14Lecture-G-Code-drill - ENGR3190U Manufacturing and...

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ENGR3190U: Manufacturing and Production Processes Lecture 14 G-codes – Drilling There are various drilling related operations that can be performed on the CNC mill: G81 – Spot or chamfer drilling cycle, (also called basic drill cycle). Use for drilling not too thick stock. G73 – Chip break cycle (also called fast peck drill cycle). Used for drilling deep holes, breaks chip G83 – Deep hole drilling cycle. Used for drilling deep holes, rapids out to “R” value. This course will only cover G81. To drill a hole in a part, you have to (a) use a centre drill tool to pre-drill and mark the hole (b) change tool to drill bit and drill the hole 1. Feeds F and Speeds S For Drilling Spindle Speed S How to calculate rotational or spindle speed S used in G-code program? Eg. N90 G00 G54 G90 X3.0 Y5.0 S1800 M03 Similar to milling (simplified RPM version): N = 4* Cutting Speed values in table/Diameter of tool N or RPM = rotational speed or spindle speed, rev/min D = diameter of tool (mm, in) Set S = N in your G-code program From formula → Fatter drill slower RPM because tool will generate too much heat if RPM too fast Feed rate F How to calculate feed rate F used in G-code program? eg. N120 G01 Z-.10 F3.0 Feed rate for “drill like” operations (eg., drill, reaming, countersink), From Chapter 22 in book for drilling: f r = Nf f r = feed rate,( mm/min, inch/min) f = feed (mm/rev, in/rev) – also called feed per rev – see chart Set F = f r in your G-code program 1
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Table of feed per rev values Drill size (inch)
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14Lecture-G-Code-drill - ENGR3190U Manufacturing and...

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