Let's build a TBot cartesian motion platform 

Addendum: bunch of folks have (correctly) pointed out that the pulleys/belt path are not parallel and going to cause all kinds of grief. They were right :) Since this video has aired, I've torn apart the mechanism and replaced some of it with ballscrews (for different reasons, but it did fix the belt issue :) ). Whoops!

Love seeing H/I/T bot designs, even better to see someone building it from scratch, can't wait to see more!

That isogrid looks fantastic. I've newly discovered your channel and feel bad pointing out a problem 🤦‍♂️, hopefully not too late but have to say there's an issue with your belt layout. The belts need to be parallel to the axes, if not you will find that motion isn't linear throughout the range of travel. Particularly towards the ends of travel where the angle between the belt and the axis becomes greater. It's hard to communicate without a diagram but when the belt and axis form a triangle shape, the angle of that triangle becomes greater towards the end of the axis and for each mm of travel of the belt, the travel of the axis is less and more importantly less than it is in the middle of the travel. I hope that makes sense, it's something I had a problem with on a CoreXY printer build

Your videos have been a great help to me, thanks, keep up the good work:) Many people already mentioned this, but I had the same problem with Mach 3 losing/ignoring z offset and I made it a habit to re-zero the z multiple time to get rid of this "bug". switching to LinuxCNC using a mesa card and linear encoders years ago gave me a peace of mind and accuracy:D

Looking good, just tighten those belts! Cartesians are particularly vulnerable to backlash in timing belts. Another trick is to deck off 5-10 thou from the top as your first op; will make sure all vertically machined surfaces are perpendicular to the top face regardless of stock warping. Added bonus: if you have a second op on the backside you have a prepped datum surface

I've never seen this kind of design! Thank you for the awesome video!

If you bend a curved surface to be flat when machining, wouldn't it just recurve itself after unclamping?

this belongs on the list of cool things and channels I found on youtube this year

this guy is very underrated

Interestingly, the motivation for a launch service provider like SpaceX to make everything as light as possible is not to save on fuel but rather to increase the potential payload mass. The more you can carry the more of the market you can serve. The maximum amount of propellant a rocket can carry is something decided by the size of its tanks rather than the mass of the vehicle (I mean in cases when you already have a rocket which you are modifying, in the initial design phase of course vehicle dry mass matters). You generally don't spec tanks to be much larger than what you would need for a max capacity launch (typically measured by max payload mass to LEO or SSO), and after the tank design is finalized there's no amount of mass you can shave off that will increase you propellant capacity so any future mass reductions are either passed on to payload mass (or to a different subsystem which needs more mass budget). As a related side note, the cost of rocket propellant as compared to the cost of launch operations and the rocket itself is relatively tiny, so paying for the propellant itself is never really a constraining factor unlike with aviation where fuel costs inevitably dwarf everything else.

We've been thread milling virtually every hole for years. Taps are never loaded into machines. The cam profile calls for 3 passes on each thread mill. I don't know if that's necessary, but that's what they are all set at. There is considerably less or a retract, and the linear (well sort of) speed is considerably higher.

Servos have encoders internal. If you want additional position information, extract it directly from the mobile platform. The sum of torques from your motor belt tension and the serpentine platform belt will stress your axle bearings considerably. I would consider adding a bearing near the serpentine pulley or moving the motors to the other side. Finally, how stiff is the orientation (angle) of the top strip to in-plane and out-of-plane torques? It seems to me that flex there is what will limit your position accuracy -- especially without direct part position measurement.

I realize it's already been said a couple times I the comments, but linuxcnc is pretty great. You can get up and running with just a parallel port and your stepper driver, essentially the same hardware you have for running mach. I've found it to be much more stable and it's pretty straightforward to set up. Additionally, you have the option to upgrade hardware later on, adding something like a Mesa card if you want to increase your speeds by generating a faster pulse train.

For a machining a big plate like that one thing you might consider is gluing it to the table. You can use super glue and double sided tape to make something somewhat removable.

Very cool. You may want to watch out, steel core belts can have the steel cores break from fatigue when they repeatedly go around a small pulley. If it suddenly goes mushy, check the belts.

I could see a design like this being very useful for the gantry on a plasma cutter

You will want to add some corner brackets to the tall legs. Otherwise it will wobble all over from the inertia. The vertical bolts into the 8020 just aren't stiff. Put the biggest triangle you can fit without interference

I've tried to find a follow up video but I couldn't. did you ever show a video of the finished version (in action) and an analysis on how accurate it got?

Really nice camera slider.

I imagine that rigidity of the setup is low because of the long belt but could be improved by a wider belt if it’s a problem. Would it be easier to mount linear encoders like a DRO system than the rotary encoders on the shafts, thereby removing errors in belt stretch and flex?

Iso grids have angled walls. Its not the triangles. Its the angled walls and there need to be holes in the vertices

the belt ends on the fixed end of the upper bar wont move - no wear to expect there. of course the loose end (the one with the single wheel) does have a relative motion to the bar - so it can be subject of wear if touching the upper bar.

Way late to the party - adding on, the x and y idlers aren't in line with the drive pulleys, which can cause a cosine error when the gantry is close to a motor as the belt pattern forms a more and more severe angle that isn't a square 90.

if anyone asks those are vernier holes for that rail. Let's you adjust its offset precisely by choosing which holes to use. :)

LinuxCNC for life! It takes a bit to learn, but once you have you can NC anything.

Possibly a scale discretion(XYZ) wise? Best bet to model is to create one side and then mirror and adjust/double check distances.

this made me really confused as to how the thing moves. don't get me wrong, the video is awesome. it's just the movement system that is really confusing. It's like a corexy design, but with 1 belt

Question regarding the kinematics. Doesn't turning one motor move the platform at a 45 degree angle? While the other moves at a -45 degree angle? So couldn't you just declare that the diagonals are the x and y axis, thus making each motor independent and simplifying the kinematics?

Nice video. Mic-6 or Alcoa's original tooling plate is actually a 7000 series aluminum.

Do you by any chance have any literature references for such a T-Bot system? I built one for my bachelor's project, but I cannot manage to find a single usable source for this mechanism.

Can this be used for plasma CNC machine? Is it a good configuration for plasma table?

Do you have enough a height for a chuck for drill bits? I have Taig mill and have a 3/8 arbor that goes in a collet then has a threaded end for a Jacob’s chuck. Makes drilling pretty easy.

Just to clear up: It's not the fuel cost that makes the difference on rockets but rather the payload increase and thrust to weight ratio (TWR), that's where they save money or more so where they can charge more.

Are you any good with an ' etch a sketch ' ?....cheers.

Awesome video. Can you, pls, share what motors did you use?

Is there a more specific term for the belt? because i only find the belts for ones pants on google xD

If it’s a servo motor it should already have an encoder, though, right?

How did you do the isogrid? I'm looking for a program to generate them.

I see a lot of people just dropping the software that comes with these things and using their own. There's even one written in NodeJS LOL

Giant etch-a-sketch

I like the ´hidden´ Subsribe button

T bot was my nickname in college

I'm a pretty big fan of LinuxCNC…

Is this mill your AvidCNC?

You gonna put a laser into it and make a kapton tape super duper capacitor?

this is a 6040 cnc? wich spindle do you have on?

Nice! Can you also blend in metric units into the video? Hard to follow, if you have to google everything

Could you make some Alu parts Out of an stl-file i would provide? We had to talk about costs, but would it be Generally possible?

mach3 is only as good as your comports! some comports can lock into a fault state easily; what's the baud rate? any controllers or direct connect to step/dir?

Real engineers use metric.

Can confirm Mach is terrible, incredibly Mach4 is even worse, if anyone learns anything watching CNC on youtube ut should be to NEVER use Mach for your CNC control.