Big Lasers!

[mt_harrison]

Hi, This is my first topic. When I say big lasers, I'm referring to cutting bed size rather than laser power. I've migrated some chat that was happening on the 2.x Laser blog. We were discussing what factors need considering when increasing size.

Alignment difficulties, motor/belt problems/what point do you need to revise your extrusion profile in favour of a larger one etc? I'm going to start posting my own A1 (841mmx594mm) build log and am going to try and get away with 2020 profiles. Has anybody had experience building a larger machine and what issues (if any) have they run into?

Matt.

[hoda0013]

Hey Matt,

I've been working on a laser with an approximately 30" x 50" bed for the past 8 months. You can find my buildlog here:

http://www.buildlog.net/buildlog/view_log.php?id=254

There is another guy on here (trwalters001) who is building a bigger machine than mine.

http://www.buildlog.net/buildlog/view_log.php?id=320

I'd recommend reading through those pages first and seeing what two other people have done and some challenges that we've run into.

Challenges that come to mind for my machine were:

Selecting an extrusion that was stiff enough to do the job as well as being light ( I chose the 60mm x 90mm extrusion from Misumi)
Sourcing linear slides long enough to complete the project
Finding closed loop timing belts of the correct size to complete my z-lift drive
Trying to drive the y-axis with one rather than two motors (I chose to go with two)
Beam divergence of the laser at the far reaches of the table (the unfocused spot can get pretty big over an 8 foot distance
Building in enough adjustment points on the machine to properly level and square it
All of the structural components (slides, frame, enclosure, skins for the enclosure, etc...) will end up costing more
Having enough room to fit it in my apartment

Don't let this stuff scare you off though. It's definitely a fun project and you will probably learn a lot.

[trwalters001]

Hi Matt,

I'm the "other guy". The cutting area of my system is 5' square.

I'll respond to the list that hoda0113 (Dillon) posted:

- Selecting an extrusion that was stiff enough to do the job as well as being light (I read the research that Dillon had done and decided that was good enough for me. After installing it on my system, I can say it does a great job.)

-Sourcing linear slides long enough to complete the project (I was lucky enough to find 4 pieces of linear rail that were 64" each on ebay. That was what really determined the size of my system. I didn't want to cut the rails!)

-Finding closed loop timing belts of the correct size to complete my z-lift drive (I haven't started on my Z-lift yet, but I'm just going to follow in Dillon's footsteps)

-Trying to drive the y-axis with one rather than two motors (I went with one motor because I didn't have the whipping problems with the motor drive shafts)

-Beam divergence of the laser at the far reaches of the table ( see: http://www.buildlog.net/forum/viewtopic.php?f=16&t=320&p=2506#p2501

- Building in enough adjustment points on the machine to properly level and square it (Dillon's system has a great alignment setup. I'm trying this:
http://www.buildlog.net/forum/download/file.php?id=919&mode=view

-All of the structural components (slides, frame, enclosure, skins for the enclosure, etc...) will end up costing more (CORRECT!)

-Having enough room to fit it in my apartment (I was surprised at how big it really is once is all put together...)

I agree with Dillon - It's big fun and you'll learn a lot. Go for it!

[mt_harrison]

Wow, great feedback guys, thanks. I've read both of your builds a couple of times now and I've found them both very inspirational. A month ago when I first tentatively typed "DIY laser cutter" into Google I didn't even think it was possible to build such a professional looking machine with mostly off the shelf parts which is equally as capable and functional as commercial machines.

Before I order any parts, I'm making a library of parametric parts and sub-assemblies in Inventor and performing some of the usual loading and displacement tests to find a suitable extrusion and I now see that it will be more likely that the timing belt size among a few other variables will drive my cutting area rather than vice versa. I hope I will have a system whereby I can simply change a single dimension e.g. belt size and have this change propagate across all parts. I will obviously share all this in the hope it will useful to others.

You guys are lucky to be able to machine your own parts at home/work. You're definitely correct about the price increasing almost exponentially with size. It's even worse here in the U.K. We don't have anything like McMaster Carr and Misumi won't sell to an individual.

I'm in no rush to finish, so I think it'll be a labour of love. Although hopefully not 20 years! I can't wait to get started!

Matt