Brand-Spanking new to Laser-cutting

Machine: Custom Built (Layzor) from K40 parts: PSU version 1

Board: Laserboard
Firmware: Smoothie

Problem/ Question:

I am Brand-Spanking new to Laser-cutting – but have years as maker and ( 3d Printer, CNC enthusiast etc.)

When I enter a new technology I build rather than buy so that I get to know the ins-and-outs and that way I don’t have any external dependencies for maintenance of the machines I build.

Building my first laser cutter is my 2020 Covid project.

I purchased a K40 off of craigslist. Stripped it of it parts. Built my frame using the Layzor ( I have tossed the digital control panel in favor of the Cohesion3d Laserboard, with the LCD display. When I discarded my digital control panel I lost my test fire button, so I am doing my test pulses via the LCD display. ( I no longer have a test fire button). Additionally, I have added an air assist, beefed up the exhaust, added a coolant system via Chillipad.

I have setup my new device on Lightburn.
I have the mechanical movement working as expected.
I have my limit switches working as expected.
I have my machine homing properly.
I have already installed an AMP meter.
I am just about through aligning + centering my mirrors. (still have both eyes.)

Come to realize from readings on this site that I would be well suited to add a 10 Turn Potentiometer 100K Ohm. I think. That’s on order should be arriving shortly.

Come to realize from readings on this site that I would be well suited to add a kill switch to the lid.

Come to realize from readings on this site that I would be well suited to add a kill switch in the way of a flow meter. That’s on order should be arriving shortly.

So I have some general questions, stemming from not having a baseline of expectations yet.

  1. The 10 Turn Potentiometer 100K Ohm ( any issues with this model?

  2. The wiring diagrams are clear enough to make an attempt at the wiring. But what I am trying to understand, if I do add a potentiometer the intention is that this potentiometer should control the MAX laser output, and I can use the AMPs traveling through the laser to gauge if the knob turns are working.

  3. If my understanding of #2 above is correct – Does the PMW signal that would be output by the Laserboard, would that be applied as a (multiplier to the analogue). (Eg. If the Potentiometer is set to let 80% of power through, and then I set the Lightburn to burn at 50% – then the laser should output at about 40% power. Is that the correct baseline of understanding?

  4. Would I be better to add the the LID kill switch to de-activate the Laserboard or the PSU?

  5. Would I be better to add the the Flow Monitor kill switch to de-activate the Laserboard or the PSU?

  6. Should I add a test fire button or just keep using the test fire capability in LCD Display menu?

  7. Can we control the length of the test fire from the LCD Panel. Mine seems to be set to like 5 sec / or I can keep it on. I would prefer to limit the test fire via the LCD panel to a shorter timeframe. Is this configurable somwhere?

Here are my thoughts.

question #1 - i think a 10 turn pot is alot of turns. mine is about a 300 degree turn from min to max. with that i get good resolution on the overall power setting.

question #2 - no idea

question #3 - that is my understanding as well.

question #4 - my kill switch kills the power to the PSU, i dont want any chance of getting my hand fried. also sometimes i want to watch the head move with the cover up, so I for sure dont want the laser to fire.
question #5 - i dont have a flow monitor, but i would have it kill the LB.

question #6 - i have a test fire button that is directly connected to the PSU, so i can hold it for a split second or longer if needed.

question #7 - sorry no idea.

Hi David,

Welcome to the forum!

It sounds like you have made great progress thus far.

I cannot speak for this particular brand, but it is similar to the potentiometer we carry and a very common type people upgrade to. You’ll want to get a 10K version. For more info: Potentiometer Installation Guide

Using the potentiometer, you can set your output to the MAX mA that you ever want to use. The potentiometer acts as a limiter to prevent over-driving the tube. You can measure your output to get an idea of changes with the knob turns, should you choose to adjust the power from the pot.

The LaserBoard uses pulse width modulation (PWM) which sets the power as a percentage of whatever your potentiometer is set to. LightBurn sends a percentage of that maximum, based on the power values you input for each layer. You can test your output by tuning the PWM levels.

These should be powered from the LPSU, usually the P or WP terminal, depending on your model. Refer to the LPSU Connection Guide to help determine the pins on your supply and also look at your power supply specs for more info.

This depends on your preference. A test fire button on the control panel means quicker access and less clicks to engage, but also means more wiring and components to keep track of.

You could look at the menu panel options for Smoothieware to see if there is a way to control the length of the laser being enabled with console commands. It’s all open source, feel free to have a play: GLCD Custom Programming