2Surface grinding is used to produce flat accurate surfaces and can be carried out on all materials, hard or soft.There may be no other way of removing metal from a hardened work piece.It is normally considered a finishing operation, but large machines are usedin place of milling and shaping machines to remove large amounts of material.
3The main elements of a typical surface-grinding machine The column, guided on a dovetail slide, carries the wheelhead at its top end and containsthe motor and belt drive to the wheel spindle.The wheelhead carries the wheel spindle, which is mounted in precision bearings.The saddle is fitted on top of the base in the two sideways and provides the cross traversemovement. The cross traverse can be applied automatically in continuous or incremental feed by hydraulic power or, alternatively, with a manually operated hand wheel.The base is a heavily ribbed box-section casting to ensure rigidity and complete freedom from vibration.
12Milling ProcessesMilling is one of the basic machining processes. Milling is a very versatile process capable of producing simple two dimensional flat shapes to complex three dimensional interlaced surface configurations.
13The Process The milling process: Typically uses a multi-tooth cutter Work is fed into the rotating cutterCapable of high MRRWell suited for mass production applicationsCutting tools for this process are called milling cutters
14ClassificationsMilling operations are classified into two major categories:Peripheral (side)Generally in a plane parallel to the axis of the cutterCross section of the milled surface corresponds to the contour of the cutterFaceGenerally at right angles to the axis of rotation of the cutterMilled surface is flat and has no relationship to the contour of the cutterCombined cutting action of the side and face of the milling cutter
15Related OperationsSide milling - machining a plane surface perpendicular to the milling machine arbor with an arbor mounted tool. This tool is called a side mill.Straddle milling - milling two parallel surfaces using two cutters spaced apart on an arbor.Gang milling - milling multiple surface simultaneously using multiple cutters mounted on an arbor.Thread milling - milling treads using the capability of a three axis contouring CNC machine.
16Operating Parameters Rpm Feed rate CS converted into Rpm based on cutter diameterFeed rateFeed per toothTable feed rate
17Operating Parameters Feed direction -- Conventional vs. Climb Conventional millingMost common method of feedFeed work against the rotation of the cutter
18Operating Parameters Feed direction - Conventional vs. Climb Climb millingLoad of the cutter tends to “pull” the work into the cutterThis results in a small feed force and about 20% less Hp than conventional millingDownward motion increases the load on the table waysThis method can “pull” the work into the cutter and scrap the work and/or damage the fixture and tool.Machine must be very ridged to safely utilize climb milling(CNC machines)USE CAUTION!
19Operating ParametersConventional vs. Climb Milling
21Milling machines Two Major Classifications - Knee & Column and Bed Knee & Column (Bridgeport type)Basic job shop type millColumn mounted to the base which is the major support frame.Construction provides controlled motion of the worktable in three mutual perpendicular directions.Knee moves vertically on the ways in the front of the machineTable moves longitudinally on the ways on the saddleSaddle moves transversely on the ways on the kneeQuill moves parallel in Z axis or, if head is rotated, X axisVersatile general purpose machine
22Milling Machines Bed Used extensively in production milling operations Rigid construction capable of heavy cutsTable is mounted directly to the bedSpindle head moves vertically to set depth of cutHead locks into position for cutBase of machine functions as a coolant reservoir