Coordinate controlled XY Table - Hardware and software help

Projects General Guidance
1

Hey Everybody,

I hate the fact that my first post on here is one asking for help, but I have a project I am working on and need some assistance. Please feel free to let me know if you think another item would work better.

Here's what the idea is.

I want to create an XY table. A system that can move along the X and Y axis. This is going to be set up as if the Z axis is going into a table top, the X and Y axis are set up so that they move around on the surface of the table. I want to control the location of a servo attached to the system by means of predefined coordinates. I want to be able to have a list of, let's say, 12 coordinates. I want the stepper motors to move a servo to each coordinate, have the servo rotate a number of degrees (approx. 30 degrees) and then back the same number of degrees, and then move on to the next coordinate and so on for all 12 coordinates. Does this seem feasible? I imagine I will have to do some calibration with the coordinates but that is fine.

Now, my thoughts for the overall control of this system. Use an Arduino Mega 2560 [ Arduino Mega 2560 R3 - DEV-11061 - SparkFun Electronics ] (I am open to suggestions for which board to use) for the main control, have a button that is pushed to initiate the sequence, a stepper motor driver that controls two stepper motors [ http://www.sparkfun.com/products/9238 ] for movement in each of the axis, and then have a servo controlled via the Arduino Mega.

Here are my problems:

  1. Can a quadstepper motor driver board [ http://www.sparkfun.com/products/10507 ] successfully control these two stepper motors in the way I would like, or do I need to interface two easydriver stepper motor drivers [ EasyDriver - Stepper Motor Driver - ROB-12779 - SparkFun Electronics ]?

  2. Code? I have experience with Picbasic and such and have been reading into the code used with arduino. I looked at some of the examples provided with the sketch environment and have an idea as to how it works, but as far as carrying out the coordinate sequence I am unsure of.

  3. Are there any other items that any one can think of that I should incorporate into this system?

I know this is a lot of information to take in but I wanted to make sure that I show that I've done my research and I just need some input as to what direction to go. Again, I've worked with pic's and picbasic but I think arduino seems a lot more user friendly and has a lot more potential. So I figured I should make the transition! Also, Check out my picture to see a simple sketch of my desired system. Thanks.

-Marcus

Table-Schematic.jpg
Table-Schematic.jpg2550×3506 393 KB

2

Now that you've made your first post, you can post links. Please edit your post, to change the part numbers to links.

3

Have a look at my CNC conversion project, that will give you some idea of the circuitry involved and the software you need to produce.
http://www.thebox.myzen.co.uk/Hardware/CNC_Conversion.html
As well as the stepping motor driver recommendations.

4

Hi SnowWhite,

here is a link for a basic CNC milling machine from
http://www.milinst.co.uk/ goto the online shop and select the software and downloads tab
then sellect the files for 3 axis machine then press the download button at the bottom of the page.
you should be able to get some information from here for co-ordinates etc especially if you can get a copy of visual basic to open the source code files.
J.

Also Grumpy_Mike's CNC is bloody excellent, wow - that is a nice piece of engineering.

5

How good your table movement is depends on how well it's made. You might make do with an X-Y vise though it would be good to measure position directly and not trust crank turns.

How does this table look as an intermediate value? Prox Tech 27100 Micro Compound Table KT 70
http://www.google.com/products/catalog?hl=en&sugexp=kjrmc&cp=5&gs_id=v&xhr=t&q=x-y+table&tok=ejePQlfOmOJRDCfTJ0Exew&gs_upl=&bav=on.2,or.r_gc.r_pw.,cf.osb&biw=1058&bih=593&um=1&ie=UTF-8&tbm=shop&cid=7523942068726318032&sa=X&ei=N7GwTqelK6b00gGOvfCtAQ&sqi=2&ved=0CHsQ8wIwAQ

6

That compound table is what I used in my project. It might be a little small for this project, but I don't know because the OP hasn't said what size he (or she) wants.

7

With all the closed down fabrication shops in this country a used, slightly worn Bridgeport can probably be had relatively cheap to someone who's got the space and a 220 line. At least I doubt they've all been scrapped.

There's no way to compete with nations that subsidize their industries AFTER your taxes modernized them and your government has been hell-bent on destroying skilled labor for the last 50 years.

8

I want to create an XY table. A system that can move along the X and Y axis. This is going to be set up as if the Z axis is going into a table top, the X and Y axis are set up so that they move around on the surface of the table.

From that comment and your diagram it looks like you are moving the Z Axis head over the table. Typically vertical axis milling machines move the table under the head, there are probably good design reasons for that so you might want to think about it. Grumpy-mike's projects look first rate and the compound table seems like a good deal.

What is the system actually for, and what sort of sizes/weights are involved ?

9

Moving the table under the tool head means you have a solidly aligned tool head. The only things I know that move the tool over the work are very light cutters, pens and the like.

10

Sensors/switches on the ends of each axis probably are useful to prevent the head moving further as possible and to set a "Home"-point where the table could start a new task.

To get ideas of other things you could implement www.cnczone.com might be a nice place to visit,
it's one of the biggest sites on all kinds of CNC-applications.

11

Thank you all for the input. I want something that is very simple, so some of the CNC stuff may be more complex then what is necessary. But I will review the code for it and see what I can decipher from the other examples.

What is the system actually for, and what sort of sizes/weights are involved ?

The size of this set up is 12" by 20". This XY "table" is going to be suspended so that it is more of a motorized truss system. All that it will be moving is a small hobby servo that has a copper rod arm on it that has a piece of 1000 degree celsius heating wire on the end of the arm. So the overall mass of the system that has to move is no more then a couple hundred grams, if that.

My original idea was brought to life due to this guys design, http://www.instructables.com/id/Low-Cost-Hobby-Servo-XY-Table/. I like his simple and straight forward, but want better control and figured stepper motors coupled with an arduino controller would be the best route.

I attached a drawing of the idea if it is suspended above a table and you are looking at it from the side. Sorry if this makes it more confusing, I'm just a visual learner and like to see pictures to grasp what is going on.

I appreciate the input from everyone. Thanks again.

-Marcus

front view.jpg
front view.jpg2866×1228 167 KB

12

How does this table look as an intermediate value? Prox Tech 27100 Micro Compound Table KT 70
http://www.google.com/products/catalog?hl=en&sugexp=kjrmc&cp=5&gs_id=v&xhr=t&q=x-y+table&tok=ejePQlfOmOJRDCfTJ0Exew&gs_upl=&bav=on.2,or.r_gc.r_pw.,cf.osb&biw=1058&bih=593&um=1&ie=UTF-8&tbm=shop&cid=7523942068726318032&sa=X&ei=N7GwTqelK6b00gGOvfCtAQ&sqi=2&ved=0CHsQ8wIwAQ

No offense, but I think buying a table and modifying it may be overkill for me. I feel like I could build a reasonable table for a good price. With the dimensions that it needs to be, it most likely will have to be custom made to fit my application. Thank you for the link though. I appreciate all of you taking the time to look into the project.

13

LOL, if you were willing to go a bit smaller then you could probably get your movement hardware out of an old flatbed scanner!

You might even be able to get away modifying a pen plotter, the head would move one axis and the work roll along the other.

14

LOL, if you were willing to go a bit smaller then you could probably get your movement hardware out of an old flatbed scanner!

You might even be able to get away modifying a pen plotter, the head would move one axis and the work roll along the other.

That is actually not a bad idea! If I can find a printer/scanner'plotter that runs on a rod as a guide system, I can just replace the original short rod that is in it originally with a longer one that gets me the length I need!

However, the mechanical part of this system is fairly straight forward for me. It is more so the electronics and determining if I have the right arduino boards or not. I'll have to dive into the code and see what I can get going. I may have to order all the parts first so that I can write code, test, reiterate code, re-test, and so on and so fourth.

15

There is another downside to moving the tool over the table. Your power and control lines have to flex to do it.

If you are measuring position by stepper rotations then are you compensating for backlash?

16

There is another downside to moving the tool over the table. Your power and control lines have to flex to do it

Printers use ribbon cable, that seems to work well at least in one axis.

1000 degree celsius is quite warm :slight_smile: Presumably you are cutting a plastic or something, what is the application?

17

There is another downside to moving the tool over the table. Your power and control lines have to flex to do it.

If you are measuring position by stepper rotations then are you compensating for backlash?

I've used the right gauge wire that is flexible enough that it allows movement, but it allows provides significant current without melting any wires or causing any problems.

Since I am a newbie, what do you mean by backlash? Sorry if that is a dumb question....

Printers use ribbon cable, that seems to work well at least in one axis.

1000 degree celsius is quite warm smiley Presumably you are cutting a plastic or something, what is the application?

That is a very good idea. If one motor is stationary and moves one axis by means of a belt, the only other thing moving is the servo and the other axis stepper motor.

The application is simple. Starting grass on fire. We are testing in what conditions this grass will ignite when it comes in contact with a tracer bullet. Hence the reason for a heating element the size of a pencil eraser that hits 1000 degrees Celsius. This entire system needs to fit inside of a climate controlled wind tunnel (approximately 15 cubic feet of air within the wind tunnel) that I have designed and built. Meaning it is humidified, dehumidified, heated, and of course, the wind speed is controlled.

Right now I am using a servo that is on a bracket that can be turned by hand from the outside. But, we need to get more tests done and so I am trying to design a truss system to allow us to covering the floor of the wind tunnel with test beds and have the entire ignition system suspended above it. So, while a moving table is best when using it as a CNC machine or something along those lines, it is not practical at all in my case. Unless the moving table is inverted and strapped to the roof, which some of these heavy drill press and lathe vise/XY tables will not suffice.

You can see in the attached picture, through the top window, our current method of igniting grass - two copper rods attached to nickel chromium wire that is rotated via a servo. Pretty ghetto rigged but it works amazingly.

IMAG0131.jpg
IMAG0131.jpg3264×1952 993 KB

18

You're going a bit far to be the Mythbusters team....

19

what do you mean by backlash?

The fact that it takes a bit of movement from the motor before the table starts to move when changing direction.

20

We are testing in what conditions this grass will ignite when it comes in contact with a tracer bullet.

Hmmm.... :~ I am glad I asked, but you have just made me even more curious :slight_smile:
My guess is that you are trying to work out when you can "safely" fire tracer bullets without the risk of a fire - is that right?

Is this a domestic or military application?
Will there not be a mixture of combustible materials such as bushes and twigs that would still leave a large element of chance?