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Topics - garyhlucas

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21
Screen designer tips and tutorials / Small changes to jog flyout
« on: June 09, 2013, 03:25:44 PM »
I've simplified the jog screen for my grandson to use. When you bring it up with the Tab key it comes up too far to the right. How can I move it to the right a little and keep it there?

Jog mode is a toggle. Any way to have two buttons, one to select continuous and one to select step?

22
General Mach Discussion / Steppers as spindle motors
« on: May 27, 2013, 08:46:14 PM »
I am setting up a fourth rotary axis for my mill, run by a stepper motor.  Most small mills and lathes use a DC motor or a VFD drive AC motor for the spindle.  If you look at the torque and horsepower curves for those motors and drives the torque is fairly flat across the useable speed range.  So at half speed you have the same torque, but that translates to half as much power too.  Which is why gears are needed to change the speed ranges without losing torque.  The thing I find interesting is that steppers are essentially constant power devices, and the slower you run them the the higher the torque, up to the motors holding torque rating. So it seems to me that a stepper matches the torque requirements of a variable speed spindle much better than a DC motor. If you have a high enough microstepping rate for smoothness and a high enough voltage to overcome the back EMF at high speeds the stepper seems like they could work pretty good.  The potential problem I see is that unlike a DC there is no overload capability that you may be using without even realizing it.  An overload on a stepper will stall it instantly.  My machine has a 1500 watt DC power supply at 68 vdc powering 80vdc 8.8 amp drives.  I have a Nema 34 800 oz/in. stepper so I am going the try it as a spindle drive.  I want to compare it to the Sherline motor currently running my mill spindle. For the fourth axis I need positioning anyway.

Gary H. Lucas

23
General Mach Discussion / SERIOUS jog problem!
« on: May 25, 2013, 03:06:16 PM »
Working with my mill today, trying to teach my grandson how to jog the machine around and pick up edges. He knows how to do it on a manual mill. He was jogging the x axis in rapid and it wouldn't stop, it ran all the way to the end limit!  I looked into it further and here is what i discovered.

Using the jog pendant brought up by the Tab key. Jog mode set to Step. Use Shift to override step mode. Press an axis key and the axis rapids.  The fun starts when you want to stop.  If you happen to release the shift key before releasing the axis button the axis keeps right on going unless you hit E-stop!  This is completely repeatable and works with all axis.  I'm using mach3 version .066. I am wondering if it my logitech wireless keyboard is the problem. The machine is extremely well shielded with metal enclosures and every motor and control cable properly shielded. Haven't seen any glitches at all.

Can someone try duplicating this problem as described above? I'll try a wired keyboard to see if that is different. This is real machine killer!

Gary H. Lucas

24
General Mach Discussion / Improving mill safety
« on: May 21, 2013, 09:17:41 PM »
I have finally gotten my machine which I call the Ifactory running.  I have also take a little paying job to run with my grandson who is nine.  The job is to drill 3  thru holes and machine 3 hex pockets in 200 2" diameter polypropylene wheels.  I have a chuck mounted to the machine table, and all the work gets done with 1 tool a 1/8" end mill.  I already did a sample part and got the customer to approve.  Mechanically the machine is very safe. Hard limit switches on all axis that cut off all power and also dumps the DC power supply to the drives.  The whole machine has an enclosure with 3/16" clear plexiglas on two sides with door switches that stop the spindle and all motion. There are two hard E-stop switches too. So the job is mount a wheel in the chuck, close the doors, press start, remove the finished part and deburr a little.  So this is safe for my grandson, but for the machine not so much.  He could easily destroy it!

I find the jogging to be quite dangerous.  There are a couple of reasons.  My keyboard is very compact, and it is real easy to lean on the arrow keys accidentally. If jog is active, away it goes.  In step mode jogging the defaults are 1, 0.1, 0.01. 0.001.  IF you are working in metric that is kind of okay.  In inches however that 1.0 is a machine killer!  It would be really nice if there were two jog step tables, one for inches, one for millimeters.  I'd also like to disable jogging from the keyboard altogether.  Using Tab to bring up the jog pendant is far safer. Then I'd like to do away with the mode switch between steps and continuous.  Needing to press Shift to get into continuous mode is a great safety feature. It takes two hands, your hand can't be between the spindle and the table when it moves except for small steps.  So I'd like to remove the mode change buttons from the pendant altogether. I'd also like the buttons for axis motion to be larger and further apart, so a small hand motion while looking at the part not the screen doesn't move you on to a different button. I want my grandson to be able to jog, otherwise you can't teach the important skills of edge and center finding, and the concepts of origins and work offsets.  Any suggestions on how to accomplish this?

25
General Mach Discussion / G41/G2 cutter comp
« on: May 13, 2013, 07:20:45 PM »
I have noticed that most software does the approach to the part with G41 or G42 with a single move. I have always done it with an additional very short (0.010") straight move after the G41/42 but  BEFORE plunging in with the Z axis.  I don't like the compensation being applied after the cutter is in the material as it often cuts material I'd like to keep. When trying to apply cutter comp to a small pocket the single move method may very well destroy your part.  The way I do it the cutter goes right into the pocket.  I also like to use a radius on and off the part, as the entry and exit points are not visible that way.

Another thing I do in the design phase of a part is I never make the inside radiuses on size for a standard end mill.  I typically design 1/4" radiuses as 0.260".  When cutting with a new full size cutter it sweeps the corner with clearance and doesn't chatter.  When someone else designed the part with a 0.250" radius I usually grab a reground end mill and sweep the corner that way.  At one shop I worked at I became very popular with the tool room guy because I was always asking for regrinds instead of new end mills.

Gary H. Lucas

26
General Mach Discussion / If not LazyCam then what?
« on: May 12, 2013, 09:17:43 PM »
I am playing with Lazy Cam and it is okay to me, but I understand it is a dead end.  So what is everyone using instead?  I worked as a CNC programmer for a year on a pair of Fadal machining centers where I did mostly castings from 50 year old prints, all hand coded. I then worked for four years doing prototypes on an old Bandit controller where my boss wrote me a DXF to Excel program, and an Excel to Bandit loader program. So I have worked with some less that cutting edge stuff!

Gary H. Lucas

27
Trying to create a G-code program for some hexagon holes and LazyCam seems to just produce coed for one of three, then a bunch of G40 G1 blocks. Is this because I don't have a license yet?

Thanks,

Gary H. Lucas

28
General Mach Discussion / Hard Limits & Home positions
« on: March 25, 2013, 10:19:17 PM »
I am building a machine with 2 NC limit switches on each axis.  The plan was to simply connect them all in series with the E-stop button to prevent a crash against the end stops.  To get jog away from a limit switch would require holding in the reset button until you've cleared the limit.  My question is, would it be possible to also use those same switches as home positions if I home each axis separately?  I'm thinking I'd just hold in the reset button during homing, so it wouldn't go into E-stop when the limit is hit. However I don't believe the switch resolution is going to be good enough to home the machine and then use that to locate a fixture, so this may all be a waste.

In the past I ran a pair of Fadal machining centers that had home positions, and you had to home the machine for the tool changer and such to work properly.  I also ran a Spindle Wizard CNC knee mill, but on that machine I never bothered homing it. I just picked up the work location with an edge finder and set tool lengths to the top of part and away we go. If there were lots of operations and lost position would really screw me up, I'd just write down on a post-it the dial readings for each axis when at 0,0,0 of the work location.

My tool holders are repeatable for length.  So my plan is to keep an edge finder permanently set in one holder, and use that to pick up all work locations. I am also considering bolting down a small block to the table that I can call home by picking up the top and two sides, then set all tools off of it.  That way on a long job where a power failure would lose my positions I could reset the machine by picking up the home block with the edge finder again. This machine does not have dials so I can't use the post it method!

Thanks,

Gary H. Lucas

29
General Mach Discussion / Some questions about Mach3
« on: March 19, 2013, 10:11:22 PM »
I am building a multi-purpose machine and I have some questions about how Mach3 operates which will influence how I wire it.  I have two milling/lathe spindles that are interchangeble.  Once is DC motor driven, the other is stepper motor driven, and therefore positionable.  I also have another stepper motor which is to be used for an extruder for 3D printing. I have a USB 4 axis breakout board.  I intend on driving the stepper spindle and the extruder from seperate drives, but using the same step, enable, and direction signals, which are switched by a multipole relay.

My questions:
What powers up the stepper drives?  Just enabling the E-stop circuit, or is there a standby mode where you can be programming and such but the drives are off?

I want to use the machine as a Vertical Mill, Horizontal Mill, Vertical Lathe, Horizontal Lathe, Shaper, Cutoff Saw, 4 axis robot with pneumatic gripper, and 3D printer.  The vertical mill and the horizontal mill need to switch the Y and a Z axis.  The lathe axis get switched around too.  When I want to 3D print the A Axis signals need to go to the extruder etc.  Is the best way to do this to create a profile for each machine type?

Thanks,

Gary H. Lucas

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