Messages

6371

General Mach Discussion / Re: Help Needed on Debounce

« on: June 04, 2011, 06:15:25 AM »

Bob,

It would help if you connected a 0.1uF (small ceramic type would be OK) capacitor between each input terminal you are using for your switches and ground (GND or 0 Volts).
This should reduce the noise pickup and enable you to run with quite a low de-bounce setting.

Tweakie

6372

General Mach Discussion / Re: My circles aren't circles, but hexagons

« on: June 04, 2011, 06:05:51 AM »

Hi Arnie,

Which drawing program are you using to create you GCode ?

Drawing programs (such as Sketchup for example) have various resolution levels which can be set and these directly affect the smoothness of the finished circles.

Tweakie.

6373

General Mach Discussion / Re: Crazy problem with getting started

« on: June 04, 2011, 05:59:42 AM »

You should follow the procedure of;

Connecting all cables etc. correctly.
Switching on computer.
Getting Mach running and set.
Turn on machine.

Plugging and unplugging cables with your PC or machine running is down right dangerous as it can damage the PC or damage the machine or damage you.

There have been videos posted in the past where users have disconnected cables from running machines and caused a machine runaway. Take care 

Tweakie.

6374

Show"N"Tell ( Your Machines) / Re: The Laser Project.

« on: June 04, 2011, 05:30:53 AM »

ntlaser,

Within Mach disable PWM spindle control.
When I refer to your pin#9 I am referring to the pin#9 from the computer's LPT parallel port.
Configure your pin#9 to the Digital Trigger and set active low.
Ensure that pin#9 is not configured or enabled to any other function within Mach.
Connect pin#9 to the PSU’s “TTL(L)” terminal (see earlier diagram).
Set the potentiometer mid travel for testing and adjust as necessary but make sure you don't set it too high and exceed the tubes maximum current specification. If you don’t already have a milliamp meter (0 to 30mA) connected in series with the earthy end of your laser tube then you should obtain and fit one.
Make whatever safety interlock, water flow etc. connections to the “WP” terminal of the PSU.

Shades are achieved within the Engraving plugin by varying the Pulse Repetition Frequency (not PWM) on the digital trigger output. A PRF of 100% would be equivalent to maximum power and a PRF of 0% would be equivalent to minimum power. In practice the Engraving plugin never gets anywhere near to a 100% PRF (see my pdf document for values related to feedrate http://www.machsupport.com/forum/index.php?action=dlattach;topic=12444.0;attach=26734 ) but manual control of the maximum tube current can, to a large extent, compensate for this.
The manual control of tube current can be adjusted at any time during operation to achieve the appropriate laser power for the job in hand. A multiturn potentiometer with calibrated dial is good because the adjustment is quite fine and the dial enables the correct settings to be recorded so that they can easily be used again at a future date for a similar job.
The Engraving plugin, as mentioned earlier, controls the laser’s output power by adjusting the PRF and this, in turn, is directionally proportional to federate and pixel value (high federate = high laser output power : low federate = low laser output power : no feed at all = laser off). It’s really just as simple as that.

I hope I have explained all your questions.

Tweakie.

6375

Show"N"Tell ( Your Machines) / Re: The Laser Project.

« on: June 03, 2011, 12:53:09 PM »

ntlaser,

From what you have said and after looking again at all the possibilities I think it is definitely a delay issue, but perhaps not as I first thought.
Looking at your double image - if the laser was fired late then the left image would be created during the right to left movement of the axis. The only way in which the left image could be created during the left to right axis movement is if the stream of trigger pulses started early or in other words there is a delay in the start of the axis movement. This would also hold good for different feedrates altering the spacing between the two images and could also explain the non-linearity in your earlier Micky Mouse double image.

I have attached a revised diagram of how I think you should consider connecting your laser PSU and Mach. (Ignore PWM control of laser current and set it manually for both Engrave and Cut operations).

Tweakie.

6376

General Mach Discussion / Re: Program hanging

« on: June 03, 2011, 12:49:46 PM »

Isn't this the reason programs should finish with a null line such as % ?

Try adding % as the last line.

Tweakie.

6377

General Mach Discussion / Re: Where can I get enclosure for my limit switches?

« on: June 03, 2011, 11:05:28 AM »

If you EBay "Enclosed Limit Switch" there are many different types of complete plunger switches at low prices, maybe there is a suitable type there that you could use to replace your existing switches.

Tweakie.

6378

Show"N"Tell ( Your Machines) / Re: The Laser Project.

« on: June 03, 2011, 07:18:53 AM »

As I see it the Digital Trigger should be set Active Low and the assigned output pin# should be connected to the laser PSU TTL(L) input and this is where the laser is turned on / off.
Are you switching the laser on / off a different way to this ?

Tweakie.

6379

Show"N"Tell ( Your Machines) / Re: The Laser Project.

« on: June 03, 2011, 07:03:27 AM »

Another question comes to mind - How exactly do you control turning the laser on / off ?
Where do you connect the Digital Trigger output ?

Tweakie.

6380

Show"N"Tell ( Your Machines) / Re: The Laser Project.

« on: June 03, 2011, 06:47:43 AM »

It is difficult to see exactly what is happening from those pictures but it could (as I said earlier) be related to a delay in turning the laser on and therefore vary the spacing of the two images with changes to federate. What I was hoping to see was if each of the two images was created by alternate line scans (one image created by the left to right scan and the other image created by the right to left scan).
Going back over earlier posts in this and the other related thread, I think it would be a good idea to investigate the PWM laser current control aspect. I never managed to succeed with the Mach PWM control and it’s a long shot but perhaps this is what is causing your problems.
As a test, would you consider the following?
As I understand it, you have a board which converts the Mach spindle PWM signal to an analogue voltage from 0 to 5 Volts which is in turn connected to the laser PSU (IN and GND terminals) to control the maximum laser current.
Try disconnecting this board and connecting a potentiometer, as attached diagram.
Set the potentiometer to mid travel (never set it to maximum unless you can monitor the tube current to ensure that the makers maximum recommended current is not exceeded).
Turn off the PWM function within Mach and then repeat the same test as you did before.
I don’t know for certain but Mach really has a lot of work to do running this plugin and it may just be too much to ask for it to generate the PWM as well.
Either way this will at least rule out one possibility.

Tweakie.