Laser Sizing Box

Over the years I figure I’ve seen close to 1,000 teams put their robot into a sizing box. It isn’t the quickest way to do a size check, but it is certainly more reliable than the VEX sizing tool which always strikes me as kind of floppy. I figured there had to be a better way.

I’m pleased to present version one of the “laser sizing box”. It made its debut to very positive reviews from students and coaches alike at the BC Fall Qualifier tournament at McMath Secondary this evening. Sizing “Box” might be a bit of a strong term at the moment, as teams still need to rotate their robot 90 degrees to get both length and width measurements, and I don’t have a height laser built in yet… although fortunately that doesn’t really matter much this year… but it works great. The students like it as they can clearly see which parts of their machine are over-sized, and easily manipulate them to poke them back within the size limits, while I like the fact that it completely eliminates having to slide pieces of paper down the inside of the box to see if the wall of the box is supporting a part of the robot. I can also inspect one team while the next team gets their robot set up. Once they have two clean lines projected on the floor they know they fit… there is no ‘interpretation’ of the results required… and no “official hands” to slide the VEX sizing tool over the robot. The lack of ambiguity made things go pretty quickly.

This version was assembled in a couple hours this afternoon using three lasers from Lee’s electronics, hooked up in parallel to three AA NiMH batteries. The batteries lasted for several hours of inspection this evening, but can be recharged in a standard VEX charger… and, as you can see, there is a holder for three spare batteries on the board.

Laser 2, the cross-beam, is largely redundant, as the students rotate their robot 90 degrees… we check length, then width. But it looks cool, so it is staying.

Version 2 will tidy up the embarasingly ugly wiring, add a power switch, and a lazy susan for the robots to rotate upon, as well as hopefully dealing with some issues regarding loose diffraction gratings and/or focus rings on the lasers. Supporting the lasers on the table has worked better than I thought it might… I only had to realign things a couple times tonight (there are a couple of screws on the underside of the plywood to serve as a reference to the edge of the table, so it stays in place pretty well.)

Version 3 will hopefully be the full box… all three dimensions at once… but that is a little way off in the future.

Version 4 will involve higher powered lasers, so any parts that are outside the sizing box are immediately sliced off. That will really speed things up. :eek:

Anyway we got 30 teams through tech this evening and have another 30 to do in the morning. So far it’s been working great… If you’ve got a mill, or a very square drill press… why not whip one up and give it a try at your next event?


The image is supposed to appear here, but – obviously – does not. Its in the Gallery at

That is incredible! Omni wheels on the intake! :slight_smile:

The laser sizer is even more incredible though. Just curious, how do the lasers project a line rather than a point? Is the light projected through a thin slot? I guess the accuracy of the sizer is only as good as the quality of the build job, but the same applies for any measuring tool. Sure adds a bit of fun and a lot of technology to the inspection process.

Awesome work, well done, Paul

I’d recommend grabbing a couple of these

Or I mean pick up a couple CO2 cutting lasers. That way, if something doesn’t fit…well… it won’t be much of a problem after sizing haha.

There’s a line generating optic after the focusing optic.

Thanks, Paul. As mentioned above, the laser has a lens on it, like in this image

I did have a few challenges keeping the lens properly aligned and had to adjust the lens a few times over the course of tech inspection… a drop of cyanoacrylate (“crazy glue”) will likely help eliminate the problem.

You are correct that the accuracy depends upon the build job… I built a couple prototypes to ensure that I would have satisfactory alignment, and had a perfectly drawn 18" square on the ground to instantly confirm that the lines were parallel and 18" apart. The lasers, themselves, were drilled 18 1/16" apart, to ensure that error, if any, went in favour of the team.

I’m looking forward to developing a more robust design for future events… this truly made the “sizing” part of inspection go more quickly, and totally eliminated any concern about the sides of the sizing box supporting any part of the robot. I provided a link for the lasers and encourage anyone with a reasonably square drill press, a piece of plywood, and a 12mm drill bit to give this a try at your next event. It worked even better than I expected it to.


In most optical systems there’s some form of fine alignment adjustment available because over at a distance you’re really only dealing with very small angles at the source. Perhaps investigate mounting the laser modules on a 2 axis optical mirror mount, that way you’d just need to twiddle 2 fine pitch thumb screws and they’ll stay exactly where you put them. Optionally you could actually use front surface mirrors on optical alignment mounts to redirect the laser beam.

With the holes for laser 1 and laser 3 (the ones that actually do the measuring) drilled square, and the board placed parallel to the floor, the only adjustment that was required was rotating the lens to ensure two parallel lines. I need to secure the lenses to the lasers themselves and once that is done should only have to adjust alignment once, at the start of the tournament.

If I didn’t have a really nice drill press to work from, I likely would have used one of the mills in the machine shop, or perhaps a CNC router, to get accurately measured, close-enough-to-perfectly-vertical holes.

The mirrors would likely be helpful if we needed to get down to the nearest couple thousandths of an inch, or needed continuous or automated adjustment, but for VEX sizing tolerances they would likely add unnecessary cost and complexity.

Given how simple this set up was, it worked far better than I had expected.


I got to make some of these. Laser cutting from an Autodesk design comes to mind

You might have to play with the I.D. of the holes to get a nice snug fit, but if you remove the “warning label” sticker from the lasers they fit nicely into a 12mm drilled hole. It is important that the lasers be snug and unable to vibrate or shake… it took me a good solid press with my thumb to get them to slide in, but tighter would likely be better.

But now that you mention it, a laser cutter would be a very appropriate way to build a laser sizing box! You could definitely cut a much nicer outline for the jig!


I was at this tournament, and the “laser” sizing box was awesome.

It really did make it very obvious when things were too big and really helped with the concept of “not pushing on the walls of the box”.

It really allowed teams to move the robot into position easily and quickly.

Besides, it looked really cool.:smiley:

Nice job Jason.


Is this the appropriate warning sticker?$T2eC16F,!zcE9s4g0uI2BQr5fu(bPw~~60_35.JPG

I have one simple request. And that is to have sharks with frickin’ laser beams attached to their heads!

I love this laser sizing box idea. No one will notice my robot is 5 inches to tall. :smiley:

I am fixing it.

Yeah, that’s why my next design will the hydraulic sizing box.

It starts out 24"x24"x24", but ends up 18"x18"x18"… no matter what is inside of it. :smiley:


Hey Jason,

This is a great idea and an innovative approach to the sizing requirements.

  1. Did you see any notable time savings by using this device, and was it easy to set up?

  2. Where are your patent numbers??? :slight_smile:


I estimate one to two minutes per team in time savings compared to a sizing box. Well, okay… maybe one minute on average. For teams that were clearly undersize there were no time savings, for teams that were right on the edge there were significant time savings. The savings came from:

a) Teams could poke and prod components to get them “into the box” without having to take the robot out of the box.
b) Teams didn’t have to wait for an inspector to tell them that their robot was being supported by the side of the sizing box. I could finish up with team A, while team B put their robot in the sizing box and got it all tucked in and aligned.
c) No one argues with a laser! :slight_smile: Okay… we rarely have anyone actually argue about the size of the sizing box, but the 18"x18" square drawn on the paper below gives instant confirmation that the laser beams are 18" apart.

It was reasonably easy to set up, but could be disturbed when the table was bumped. I plan to have version two stuck to the wall. I also have to improve how I keep the laser lenses aligned… one of them seemed to want to go out of alignment every hour or so… usually it took just a minute or so with a pair of pliers to twist the laser back into alignment.

Ha! My wife just happens to be a patent agent, and is more than happy to write a patent for me any time I want. All I need to do is present her with a business case explaining how the patent will generate revenue. Anything else is a vanity patent, and vanity, apparently, is something I do not require!

However if I can come up with a business model for the “laser sizing box” and an argument that it is “novel, useful and non-obvious” I still have a one year window following disclosure in order to file… at least in the USA and Canada. For most of the rest of the world, it has been disclosed and is thus non-patentable.

So if, in the next year, anyone can figure out how I could make in excess of $50k (her baseline estimate on the minimum revenue required to make patenting worthwhile), or how I could explain that “putting two lasers in parallel and using them to measure something” is novel and non-obvious… please let me know. The patent will follow… and I’m willing to license!


P.S. Thanks for the kind words and encouragement!

Well, it sounds like you are on your way to becoming the newest capitalist in the Great Northwest. If you can get your neighbor Mr. TyLer to help influence the powers-that-be at IFI, you may need to ramp up your shop to be able to produce a couple of thousand of those to ship worldwide! :wink: