Here is a list of all the postings Vasantha Abey has made in our forums. Click on a thread name to jump to the thread.
|Thread: John S and Adam's CNC Crankshaft code|
I am from Sri Lanka and if you can let me have a copy I will appreciate that too. I tries to make a Mitusubishi Evolution Crank shaft from a a billet of EN19 steel. I tried a 2d sketch of pin and journal plan view on Solid works, and the curser allows the coordinates to see at the bottom.You can divide the contour to say 60 points, note down the x,y points.
later you can write a G code program, switching y axis to z on you MS Note pad. keep the x as 0. Of course you need a 4th axis to turn the crank shaft. This is a very difficult process, but you can do it. The end mill on the spindle need to rise and fall during the rotation of the dividing head. I have used a servo motor driving a toothed belt that slips on an aluminum toothed rim tightly fitted to the pheriphery of the divider plate. The servo motor also has a toothed wheel and with an encoder. The cnc mill has a Centroid CNC 4 axis installed and the mill is an OKK Mill.
Remember that the pin travel like a clock hand and round the center of the journal . On solid works 2D drawing, you have to draw at least 20 circles or more right round the journal center and circles are in orbit. Then you can use the curser to plot suitable cordinates on top of each circle and write a gode program. the X cordinate should be made Z. I will soon send you the G code program I used but to day is Sunday so will do it on Monday.
|Thread: Current leakage om CNC|
You need to fix an Earth wire to the body of your cnc, then at the end have a piece of flat metal like copper with a rubber sponge pasted to the bottom and wet the sponge with a bit of salt water.
this will allow the charges to go to the earth. This is because you have the machine on wheels is the problem. You can also change the rubber wheels to steel wheels that can solve the problem.
|Thread: 4 jaw chuck axial allignment|
It may be your headstock is misaligned by a few 1/00 degree, ie not 90 degree to the bedways.
You can adjust this by removing all the jaws from the chuck, fix a dial gauge to touch the chuck face, let the gauge start reading a max of 10 thous after touching. This will make sure the dial gauge tip but will not unnecessarily get stuck on the circular grooves on the chuck faces when you move your cross slide forward and backwards. These grooves help one to center the jaws quickly by observing those line relative to the jaw end position.
if your chuck face is not perpendicular to the bed you will find a variation on the dial reading.
loosen the bolts that clamp the Head stock to the bed, give a smart tap on the head and it will move a few thou till you get the reading constant. Tighten the bolts and you are on. Your problem could be this.
with love from Sri Lanka, a 75 year guy.
|Thread: Motorcycle General Discussion|
About lubrication, all oils have the following additives.
Detergents ( to dissolve sludge)
Dispersants ( to disperse oil to every nook and corner by wetting)
Viscosity indexer ( to keep the viscosity constant as far as possible keeping up with temperature)
Extreme Pressure Additive ( to cushion the impact of the power stroke acting on rods and journals, bearings and pins. They add Molybdenum Dysulphide, "Molyslip" is one oil like that some times add PTFE)
By the way Castrol name was due to Castor Oil which is an oil that dont attack rubber so used to prevent deterioration of rubber brake washers.
The oil if thin, will wet a surface and penetrate into corners, Best wetting oil what WD 40 ? OH NO NO NO, ITS SIMPLY SINGER SEWING MACHINE OIL, NEXT 3 IN ONE OIL.
|Thread: Lathe - dead centre wont reach the workpiece|
Drill both ends of the job with a center drill, Mount a steel rod on the lathe chuck perhaps 6 inch long , turn a tapered point so the chuck end looks like a dead center with the steel pointed rod clamped with the jaws. Make a bush ( or get a lathe carrier), drilled and tapped with hole at a side for a bolt, welded with a short bent steel rod.
Slip it on your work piece, tighten the screw, mount the work piece between centers and you got the additional lee way of length to play about. Remember to adjust the taper on the turned surface if any, by the lathe tail stock off set adjusting screws.
Vasantha from Sri lanka
|Thread: HONING OF HOLES|
I had a job in inserting a steel sleeve (bush, hole 25 mm) into a nozzle head of an injection molding machine. My worker used a hard steel bush and finally when I mounted the contraption on a cnc mill and bored it , even after many adjusting of the boring tools, regrinding the carbide tool, I found the bore tapering down at the bottom. Finally I reduced the rpm to 120 and did a very low feed and managed to get the bottom almost parallel.
Now I needed to hone it. I turned out a wooden short pole 100 mm long, 23 mm dia, used a hack saw and split one end (made a slit) in the center to a distance of 50mm.
inserted a strip of water proof abrasive paper strip, 3 inch long 50 mm wide into the slit and wrapped clockwise looking from the slitted end. The other end of the wooden pole was turned to a dia of 15 mm so that end could be held in a chuck of a drill.
kerosene was used as the lubricant and after some time starting the drill, moving it up and down many times,, I got a perfectly honed polished surface. YOU CAN USE A PVC rigid water pipe slitted at one end and do this too provided the chuck end is made of a tight fitting plug of nylon, alu , brass, or steel plug with a reduced dia at the stem to fit into a chuck.
For big bores , I have use several 90% bends of PVC piping and straight pieces, glued to gather just like a honing tool with four limbs, slit the limbs in middle and inserted water proof abrasive paper with rubber pad glued to the limb.
the rubber pads helped in applying honing pressure . I turned the contraption with a drill, reduced speed, using kerosene as lubricant.
I have honed 12 inch, 15 inch old Ruston Engine sleeves with this. Hope some on can pick up this to do some interesting work. With love from Sri Lanka.
|Thread: Graphite sealing cord|
if y ou can buy asbestos cords say 2 to 4 mm or so, apply graphite grease on the surface and you got graphite sealing.
|Thread: 316 Stainless|
316 steel or any ss material to cut, you need correct type of carbide tools. The hardness of the tool has to be atleaset 65Rc . Mind you that Tungsten carbide has different grades to suit different materials to machine.
Tungsten carbide in micro particles mixed with Cobolt is suitable for cast iron, but addition of Titanium Carbide makes it more suitable for steels. However I found that the first grade with Cobolt and Tungsten carbide only, does not fracture easily at heat and shock loading. I do not use any coolant but slow speeds and a medium depth of cut helps.
If you are using tip changing tools ,then of course you have to go at 6000 RPM with low depth of cut ( .05 mm), medium high feed will do the trick. CBN tools will also help at high speed without any appreciable wear,
|Thread: Chuck out of true|
It seems that your chuck back registering area has a tiny protrusion may be by an object while keeping aside. Its like a single knurl which makes the chuck slightly off set on face. The register or the nicely polished neck of the spindle has to be spot on mating with the female area of the chuck. If all that is not the trouble, swarf inside the chuck scroll, or the jaws assembled in different numbering to the embossed numerals on the chuck body.
If all fail, what you can do is hold a circular ring on the chuck but locking by opening outward. Then use pencil like die grinder mounted on the tool post and slowly do an internal grinding of the chuck jaws.
usually after long use, the jaws develop end plays with reference to the face as there will be wear on the T slot on the chuck body. If its so, and you cannot do anything else then pls go for a new chuck. Any way any brand new chuck is out by a few thou, may be .01, /.02 mm
There is a lathe called Cazenuve made in France which has a separate chuck holding plate that has a protruding ring, and this protrusion has 4 threaded holes and 4 threaded bolts with square holes to adjust , that which shift the chuck by a few thous to correct out of roundness. The three jaw chuck is held to this back plate by alan bolts sunk in behind the plate, and holding the 3 jaw chuck from behind at a 90% torque so it is free to shift to allow correction.
|Thread: Why are CNC lathes more expensive than a CNC Mill|
Having converted over 12 used original scrap cnc lathes and cnc mills let me give my experience about this.
Buy used machines mills or used at rock bottom values may be pound per kilo if you can like me here in Sri Lanka.
Make sure the bed ways are not excessively worn out. You can check ont he gibs for play and adjust. Checkthe ball screws for play and if you can remove the buts, its always a double ball nut means you can adjust backlash by either grinding a small shim between the ball nuts or putting in a shim. An empty bear can cut with a seamstress sissors will help. Check if you have the power supplies usually for a retrofit you will require 24 volt DC, 5 volt DC for relays and logic and for powering up the motors 30 to 60 V DC ,
Go for the best control system now in the market Centroid cnc Acorn Controller and software. Just go to the website Centroidcnc.com.
I am not a commission agent but talking from my experance. any questions please email me for help. email@example.com
|Thread: Worm and Wheel manufacture|
the following link allows a download of gear cutting software.
Use a Vertical feed with gear tooth shape grounded end mill with two lips only. Do not modify the software. Only fill the blanks.
If you have a swivel head Vertical Mill, you can feed from the side using standard Module or DP cutters too and use side feed and not the Z axis. To edit or modify the Gode program copy the generated Gcode file into MS Notepad, then edit, replace, or simply edit. I have got many tricks invented for this software juggling too. Dont try to juggle with the software letters unless you save the software on a separate USB. If the software gets corrupted, reinstall again after uninstalling the corrupt version.
If you have cnc mill with 4th axis only this software is useful. Very easy cutting a helical gear i with this software.
Entry and exit of tool path should be increased by simple arithmatic. eg:- if 20mm X distance, 10 degree rotation, for 30 mm X distance how much rotation?
10/20 x 30 gives degrees for more starting and end feed distance
Vasantha from Sri lanka
Edited By Vasantha Abey on 16/07/2019 08:35:43
|Thread: Rounded Torx Screw Removal|
get a concrete drill bit of the smallest size with a carbide tip, grind it carefully, the tip to the screw head diameter, with a positive rake angle or flat rake. Normally the concrete drill tips are with a negative rake, blunted to prevent shatter .
use a silicon carbide grinding wheel for this grinding business. then with slow speed drill out the head only, remove the tip and use a plier to remove the end
If you are an expert in welding, use a very thin welding electrode or may be a mig or tig and build on the screw and then weld a small steel rod end to the screw and you are then in business to remove the screw.
|Thread: Different ways of boring a hole|
boring on any machine tool , you must remember that if the work is held in a chuck 3 or 4 jaw, the chuck jaws should not be tightened too much, just lightly or else after you bore and remove the job, you will find the bore slightly bigger on the places where your chuck jaws were. This is due to spring back of the item after removal of clamping forces.
To correct you can hone the bore
If you bore on a mill with swivel head, unless the vertical spindle down feed is not used but table up feed is used, you can get an accurate bore. If you use the quill feed make sure that the quill is absolutely vertical to the table in Z axis by using a dial gauge to true the quill on both horizontal and vertical axis. If not the bore will be slanting to the error of the quill.
The boring tool should preferably made of a rigid carbon steel rod hardened and tempered to prevent vibrations. the tool cutting edge to have a very minute radius on the tip, approach angle of about 80 degree. To hone the hole what you can do is turn out a wooden shaft to about 1mm smaller than the bore, split the wooden shaft about 25 mm depth in the longitudinal axis, slip in a short strip of SiC abrasive grit 200 to 400 paper , roll it round the wooden pole and you got a honing tool. Use kerosene as honing fluid. Flush out regularly to get good finish.
Vasantha from Sri Lanka
|Thread: cnc, castings, gear cutting|
aluminum toothed rim fitted to the divider plate on a tight fit a timing belt and then a smaller timing wheel on the drive servo motor is how to convert your dividing head to bcome a 4th axis drive. By the way I have a few centroid cnc controller fitted machines, 2 Bridgeports, one OKK, One Okegai, One Chinese, one Emco Minimil and one Emco Mini Lathe,and another mini mills of chinese origin. I also have one 25 kw Induction Heater, 60 Kw Induction Heater, 60kw medium frequency melter, and one 100 kw Induction melter. I do make many things and order book full.
I make centrifugal castings of Cylinder Liners, Bushes and all machines made by me. All pictures available on request with no expectations of businesses. This is purely give what I have learned. For example I repair Turbo chargers of any size and the bushes are made of CW713R which you can buy from company called Zabrak Metal, Turkey. The turbos will run for another couple of thousand hours. I can give the gen on it. The thrust bearings can be made of Alu, and thrust plates with MS, case hardened fianlly and polished. Pics available on request.
Further Centrifugal casting pics for vertical axis machine built by me for small bushes in Brass available.
First I will give a tip on helical gear cutting. My cnc machine, 4 axis mill, I fitted a ttothe alu rim round the divider plate and a timing belt on a servo motor with encoder. The counts per rev was fed to the computer. I grind an end mill to suit the teeth form ( need good practice) then use a small softwar for calculating how much degees to turn in how much X axis movement. If any one can contact me on email firstname.lastname@example.org, I can send the zip file.
you can use an end mill ground to the shape of the tooth ,on vertical spindle virtically placedand fed down ie Z axis feed
cutter of standard module or DP fitted again to the virtical spindle but fed from a side ( ie fed on Y axis)
You have to enter the number of teeth, X axis distance, angular movement and then auto generates the G Codes
You can even cut a spiral bevel with this software
Dear All, I am 75 with 45 years in casting, machining cnc retrofit, cnc work. Studied in the UK in 1966 to 70 and back at home from 1971 without troubling old Blighty. Can give my aqquired junk knowldge. Helical gear cutting free software link, induction hardening, case hardening, castings of ferrous and non ferrous, how to retrofit a cnc with centroid cnc , special tooling tips for boring grooving etc etc
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