Messages

61

General Mach Discussion / Re: More toolholders than space in the ATC carousel

« on: July 22, 2012, 06:24:21 AM »

Hi All,

Just got back home after a week away in Cornwall where I only had infrequent access to a computer so my appologies for not really contributing to the thread I started.

I will most likely be using a CAM program as I have one available so all my tools will be set up within this with lengths, offsets, speeds etc. As I have not yet used the CAM program I am just having a play with it to see how it presents the information about the tools used as, if I am using the DRO as suggested by cncalex, I will need to see which tools are being called for on each program, hopefully, without having to read through several hundred lines of Gcode.
When you guys start taking about 'modulus commands' I am out of my depth and I have never written VB or any other type of code.
With the Denford toolchanger I have figured out that it requires strings of code sent from the PC to the toolchanger, via 9pin serial, to initiate the tooll change cycle. Even though there are various return strings, to PC, during the change cycle these have no effect on the cycle completeing sucessfully. The toolchanger also has a couple of relays installed; one is only actauated if a faulty code is recieved, whilst the othere opens and closes at various points during the cycle. I am sure these will be useful to integrate at somepoint with my Mach3 inputs.  

The other thing is that at the start of the tool change cycle the spindle drive dogs have to be pretty much aligned with the position of the matching slots in the tools held in the carousel. I do have a spindle speed monitoring proximity switch which works perfectly and I would like to use the input from this to switch off the spindle drive as it passes. That way at the beginning of the change I can instruct a very slow speed, say, S60 and as the spindle passes the proximity switch stop the spindle without too much run-on from inertia. I may need to adjust the position switch to trim theh stop position but that would be easy enough.
I have attached a copy of the logic that relates to the tool change. The Gn & Y is the action of the relays but as I did this logic before I stripped out the old Denford motherboard it is showing the voltage, not the open/closed I see now. There is another set of logic that applies to machine set up, to datum the carousel and decide which tool is installed at start up, but this is something that should probably be added to the machine datum sequence.

I will have a play with the CAM and let you know how it instructs the operator which tools to load.

thanks ...Sweep

62

General Mach Discussion / Re: More toolholders than space in the ATC carousel

« on: July 17, 2012, 06:49:18 PM »

Hi Alex,

This is great news, though something i am sure will need a lot more trial amd error as i have never played with vb yet.

thanks ...Sweep

63

General Mach Discussion / More toolholders than space in the ATC carousel

« on: July 17, 2012, 11:49:27 AM »

I would be suprised if this hasn't been asked before but its difficult to narrow it down in search due to how popular this site is!

I have a Denford Triac with 6 position carousel ATC but have a lot more toolholders than spaces in the ATC.
Can I give each toolholder a number (T1, T2 ...T30 etc) and then assign a seperate slot number in the ATC where it is located, and what would a line of VB look like to represent this, or am I limited to give the slot number the T value?
By having as many T numbers as I have toolholders (30+) will be great as I only need set the offsets and diameters once. If not it would mean setting up each toolholder for every program I ran.

thanks ...Sweep

64

General Mach Discussion / Re: PWM spindle - Circuit advice

« on: June 09, 2012, 06:44:27 AM »

Considering that my old Lynx08 is really just designed for a mechanical potentiometer control, and everything I seem to do with the original circuit compromises max speed or min speed, I have started to have a look into digital potentiometers. All of the control methods I can find, however, are based on either push button or encoder pulses to raise and lower resistance, i.e. speed in my case.
Does anyone have any ideas how I can build a circuit with a digipot to utilise the PWM signal from Mach, or is there another way that Mach can output a 'push button' type command until the required spindle speed is reached. I do have spindle speed monitoring enabled.

thanks ...Sweep

65

General Mach Discussion / Re: PWM spindle - Circuit advice

« on: June 04, 2012, 01:11:26 PM »

Hi Alex & Mike and thanks for your support.
I am pretty much an amateur with electronics so all help would be appreciated.
I am pretty happy today as my homemade home-switch & index pulse circuit board for my 2-wire proximity switches worked perfectly. Result!
Reading through the Lynx manual it mentions, with regard to Speed Reference, "10kOhm potentiometer, 0-10 volts, input impedence 100kOhm filtered" which I guess is something you were taliking about Mike.
There is something in the book (page 16, section vi, attached) which mentions scaling maximum motor speed. I wondered if this would allow me to adjust RV1 to give maximum motor speed (2950rpm) from the 7.5v I get from my existing circuit board or would you suggest that i make a new board to work with 12v supply? I do have a 24vdc (250mA) on my drives motherboard which is designed to power external devices which I could use to reduce to 12vdc. I am already using this to get 9vdc for my home-switch proximimity switches.

Thanks ...Sweep

66

General Mach Discussion / PWM spindle - Circuit advice

« on: June 02, 2012, 12:16:18 PM »

I have built a circuit board to change the PWM output from Mach3 into a 0-10v signal required by my DC motor controller. The board is based on a couple of designs that are readily available on the internet and the DC controller is a Control Techniques Lynx 08 that was fitted to my machine in its original condition. The Lynx is around 20 years old but works fine.
The Lynx has its own on-board 10V supply that is used for external speed control via a potentiometer. See extract from handbook below, fig2 Basic connection.
Connecting up a simple 10k Ohm potentiometer gives me a full speed range from close to zero up to 2950rpm which I have measured using a calibrated handheld laser tachometer.
When I connect the PWM circuit board and control via Mach3 "S3000" the maximum speed that get drops down to around 2250rpm. I have my oscilloscope connected to the designated output and can see a good square wave as expected (actually a continuous high line for full speed). Measuring the input voltage at the Lynx, however, I can only see a maximum of around 7.5v which makes sense as this is proportional to the voltage at full speed.
So I guess the problem is something to do with loss of voltage, possibly over the resistors, within the board, but as I don't have a full understanding of how the board works it makes it difficult to come up with a solution. I have tried changing the resistor values at various points, and adding a potentiometer into varios parts of the circuit for experimentation purposes but without success. I felt comfortable doing this without damage to the Lynx as the 10v originated from the Lynx.
So, if anyone with a better understanding of whats going on in this circuit, and how I can get my 10v out for max speed, I would really appreciate your advise.
Thanks ...Sweep

67

General Mach Discussion / Re: Electronics experts - Why wont this work?

« on: October 24, 2010, 04:01:36 PM »

Hi Tweakie,
I have changed the 470 resistors for some of my stock 10k and have tested the breadboard and it works fine with overtravels and 1x home switch connected so it looks like i've sorted it. I will build a prototype board with 12k's where I can have all 3x home switches and the 1x daisey chained overtravel inputting at the same time and see how it goes

Many thanks ...Sweep

68

General Mach Discussion / Re: Electronics experts - Why wont this work?

« on: October 22, 2010, 04:33:05 AM »

I did consider that the parallel pin 5V might not be sufficient, but it isn't powering anything only being switched by the output side of the opto-isolator between hi & lo on the input.
Thinking about that it might be the case that my resistors on the output side of the opto's (inputting to PC) arn't big enough as being 470ohm they would each allow 10mA to flow but the total available to source, i understand, is only 2.6mA!
According to the Mach3 manual which I have just re-read (page 4-4, logic signals), "the computer will need to be supplied with some current (less than 40 microamps) for 'hi' inputs and will supply some (less than 0.4 milliamps) for 'lo' inputs"
As such it might be worth increasing the 470ohms to something like 12k ohms as all my available current could be 'absorbed' from just one input.
The reason I didn't want to use a seperate 5v supply was I thought this was compromising my opto isolation of the PC.

I'll keep you posted but will double check all my wiring first.

...Sweep

69

General Mach Discussion / Re: Electronics experts - Why wont this work?

« on: October 22, 2010, 03:21:50 AM »

Hi Tweakie,

and thanks for adding your reply.
Are you saying that 'on paper' the circuit looks ok so the error must be in my wiring? If so i'll recheck everything. This could be a possible cause as breadboard wiring does look like a rats nest!

Thanks ...Sweep

70

General Mach Discussion / Re: Electronics experts - Why wont this work?

« on: October 19, 2010, 12:02:06 PM »

Sorry for 'bumping' this post but I don't seem to be able to edit it. I re-read the message and the paragraph 'problem' which seems a bit confusing ay the beginning and would be better read as:

When only the overtravel loop is connected, the osilloscope shows a very clean switching of input pin on CN7 (pin1) from 0v when in safe working area, and a good 5V when Overtravel switch is thrown.
When only Z home is connected, osilloscope shows switching of input on CN7 (pin2) from 0v whilst in 'working area' and a good 5v when the Proximity switch is triggered when homed.
When I connect both Z home and Overtravels (haven't built breadboard with Y & X homes yet), and monitor on 2 channels of oscilloscope, both traces show 0v whilst in the safe working area, but when I move the Z axis towards home I only get 1v when the proximity switch is triggered until I continue moving the Z axis to trigger the Overtravel at which point both traces hit 5v.

thanks ...Sweep