( This link will provide you with a list of all ISO-6983 G-Codes

Transcription

1 CUSTOM HAZARDS

2 CUSTOM HAZARDS

3 CUSTOM HAZARDS

4 In this lesson I am going to explain how to circle interpolate a 1/8-27 NPT with a formed thread E-Mill using G-Code on a vertical mill. I have provided the Standard American Pipe Thread specs on the last remaining pages. Also there is a link providing you with access to a standard drill & tap chart as well. I am going to cover the circle interpolation of the taper, the thread E-Mill process along with the trigonometry involved with circle interpolating an NPT thread. If at any time you have any questions pertaining to this lesson or anything involving programming, machining, manufacturing design I can be reached at this address CustomHazards@yahoo.com Items required for this project are as followed; 6061 Aluminum scrap piece (round or squared) Center drill The letter Q drill - ( diameter E-Mill - ( 45 chamfer E-Mill 1/8-27 NPT plug gauge Scientific calculator Machinist Handbook Pen and paper Let us begin... ( This link will provide you with a list of all ISO-6983 G-Codes TPI = Threads per Inch P = Pitch / Quad = Quadrant of a Circle We will start as if the hole is drilled (letter Q) and the 45 chamfer has been cut as well. X 0.00, Y 0.00 will be the center of the part and Z 0.00 will be the top face of the part. When we use a E-Mill to interpolate a I.D. Taper we must calculate the change in X at each Quadrant (there are 4 Quadrants in a circle 90 degrees apart) of the circle as we cut down from Z 0.00 to our finish depth.400) sweeping across a helix. We will use a Z pitch of.025 using this number (.025) we can calculate the distance the E-Mill must move in X as we travel.025 per revolution in Z. The formula to calculate the X distance is tang x.025 the calculation equals a move of.0007 in X per revolution. With this information we can now program our I.D. Taper. When cutting this taper we will cut using line center and will not use the G41 code (line left of). Knowing that a circle contains 4 quadrants and that we will be programming from quadrant to quadrant we can take our pitch, X distance and divide these by 4. Let's take the information we have calculated and organize it. Drilled Hole = Q (.332 diameter)

5 Finished Z Depth =.400 P in Z =.025/4 =.0063 X per Quad =.0007/4 =.0001 As we move from the first quad to the 2nd quad we will have made a ccw motion in X of.0001 while moving in Z.0063 simultaneously. Here is the G-Code program for interpolating the taper. With the numbers we are using this program will be rather long. You can always run your Z pitch at.05,.100 etc. I chose.025 because you will be forced to repeat the fundamentals over and over again. There are faster, more efficient ways of cutting this process, but this approach is for learning purposes. G00 X 0.00 Y 0.00 Z 3.00 S8000 M3 G00 Z 0.00 M8 G01 X F.005 G17 G3 X0.00 Y Z R.0534 G17 G3 X.0533 Y0.00 Z R.0533 G17 G3 X0.00 Y.0532 Z R.0532 G17 G3 X Y0.00 Z R.0531 G17 G3 X0.00 Y-.053 Z R.0530 G17 G3 X.0529 Y0.00 Z R.0529 G17 G3 X0.00 Y.0528 Z R.0528 G17 G3 X Y0.00 Z R.0527 G17 G3 X0.00 Y Z R.0526 G17 G3 X.0525 Y0.00 Z-.063 R.0525 G17 G3 X0.00 Y.0524 Z R.0524 G17 G3 X Y0.00 Z R.0523 G17 G3 X0.00 Y Z R.0522 G17 G3 X.0521 Y0.00 Z R.0521 G17 G3 X0.00 Y.0520 Z R.0520 G17 G3 X Y0.00 Z R.0519 G17 G3 X0.00 Y Z R.0518 G17 G3 X.0517 Y0.00 Z R.0517 G17 G3 X0.00 Y.0516 Z R.0516 G17 G3 X Y0.00 Z-.126 R.0515 G17 G3 X0.00 Y Z R.0514 G17 G3 X.0513 Y0.00 Z R.0513 G17 G3 X0.00 Y.0512 Z R.0512 G17 G3 X Y0.00 Z R.0511 G17 G3 X0.00 Y Z R.0510 G17 G3 X.0509 Y0.00 Z R.0509 G17 G3 X0.00 Y.0508 Z R.0508

6 G17 G3 X Y0.00 Z R.0507 G17 G3 X0.00 Y Z R.0506 G17 G3 X.0505 Y0.00 Z-.189 R.0505 G17 G3 X0.00 Y.0504 Z R.0504 G17 G3 X-.053 Y0.00 Z R.0503 G17 G3 X0.00 Y Z R.0502 G17 G3 X.0501 Y0.00 Z R.0501 G17 G3 X0.00 Y.0500 Z R.0500 G17 G3 X Y0.00 Z R.0499 G17 G3 X0.00 Y Z R.0498 G17 G3 X.0497 Y0.00 Z R.0497 G17 G3 X0.00 Y.0496 Z R.0496 G17 G3 X Y0.00 Z-.252 R.0495 G17 G3 X0.00 Y Z R.0494 G17 G3 X.0493 Y0.00 Z R.0493 G17 G3 X0.00 Y.0492 Z R.0492 G17 G3 X Y0.00 Z R.0491 G17 G3 X0.00 Y Z R.0490 G17 G3 X.0489 Y0.00 Z R.0489 G17 G3 X0.00 Y.0487 Z R.0487 G17 G3 X Y0.00 Z R.0486 G17 G3 X0.00 Y Z R.0485 G17 G3 X.0484 Y0.00 Z-.315 R.0484 G17 G3 X0.00 Y.0483 Z R.0483 G17 G3 X Y0.00 Z R.0482 G17 G3 X0.00 Y Z R.0481 G17 G3 X.0480 Y0.00 Z R.0480 G17 G3 X0.00 Y.0479 Z R.0479 G17 G3 X Y0.00 Z R.0478 G17 G3 X0.00 Y Z R.0476 G17 G3 X.0475 Y0.00 Z R.0475 G17 G3 X0.00 Y.0474 Z R.0474 G17 G3 X Y0.00 Z-.378 R.0473 G17 G3 X0.00 Y Z R.0472 G17 G3 X.0471 Y0.00 Z R.0471 G17 G3 X0.00 Y.0470 Z R.0470 G17 G3 X Y0.00 Z R.0469 G00 X0.00 G00 Z 3.00 M9

7 Now we will move on to the threading process. We will use the same formulas we used to interpolate the taper except for the distance needed to move in X. We are using a formed tool and do not need to sweep the tool on a tapered helix. TPI = 27 P = 1/27 =.037/ 4 =.0092 Here is the G-Code program for the formed threading tool. G00 X0.00 Y0.00 Z0.00 S8000 M3 G00 Z-.400 F.003 M8 G01 X-.08 G17 G3 X0.00 Y-.08 Z R.08 G17 G3 X.08 Y0.00 Z R.08 G17 G3 X0.00 Y.08 Z R.08 G17 G3 X-.08 Y0.00 Z R.08 G17 G3 X0.00 Y-.08 Z R.08 G00 Y0.00 G00 Z 3.00 M9 This completes the lesson. I hope the people who read this find it helpful. The processes described above can be used for more than just threading. The fundamentals can be carried through to 3d profiling and many other processes. Understanding this simple process is just a small part of a sound machining foundation and will benefit you in your trade down the road. Trey Haney

8 Machinery's Handbook 28th Edition AMERICAN PIPE THREADS 1861 PIPE AND HOSE THREADS The types of threads used on pipe and pipe fittings may be classed according to their intended use: 1) threads that when assembled with a sealer will produce a pressure-tight joint; 2) threads that when assembled without a sealer will produce a pressure-tight joint; 3) threads that provide free- and loose-fitting mechanical joints without pressure tightness; and 4) threads that produce rigid mechanical joints without pressure tightness. American National Standard Pipe Threads American National Standard pipe threads described in the following paragraphs provide taper and straight pipe threads for use in various combinations and with certain modifications to meet these specific needs. Thread Designation and Notation. American National Standard Pipe Threads are designated by specifying in sequence the nominal size, number of threads per inch, and the symbols for the thread series and form, as: NPT. The symbol designations are as follows: NPT American National Standard Taper Pipe Thread; NPTR American National Standard Taper Pipe Thread for Railing Joints; NPSC American National Standard Straight Pipe Thread for Couplings; NPSM American National Standard Straight Pipe Thread for Free-fitting Mechanical Joints; NPSL American National Standard Straight Pipe Thread for Loose-fitting Mechanical Joints with Locknuts; and NPSH American National Standard Straight Pipe Thread for Hose Couplings. American National Standard Taper Pipe Threads. The basic dimensions of the ANSI Standard taper pipe thread are given in Table 1a. Form of Thread: The angle between the sides of the thread is 60 degrees when measured in an axial plane, and the line bisecting this angle is perpendicular to the axis. The depth of the truncated thread is based on factors entering into the manufacture of cutting tools and the making of tight joints and is given by the formulas in Table 1a or the data in Table 2 obtained from these formulas. Although the standard shows flat surfaces at the crest and root of the thread, some rounding may occur in commercial practice, and it is intended that the pipe threads of product shall be acceptable when crest and root of the tools or chasers lie within the limits shown in Table 2. Pitch Diameter Formulas: In the following formulas, which apply to the ANSI Standard taper pipe thread, E 0 = pitch diameter at end of pipe; E 1 = pitch diameter at the large end of the internal thread and at the gaging notch; D = outside diameter of pipe; L 1 = length of hand-tight or normal engagement between external and internal threads; L 2 = basic length of effective external taper thread; and p = pitch = 1 number of threads per inch. E 0 = D ( 0.05D + 1.1)p E 1 = E L 1 Thread Length: The formula for L 2 determines the length of the effective thread and includes approximately two usable threads that are slightly imperfect at the crest. The normal length of engagement, L 1, between external and internal taper threads, when assembled by hand, is controlled by the use of the gages. L 2 = ( 0.80D + 6.8)p Taper: The taper of the thread is 1 in 16, or 0.75 inch per foot, measured on the diameter and along the axis. The corresponding half-angle of taper or angle with the center line is 1 degree, 47 minutes. Copyright 2008, Industrial Press Inc., New York, NY -

9 Machinery's Handbook 28th Edition 1862 AMERICAN PIPE THREADS Table 1a. Basic Dimensions, American National Standard Taper Pipe Threads, NPT ANSI/ASME B (R2006) L 4 Taper of Thread 1 in 16 Measured on Diameter L 5 L 3 L 1 L 2 2p V Imperfect Threads due to Chamfer on die E 3 E 0 E 1 E 5 E 2 D For all dimensions, see corresponding reference letter in table. Angle between sides of thread is 60 degrees. Taper of thread, on diameter, is 3 4 inch per foot. Angle of taper with center line is The basic maximum thread height, h, of the truncated thread is 0.8 pitch of thread. The crest and root are truncated a minimum of pitch for all pitches. For maximum depth of truncation, see Table 2. Nominal Pipe Size Outside Dia. of Pipe, D Threads per Inch, n Pitch of Thread, p Pitch Diameter at Beginning of External Thread, E 0 Handtight Engagement Length, a L 1 Inch Effective Thread, External Inch OD OD OD OD OD a Also length of thin ring gage and length from gaging notch to small end of plug gage. b Also pitch diameter at gaging notch (handtight plane). c Also length of plug gage. Dia., b E 1 Length, c L 2 Dia., E 2 Copyright 2008, Industrial Press Inc., New York, NY -

10 Machinery's Handbook 28th Edition AMERICAN PIPE THREADS 1863 Table 1b. Basic Dimensions, American National Standard Taper Pipe Threads, NPT ANSI/ASME B (R2006) Nominal Pipe Size Wrench Makeup Length for Internal Thread Length, c L 3 Dia., E 3 Vanish Thread, (3.47 thds.), V Overall Length External Thread, L 4 Nominal Perfect External Threads a Length, L 5 Height of Thread, h Basic Minor Dia. at Small End of Pipe, b K d d OD OD OD OD OD a The length L 5 from the end of the pipe determines the plane beyond which the thread form is imperfect at the crest. The next two threads are perfect at the root. At this plane the cone formed by the crests of the thread intersects the cylinder forming the external surface of the pipe. L 5 = L 2 2p. b Given as information for use in selecting tap drills. c Three threads for 2-inch size and smaller; two threads for larger sizes. d Military Specification MIL P 7105 gives the wrench makeup as three threads for 3 in. and smaller. The E 3 dimensions are then as follows: Size in., and size 3 in., All dimensions given in inches. Increase in diameter per thread is equal to /n. The basic dimensions of the ANSI Standard Taper Pipe Thread are given in inches to four or five decimal places. While this implies a greater degree of precision than is ordinarily attained, these dimensions are the basis of gage dimensions and are so expressed for the purpose of eliminating errors in computations. Engagement Between External and Internal Taper Threads. The normal length of engagement between external and internal taper threads when screwed together handtight is shown as L 1 in Table 1a. This length is controlled by the construction and use of the pipe thread gages. It is recognized that in special applications, such as flanges for high-pressure work, longer thread engagement is used, in which case the pitch diameter E 1 (Table 1a) is maintained and the pitch diameter E 0 at the end of the pipe is proportionately smaller. Tolerances on Thread Elements. The maximum allowable variation in the commercial product (manufacturing tolerance) is one turn large or small from the basic dimensions. The permissible variations in thread elements on steel products and all pipe made of steel, wrought iron, or brass, exclusive of butt-weld pipe, are given in Table 3. This table is a Dia., E 5 Copyright 2008, Industrial Press Inc., New York, NY -

11 Machinery's Handbook 28th Edition 1864 AMERICAN PIPE THREADS guide for establishing the limits of the thread elements of taps, dies, and thread chasers. These limits may be required on product threads. On pipe fittings and valves (not steel) for steam pressures 300 pounds and below, it is intended that plug and ring gage practice as set up in the Standard ANSI/ASME B will provide for a satisfactory check of accumulated variations of taper, lead, and angle in such product. Therefore, no tolerances on thread elements have been established for this class. For service conditions where a more exact check is required, procedures have been developed by industry to supplement the regulation plug and ring method of gaging. Table 2. Limits on Crest and Root of American National Standard External and Internal Taper Pipe Threads, NPT ANSI/ASME B (R2006) INTERNAL THREAD H Max. h Minimum Minimum Maximum Root Minimum Maximum Crest Crest Threads per Inch Height of Sharp V Thread, H Maximum Root Minimum EXTERNAL THREAD Height of Pipe Thread, h, f Maximum Width of Flat, F, Equivalent to Max. Min. Min. Max. Min. Max All dimensions are in inches and are given to four or five decimal places only to avoid errors in computations, not to indicate required precision. Table 3. Tolerances on Taper, Lead, and Angle of Pipe Threads of Steel Products and All Pipe of Steel, Wrought Iron, or Brass ANSI/ASME B (R2006) (Exclusive of Butt-Weld Pipe) Threads Taper on Pitch Line ( 3 4 in./ft) Lead in Length 60 Degree Angle per of Effective of Threads, Nominal Pipe Size Inch Max. Min. Threads Degrees 1 16, ±0.003 ± , ±0.003 ±2 1 2, ±0.003 a ±2 1, 1 1 4, 1 1 2, ±0.003 a ± and larger ±0.003 a ±1 1 2 a The tolerance on lead shall be ± in. per inch on any size threaded to an effective thread length greater than 1 in. For tolerances on height of thread, see Table 2. The limits specified in this table are intended to serve as a guide for establishing limits of the thread elements of taps, dies, and thread chasers. These limits may be required on product threads. Copyright 2008, Industrial Press Inc., New York, NY -