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Messages - RICH

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2841
I have redrilled and reamed a lot of timing pulleys and never had the problem you are describing. The cast ones from Browning are quite good, by that i mean, if you have an accurate three jaw chuck it will center them accurately. If the casting is bad one can always use a mandrel to true up the hub of them before placement in to the chuck. As you said repeatable inaccuracy per revolution can appear. Timing belts to my surprise are really quite accurate but you can loose a few steps per rev depending on the tension used but that is repeatable.
I would think that it's more a problem of the lead screw and backlash / non use of a good ball screw . A small backlash can come from the thrust bearings if not adjusted just so and can
make a big difference. Another item to look at is the coupling ( if say a bellows type  ) since they can give some and cause inaccuracy and you may not notice it.
The smaller the error you try to get to the more anal one must get and comes at a price also. Just a fact of CNC.

BTW, 0.02 mm =.0008" on a diameter.... you must have some backlash ( zero is imposssible else the axis wouldn't move). Only you can define how much time, effort and money
you want to put out to get  1/2 the current value?

RICH

2842
General Mach Discussion / Re: How to alter jog wheel adjustments
« on: February 29, 2012, 07:40:09 PM »
I don't have my MPG's  calibrated, and use them such that.... turn really slow they move in small increments ( i think abot .006" per rev so can easily creep in to a tenth ). Turn them
fast and can i can move the axis some what  quickly.  No indents either....Great for creeping in to touch off :o
Play wih the counts per unit and velocity under MPG settings  to get a "turning touch" or "feel" that suites you . To each their owne ;)
RICH


2843
General Mach Discussion / Re: Speeds and Feeds with Micro end mills
« on: February 29, 2012, 07:26:08 PM »
I know the feedrate needs to be slow but how slow...?

Don't fool too much with wood so someone else may be of more help on the micro machining. Some of the exotic harwoods like Babinga, Ebony ( some has rock in it!),
Cocobola ( however ya spell it ) can get darn hard in spots.
The stuff i was doing was in 6061 Al and s/s, and i will remark that it's different than using an engraving type point tool.
By slow i think what would is important is that you let the mill cut into the material and not "plunge" into it because the thin end mill is not very forgiving.
If the spindle is good and you don't have much runout and enters the material perpendicular your less likely to have problems.
Watching under a microscope you can see them bend with little force when machining and you don't want that.

RICH

Carbide or HSS, each has it's pro's and con's and suggest you read up on the use. Old saying when designing is that a little ductility will go a long way as compared to hardness.


2844
General Mach Discussion / Re: Speeds and Feeds with Micro end mills
« on: February 29, 2012, 05:38:37 PM »
We imperialist's ( .008" dia end mill and .040" total depth ). The end mill will snap in a heat beat ( I'll assume carbide). SO very very slow plunge rate into the material, spindle speed of 20000 to 60000 rpm and cut depth maybe limited to no greated than the diameter of the end mill ....try .005". Clog the end mill and you'll break it. If you have backlash in any axis be prepared to break the end mill quickly. Feed in to fast and you'll bend the end mill and break it. Some spindle runout and you will break it. BTW what's the length of cut on the end mill? $20 to $30 each and it can get expensive quickly.

BTW, for folks reading this ,a human hair is like .003" dia so picture cutting wood or metal with a dirty hair.... ;D

Don't know what kind of hardwood as they are all different, grain, knots etc so a little practice on your part  for experience will surely help.

For What the above is Worth, ;)
RICH

2845
LazyCam (Beta) / Re: Lazy Cam Beta Limitations
« on: February 29, 2012, 04:57:11 PM »
You will find a manual for LazyCam in Members Docs.
Read the manual and you'll be fine.

RICH

2846
General Mach Discussion / Re: Use of tools in a turret?
« on: February 27, 2012, 11:27:52 PM »
Quote
we are way past me being confused
Your trying to do too much at one time.  

Can you take a call? send me a PM with a tel # in the next 5 minutes and i will call you.

RICH



2847
General Mach Discussion / Re: Use of tools in a turret?
« on: February 27, 2012, 08:13:16 PM »
Quote
I tried it quite a few times attempting with and or without pressing enter, with or without pressing "part X or Z" and using only the touch button

Hmm......
My quickie simply says touch off tool #0, then touch off tool #2, and then tool#3, until you are finished touching off all of the tools.
Move the carriage any way you want, matters not where you go, but with the next tool in touch it off in a similar fashion to the same point.
As soon as you touch off a tool Mach keeps track of the tool ( the controlled point ), it knows where that tool is, when you put the next tool ...and tell Mach ..... via ithe box and touch it off, Mach does the accounting and
puts the value in the tool offset table. When your done touching them all off.....leave your pinkies off any buttons........your done with the tool table.

Do it that way maybe. Then try the machining way. BTW, you don't need to run the lathe spindle, maybe put a plastic straw in the chuck and use flexible pieces of plastic to fool around. This way if you get things mixed up
the only thing you end up with is a bent straw and twisted plastic tool.........works for me when fooling around! ::)

RICH



2848
General Mach Discussion / Re: Use of tools in a turret?
« on: February 27, 2012, 07:45:51 PM »
A few comments:
-Mach assumes that G54 is the default offset, so you don't need to put G54 in the command.
  ( assuming that a G54 exists and you didn't have a call for a different fixture offset like G55)
- I don't have switches on my lathe so i need to define a home position.
- If there is a G54 and you want to test the tool moving to the part zero at a feed rate then either G0 x0.0 Z0.0   or   G01 X0.0 Z0.0 in the MDI
  for a rapid move or move at a feed rate to part zero. Clicking the Home All will take you back to home.
- One can also set the feedrate in the input box on the screen
- One can change the tool in the MDI:
   T0000 - will change to the master tool ( providing you defined tool #0 as the master)
   T0101 - changes the tool to tool #1 and its offset
   T0100 - changes the tool to tool #1 with the tool offset of the master tool
    ALL THE TOOLS ARE RELATED TO THE MASTER TOOL  AND ALSO RELATED TO EACH OTHER

When you first finish referencing your machine using the switches, you are at your home position ( open the fixtures and see if a G54 was created, if not, then you need to  
define that position by setting Set Home X & Z).  ......don't use the fancy gadgets here........ or move somehwere else and set home. Now if you touch off to the part
and set the x and z axis mach will change the G54 fixture offset.

I deliberately didn't say how to set a tool because everbody will do it differently, Hood machines a stock for setting the postion, some just move it near  0,0, and say good enough, if my microscope is attached i use it,
in the write up i used the "conventional " method which is described so often,  the main point is that you need to set the master tool and and follow thru with the others. If i say anymore you may get confused......me too! :D

RICH

 





2849
LazyTurn / Re: strange behaviour
« on: February 26, 2012, 05:54:02 PM »
Glad it's working for you.
RICH

2850
LazyTurn / Re: strange behaviour
« on: February 26, 2012, 08:45:44 AM »
Try my dxf as it's just a redraw of yours and it works as shown below.

RICH

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