crashsite

I was browsing the internet for info on an easily adaptable X-Y table and, while there are a lot of web pages, didn't really find a good "general purpose" one. I'm sure they exist but, aren't "easy" to find so, I thought I'd try a post here. I'm thinking of the, X-Y Tables for Dummies version.

The initial assumption is that the mechanical table will be stepper motors that will rotate lead screws for the physical motion in all three axes (horizontal (X and Y) and vertical (Z)). I'm not thinking production speeds so inertia problems would not be an issue. In fact, a way to slow the speed down would be essential for most applications.

I'm thinking about using the table for engraving, painting, forming, indexing and for plasma cutting of metal plates as the main uses but, there are limitless uses for such a table. By having a "general purpose" hardware/firmware/software interface the outputs to the motors could be easily scalable (by a NON-programmer type) to allow various sizes of tables, stepper angular resolutions and lead screw pitches to be used in the mechanical portion.

If you are sitting there thinking, "Gee, that sounds like something I know how to do" then you're the sort I'm looking to respond.

In keeping with the concept of not having to be a programmer to use the setup, the soft/firmware interfaces need to be truly intuitive. Lets say there is a need to engrave a sheet of plastic with a pattern using a high-speed cutter (like a Dremel motor mounted on the X-Y-Z axes of the table). The table (or possibly the tool) would move such as to engrave the pattern while also controlling the depth of the cut.

One "programming" method could be to simply use the pantograph approach. That is, to trace the pattern with some sort of digitizing tablet and have the engraver follow. A slightly more sophisticated version that would store the digitized points in a buffer would be very desirable since it would "smooth out" times the tracer might get ahead of the engraver and thus not force the engraving cutter to travel too fast.

If the coordinates of the pattern were known, another "programming" method could be to manually enter the points into a memory and then allow the table and cutter (continuing with the notion of an engraver as the device) to either go point-to-point (for simple patterns), at a user defined speed or in a "connect the dots" mode where the cutter would travel from one node to the next in the pattern (for more complex projects). In either case, the programming needs to be as simple as entering the coordinates as X-Y-Z memory addresses (binary or hex) without having to learn computer programming.

Another programming method would use computer generated X-Y-Z coordinates from a CAD file. Probably the easiest would be to assume the file to be an AutoCad DXF file since most CAD programs seem to be able to generate and read those. Also, an X-Y-Z table is a simple device well suited to the limited "abilities" of the DXF files (ie: No fancy shading or 3-D modeling). The CAD approach would also allow the draftsman to scale the project to the table, if necessary, without any external mechanical or microprocessor scaling needed. This approach would allow a person to only need to know the CAD program and not computer programming but, would require a way to specify the X-Y-Z table as the output device.

I can think of the mechanics of this and I can think of the electronics of it. Where I falter is in thinking of the microprocessor and computer interfaces for it. That's where I'm hoping some of the expertise here will help.

I think that a table with the attributes I've described (obviously a very cursory description here) is a salable item. Also, key components would be salable (motors and lead screws, mounting fixtures for mechanical devices and boards to provide the stepper drivers, the processor, memory interfaces, digitizer interfaces, computer interfaces, etc.).

Any and all ideas, thoughts or additional concepts or features will be welcome.

picbits

check out www.cnczone.com for lots of DIY 3 axis machines.

There was a very similar question asked on here earlier.

http://www.electro-tech-online.com/m...tml#post291046

crashsite

Yes, virtually exactly but, it lacked the detail and, more importantly, the focus of my post. Conceptually and practically this function has been done and done and done some more but, what I think is lacking is the need for a component unit that can be both built and used by people without degrees in computer science or mechanical engineering. The "store-bought" units are usually designed for their purpose and are not easily adaptable to varied tasks.

This seems like the sort of forum to sort out the details of the "general purpose" approach. Perhaps no?

ikifar

Hi
if you go back to cnc zone there are several sets of free plans for building
what you want available

Les

picbits

Also look out for Roman Blacks Linistepper for the motor drives.

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Papabravo

I'm one of the ones who did this(engraving table) in a former life, and I even tried to repeat the feat a second time in another medium(wood routing). There are numerous practical problems to doing what you want to do. Probably the biggest reason for the complete unavailability of general purpose solutions is the complete lack of agrrement about what a simple easy to use interface requires. It's a bit like Potter Stewart's (former Supreme Court Justice) characterization of obscenity. He couldn't define it but he knew when he saw it.

The most critical things we did were to design the unit to fit on the existing pantograph bases so the vises and other workpiece holders could be used, and we designed a scaleable digital font library. We found that we needed about three dozen fonts prior to introducing the product.

The killer was, we couldn't get the Things Remembered employees to pick up a ruler and actually measure the work pieces so they could tell the machine the size of the workpiece. We couldn't even get them to comprehend that a name badge was fundamentally different from a trophy plate. We also could not get them to understand that air pressure and flow rate for the tool up-down function were different for doing diamond drag engraving on a silver aniversary tray and using a single fluted cutter on plastic laminate.

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ClydeCrashKop

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student1616

well i was planning to make a small CNC engraver for my self.
i browsed lot of sites and forums.
my aim is to finish the setup as cheap and as simple as possible.so i went for motor from printers.they are good(mostly unipolar)
i made the circuit from instructables cheap controller post.
http://www.instructables.com/id/Easy...r-ci/?ALLSTEPS
it worked i can run my motor using mach3.but the problem is motor is giving very low torque.i can stop its shaft using my finger.
so i tried DAK engineering u2-stepper controller.it uses pic16f84.it also worked but the rotation is too jerky and uneven.

for mechanical iam planning to get existing X-Y table and replace the hand wheels with motors.
but before going to mechanicals i want to finish electronic design.
linistepper is nice but as i said i want the controller as simple as possible.

Papabravo

The simplest controller for a four phase unipolar stepper motor is an 8-bit bidirectional shift register that is preloaded with a magic constant. Is that simple enough? I can get you a ton of torque with a bilevel power supply at the expense of some additional bipolar switches. What are the specs of the motor you are interested in?

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student1616

these are the motor i am using.the are 24v dc motor but either i run them with 5v or 24 issue is same.a little improvement in torque.but not enough to drive a small axis.
http://helitp.dyndns.biz/material/motores/55spm25d.pdf
http://helitp.dyndns.biz/material/motores/pm55l048.pdf

i'll be thankful if u can help in the controller issue.i already bought bunch of irlf44's.so if u have any idea where i can include these mosfets.i'll be the happiest man on earth :-)

Nigel Goodwin

Try 96V or so, and suitable current limiting, more torque, more speed, and it's how they are generally run in printers etc.

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student1616

in the above circuit
http://www.instructables.com/id/Easy...r-ci/?ALLSTEPS
i used in4148 instead of normal diode.is this gona effect the result?

picbits

Yup - if you've used them on anything other than a tiny motor then you've probably killed them.

student1616

they are just protection diodes,to avoid back emf to the controller.
in my search i found out that bi-polar are much better than unipolar.imean they give much torque.and any motor with 6 or 4 wires can be used as bi-polar.so i think in shld give it a try.
probably i'll try this circuit with bi-polar stetting.
http://en.wikibooks.org/wiki/Practic...Stepper_Motors