As nice as torsion boxes are they are not magic, for all the complications building them there is very little to gain.
A flat piece of wood on a basic box or other table is 98% as good. I have built my first torsion box and have only used twice so far. 8+years of a sheet of wood on top of a work bench.
When everything is up and running and you have learned how to use it well, then maybe use it to build a torsion box. This is the reason my parametric table does not use interlocking joints, CNC not required if you want to build a fancy table first. Also, the reason I have never made one before. I do not want people to think they are needed, or a magic bullet. Chasing zero’s quickly gets diminishing returns.
I understand and certainly don’t disagree with everything that Ryan has stated here. The one piece of the puzzle, though, that comes into the equation is that for a full size table, that piece of board needs to be bigger than any board that can be bought. For newer LowRider makers who want to be able to do full sheet cuts, the torsion box solves a big problem - how to make a table that big. I think this is why the CNC-cut “bootstrapped” torsion box table has such appeal.
I don’t agree. I think it is a way to make a larger than a full sheet table, but the other way is just stick some wood on another table or some 2x4’s. What I am getting at is this is a very nice table, it holds it’s flatness very well, but so can a regular box table which is far easier to build.
Anything we add, adds difficulty. Touchplates, endstops, tables, lasers, homing. For someone new to CNC there is a lot to learn. Once you have made a crown or other fisrt projects things get easier but telling people they NEED a touchplate, homing, lasers, or a fancy table just make the barrier to entry far far harder.
Quick question: What is the work bench made of? Specifically the bench top. When you say “work bench”, I often think of a woodworker’s bench, which is usually 3-4" thick laminated edge-grain slab. Which is pretty dead-flat and stable when done properly. So yeah, you don’t need a torsion box. But the torsion box would replace your benchtop. A 3-4" thick torsion box would have the same flatness and stability as your benchtop at a fraction of the weight, when properly constructed. Putting a torsion box on top of a slab benchtop is a redundant mess, but putting one on a couple of saw horses or a simple frame makes for a lightweight bench.
There is nothing to “gain”, but a LOT to “lose”. Namely, weight. When properly constructed, a torsion box has the same flatness and stability as its equivalent solid slab (whether monolithic or built-up), but can be significantly lighter.
But I will also grant you that they aren’t the easiest thing to construct correctly (you have to make sure the cross members are connected properly, and the skins are well glued to all the cross-members, etc.), and are not a magic bullet for all applications. But I think that for the large format table needed for the LR3, especially as you start looking at full-sheet capability, a torsion box makes pretty decent sense.
2x2" cheapo lumber and 1/2 MDF. You can see it in my older pictures.
I don’t agree with that either. My new table is far heaver than my previous one.
We have a machine that is capable of flattening its own surface. If you have noticed, a lot of the youtube woodworkers are moving back to slab tables. Torsion boxes are kinda cool but a box is a box is a box.
I’m not meaning to imply that the torsion box, let alone a CNC cut torsion box, is the only way to solve that problem. Just that it is a way to solve it.
Had that been an option known to me when I first started, it would’ve been the path of approach I would have chosen. It would’ve certainly had its challenges, but trying to build what I built by hand without a CNC was extremely challenging for me. It was the hardest thing that I’ve ever tried to do. I think, looking back on what I had to go through to learn to cut plywood, etc. accurately with the Lowrider, it would’ve been an easier path for me than the two table parts that I built that were not flat and didn’t provide a very suitable surface for me.
Edited to add: it’s not just that the two parts assembled together weren’t flat, it’s that they weren’t able to retain their position in relation to each other, and in relation to the ground, without sagging and shifting, and thus merely flattening the spoil board attached to the top of them did not produce a lasting usable surface. I had to disassemble that thing, entirely, and rebuild it in order to get some kind of a base to hopefully hold the torsion box that I eventually put on top of it. For me, the table has been the absolute biggest entry point challenge. I’m basically three iterations into it before finally (from my viewpoint) getting help from a torsion box to finally arrive at something that is long term usable.
We have some experienced woodworkers coming in, and some that have never done anything as big as a table. The recommend route is Any flat surface you can find. A fancy table of any kind is a great project, but I feel it is far from a beginners project. A beginners project is the crown. Then some foam carving. Jumping straight into overlapping joints with tolerances to worry about and squareness is a brutal first project. The strut plates are a extremely brutal start to CNC but you can do all sorts of stuff before even using them, and if you get them wrong a couple screws and you can swap them out. If you build a skewed and bowed table that is glued together, that is a huge expense and no easy way to really fix it other that deal with it or rebuild.
You would be surprised at how many people have done little to no woodworking that are starting this. A couple sheets of MDF on the floor are perfectly suitable.
A couple 2x4’s with sheet wood on both sides are nearly as effective as a CNC cut torsion box. No fancy cuts are needed. You can have nearly all big box stores rip the ply down for you and screw it to a couple 2x4’s, done. There is no way that is more difficult than even buying a precut torsion box kit.
For all newcomers who do not aspire to a table big enough to address the blade at every square inch of a full sheet of MDF, or full sheet of plywood, this whole question is a non-issue. It is only that percentage of new LowRider makers who have as a set goal that they want a table big enough that they can address a full sheet in their usable cut area that have this challenge. For that newcomer, the challenge of building a table that is bigger than any piece of board they can buy, is a question that is in search of an answer. There’s no doubt more than one way to accomplish it. In this regard, although it is a great challenge for them as a newcomer, it is a challenge they have laid upon themselves. At least in my case this was certainly the case. I set this challenge for myself.
Have you seen his shoes? The whitest shoes I have ever seen (a long time ago, in a galaxy - errr forum post, there was a pic of his shoes as he was showing something, and then a reference to Fred Durst was made)!!
Heh… I think we’re probably talking past each other at this point.
Something that struck me when I actually saw your picture of a “janky table”: On the grand scheme of things, we’re not putting a lot of load on the table. The gantry rides on the edges, and the stock is distributed across its face, and the work we do is relatively gentle. So yes, your table is likely more than sufficient for the work. But I’m guessing that it might not be stable enough for some serious woodworking tasks (I’m thinking assembly, maybe something requiring hammering, etc.) due to flexing/springiness in the center. This is where you would either laminate dimensional lumber for an edge-grain slab, or build a torsion box. And there’s a reason why most “beginner’s workbenches” have glued up slab benchtops rather than torsion box benchtops…
Edit: And let’s be honest, this forum is not exactly known for under engineering anything…
This is what I was referring to above. Any machine with a footprint bigger than a full sheet, can have sheets cut at the store and put them together in many ways. I am just discouraging overlapping joints as a beginners project. Plotting, cutting strut plates, carves, or lots of other things are good for learning. It is cheap and mistakes or poor choices have very little consequences.
My viewpoint is that of the MPCNC, and now the LowRider. So many people used to build giant MPCNC’s because they could. I strongly strongly advised against it, and now lots of people are building full sized LowRiders…After some use they realized they did not need huge machines and a common reason to rebuild is to downsize and cut faster.
If people are getting frustrated with making so many larger precision cuts, or spending a ton of time or money on a Torsion box only to realize they will never ever cut anything 8’ long just makes the barrier to entry a worse experience and the barrier to cut it down to a reasonable size for their use impossible without a rebuild in most cases (glue).
I want people to dip their toe in, not spend a ton of money, enjoy using the machine, get them over whatever hurdle they are having (building, wiring, cad, cam). Then make an informed choice about the size and permanence of the machine…or if CNC is even for them. I feel the best way to ensure people stick around is make sure they get some time under their belt before getting too frustrated or spending too much.
One day when we make $20k CNC’s than overkill is the best option, but for now users first experiences are my biggest concern.
There are a few 1x’s in the middle. That is kinda what I am getting at. My Janky table was made with scraps, and every machine and project I have built was made on it or a table just like it for years has been great.
The point I am getting at is for CNC work, it is simply not needed. If down the road you decide to use your janky table for beating on, by all means build something fancy. I am just trying to stress not pushing people to make something so extravagant so early in the CNC journey.
If you know you are building cabinets on it, and know you will get use out of it, woodworking is no big deal and you have made overlapping joints before…heck yeah go big or go home.
WE know that but people new to the scene might not understand that part and think it is required.
Perhaps if you (or someone else) create illustrated plans and instructions for building a table large enough to accommodate a cut area of say 49 x 97, which is an easier approach, doesn’t involve cross lap joints, or perhaps even doesn’t involve CNC cutting, then it would allow an easier path for what my intended goal was for the parametric torsion box offerings that I have made. My goal is not Parametric, or CNC cut, or torsion box. My goal was to get a full-sheet-cut-capable table within entry reach of the new LowRider maker, who, like myself, had that as a set goal. If there are easier ways to do it, then, by all means.
There is certainly nothing wrong with communicating to newcomers that a full-sheet-cut-capable table is an advanced path that they may find was not necessary after they get their bearings, and still offer plans for it for those who are dead set on it anyway.
I’m in the process of doing exactly that . The end goal is to create a torsion box table (permanent), but the interim step is to take one full sheet of 3/4” ply, cut a second sheet into one o12”x8’ strip, and a second piece of 2’x5’.
I’m purchasing 5 or 6 10’ 2x4s with the intent to use the Full length pieces on 20” centres, using a remaining 1’ wide scraps from the second sheet to “scab” together the full sheet to the 1’x8’ piece. And then cut 1 or 2 of the 10’ boards in half and use them as cross braces. This whole assembly will sit on a couple of sawhorses with planks supporting the cross braces.
This will make a whole lot more sense when I get off my phone and onto my computer and sketch out the design visually.
Edit, I just realized that scabbing the plywood together won’t have any structural integrity, so I’ll use 6 boards on 12” centres, and toenail the plywood to the one board that supports two pieces.
Aaaargh, I hate trying to edit these posts on my phone!.
It’s not fancy at all, and all I did was shim the spoil board to take out some of the bigger dips and make surfacing easier.
The CNC cut parametric tables are nice and take a lot of the guess work out of sizing etc if the calculators are nice, but I think my table is about as entry level as it gets.
I did take the time to flatten and cut down my 2x4s, but I don’t think it was strictly necessary. No lap joints, just screws and butt joints.
He said it only has to be “flat-ish” enough times that I believed him.
It was half scraps, and a purchased sheet of plywood, and a purchased sheet of MDF or two to cover it.
I started with the idea that I needed a fancy table, because I wanted it to fold out the way, etc. but this “design” (I use that term loosely, because I was winging it) easily would do a full sheet if I had bought longer 2x4s for the side, and is sturdy and really all anyone needs if they have the space for it.
