DIY Laser part 1: The Bones

There’s no such thing as a cheap laser engraver. Though you might think otherwise if you’re like many DIY types, trolling eBay in the hopes of finding something reasonably priced that will get the job done without maiming anybody.

The trouble with cheap laser engravers is that every corner that can be cut, will be cut. The race to the bottom is a sordid path strewn with incorrectly rated components, cheap wire, hand-hewn “precision” parts made of inappropriate materials, and (literally!) shockingly shoddy high voltage supplies.

I’ve spent the last two years taking care of a $4000 50 Watt Special from Hong Kong. In that time it was offline much of the time, always needing some adjustment or emergency repair. One evening the gantry suddenly stopped moving altogether, while the laser blithely continued to burn deeply into the acrylic on the bed. After disassembling the gantry to find that the Y stage had vibrated itself apart due to a complete lack of washers, locking fasteners, or even Loctite, I decided I had had enough.

Rather than apply yet another band-aid, I’ve spent the last six weeks or so working on my first CNC project: a DIY 60 Watt laser engraver.

Design goal: nobody dies. Also, fun.

This project would be my first large robot, and certainly the first that I would arm with a laser that could kill me. I’m no stranger to questionable project ideas, but I knew that other folks would likely be using this tool, and I wanted it to be bullet proof. Or at least safer than the death trap we had been using.

I also didn’t want to start completely from scratch. I knew I had a lot to learn, but I also knew that CNC gantries are nothing new, and there is very little need to reinvent the wheel (even if it is a trapped v-wheel on bearings). So I decided to start by looking at various other DIY laser builds, like Lasersaur, various boot-strappable designs, and especially Barton Dring’s CNC laser.

I had backed Barton’s MakerSlide project back in 2011, and it seemed like a good basis for my first laser build.

Easy, Tough, and Repeatable

MakerSlide is fun stuff, especially for a CNC newbie like me. It elegantly solves the problem of how to keep your axes perpendicular to each other without twisting– a problem that only gets worse as your dimensions increase. Sure there are many ways to solve this problem (some of which involve less weight than MakerSlide), but this stuff makes it cheap and easy. Plus it offers a very solid and yet frictionless rolling bearing for any sized shuttle you care to throw at it.

Best of all, MakerSlide can be cut with a band saw (or even a hack saw) and it’s compatible with standard 20mm t-slot.

Grown-up tinker toys

If you’ve never used t-slot before, think of it as grown-up tinker toys. You can get aluminum in just about any length or thickness, and it all fits together with simple screws, spacers, and steel tabs. Tighten the screw and you’ve got a very strong joint. Add an appropriate spacer and you can set the angle to whatever you need. The aluminum is a strong, light alloy that easily drills, cuts, and taps. Given a chop saw and a couple of hours, it’s easy to prototype just about anything out of t-slot. Best of all, adjustments are as easy as adjusting a screw, and shifting a piece around leaves no visible tool marks on the aluminum.

I found that Misumi’s online store had everything I could possibly need. They’ve got data sheets on everything, reasonable prices, and packages typically show up in a couple of days. And they will cut their t-slot to order, so getting started was as easy as downloading Barton’s drawings and placing the order for all the t-slot I would ever need.

Or so I thought at first. It didn’t take long before I realized I’d want to deviate a bit from the original design to fit with parts I had ordered or already had on hand. Two or three round-trips to Misumi later, and I had a reasonable first stab at a laser chassis.

The wonderful thing about standards

I also realized early on that I had better get my act together regarding fasteners. I had been lugging around the same bucket of screw-compost since high school: a morass of sheet metal screws, wood screws, and hex caps. Lock nuts, wing nuts, and washers. Zinc, brass, steel, and anodized. Metric and imperial. All mixed together in a little box that I’d occasionally dig through, wondering why I could never find something that matched what I needed.

I performed one of the most liberating acts I’ve ever done in my shop.

I threw the whole thing away.

It seemed obvious that if I was working with t-slot, I’d need the right fasteners in easy reach, in copious quantities. So I placed another order to the fine folks at the Bolt Depot and standardized on:

18-8 stainless
metric sockets
4mm and 5mm
regular and nylon lock nuts
various lengths (mostly 8mm and 10mm, with a few longer selections for variety)

I also picked up a couple of cheap plastic organizers at Harbor Freight. After a few minutes of organizing my new stainless steel bounty, I’d never have to hunt for the right screw for the rest of the project. This planning probably saved me days of effort, since I would only need two hex keys to completely assemble (and later, maintain) the machine. It also let me banish the false god of fractional inches from the project early on. Plus the hardware looks fantastic and will never rust.

Get it together

Once I got into the rhythm of grabbing the right screw and the right hex key, assembly went much more quickly. I soon had a free-standing chassis with a rolling X and Y gantry on casters (thanks again, Harbor Freight).

But there was still the problem of the Z axis. They’re surprisingly tricky to design, since they need to hold quite a bit of weight perfectly flat while slowly raising and lowering it. That would have to wait until later, when I had a better idea of how this whole thing was going to fit together.

I had made a nice skeleton, but how exactly was I going to keep the dangerous BURNINATING BLINDING PEW PEW PEW LASER inside?

Tune in next time for DIY Laser Part 2: The Skin

In the meantime, here is the photo album for more bone photos, and the completed build.

lasers > robots

#robots #don't look at laser with remaining eye