Messages

4241

Show"N"Tell ( What you have made with your CNC machine.) / PEN HOLDER FOR MILL DRAWING

« on: September 22, 2010, 10:04:55 PM »

A user wrote me and asked what he could make such that he could draw to paper the gcode for an image using his mill.

Here  are pictures of my pen holder that I use.
A holding plate to mount the holder to the mill was made and an extended handle was added for fine manual adjustment of the pen to the paper.
The ball point pen was modified using the original parts. Just reversed the pen in the holder and changed how it was held in the pen body.
There is a 1/4" of spring travel so it's very easy to just bring the quill down and then manualy adjust the pen tip into the paper some .005" to .010" or so. Works great and frankly travels quite accurately.You don't have to worry about Z backlash but make sure you allow a proper Z change in the gcode to lift the pen tip away from the paper.
BTW, purchase a few extra pen refills or pens. Not fancy, but for a couple of buck's, it does the trick. 

RICH

4242

General Mach Discussion / Re: default position of cut

« on: September 22, 2010, 06:04:51 PM »

There are two different books, Programming Handbook and Programming Techniques. I have both and like The Handbood as that gives you more background info and is an easier read. They are both good.
RICH

4243

General Mach Discussion / Re: default position of cut

« on: September 22, 2010, 05:48:56 PM »

If you do a search you will find an explaination about using G41 /  G43 that was posted by Graham.
You could also use one of the wizards and try an inside, outside , and on line cut of simple shape and compare the Gcode.
There are a few rules that apply to compensation as to how it is programmed.

You may also want to consider purchasing a book on programming written by Smid.

If you were to cut completely around the S and the offset used  left say .005" uncut for the letter , then the S would be .005" thick and true in shape about the center of the width.


RICH

4244

General Mach Discussion / Re: Loosing steps or backlash

« on: September 22, 2010, 07:05:45 AM »

Should be interesting to see what the new motors will do. A motor that dosen't get warm is not doing any work, the more work the motor does the hotter it will get. As long as the motor is operating in a temp range below the rated insulation you should be ok and with age it would be prudent to operate it taking age into consideration. Greater than 140F  you can't hold your hand on it very long and can get burnt. The motor case temp you see is influenced by the how well heat is being removed from it so dirty fins or evan different paint thickness and location can influence it. So relatively small temp changes of say 10 deg diff is subjective for any conclusion.  I have motors on my mill that are  are older than me and work great. don't be suprised if you see a difference in microstepping position as i found different motors required small change in the steps per unit and would attribute that more to the quality of the motor. Let me remark that it's within a roatation or very small moves.
Just some comments on the motor end they are  generalizations.
RICH

4245

G-Code, CAD, and CAM discussions / Re: Code Sample

« on: September 21, 2010, 07:43:42 PM »

Jeff,
I would recommend: CNC Programing Handbook by Peter Smid

RICH

4246

General Mach Discussion / Re: Motors are buzzing???Help

« on: September 21, 2010, 06:46:27 AM »

Peter,
You may skip the theory part but some understanding of it will help you achieve what your trying to achieve.
You need the steps per unit to be correct or the axis moves will not be correct. Sort of like having having big tires on a truck and it screws up the speedometer reading.
Your motors may not be able to run at 500 rpm when connected to the machine. Steppers run approx to 1000 rpm. Could be like using  a grass cutter engine in a big truck. It dosen't have enough power to start moving the truck and stalls or the truck moves but should someone push back on the truck it comes to a stop.
Got to go but will try a different level of writing when responding.
RICH

4247

SmoothStepper USB / Re: backlashcmpensat1on,and THC control

« on: September 20, 2010, 09:50:26 PM »

Greg is still working on the backlash for the SS. You can follow the backlash thread on the Warp9 site.
 RICH

4248

General Mach Discussion / Re: Loosing steps or backlash

« on: September 20, 2010, 09:43:04 PM »

Hmm....
A program with a prep move to take out backlash along with the dro's referenced to zero moving in one direction and then backtracking exactly  in reverse you should end up at 0,0,0. For testing over time just make it a subroutine. So you could test linear or circlular movements.
Add the poor mans pulse counter using a disc to rotate along with the motor shaft gives you a phyisical reading if a step is lost. The bigger the disc the more accurate or even a 75 cent protractor ie; approx 2 deg=a step.

The smaller the number the harder it is to isolate what is contributing to it. Heck it could be the indicator, a little backlash, etc and gets difficult to isolate each part. Even timing belt tension can account for lost movement which you may think is an electronic pulse missed.

FWIW,
RICH

4249

G-Code, CAD, and CAM discussions / Re: is there a name for this kind of cut

« on: September 20, 2010, 06:40:23 AM »

You can use wizards or LazyCam to provide the Gcode. Wizards would be easier as LC requires a learning curve.

RICH

4250

General Mach Discussion / Re: Motors are buzzing???Help

« on: September 20, 2010, 06:32:31 AM »

I am using steppers.
I use  Geco drives and what i did was provide, via dip switchs ( some have used a PP switching box ), such that they switch between using
Mach or  DeskCNC as the controling software. Frankly, even though i did that it is never used and wasted my time. 

Sounds like you have them working and Hood's reply applies.
Find the max velocity until they skip and lower it by 30%,then play with acceleration until they skip and lower it 30%. This is done with the motors installed on the machine since the motors will see a different loading when installed. Yes, you want speed but  reliablity is more important.
Reliable operation at max power ( speed x torque ) so it's a comprimize  and no two  machines are alike.

Motor torque decreases as the speed increases. No value in having a fast machine and the stepper skips as  soon as you cut sonething.

I suggest you go to the Geco site as  it provides a lot of  information on steppers.

RICH