Messages

121

General Mach Discussion / Re: Radius to end of arc differs from raduius to start line ...

« on: April 23, 2010, 11:39:23 AM »

I am cutting some 1/2 thick countertop material, some kind of plastic. Some scrap I have that works nice for testing. I am using a 1/8 endmill and I could go faster, but choose not to so I lessen my chance of tool breakage. I was working on a project yesterday that gave me errors, and recoded it today witht the same tools,( a Visual Basic app I am working on in ProgeCAD) in the same sequence and had no problems whatsoever. Is there an Odd/Even date randomizer in the arc routines? Or maybe I am holding my mouth wrong. Having written some programs for PC and PLC I have had those things show up that only seem to happen during the right phase of the moon or some other obscure outside occurence.

I have a copy of Mach on 2 machines, both older Dell Optiplex 260's @ 1.8GHz, with the one tied to the Seig XE CNC not connected to the network. So far, when one does something strange the other does the same thing.

Pete

122

General Mach Discussion / Re: Radius to end of arc differs from raduius to start line ...

« on: April 23, 2010, 09:24:57 AM »

Here's the actual code to the point where the error occurs.

G90
G92 X0 Y0
M6 T1
S2000 M3

G0 X0.1250 Y1.9622
G1 Z-.1 F3
G1 X0.3388 Y2.0681
G2 X0.4554 Y2.1763 I0.4992 J2.0121
G3 X0.5444 Y2.2738 I0.4077 J2.3092
G2 X0.6253 Y2.3301 I0.6103 J2.2654
G2 X0.7749 Y2.4246 I0.7759 J2.2573
G2 X0.8486 Y2.4818 I0.9086 J2.3283
G2 X0.9249 Y2.5227 I0.9063 J2.4658
G2 X1.0291 Y2.5469 I1.0096 J2.3945
G2 X1.1100 Y2.5793 I1.0863 J2.5213
G1 X1.3539 Y2.4535
G0 Z.1

G0 X1.1682 Y1.9091
G1 Z-.1 F3
G3 X0.1250 Y1.9622 I0.5713 J0.4561
G0 Z.1

I can get this code to choke if I oload only the last 'paragraph' of code.

It is the start of a Rose. I have a version of it that does work, just that 0,0 is in a different position. I am working on a nameplate for the Principals door here and at one point it does the same thing. And those arcs all start at nice 90 degree positions.

Mach is Version R3.042.029

Pete

123

General Mach Discussion / Re: Radius to end of arc differs from raduius to start line ...

« on: April 22, 2010, 10:54:32 PM »

Mach is configured Absolute positioning, Absolute Arcs. I find it much easier to think in absolute, and the G-Code is much easier to read.

Lots of arc segments with much smaller radius, this is an arc with 1.5"+ radius

the code fragment that these numbers came from looked like this -
G90
G92 X0 Y0 Z1
M6 T1
S2000 M3

section of code...
G0 X.1

G0 X1.1682 Y1.9091
G1 Z-.1
G2 x0.125 Y1.9622 I.5713 J.2651
other code.

I pulled these numbers from my CAD program and transcribed some numbers wrong in my first message, the stuff after the equal sign was correct. Like i say - the radius error is out there in the 100,000 ths place and I don't have a lot of influence on it.

At first I thought it was improperly drawn entities in my CAD program, but the only way to get it any more accurate is to go more decimal places as at 4 decimal places it is as accurate as can be had.

Will post the first part of the code tomorrow from work. The machine is in my classroom at the school where i work.

124

General Mach Discussion / Radius to end of arc differs from raduius to start line ...

« on: April 22, 2010, 02:22:57 PM »

I keep getting the error - Radius to end of arc differs from raduius to start line ...

Using absolute I & J

When I go back in and check the difference it comes to less than 0.00001 (1/100,000) error, and is awfully hard to get rid of.

For instance -

startpoin to center radius -
X 1.1682 - I .5713 = .5969, squared = 0.35628961
Y 1,9091 - I.5713 = 1.453, squared =  2.111209
added together = 2.467499
square root = 1.570827365


End point to center radius -
X0.125 - I .5713 = -0.4463, squared = 0.199,183,69
Y1.9622 - I 0.4561 = 1.5061, squared = 2.268,337,21
added together = 2.467,520,9
square root = 1.570,834,46

Difference =
1.570,827,365 - 1.570,834,46 = -0.000,007,095,0

Add 0.0001 to any of the dimensions and the radius grows too much.

Any clues as to how to minimize this problem so Mach3 can tolerate this insignificant bit of error?

I am doing some "artsy" stuff that has many arc segments but have to deal with this only 2 or 3 times in a program.

Pete

125

G-Code, CAD, and CAM discussions / CAM Application for inside ProgeCAD or AutoCAD

« on: April 19, 2010, 05:52:11 PM »

I have been working on a simple CAM application that works in side ProgeCAD or AutoCAD. It is written in VBA and lets you pick a line or an arc and create the CNC code. By picking sequential entities and clicking the appropriate button it creates teh CNC code which you can then save to a file and run. Right now I am working on it in ProgeCAD Professional and I am planning to get it working under AutoCAD after I get a couple more features working. It is one step above manual - you just have a few buttons to click and the code it created 1 entity at a time. you can also enter lines manually for G & M codes and Z axis moves - It is primarily 2D at teh present, but I plan to do more as I develop it further.

I would like to get some feedback from others, so please post if this interrests you.

Pete

126

General Mach Discussion / Re: Non-linear motion/acceleration profiles?

« on: April 16, 2010, 08:48:31 PM »

I built some welding manipulators and actually got better motion out of them when using trapezoidal motion. The acceleration is higher when using sinusoidal motion rather than trapezoidal. The higher accel in the middle of the move actually caused a problem with rough motion. We were not moving real fast - welding moves at 10"/min, and rapids at 100"/min.

127

Tangent Corner / Re: Using a PC to control a DL06 PLC

« on: April 16, 2010, 08:43:40 PM »

If i were doing this i would look at using a little higher level PLC. I have used an Omron PLC and CXserver Lite and was able to write an application in Visual Basic 6 that was able to change settings and manipulate anything in the PLC by just writing to the appropriate registers. I programmed push buttons on the touch screen and was able to reduce my I/O requirements by not needing switches. The Omron PLC;'s that have motion in the CPU are unique in that you can change a motion destination on the fly and it is able to update immediately. It requires you to do some comparisons to tell when you are in position, but is much easier than any other type of motion control I have seen in any other PLC. The CP1-H series connect using USB which is fast and cheap, and doesn't require ant real effort on the programming end.

How many positions would you have to keep track of?

Pete

128

General Mach Discussion / Re: Artsoft logo's

« on: April 15, 2010, 11:38:31 AM »

And this is a sticky topic because....?

Because it's his toy we are playing with...

129

General Mach Discussion / Re: Ballbar test

« on: April 15, 2010, 11:36:31 AM »

Another reason for the ballbar test is to adjust the servo perameters on a true servo based machine. Using steppers the performance is different because we are using steps to position, not torque and feedback. In otherwords - on  a true servo based system the exact position is controlled by adjusting the speed of the motor by changing  voltage current, and the motor has no position that it will stop exactly like a stepper. On a true servo based system the gain and accel values have to be adjusted to minimize over/undershoot on positioning moves. With steppers we send the stepper a specific number of steps and the motor locks in positin based on which coil(s) is/are energized.

130

General Mach Discussion / Re: Ruminations on Computers for Mach

« on: April 15, 2010, 11:10:31 AM »

Hit CTRL-ALT-DEL and bring up the task manager and take a look at the runing processes. Anything you don't recognize - do a search for that name on the web and determine what it does and if you need it. Some processes can be terminated without anything compailning,others refuse to ... Worst that can happen is that you need to reboot.