Let's Make Robots!

Wild Thumper as a LINE CUTTER robot. Who wants to build it?

Hello you robot builders,

Due to lack of time (and experience) I would like to find someone, who wants to help 'build' my robot.
I bought the wild thumper + the mainboard WTR-CK1.

What do I want:

The robot will be placed on a table that has a 'printed banner' on it. The banner has a 'black-white-black' stripe on the side

where it needs to be cut. The robot has to 'drive' along the line and pushes down a 'knife' while driving.

When it gets to the end of the marker, the robot has to make a 90 degree turn, adjust to the next 'line' and continue
its cutting. This has to be repeated until the banner is cut (4 lines, 4 sides).
In the picture, you see an example of what we might be able to print.

The 'cutter' is a very easy 'autorotating' knife, that has to be pushed down with an electro magnet.
If the robot produces a 5 volt signal at te time of cutting, I will get the knife myself.
Of course, the knife will be a little bit 'behind' the sensor, so it needs to 'start' cutting with a delay.

We are situated in the Netherlands.

I'm serious about this project, so please react if you think you can help me build this!!!
Of course this has not to be done for free ;-)  We will discuss costs and I'll pay them using PayPal.

Michael Jerie

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Hi

I think the task might be done by a robot but not using differential steering, which may leave tire marks on banner, as Oddbot said, and using an steering mechanism as most of the cars use (like Ackermann).

In this way, you can use a line follow module to track the lines you print on the banner and adjust your robot path accordingly. In this way the precission of cutting is given by the resolution of line sensor and by the width of line to be followed.

To turn for next cutting line you could have an additional turning path, not included in banner print.

How accurate does it have to cut? The simplest way is to put encoders on the motors. Then let the robot drive for x number of encoder pulses. But it will be extremely difficult to make the robot drive in a perfect straight line. The resistance of the knife, loss of traction of the wheels will make it near impossible in my opinion. I think you're better of trying to find another solution...

I agree with Bajdi that aside from leaving tire marks on the banner, getting the robot to cut a perfectly straight line (even with encoders) will be impossible.

If you insist on trying to use a robot to "line follow" around the banner then the Rover 5 (2 motor version) would be a much better choice. It has encoders built in and won't rip up or mark the banner material like the Wild Thumper can.

I would suggest this combination / kit from Robosavvy. If outfitted with line following sensors and the knife mounted on a servo (to raise or lower it) then I suspect this would be much more controlable and easier to program.

The material we print on could be very large. 10 meters x 320 cm.
Any XY table (even self build) will cost much MUCH money.

An XY table also takes a lot of space and the table will propably not be useable for something else.
Thats why I thought a 'robot' that 'runs over' the material makes it very flexible.
'Size' than doesn't matter. I just need to make sure the surface is flat.

@chris. Due to the nesting of small and large 'banners' the cutting rod you mentioned doesn't work.
Cutting out a smaller job that is enclosed with 2 longer banners is too much of a hassle.

@ birdmun.
Controlling the location? I though that the 'robot' is to be placed my someone at one start point of a banner (either
driven there by a controler or just put there). Then it just runs until it reaches the end of the banner (mayby by using a pattern
in the line so that it knows the end is within 10 cm). Then, by making some forward/backward motions, it makes a 90 degree turn
and continues its path. Doing this 4 times gets it back to were it started.

 

On the other end you could just skip to draw the outline of the banner on the paper by using that one out of OddBot's lab http://letsmakerobots.com/node/34226 and a very sharp razor blade.

So, if we were to look at the goal here, it seems we need to cut a rectangle out of banner material (vinyl, I would assume). I think a utility knife might be a better way to go.

  • Long table designated for just this operation
  • A long rod with 2 "pizza cutter" wheels on it --The width of these cutters is determined by the height of the banner
  • 2 people walk the length of the table with this double-pizza-cutter-rod and cut the two long sides in one go
  • A simple draftman's T-square (or drywall square) is used to cut the ends

From there, you can get as fancy as you want --maybe just a series of "tracks" that a knife could run in? Etc. etc.

 

Don't get me wrong, I like the idea of adding a robot to just about anything. That said, I own a $2000 rotary laser level, but I almost always use my water level instead --A $2 piece of clear tubing with some water inside.

KISS

I believe controlling the location of a robot is a good deal more difficult than controlling the location of an X/Y table. You will need to take a bit of time to make sure your steppers aren't missing steps due to accellerating too fast, or, too much drag when they start to move.

The problems you will run into with covering 3.5m is gravity. Any mass over that kind of length will require a bit more engineering than a simple X/Y table. I'm not saying it will be difficult. Just not as easy as an inexpensive DIY table.

A home made X,Y machine should cost a lot less. The knife is not a heavy load so a simple XY machine with 2 stepper motors and a solenoid to raise / lower the knife is all that's needed. Then you just need a simple Arduino controller and some basic software.

Admittedly you can use the Wild Thumper as a line follower to cut along the line but it seems to be over kill. If it overshoots a line then you could have a berserk robot with a knife running about :(

What gear ratio did you buy?

 

@ChuckCrunch

Thanx for the knife idea!

@OddBot

1) The picture. I thought I had one with the marks I meant but I don't. I'll have to make it.

2) I was hoping to find someone who would want to do it. It doesn't cost to ask.

3) A dual axis machine would do the job to BUT because the printer we use prints at a width of 320 cm.

We have a table that is 350 cm width and 12 meters long. The 'thumper' could just drive around it.

A dual XY plotter (we have a 160 x 250 cm one) in that size costs $120.000 and up.

At present, we roughly cut the banners (different sizes are nested on the 320 cm width) and then use

a linear cutter that slides along the table to make a 'clean cut'.

This means that every banner has to be rotated 4 times and positioned 4 times to cut it nicely.

That's why my thoughts were to something that runs over it.

Another problem I just thought of with the Wild Thumper is the tires tend to leave black skid marks on smooth surfaces. My laptop still has tire marks where it got run over by one of my robots.

I don't think you want tire marks on your banners.