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Topics - 10k

Pages: 1
1
General Mach Discussion / Losing Pulses at lower accelerations
« on: April 04, 2013, 02:17:56 PM »
I recently became interested in high speed machining.  My homebuilt CNC mill is several years old, and has always worked fine at the lower feed rates that I usually use (1-8 ipm).  I started testing what feed rates that I could get out of the system, and got some unusual results.

First, I ran a short program to run the mill back and forth on one axis:

G01 X2
G01 X1
G01 X2
G01 X1
G01 X1.5
G01 X.5
G01 X1
G01 X0
M30

I ran the program using increasing feed rates.  I have a digital probe, and set X= zero before the run, then checked it after the run.  I was able to get up to 200 ipm with an acceleration of 25 ips/s with excellent repeatability.  I didn't go past 200 ipm in my tests.

I ran a similar test on the Y axis.  I could get 150 ipm using an acceleration of 10 ips/s before I started losing steps.  I found that holding this speed and increasing the acceleration made me lose steps.  This all made sense to me.

I then ran a program that moved the X and Y axis:

G01 X2
G01 Y2
G01 X1
G01 Y1
G01 X1.5
G01 Y1.5
G01 X.5
G01 Y.5
G01 X1
G01 Y1
G01 X0
G01 Y0
M30

I found that using a feed rate of 150 ipm for X and Y that had worked OK on the single axis tests made me lose steps. (About 0.070 on both axes)  Then things started getting strange.  At a value of 50 ips/s, I got no lost steps.   I increased to 75 ipm, and started losing steps.  At this point, I held the feed rate at 75, and started playing with the acceleration.  I found that low accelerations, like 5 ips/s LOST a huge amount of steps.  Increasing the acceleration led to less lost steps.   At the low accelerations, the stepper motors sounded OK, but the deceleration noise was not a happy one.  The higher accelerations cause the stepper motors to stop dead nearly instantly, and really jerks the mill around (relatively - it's a big hunk of iron).

One of the things I thought might be happening is that the stepper voltage could be dropping when two motors are running simultaneously.  I monitored the supply voltage with an old analog voltmeter.  The voltage is only dropping briefly about 5V on the 70V supply during transitions.  I added about 1F of capacitance on the power supply.  It didn't change the testing results.

Any ideas?

2
The attached file contains a screen set (Probe.set) and other files that support use of a digital probe, plus a pop-up keyboard designed for use with a touch screen.

The screen set is based on the default Mach3 screen.  I took out the tool section on the first screen and replaced it with several buttons to support using a probe.  Other inclusions are pre-set spindle speed buttons and an MDI line on the first screen.  I made a few other minor modifications. 

I recently installed a touch screen monitor (from ELO) to display Mach3 on my mill, held by an adjustable arm (http://www.homemetalshopclub.org/news/11/presentation_monitor_arm.pdf).  It worked out of the box with all the screen sets I tried.  I loved it!  The only problem I ran in to was that I sometimes needed to use a keyboard to input data.  I thought about installing a keyboard, a mini keyboard, a numeric keypad, and a wireless micro keyboard.  All of these would work, but seemed inelegant.  I tried Mach 3s built in calculator (Operator - AutoCalculator). I installed Click-N-Type (http://cnt.lakefolks.com/), a pop-up keyboard, and this worked OK but was a bit kludgy.  I  tried the Plugin Virtual Keyboard (http://www.kd-dietz.com/klausphp/pages/eng/machscreen/description/ms_description.html), but again, it didn't do some of the things I wanted to do. I decided to write an application that had all the functionality I wanted.  I started trying to develop a keypad within Mach3.  This proved difficult, if not impossible.  I moved to a standalone program written in a language called Visual DialogScript, and eventually built just what I wanted.

Installation of the files is simple - just unzip the files and sub directories into your main Mach3 folder.  From Mach3, select View - Load Screens and point to Probe.set.  That's it!

Instruction for configuration of the keypad are included in the TouchKeypadReadMe.txt file.  If you want to use it with anything other than the screen set I built, it'll take some configuration of the TouchKeypad.ini file.  The configuration is described in comments inside the .ini file.

- 10k

3
Mach Screens / Display Slow Jog in IPM
« on: December 24, 2011, 02:33:03 PM »
Is there a way to display the Slow Jog rate in IPM instead of as a percentage with OEMDRO 3?

4
VB and the development of wizards / User Defined Function
« on: December 23, 2011, 09:51:58 AM »
Is there a way to create user defined functions that are available globally?

In the screen designer, I have defined several buttons that execute VB code.  The functions are similar, but not identical.  I have a VB function that's defined in a large section of code.  I'd prefer not to include the code that defines the function in each of the calling buttons.  If I do, I have to keep editing every instance when I make a change.  What I'd like to do is:

     Button 1-10 - just a few lines of code that call function using different parameters.

     Large chunk of code defining function - located somewhere else.

I need to pass parameters to the function, and receive return parameters from the function.  The function needs to complete execution before returning control to the calling VB code.

Is there a way to do this?  I've searched the forum and so far it appears that you can't do this.

Thanks.


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