Plywood - talk to us about how you use plywood
 

Back in the 70's everything I owned would fit in the back of a VW Micro bus. A Combination of being a hippy (I had Wildstang shirts before there was a Wildstang) and building things that were minimal in design. For example, the stereo rack of turntable, receiver, 8 track (you get a smack for laughing) and dual cassette player was tensioned 2*2" between the floor and ceiling supported by 1" birch rods. Gave the hovering in mid air look. Psychedelic

Other items was made out of birch plywood. Yes think IKEA, but nice plywood not particle board. All my stuff came apart, stacked flat, fit in the VW microbus.

Fast forward to today. Lots of books / sites about plywood construction. I need to build some things, but want to learn the state of the art, I'm not into using my Japanese micro cutting saw.

The teams that build with plywood help me with:

-- Plys seem to be thinner and they are doing more and more cross ply work. Is there a common way to ask for this?

-- Final surfaces are now coming into play, used to be birch only, now more wood types. Plus double sided finished sides are available for a reasonable cost. Where do you go for these items? whats the right way to ask for nice surfaces.

-- Laser cut is the art - +/- a 64th. So tight fit is possible. Who cuts this for you? Is it very expensive? What CAD do I need to supply?

-- Other cuts -- I have a carbon tipped 1/64" blade to make clean and smooth cuts. Is the laser cuts as good ?

-- Assembly -- Fine miters and dados with some screws worked. Now there is lots of camber bolts/lock devices. What do you use to keep things from coming apart. I'd like to take this apart, so "glue" isn't a primary option. I'm good with 'biscuits" for support, but don't want to glue them, unless I'm building a larger surface. I've been surfing the Blum catalog, lots of choices there

-- Finish -- I'm a master at raw edge finish with glue and veneer. I see the T plastic and some T wood edging available. Do you finish the raw edges or go "its a robot that kicked you in points, deal with the edges"

Thanks for your help!

Just as an aside, if you can't answer the question, but you build robots that are 51% wood, post that you use wood.

Re: Plywood - talk to us about how you use plywood
 

I can only competently answer a few of these:

S2S (Sanded two sides) is the term for very smooth on both sides.

Aircraft Plywood is one term for high-ply material, 'hardwood plywood' is the term for what used to be available only in Birch (but now in oak, maple and cherry for example).

Both are available at my local Lowe's, and the really thin aircraft stuff is available at Michael's and A C Moore (craft store chains here in NJ).

Lasers leave a charred edge, most saws don't. Straight cuts are superior on a table saw, curves and complex shapes are trivial for a laser. But thick material (3/4") isn't easy on some lasers.

Re: Plywood - talk to us about how you use plywood
 

We have not used that much of it in the past, but our pit neighbors in Seattle did. 1899 had a gorgeous plywood robot, and we plan on borrowing some of their construction techniques this season.

I've attached a few pictures I took at Seattle this year. For robot building they had cycled through a bunch of different kinds, but ultimately settled on this 5mm sanded ply, which is actually slightly thinner than 5mm. It is super cheap (under $15 for a 4x8 sheet). They sealed it as sheets, and then just put it in the laser cutter and got out puzzle pieces. In cutting the joints they didn't consider the kerf of the laser and the joints were definitely plenty tight.

Because the wood is so cheap, they built multiple iterations of their frame. I forget the exact number but it was at least five. Due to the puzzle-piece nature they also had some fun figuring out the best order to put it together. To hold it together they buy wood glue in 5 gallon buckets, and spent a sizable amount of money on Harbor Freight clamps. Anyone who went to their pit can attest that they had a lot of clamps.

If someone from 1899 is around feel free to correct me or send me a PM, because I've actually got a few more questions.

Re: Plywood - talk to us about how you use plywood
 

We used layered plywood to make prototypes, such as our shooter this year.
Other than that, we dont really use much plywood.

A bandsaw is great for making curved cuts when you don't have a laser. smaller cuts may require thinner, wood specific blades, but other than that, bandsaw, table saw, and jigsaw are all the tools you need to make just about anything out of plywood.

My favorite for assembled/disassembled are dowels and screws. I made a locker organizer that was assembled in situ, and disassembled when you had to swap lockers. Just used dowels with some #8 screws to hold it all together. I could easily stand on the shelves in place (3/4 marine ply ftw) and it all came apart in about 5 minutes.

Re: Plywood - talk to us about how you use plywood
 

We've never used much plywood, In the past we used 1/4" to fasten and support the electronic components since it made it easy to mount them but now we have been using a lighter corrugated plastic the past few years.

In the past 4 years I've been on the team, we haven't had any plywood on our bot (besides bumpers). We try not to use it in prototypes with high speed applications (our shooter this year for example). It causes far too much binding. Even in other prototypes, we rarely use it. We just find it easier and quicker to use other materials such as 80-20

Re: Plywood - talk to us about how you use plywood
 

It causes too much binding? I think that's a design issue and not a material issue.

We've run multiple shooters (both this season and last), along with many other systems out of plywood.

Wood is good.

We primarily use 6mm baltic birch ply that we get local in 5x5 sheets and we usually router it. We have used some 12mm for thicker items.

It's a great material, VERY STIFF. This stiffness if often very useful. Cutting it at .25" depth 300 ipm is nice too!

I'm sure if you took your time in planning and designing to build with wood, it would be fine. But whenever we use it, it ends off being off just enough to where it isn't running at the efficiency that it should. Then you have to re-drill holes, and it becomes a pain. Where as with aluminum extrusion such as 80-20, if you are off by a bit, you loosen the bolts on the sliders, move it to where it needs to be, and you're done. Now,
with the competition not, we waterjet all parts that require that amount of precision. If something is off there, then its most likely a CAD problem, not a machining problem.

Again, I'm not saying that wood is bad, especially in the right application, its quite good. We just don't have the time and precision to use it.

BTW, we don't have access to a router in house. Any machining we do on wood is with a cordless drill and a chop saw.

Re: Plywood - talk to us about how you use plywood
 

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to clarify, I wasn't criticizing you. I was just making sure impressionable students who crawl all over chief weren't interpreting information the wrong way.

Re: Plywood - talk to us about how you use plywood
 

We've used 5'x5' 9-ply baltic birch on our last three bots, two of which did very well at competition, includes finalist at regionals and two time champion at off season events. The last two years our frame was also plywood. In 2011, our telescoping elevator tower was plywood--many thought it was aluminum until getting a closer look. 2012, our frame and ball path and shooter assembly was plywood with an aluminum gearbox for shooter wheels.

We've done all the cutting on basic wood shop tools, including hole saw for weight reduction, until 2013, where the parts were cut on a CNC router.

Re: Plywood - talk to us about how you use plywood
 

Wood is a friendly material. It's cheap, easy to machine, and "easy" to assemble.

There has always been wood on our robots (in recent years anyway). 2013 had a wooden shooter, 2012 had a wooden shooter, 2011 had wooden panels, etc.

When buying, we just find plywood that is as stiff or as flexible as the application demands. "Machining" is done with a table saw, jigsaw, and rotozip combination. Wood is material that we do not worry about tolerances. Engraving can be done with a laser engraver.

Good luck on your endeavors!

Re: Plywood - talk to us about how you use plywood
 

Wood is useful for prototyping. Our main use for plywood is for a core material. We use 4mm, 1/4" or 6mm Baltic Birch ply and put a layer of 5.7 oz plain weave carbon fiber on it using vacuum bagging method. In 2013 our shooter platform and electronics boards were done this way. Could we use other materials, yes, But it's a good intro to composites lesson. I'm being pushed to try honeycomb or foam core materials for 2014. You can't beat plywood in availability, price and performance in this app.

Re: Plywood - talk to us about how you use plywood
 

-- Plys seem to be thinner and they are doing more and more cross ply work. Is there a common way to ask for this?

Baltic Birch is my "grade" of choice, however my local plywood shop also introduced me to "Russian Birch" plywood, which they said was less expensive because the glues were less water-resistant. You can also take a look at radio control modelling shops (or even airplane shops) for a range of plywoods. My main concern, rather than the number of plys, was always that they be relatively void-free. http://www.aircraftspruce.com/menus/wp/plywood.html

-- Final surfaces are now coming into play, used to be birch only, now more wood types. Plus double sided finished sides are available for a reasonable cost. Where do you go for these items? whats the right way to ask for nice surfaces.

S2S has already been mentioned, I believe you may also see it as "G2S", short for "Good 2 Sides". My experience is that most of the high-end, low-void plywoods might have one side that is slightly better than the other, but both sides are usable.

-- Laser cut is the art - +/- a 64th. So tight fit is possible. Who cuts this for you? Is it very expensive? What CAD do I need to supply?

Laser cutters are becoming more and more affordable. Ones that would be useful for FRC chassis sized pieces are starting to come down around $10k or so... more than a team might spend, perhaps, but a local hackerspace or similar community might have them. Commercial providers are also seeing the potential in this business http://www.umake.ca/ but your best bet, of course is to find a local college or woodworking business with a laser cutter and an interest in sponsoring your team. The cool thing about laser cutters is that the cost of operation is essentially zero. Photons come pretty cheap.

-- Other cuts -- I have a carbon tipped 1/64" blade to make clean and smooth cuts. Is the laser cuts as good ?

The advantage of the laser cut is the CNC speed and precision. We didn't use a laser for our machines, but rather a CNC router. (I do, however, bow to 1899 and their laser-cut awesomeness.) Mechanical cuts will likely be slightly cleaner, and in thicker pieces where the laser focus comes into play, may be slightly more square and will be free of the "burnt edge" finish, which you can see as either a "feature" or a "bug", depending on whether the burnt edge looks good in your final product.

-- Assembly -- Fine miters and dados with some screws worked. Now there is lots of camber bolts/lock devices. What do you use to keep things from coming apart. I'd like to take this apart, so "glue" isn't a primary option. I'm good with 'biscuits" for support, but don't want to glue them, unless I'm building a larger surface. I've been surfing the Blum catalog, lots of choices there

There are so many choices... and so much of the choice depends upon design. For a simple and robust design in 2010 (our last FRC bot) we just ran a piece of 2x2 on the inside corner joints and screwed the machine together. Key structural pieces that we weren't going to disassemble were glued up with white glue. It was more than enough to smash the aluminum bots around pretty good. http://www.chiefdelphi.com/media/photos/34972 (and, just for the record... most of the cuts on the machine in that link were done using table saws and drill presses... only a few crucial connections were made using a CNC router... no laser was used in the design.)

-- Finish -- I'm a master at raw edge finish with glue and veneer. I see the T plastic and some T wood edging available. Do you finish the raw edges or go "its a robot that kicked you in points, deal with the edges"

Baltic Birch offers up some nice edges, especially as the low void content allows you to router half-round and quarter-round edges, but the key thing to building with plywood is to make it look nice. Well, make it work does come first, but then make it look nice. The key detail is to stain and seal the wood before it has a chance to get dirty. Unlike metals, wood is porous and will absorb oil and grease at the first opportunity. My experience is that a nice clear coat finish (stains and dyes can help achieve team colours while letting the wood grain show through) and good sanding job will catch the judges eyes every time. We have received at least three engineering awards over the years that specifically recognized our use of wood. When I had to give up mentoring and took up volunteering instead, I spoke with one of the judges and he told me, "Oh... you're from the team that always used wood. Lots of teams build with plywood, but you guys made it look NICE."

So let your woodworking aesthetic come through, and remember that wood comes in many more forms than just plywood! http://www.chiefdelphi.com/media/photos/22924

Jason

Re: Plywood - talk to us about how you use plywood
 

We have access to laser cutting via a sponsor (Edgetech). Results are extremely accurate (based on CAD file), but edges are scorched. We've used laser cutting sucessfully for plywood, polypropylene and steel. I love the results when cutting complex shapes and patterns and multiple pieces.

We would only use laser for complex patterns. For most of our plywood cutting, we use saws.

Re: Plywood - talk to us about how you use plywood
 

If you don't have access to a CNC router, but do have access to a 3D printer, here's a technique we've used.

Print a template of the part you'd like to (accurately) produce, at least 4mm thick (and in multiple interlocking pieces if the piece is larger than your printer envelope). Fasten the template to a rough cut piece of plywood using screws or double sided tape, and run the sandwich across a router table with a pattern trim bit installed (A team member with woodworking experience is a plus for this part). The resultant part is accurate and has a nice clean, smooth edge.

We used this technique for making our shooter rail (2 pieces of 3/4" oak plywood laminated together), and a support ring for the feeder bucket.