My team has had issues designing with aluminium in recent years. Since we are based in a school with no machine shop, we do not have many aluminium resources other than the basics (we have a hobby mill, hobby lathe, a decent drill press and that’s it.) In Previous seasons we have reached out to teams like 1360, and were lucky to be able to use their waterjet. However, 1360 will not have access to the resources they had at sheridans machine shop, due to the fact that sheirdan is relocating. Personally I did not enjoy having to rely on another team to help build our parts, because I felt bad that we were taking time from them, and we had to follow their schedule, which made things kinda rough during build season.
Although we do not have a machine shop, our school does have a wood shop with pretty interesting tools we can use. We have had a laser engraver for quite some time that is powerful enough to cut through acrylic (which we have used to make trophy’s for our sponsors in the past). We have run a lot of tests and we found out that we are able to cut through 1/4" Baltic birch. Although the laser engraver is only 1’ by 2’, we have still been able to make interesting parts with it.
Another machine we have access to is a wood CNC. We are currently working on learning how to use it, so we are able to make larger parts (I.E. chassis, superstructure).
What I am wondering is what your experience is with wood, and how did you implement it to your robot. We plan on not only using it for quick prototypes, but to build the majority of our robot out of it, by using techniques such as slots, and t bolts.
Teams have been successful with this in the past (I.E. 4039), and we believe that this will save us time and money during build, and we will be able to focus on building good robots with the resources we have.
Couple teams come to mind who you should research on CD and TBA:
1771 (older bots)
2415 (i believe they still do wood)
558 (heavily rely on wood)
58 (almost all wood)
4183 as Ty mentioned (based off of 2415 style construction)
I believe 4039 MakeShift is also heavily wood based
1726 (similar origins as 4183)
Definitely the teams to check out first. I don’t have others off the top of my head.
While we definitely use wood each year, if you can cut wood, you can absolutely cut polycarbonate. We have been printing CAD drawings at 1:1 scale and using them as templates on 1/4" polycarbonate for years with excellent results. You can see this on our intake assembly this year, and our intake/shooter assembly from last year.
Team 58 uses a lot of wood on our robots. Wood is strong, flexible, easy to work with and easy to repair. We use Baltic birch plywood because of the number of plies add to the structural strength (and it looks good).
We are in a similar situation, we don’t have access to a machine shop but do have access to wood working tools. We generally use 80/20 (8020.net) for our drive base and build up from there.
Paulius,
I have no experience with wood to provide guidance. My team only uses wood for prototyping. However, any system you switch to takes experience and understanding of how the robot will hold up in competition, how to design within weigh restrictions, etc. Lessons learned from other teams in this forum would be a good start.
However, VexPro VersaFrame is a great option if you want to build with aluminum without a lot of machining resources. You should only need a drill press, saw, and a rivet tool. This system is very robust if your riveting process is sound. We found a pneumatic rivet gun and high strength rivets work best.
I’ll add my old team, 1346, to your list of teams to check out. We progressed from winning our very first FRC award for a plywood arm to winning our final FRC award for an entire plywood chassis.
If you look at specific stiffness you’ll see that wood is exceptionally high. Specifically that means that for solid cross sections you can build stiffer and lighter parts with wood than you can with aluminum. This doesn’t necessarily apply to hollow cross sections, but it does show that in many ways, wood is “nature’s carbon fiber”.
There are many advantages to working with wood, ranging from price to repairability. Consider that if you have a standard wood shop… or even just a good table saw and drill press, that you can build some pretty amazing structures. Not only that, but given the price of wood, and the fact that you’re usually using a jig or fence setting to get a precise cut, you can duplicate that cut… making it easy to build a duplicate practice robot. If you need to repair damage, you don’t need a welder… you just need some five minute epoxy and a bit of fiberglass cloth (or a piece of wood) to slap over top as a stiffener or brace. Heck, you can do it with carpenter’s glue if you’ve got time to let it set, or Cyanoacrylate if you need to get it done between matches. If you need to add a component or fitting, well, you can screw, bolt or glue to anywhere on a piece of wood. If you want to do CNC machining, then a CNC router costs less than a CNC mill and a Laser cutter costs less than a waterjet. (Although you can probably get a CNC plasma cutter for close to the same price.)
A few words of advice, however:
“Baltic Birch” rocks. Use this high grade plywood and avoid the voids and inconsistencies of construction or cabinet plywood.
Pre-drill holes when using screws. No need to split solid wood. Use fender washers when using bolts to distribute the load over a broader surface than you would with a harder material.
FINISH the wood BEFORE you touch it with grubby robot hands. Seriously. There are many teams out there that do a crappy job of building with wood, and their robots look grubby and low-budget and give wood a bad name. If you want to win awards for building with wood the #1 tip I have for you is to varnish (clear coat, stain, seal, etc.) the wood before it leaves the wood shop. Once it has a coat of finish on it the pores are sealed and you can clean grease and dirt off of it. Until you do that, however, the pores are open and dirt and grease embeds itself in the wood and you may never get it out. You’ll have the choice between painting over it (and losing that cool “wooden” vibe) or having a robot that looks sloppy.
I could go on… but here’s a link to some of the stuff we did.
I used laser cut 1/4 birch for the structure of hopper and gear holder and 1/2 birch for bumper mounts, battery mount, and the electronics board. Most of the wood was mounted on welded/vexpro-gusseted aluminum tubing upper frame. If your team has the resources to CAD and CAM wood structure, wood will substitute for metal as long as you protect it from collisions. Where needed, we used VEXPro products to provide extra strength. In competition, the wood held up just fine.
Something else that is nice about wood is that, in a repair emergency, it is much easier to cut away than aluminum.:]
A wood CNC should be able to cut polycarbonate just fine. We built our gear pickup late in the season completely out of CNCed polycarb, and it survived plenty of hard collisions. I would have replaced most of the wood with polycarb if I had to start from the beginning again.
418 uses a lot of wood in their robots, it’s cheap and easy to replace when you screw up! However, the big bonus is that wood is FORGIVING, and this saved our bacon in 2009. Our robot crate showed up at Championships all mangled up, and our robot was literally BENT AND TWISTED by a fork truck. We removed the crate to relieve the pressure from the robot, and the wooden robot structures returned to normal - aside from having to redo some of our electrical connections, we were spared any serious damage.
Oh, and I would bet that 254’s all-wood practice bot could have won championships in 2014. It’s not the materials, it’s the idea!
Hello I am the vice president of 4183 and the head of our laser cutting operations. I have been using the laser cutter for 4 years and the team has been using wooden bots for just as long. My advice is to build in boxes and to use tabs and slots for construction. CADing for wood is very different then for aluminium and will take some getting used to but the advantage of being able to build 15 prototype arms in a week are well with it. Wood is only strong if property designed and boxes tend to be the best for that. I would recommend building a practice drive train in the off season if possible as it will help tremendously. Also I know I have already said it once but tabs and slots are a God send so definitely give it a try. If you have any questions feel free to contact me. Also we use trotec and epilog so those are the ones we know how to use.
OP, definitely check out 973’s work with wood both in their robots and their prototypes. I think a lot of teams sometimes use it as they’d use metal and don’t consider how the change in material would change the design, but 973 knows how to make wood good.
Depending on what you are doing for finish, you might want to consider doing a primer coats on the uncut plywood before you start. You’ll need to go back and seal the edges, etc. but it will offer some protection from the grease and dirt that come in the shop. It means you need to be a little more careful with layout lines, etc.
Baltic birch plywood is great to work with. If you are routing / cutting dados to put plywood pieces together remember that they are slightly smaller than their nominal size. So 3/4 plywood is actually 23/32, and you can get router bits in that size to give you super tight joints.
Concerning finishing, we use Boston Polish Wax. A light sanding job then apply the wax according to directions.
I would not apply any finish until the wood is assembled. The finish, wax or others, may get into the glue joints. The result may make the joint strength questionable.
Also remember to use gussets for all joints you can. These will strengthen the joint. We use 2 3/4" pieces of baltic to make the gussets. You glue them together and then cut then at 45 degree angles so they fit into the joint.
Boston Wax may be difficult to find locally but you can purchase it from the company directly.
Perhaps there should be a thread called “Fear of Wood”.
DiscBots, 2587 had a partially wood robot in 2016. My son and I were assigned the task of finishing the design of the upper structure, the bumpers and their mounting system. The upper structure was originally designed as a “birdcage” of 1" square tubing that was very 3-D. Based on the rate that the team was building the other, similar structures, I determined that it would be best to have my son redesign it to be simpler and faster to manufacture.
The original design had “pods” that stuck out on each side to hold the bumpers. We found that we could exactly replace each of these complex structures of 1" x 1" tubing and gussets with two sheets of 3/8" Baltic birch plywood and spacers cut from 3 x 1 (2 1/2" x 3/4") dimensional lumber (pine). As dtengineering indicated, it was very easy to accurately cut a pile of the spacers in one afternoon. We were then able to assemble the two side pods using glue and clamps in one evening. Assembling the major pieces took another evening.
It was very easy to install the hardware for the bumper mountings and other attachments by driving sheet metal screws into the wood wherever it needed to go. The pine was thick (3/4") but was not very dense so it ended up pretty light. The structure proved very rugged, surviving a lot of heavy impacts. Using wood for part of the robot freed up some of the machinery needed for manufacturing parts out of aluminum (bandsaws, sanders).
The following are some tips for using wood in your robot.
Use Baltic Birch, not the stuff from the big box home improvement stores. You want the stuff with at least 5 layers.
Make and use a cutting guide to quickly get straight and accurate cuts.
Use the thin cyanoacrylate adhesive to reinforce the wood at high-stress points such as holes for screws. It turns soft wood into very hard wood once it sets. Screws will break before they strip out.
*]Finish the wood with water-based polyurethane. It is odorless, cleans up easily, dries in a couple of hours and makes the surface of the wood harder and more scratch resistant.
Haha Justin definitely isn’t saying do that on a laser. He’s saying you can also print out 1:1 dimension drawings, lay them on wood and plastics as templates, and cut using bandsaws, scrollsaws, etc.
It’s an easy way to get complex parts made manually.
+1 to 1:1 drawings and using band saw + jig saw. My teams entire IRI rebuild was done that way. The only exception to that was some of the flat lexan plates being cut on a cnc router due to lack of time. It works well and it can be very successful.
Just my $0.02, rivets are usually a better option than glue. It’s a lot harder to screw up setting a bunch of rivets in plywood than it is to pull glue off. That doesn’t mean never to use glue, but rivets + plywood make a great team.
I seem to recall seeing a video of 4183’s test base one year–just the assembled wood–being run over by one of the Forbes family fleet of older (and if I’m not mistaken, heavier) vehicles. I also seem to recall hearing that said vehicle was less one intact tire after the second pass.
And wood is great for bellypans and miscellaneous robot parts too. Takes an impact, workable with just about anything, and a quick repair is “Quick! Wood screws, driver, and that scrap piece we just had a minute ago!”
