#61
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Hi here is a good example of 4axes work.The rough is xyz then flip 180. The second part is where the 4 axes are working ''simultaniously '' .Indexer work and 4axe work are different. With the right software you will be able to do both with .
Normand http://www.dailymotion.com/video/x9w...nc-4-axes_tech Last edited by normand blais; Fri 22 January 2010 at 09:22.. Reason: link missing |
#62
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In that video, with all 4 axes running simultaneously, notice that the cutting bit is always perpendicular (90 degrees) to the surface of the work. That was a strategy decision by the programmer. I wonder why he decided not to use the side of the bit . . .
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#63
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He waisted lot of time machining the mass instead of contouring the wood last. Machining 4 axes allow also to do undercut.
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#64
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Gerald,
Most likely, if he was using a package like Rhino 4th Axis, cut3d, etc...it's easier to write out a 4 face cut file with indexer being either manually written to index 4 times or as I like to do it, write four files and have Mach play them in sequence. It looks like the file did the following: 4 - face, spiral roughing, parallel to face with collision detection for bit 1 - 4th axis continuous rotation final pass with a very high overstep for resolution. On the larger index models, I found that the 3d model software would crash after about 3 million polygon faces. Thus, I had to do each face separate to generate a toolpath before trying to let the software "remove" all that material for a final toolpath. Computer crashes are my driving factor when trying to produce a part file. Have a great day. Sean Last edited by smreish; Tue 26 January 2010 at 14:06.. |
#65
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Completing the rotary axis homing system
A piece of copper was cut and filed to make a bump for the rotary axis homing system. A strip of sand paper was fixed on the rim of the plate and the copper piece manually rubbed against its perimeter to get the exact diameter of the rim.
It was then fixed with Loctite. I usually cover parts that I fix with Loctite with adhesive tapes, so that they are isolated from the air and speeding up their curing. Ahomingarrangement01.jpg After curing, the top surface is manually finished with grit 600 sandpaper. Next the microswitch is adjusted against this bump to have the least movement. Ahomingarrangement02.jpg Ahomingarrangement03.jpg |
#66
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Setting up the 4th axis in Mach
Is discussed in post #116 in the following thread:
http://www.mechmate.com/forums/showt...?t=2189&page=4 |
#67
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Did you get your 4th axis working?
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#68
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Hi Brad,
Yes it is working fine and quite precise. |
#69
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Excellent. I'm thinking of doing a 4th axis build like yours. I've just picked up a 100:1 harmonic drive. Im a little concerned the 100:1 isnt divisable of 360 so not sure how mach3 will go with the steps.
Brad. |
#70
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Hi Brad, don't know how the harmonic drive will interface with Mach 3 on the indexer.
I have a 130 tooth module -1 gear fitted to my lathe shaft. The Stepper motor has a 24 tooth pinion fitted. Mach-3 has a function to calibrate the movement. All I did was to set the indexer with a spirit level. Tell Mach-3 to go 360....full revolution. Eyeball the spirit level after this movement and told Mach that it moved 280 for instance (depending on where it stopped) Within 3 or 4 calibrations I was going exactly one revolution when mach moved 360. |
#71
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Excellent.. I'll try that method. I was doing the maths method and 1 degree movment was calculated at 555.555555556 steps per degree. I'll give the calibration a try and if it doesnt work perhaps use a pulley on the stepper 20:18 HD to reduce the ratio down to 90:1 to give an even 500 steps.
Brad. |
#72
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Brad,
Maybe you would give a second thought to that. A harmonic drive is virtually a zero backlash gearbox. Interfacing it with another set of gears might introduce some backlash. You can add as many decimal places as Mach accepts. It will not round it up. And don't worry about 555.555555 and 555.55555. it will be less than 1xE-6%. there is a note that should be considered when using microsteps with the fourth axis. As long as the fourth axis is rotating, it will provide a fine machining, but if your toolpath should require that the fourth axis to stop, while e.g. the Y and Z axes is working on the workpiece (like making fine splines along the length of a cylinder, then microstepping will be neglected and the fourth axis will stop at full step, or at the best at half steps, depending on your wiring, since positioning will not obey microsteps (or at least this the case with my driver). |
#73
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Hi Nader,
So good to hear from you. I think of you and your build from time to time and wonder how you are doing. Perhaps you would consider "showing" us your final (latest) machine and some of your results. I'm especially interested in your indexer experience, since I'm planning to use a similar design on my next MechMate. Regards, John Higgins |
#74
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Nader - I would also need some more inspiration! do post some pics
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#75
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Brad get a servo for your harmonic drive - there are lots on ebay - they top upto 3K rpm and would definitely work with the harmonic drive
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#76
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Hi John and Irfan,
Thanks. Right now I am working on another new design which is intended for cutting mainly Aluminum. Also I am doing some research and experiments to introduce a 4th and 5th axis on this machine. But I will send some of the workpieces made before. |
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