Things to think about when designing

General discussion of laser machines

Things to think about when designing

Postby buildsomething » Tue Jan 12, 2010 1:03 pm

MY HOMBEREW 60W CO2 LASER CUTTER

Overview

What I have tried to do here is to provide a list of things to think about when you are planning to design and built a laser cutter or for that matter and kind of machine whether it be fully automated, semi automated or manually operated.

Some points are more valid than other depending upon your requirement, but in each case should be addressed and reviewed. There is no order of importance in the list below…its just what came to mind.

There are probably hundreds of more items that can be added or subtracted.

If you feel that you would like to add to this list, then please feel free to do so. The intent here is to make you think what you are about to undertake and to maximize safety as well as design and operating procedures.

It is better to make a mistake on paper than to have it occur in real life. Its so easy to design yourself into a corner…….don’t I know it!!!! :oops:

Since this is only a hobby, taking your time to think things out is a luxury that the home hobbyist has that the real industry starves for. I believe that its the journey and not the destination which make DIY CNC machines so much fun

Richard....aka....buildsometing


My Machine Design Requirements

• Used primarily for cutting balsa and light ply
• Large operating window. 15” wide x 48” long
• No Z axis auto adjustment
• Safety an integral part of machine
• Modular design for serviceability and easy access
• Ease of replacement parts
• Accessibility of all moving and non moving parts
• Low cost
• Any one with some advanced building skills can tackle this project
• No rush to build machine
• Some return on investment
• Must look semi professional when completed.
• Must have resale value
• No kludging of parts

Structure or Base
• Low cost with minimal machining.
• Frame must be stiff to minimize bending in X and Y axis
• Large footprint to minimize tip inadvertent tipping
• On wheels for ease of movement around the shop

Pneumatics & Exhaust• High volume with high water column exhaust. 600 CFM @ 8” of water
• Minimum of 4” diam exhaust ductwork
• Low volume low pressure air assist

Cooling• 5 gallon plastic paint can
• Small boat bilge pump…..self priming
• 12 volt supply for pump

Cabling• All external cables must use be quick disconnect
• Internal wiring must have lugs
• Strain relief’s on all fastened power supply cords


Controls and power distribution• In my case 1 240VAC line coming to the machine with 120VAC distribution
• Everything must be fused
• 1 switch kills everything
• 1 separate control panel to turn power on to each individual item with indicator lights


Safety
• One main power cutoff switch
• EPO and safety interlocks
• Fire extinguisher located in and easy and accessible area.
• Protective eyewear…..with documentation for possible liability issues
• Outdoor exhaust
• Thermocouples and alarms within mechanism to sense delayed potential fires.
• Minimize stray beam scattering.
• Heavily darkened lexan viewing area.
• Safety labels displayed

Sensors
• Cooling water flow
• Exhaust on
• EPO
• + / - limit sensor for both X & Y
• Home limit sensor on X & Y
• Temperature sensors throughout machine base and vacuum exhaust ducting
buildsomething
 
Posts: 69
Joined: Tue Jan 05, 2010 12:54 am
Location: Toronto, Ont

Re: Things to think about when designing

Postby bdring » Tue Jan 12, 2010 1:23 pm

That's a great list. I pays to have a good plan before you start.

One thing I always tried to keep in mind was weight of the moving parts. A lot of us come from wood and metal CNC where stiffness is eveything and weight is a helpful thing. On a laser, speed is a big factor. An engraving will take forever if you don't have speed. At least the X axis should be as light as possible. High acceleration with any weight will put a lot of stress on everything else.

Pick a target speed before you design.
Bart
"If you didn't build it, you will never own it."
bdring
Site Admin
 
Posts: 2966
Joined: Sun Nov 22, 2009 7:33 pm
Location: Chicago, IL, USA

Re: Things to think about when designing

Postby buildsomething » Tue Jan 12, 2010 1:36 pm

Thats an excellent point wrt reducing the mass of the Y axis :idea:

In my particular case, mass was not an important part of my decision making process since I would be cutting at speeds between 30 ipm to 120 ipm maximum, while the speed moving to the next location was in the order of 720 ipm. Once I get my pictures of my system up, you will kill yourself laughing at the mass of my Y axis.....its built like the proverbial brick outhouse. :lol:

Mine design is more like something out of the 19th century, good solid boiler plate design....Maybe I should put up a little smoke stack with flared ends behind the machine....maybe with some steam..... :lol: I just might do that :geek:

Richard
buildsomething
 
Posts: 69
Joined: Tue Jan 05, 2010 12:54 am
Location: Toronto, Ont

Re: Things to think about when designing

Postby buildsomething » Tue Jan 12, 2010 1:46 pm

Here is a pic of my Y axis without the last mirror or the focusing lens support.
As you can see, this thing is solid!!!

At full speed ~ 720 ipm, I have been able to stop the platform with about .001" to .002" overshoot. Not bad moving a 3-4 lb mass.
Not sure how its going to affect the repeatiblity of the cut, but only time will tell.

Richard
Attachments
DSC00782.JPG
Y axis without mirror or focusing lens
DSC00782.JPG (393.6 KiB) Viewed 12306 times
buildsomething
 
Posts: 69
Joined: Tue Jan 05, 2010 12:54 am
Location: Toronto, Ont

Re: Things to think about when designing

Postby lasersafe1 » Wed Jan 13, 2010 1:45 am

Looks great! I especially like the needle approach to the limit switch. Just enough extra room to let it go without crashing into the end. I can see your RC aircraft propellors in the background. I guess I know what "this" machine is going to be doing.

I was a little concerned when I saw "small boat bilge pump". This seems like overkill for water volume through the typical Chinese tube. Is that what you are using? Right now you seem to be satisfied that you will only be cutting. I think as soon as you get it running and see the possibilities, you will wish you could raster. As an example:

http://s915.photobucket.com/albums/ac353/cdm8848/?action=view&current=LASEREAGRAVINGMACHINE.flv
Attachments
snap.jpg
snap.jpg (289.71 KiB) Viewed 12287 times
lasersafe1
 
Posts: 599
Joined: Fri Nov 27, 2009 8:23 pm

Re: Things to think about when designing

Postby buildsomething » Wed Jan 13, 2010 2:38 am

Well when I started to do this work on the laser, my intention wasn't to do any engraving but more RC model aircraft laser cutting. After I understand a bit more about laser cutting, I might attempt at designing an engraver as well, but keeping the mass of the system down to a minimum. Since I have a lot of the electronics, exhaust and power requirement available, I would only need to design the engraver....maybe next year :D While I am working on my laser, I am working out a lot of design details in the back of my mind on a CNC propeller cutting machine.....just for the heck of it!!! I'm not going to use a laser, but just a small mill. Haven't figured out what would be the best approach to solving that problem.

As for the boat bilge pump, its actually not very big and sits in the bottom of the 5 gallon pail. Nice thing about bilge pumps is that there is no priming and she starts pumping everytime. With all the resrictions through the plumbing, tubing and the laser tube itself the flow is not that bad.....more flow than less I suppose. Once I get the laser up and running and start doing some serious cuts, I'll start taking a closer look at the thermodynamics of the cooling system based on flow rates, pressure and temperature over time. Since there was no book on "Buildling Lasers for Dummies"....lol...I had to use whatever I had available. Probably overkill.....naw....more like total overkill!!!

I love that carving of the Aztec calendar. Once I get my laser up and running, I might give it a try and see what happens. In the meantime, back to the basement for me. :geek:

Richard
buildsomething
 
Posts: 69
Joined: Tue Jan 05, 2010 12:54 am
Location: Toronto, Ont

Re: Things to think about when designing

Postby lasersafe1 » Thu Jan 14, 2010 3:11 am

I recall reading some warnings somewhere that cautioned about too much water flow. I think it was on the SAMS laser pages. It mentioned that these tubes don't like the turbulence of water or vibrations from a blower, motors, etc. Apparently the cathode can "droop" into the plasma and get ruined. When I look at my tube, I can't see how any of the metal elements can droop or fall. They seem to be a pretty tight fit.
lasersafe1
 
Posts: 599
Joined: Fri Nov 27, 2009 8:23 pm


Return to General

Who is online

Users browsing this forum: No registered users and 2 guests

cron