Messages

1

General Mach Discussion / Re: Need help with Mach3 Modbus to BRX PLC

« on: January 01, 2021, 06:47:44 PM »

I got Mach3 sending ethernet data to the PLC registers using the ModBus TCP test mode. What I want to send is just the S word, Spindle speed. Based on using Machscreen to view the displayed DRO value this should be OemDRO code 17. However I can’t seem to transmit the value of that code. The modbus tutorials all seem to be for serial. 

Anyone point me in the right direction?

2

General Mach Discussion / Need help with Mach3 Modbus to BRX PLC

« on: December 14, 2020, 08:45:11 PM »

I am trying to get Modbus communication going between Mach3 and a BRX PLC.  This looks like it should be simple but I am stumped.  On the PLC Ethernet Monitor I can see packets going back and forth as the PLC programming software communicates with the PLC.  I have added some screen shots here that may give someone with expertise here in Modbus to help me.  At the moment the only thing I want to do is send the Spindle Speed S to the PLC as I have 3 different spindles and the PLC can then send the appropriate signals to each device.  That part works just fine already.

Thanks

3

General Mach Discussion / Re: Coordinates not at zero after restart

« on: December 19, 2018, 12:27:53 PM »

Completely normal, even on pro machines unless they have absolute encoders which few do. They must be shutdown near a location and then pickup an encoder reference for exact location.

So you need to home to accurate limit switches if you want your zero reference to be relative to the physical machine dimensions. On old converted knee mill the axis had dials. I would zero the machine to the work and on a post-it note simply write down the location of each axis off the scales at the table edge and then add the position indicated by the dial on the screws. On startup I would move there and zero the DROs.

4

General Mach Discussion / Re: Understanding Backlash Compensation

« on: December 16, 2018, 01:54:13 PM »

If you have backlash you should not climb mill even with compensation on, as the backlash will allow the cutter to drag itself forward possibly breaking the tool.

5

General Mach Discussion / Re: Why does it follow different tool paths from G code preview?

« on: November 29, 2018, 10:10:08 PM »

Beginners often think there must be lots of bugs. After you use software for a while you start to realize they kind of have personalities like people. Ask them to do something they aren’t comfortable with and you may get bad results. So sometimes you have to rephrase your request!

6

General Mach Discussion / Re: Why does it follow different tool paths from G code preview?

« on: November 28, 2018, 10:26:58 PM »

Post problem. Likely arc centers are not defined properly as one possible problem. You will find it really helpful to start with a much simpler part. Then post the code and with the g-code definitions handy go through the code that 360 posted line by line and see exactly what the code tells Mach to do. CNC is not Alexa, you have to figure out how to make the part as it is completely stupid.

7

General Mach Discussion / Re: Trouble with parametrics & subroutines

« on: November 09, 2018, 01:36:14 PM »

I used to program everything using G41, G42 when I programmed by hand and used parametrics on a Fadal VMC. I have also done it on a number of other controls. My suggestion is to apply the G41 and make a very small X or Y move say 0.01” which causes the tool to move to the offset position. Now you can plunge to Z depth and go. Always raise the tool then cancel the offset before any other moves or it will be unpredictable. I get that first little move location simply by adding or subtracting the 0.01 in X or Y from the actaul start point. Of course you don’t want to create an inside corner with point or that will screw you up as well.

8

Mach4 General Discussion / Re: A very, very general question

« on: October 31, 2018, 01:12:46 PM »

I have used a Click twice but won’t anymore. We use a Do-More instead.  The instruction set in the Click is extremely limited and the Do-More costs a little more. However unless you are building lots of identical machines where the PLC cost is more important than programming cost the Do-More saves a lot on the programming side. You can even drive a stepper or servo from the Do-More or use an encoder to position tools and keep track of which tool you are on much easier than with the Click.

9

General Mach Discussion / Re: Ref. Tool in Tool table

« on: October 26, 2018, 01:30:39 PM »

The tool length thing is just about the most misunderstood part of CNC! The tool length for any tool is simply the difference between any surface and the end of the tool. So if you are say using the Tormach tooling system and their offline tool setter you might want to use the end of your spindle as a physical reference point. Touch the spindle to whatever you are using as a touch off surface and zero the Z axis. Put any tool in the spindle and touch it off on the same surface and the Z value is now the length of that tool referenced to the spindle nose. Set a tool holder in the offline setter and measure to the end. That value is what you put in Mach for the offset of that tool.

One a tool is in the spindle and it has an offset in the tool table and the tool number has been called that tool can now be used to locate the top of a part. All other tools with offsets called will go to the right place.

10

General Mach Discussion / Re: Drill stuck at top of Z-axis

« on: October 19, 2018, 05:36:31 PM »

Opinions differ on this one but my preference was to fit an ‘override’ push button across my EStop  (Limit Switch) circuit. Pressing and holding the button allows me to jogg-off the triggered limit switch. Once the axis has cleared the limit switch and the button is released everything returns to normal.

Yep.