stepper motor input question
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Posts: 46,084
I am just getting started with this and want to know if i am running down
a dead-end street with this. I want to make an engraver where i control
the x and y axis of a cutting tool to make, for example, wooden signs.
Here is the question: I also want the ability to take an existing sign and
'trace' over the lettering. I want the stamp to be able to record several
sets of X,Y data points.
Is this possible? I know you can control the motion of a stepper with
some of the stamps accessories, but can you also use that same set-up to
record points (and then send that file to your pc)?
I would like some opinions before i start this project. Maybe using s
stamp is not the solution.
[noparse][[/noparse]Non-text portions of this message have been removed]
a dead-end street with this. I want to make an engraver where i control
the x and y axis of a cutting tool to make, for example, wooden signs.
Here is the question: I also want the ability to take an existing sign and
'trace' over the lettering. I want the stamp to be able to record several
sets of X,Y data points.
Is this possible? I know you can control the motion of a stepper with
some of the stamps accessories, but can you also use that same set-up to
record points (and then send that file to your pc)?
I would like some opinions before i start this project. Maybe using s
stamp is not the solution.
[noparse][[/noparse]Non-text portions of this message have been removed]
Comments
> I also want the ability to take an existing sign and 'trace'
> over the lettering. I want the stamp to be able to record
> several sets of X,Y data points.
What you're describing is a digitizing process. Whether or not a stamp
is suitable for the task, depends on how much you're willing to do
manually. The simplest implementaion would be to move a pointer
(attached to feedback pots - X, Y, *and* Z?) to the point(s) you wish
to capture, and then push a button telling the stamp to capture the
values and send them to the PC. Actually a stamp is overkill for this,
but it should be straightforward to program.
Stephen Weller
American. Veteran. Patriot.
> a dead-end street with this. I want to make an engraver where i control
> the x and y axis of a cutting tool to make, for example, wooden signs.
> Here is the question: I also want the ability to take an existing sign and
> 'trace' over the lettering. I want the stamp to be able to record several
> sets of X,Y data points.
>
> Is this possible?
I think this is way beyond a stamp ability.To make angled or curved lines
you must run both motors at precise step rates. You also must precisely
control the acceleration and max speed of the motors. The stamp does not
have the timing accuracy for this.
There are many PC based pckages that will do the step generation, TurboCNC
is only $20, Mach2 is about $150. There are anumber of driver boards
available.
The best source for info is the yahoo group CAD_CAM_EDM_DRO. Its a huge
list, very active, VERY on topic. Look first in the archives, your question
ahs been handled at least a thousand times.
Ive done couple small CNC machines- see plsntcov.8m.com
ron ginger
> From: <manning.pj@p...>
>> Here is the question: I also want the ability to take an existing sign
>> and 'trace' over the lettering. I want the stamp to be able to record
>> several sets of X,Y data points.
>>
>> Is this possible?
>
> I think this is way beyond a stamp ability.To make angled or curved lines
> you must run both motors at precise step rates. You also must precisely
> control the acceleration and max speed of the motors. The stamp does not
> have the timing accuracy for this.
>
That's interesting. I would have thought the right model Stamp had more than
enough bandwidth to handle sign cutting. Not all CNC work is so generous in
tolerances of course, but signs seem like an easy match for Stamps.
You must keep in mind that it sounds like Ron has tried this and knows many
others who have as well -- without success. But personally, I wouldn't
hesitate to accept a job using a stamp that way. (Of course, this sort of
thing is/was my job, not recreation. That matters.)
You would not be generating the curves in real time of course, nor even
controlling the stepper motors. The Stamp would simply being issuing
commands to a dedicated controller based on previously loaded cutting
templates for each character in the set. The only dynamic information for
the Stamp would be the specific characters to cut. Dynamic spacing of the
characters (kerning for example) would be within a Stamp's range, but not
much more I'd think.
As to your specific question about digitizing the shapes from tracing an
existing letter... That's one of those open-ended problems. The answer is
always: "that depends on how well you want to do it." Gathering data instead
of using pre-recorded data is a different kind of problem. You command a
stepping motor by saying "Go there, go here" but it doesn't report back. You
have to assume it has gotten there after the necessary time has elapsed. You
see steppers are designed to have a high holding torque. You would not want
to move a stepper motor around by forcing it off position. You can use one
of two methods for such jobs:
1. Command the stepping motors in such a way as to zero the force placed on
a control by the user. Think of it as power steering. The user closes the
feedback loop by watching how the pointer (or the idle cutter) moves, and
either pushing harder or faster or just in a different direction in response
to the result. People are good at this, but the better your internal
response loop, the better the user will be at following delicate curves.
Then you just record the positions you commanded the stepping motors to
take. That requires an external memory because you're going to have a pretty
large set of data. A PC has enough bandwidth to reduce that data to simpler
forms on the fly while capturing it, but a Stamp would not have a prayer.
It's a complex geometric algorithm using floating point extensively. I would
do it after the fact even in a PC just to simplify my life.
2. You disengage the steppers in some way. Declutch them, if you will. The
user moves the pointer/tool around with muscle power. You passively record
the positions the tool reaches. This requires that you have some position
sensor for each axis. Such sensors range from trivial to amazingly
expensive. This method requires less programming expertise, because you are
not designing that control loop for the "power steering" -- but it will give
you pretty crude results unless you spend a lot more on position sensors
than the simple pressure transducers that method one requires to know which
way the user wants the head to move.
So to answer your question, my experience suggests you could use a Stamp to
do this. And you should if you were choosing it for the challenge of doing
so -- for the learning experience -- or to have an economical design for a
production run of 10,000 sign cutters. If you just want to get the job done,
then go get that software Ron Ginger recommended, hook up to a spare PC,
which everybody seems to have these days, and linger on those other
newsgroups where people do this stuff all the time.
Pick the way that sounds more like fun. Usually a good guide unless
compelled by circumstances to do otherwise.
Gary