimensional Profile Simulation of Focused Ion‐Beam Milling of LSI

Focused ion‐beam milling has recently been used for modifying and debugging LSIs, where precise depth control is required. In order to analyze the effects of scanning width and redeposition on hole depth, we have developed a two‐dimensional milling profile simulator, which takes redeposition into consideration. The results of the simulation are in good agreement with our experiments. It has been demonstrated that when the beam scanning width is less than the beam tail diameter, the milling depth declines due to dose deficiency. When the aspect ratio (depth/width) is high, the depth is less than proportional to the dose due to redeposition.

Determination of Propeller-Ice Milling Loads

In designing ice transiting ships, a major concern is the design of the propeller to provide adequate strength to resist ice loads due to propeller ice milling while still providing good propeller efficiency for open water observations as well as high icebreaking thrust at slow advance speeds. As a result, propeller design is a compromise between strength and efficiency. This is especially true for ice transiting ships that must transit long distances on ice-free routes and then perform difficult ice-breaking operations. The geometric properties of a propeller blade that provide good strength are blade width and thickness. Unfortunately, increasing these properties does not provide the best efficiency. Propeller design for ice transiting ships in general has tended to favor strength and reliability over efficiency in design compromises. The purpose of this paper is to outline a methodology for determining propeller ice milling loads as a function of propeller characteristics, propeller speed, ship speed, ice conditions and depth of ice milling to help in the propeller design process.