Messages

3311

Mach4 General Discussion / Laser Cutting.

« on: June 18, 2014, 10:05:09 AM »

I have said it before but I just can’t say it enough – my congratulations go out to the Mach4 team and of course, Art for the excellent Darwin driver.

Just couldn't resist making a short video of Mach4 (build.1767) with Darwin laser cutting.  http://www.graytel.talktalk.net/Mach4.wmv

Tweakie.

Addition;

This is the video of the latest test engraving and cutting  http://www.graytel.talktalk.net/Darwin 2.wmv

3312

Mach4 General Discussion / Re: Mach4 Printer Port Discussions

« on: June 18, 2014, 02:18:57 AM »

Thanks Art.

Another issue which is probably just M4 v.1767 related and maybe not of interest here but I am just reporting as I find.

In Imperial mode everything is OK but in Metric mode G00 X1 Y1 Z1 moves X,Y,Z axis 1mm whereas G00 A1 moves the A axis 25.4mm (all DRO’s reflect the correct physical movement).

Tweakie.

3313

Mach4 General Discussion / Re: Mach4 Printer Port Discussions

« on: June 17, 2014, 01:58:26 PM »

Just thought I should mention this...

I don’t know if this is a Mach4 v.1767 issue or a Darwin issue but for those like me, that work in metric, the motors Counts per Unit : Velocity and Acceleration all have to be entered in Imperial units irrespective if metric is selected in general config. Not a problem once you know but it was puzzling initially.

Tweakie.

3314

G-Code, CAD, and CAM discussions / Re: G-Code scaling program, mm to Inches and back

« on: June 17, 2014, 12:22:26 PM »

Hi Greg,

Just one point of note - if your part origin (X0,Y0) is centre of the work then it's OK but if your part origin is bottom left then by changing the scale DRO to a negative value the origin will become bottom right (the GCode for the work has been flipped horizontally so has the starting point X0,Y0).
Not sure if this makes sense but you will see what I mean when you do it.

Tweakie.

3315

G-Code, CAD, and CAM discussions / Re: G-Code scaling program, mm to Inches and back

« on: June 17, 2014, 12:14:04 PM »

No worries Greg - I have been using Mach for the last 10 Years and I still don't know the half of it. 

Tweakie.

3316

Mach4 General Discussion / Re: Mach4 Printer Port Discussions

« on: June 17, 2014, 12:05:29 PM »

Hi Art,

I have been searching my PC but cannot find the link to it - The Synrad UC2000 controller data sheet gives a lot more information on Duty Cycle and Pulse Repetition Frequencies and how they should be managed - perhaps may be worth looking for it if it is still available on the Synrad site.

I have no practical experience of mounting a tube vertically I am just going on the manufacturer's advice trusting that they are correct.

Tweakie.

3317

G-Code, CAD, and CAM discussions / Re: G-Code scaling program, mm to Inches and back

« on: June 17, 2014, 11:39:09 AM »

Hi Greg,

Just click the scale DRO box, enter the new value (-0.0000) then press (keyboard) return. The associated LED will flash to indicate the change.  

Tweakie.

3318

Mach4 General Discussion / Re: Mach4 Printer Port Discussions

« on: June 17, 2014, 11:32:37 AM »

@ Craig,

I understand what you say, however, the logic gates invert the signal - connecting another gate in series restores the state. As there are 4 'and gates' in a package it makes sense to use one of them this way rather than use a separate inverter chip.
The output shown from the tickle pulse generator is signal 1 and GND. Signal 2 is fed from the Mach PWM or a stand alone PWM generator then the output goes to the laser control circuitry. Hope this makes sense. 

@ Art,

I think the Synrad CW operation may only apply to the relatively new models of their RF lasers. I don’t know for sure but I suspect that externally we can apply 100% duty cycle while internally the electronics is still pulsing at a reduced duty cycle and I would be concerned that older models do not have this safeguard. Perhaps we need to contact Synrad for more information.

As far as I am aware the grey scaling was not incorporated into the version of the plugin that you released.
If it’s any help this is typical of the shades of grey that can be achieved from the plugin as it stands http://openbuilds.com/attachments/a1-jpg.1862/

Tweakie.

3319

Mach4 General Discussion / Re: Mach4 Printer Port Discussions

« on: June 17, 2014, 08:20:34 AM »

Hi Art,

For the Synrad I use an external tickle pulse generator. It is a very simple circuit and has approx 10% of adjustment for both the frequency and pulse width – this enables it to be set to just below the point of lase. The Mach PWM and the tickle pulse are then switched in or out by a separate trigger circuit (diagrams attached).

In order to get the best laser versatility (never know what we will want to do tomorrow) I think you need as many different individual levels of power as you can achieve (I believe Synrad use 5% step variation of the duty cycle between 0% and 95%).

You will have to be careful if operating the Synrad above the recommended 5kHz PRF – for example at 20kHz then a 95% duty cycle will exceed the maximum recommended internal photon density for the tube (overheating the output coupler and / or the rear mirror). The Synrad controllers software limit the maximum available duty cycle as PRF is increased thereby negating the problem.

I am no expert here but it is my understanding that the Mach3 engraving plugin allocates a set number of ‘dots’ per each individual pixel value and because for high pixel values the dots overlap each other many times during one X axis scan it produces ‘dot-gain’ and thus a shade of burn in accordance with actual pixel value. In my opinion this process works extremely well and I think I am able to get results that are up there with the professional laser systems. Overall the engraving plugin is going to take a lot to better but you are the expert and I am really looking forward to trying the Mk II.

On the other side of the coin those using diode lasers have found that DC variation in actual laser output power level in accordance with pixel value is the way to go.
I can actually do this with my DC excited laser but I still prefer to vary the output power level by varying the PWM in the same way as the Synrad is controlled.

Tweakie.

3320

Mach4 General Discussion / Re: Mach4 Printer Port Discussions

« on: June 17, 2014, 06:04:25 AM »

My first laser test with Mach4 and Darwin (using a well trusted GCode toolpath that has been run many times before). Although this is not a method I would prefer to use the laser switching was done by using the A axis direction pin (A1=on and A0=off) and everything ran exactly as expected with no errors.

The problem mentioned in my earlier post regarding the final G00 X0,Y0 home move has now been identified as being the M30 command which, on my old and perhaps rather slow PC causes, both motors to stall during the GCode rewind. Removing the M30 cures this problem.

The ‘run today and not tomorrow’ problem I was experiencing has also been cured so it’s onwards and upwards with perhaps some more adventurous testing. 

You need to get that Synrad hooked up and running Art. 

Tweakie.