SetBlock Design Issues August 12 th 2008 Frederickson

Set-Block Design Issues August 12 th, 2008

Frederickson Skin and Spar MBU Background § Set blocks are used to verify the distance between the bed of the machine and the cutter is 2. 100”. § Skin Mills have dual spindles, which need to be set as close as possible to eliminate miss-match between cutters. § Even though cutters are set on presetters accurately to +/-. 0002, changes in temperature and the machine cause slight variation. § For many years the cutter height on the Skin Mills was set using a 2. 100 cube with brass surface on the edge that contacts the cutting tools. This was replaced around 2003 with the current 2. 100 dial indicator block designed in the mid 70’s for other Boeing areas.

Frederickson Skin and Spar MBU STP § Situation- Current plunger design binds when side loads are applied from tapered cutters, causing the cutting edge to chip. The dial is small and difficult to read under the low light conditions where it is used. Reaching under the vacuum shroud and trying to see the small dial in the shadows makes it difficult to get accurate readings. Several vendors offer solutions, but none have met our needs. § Target-2. 100 tall block that can be set to master and gauge and repeatably measure to within +/-. 0002 of gauge. Features would include digital gauge that can be zeroed in master, back light, lever to depress plunger, linear bearing plunger guide. § Proposal-Work with University of Idaho to develop this device as a Senior Design Project for the Mechanical Engineering Department.

Frederickson Skin and Spar MBU Current Boeing Designed Setpoint Block (ST 8738 C-4 SG gauge ST 8738 C-3 MG setup block, Federal 2 X-344501 dial indicator) 2”cube Zero indicator to 2. 100 certified gauge

Frederickson Skin and Spar MBU Typical Skin Mill Machine and Use 2. 1000 Cutter Set. Point Cutter height set to 2. 100 above bed of machine. Small dial and shadows makes it difficult to accurately set cutter to +/-. 0002. Plunger binds when slid under cutter and give inaccurate readings, or possibly chip the carbide cutter. Additional travel will eliminate the majority of accidental over travel destruction of gauge.

Frederickson Skin and Spar MBU Skin Mill Mis-Match § If cutters are not accurately set, the areas must be sanded to remove the variation

Frederickson Skin and Spar MBU Spar Mill Use § Cutter height is checked off from top of spar to verify 2. 100 dimension § Gauge is used by several areas throughout Boeing

Frederickson Skin and Spar MBU Gauges Already Tested Digital Prototype Not accurate over range of travel, and not enough travel Separate Transducer Plunger motion smooth, very accurate, but not enough travel, handle gets in way of measurement Metric Dial Plunger motion not smooth, not enough travel

Frederickson Skin and Spar MBU Gauges Already Tested Dial Smooth motion, not enough travel, to tall Dial Plunger motion rough, inaccurate, not enough travel, difficult to read Metric Dial 4” tall, not enough travel Dial Plunger motion smooth, very accurate, but not enough travel, 4” tall

Frederickson Skin and Spar MBU Revised Boeing Designed Set Block 2”cube Plunger does not have smooth movement, indicator has. 020 backlash which causes gauge to be inaccurate. Overall size and weight larger than original.

Frederickson Skin and Spar MBU Plunger slides in green pushing and is attached to blue ring. Red finger from indicator follows ring movement. The problem is that even if there is not any gap between the ball on the end of the finger and the blue ring, the finger has about. 020 backlash from upward to downward travel. 2”cube

Frederickson Skin and Spar MBU Design Preference § Digital indicator with. 500 travel. 1. 750 -2. 250 § Easy to read LCD with back light § Smooth travel on plunger, prefer linear bearings § Gauge can be zeroed or set to true height of set gauge (2. 100) § Resolution. 0001, repeatable to +/-. 0002 when inserted in set gauge § Overall accuracy +/-. 0005 § Replaceable plunger § Lever to depress plunger instead of dragging measuring surface across cutting edges

Frederickson Skin and Spar MBU Proposed Modifications § Replace analog gauge with digital gauge, preferably with analog bars similar to Mitutoyo 543 -266 B § Resolution. 0001, accuracy needs to be. 0002 § Preference would be to have replaceable plunger in case accidental machine over travel occurs. § Plunger needs to be very minimal resistance even with side loads produced from pushing under cutter. Suggest Thompson Precision Ball Bushing Bearings

Frederickson Skin and Spar MBU Proposed Plunger Support § Thompson Linear Bearings http: //www. danahermotion. com/products/product_detail. php? parent_id=245 Mar. Motion Rotary stroke bearing