On all of the systems I've built, the mechanical stuff has cost *way* more than any of the electronics.
Bob
can you recommend motors for me to work with in the range of sub 100$
I don't have any experience with motor's torque and how much would be enough
how to evaluate a motor torque whether or not it would be good for the job without spending money over a lot of motors to just try them
I have already a lot of small stepper motors vary between bipolar and unipolar and all of them came from various consumer printers, but I feel they can't do the job (I can't find enough info about them)
most of the time when I try to drive them with a basic drivers using arduino and discrete components they get hot after some time and soon enough they are getting ugly hot
another example the one that I have introduced, the sanyo denki one, the spices os over there
http://store.lipsiasoft.com/uploads/415640_103-H7126-1740.pdf
How I can evaluate that motor and have a good estimation about whether or not it is good enough for my application and it wouldn't be over-killing
it says in the datasheet the following
Holding torque:165 Ncm
Rotor Inertia: 350x10-7 Kgm2
back E.M.F: 31 V/Krpm
I hope there is a guide line for something like this that would be easy enough to start with
I think we are drifting over here and the discussion is no longer related to the topic
Hi
Motors are part of the "mechanical" side of the system. You can easily spend $1,000 apiece on motors for some of this stuff. That same $1,000 motor runs fine with a pre-built driver that costs less than $50.
The sizing of the motors and what you "need" is mechanical engineering. You do a design, run through the math and that is what gives you your requirements.
You start with:
How fast does the head need to move in mm/s
How much does the head weigh
How much does the structure to hold the head weight
How much back force does the tool generate (you may have to measure this).
Next up:
How rigid does the system need to be
How accurate does it need to be
How repeatable does it need to be (different than accuracy)
How small a step do you need to get a good finish (different than the other two above)
All of these basically are "how good does it need to be".
Next:
How large an area does the machine need to traverse in X, Y, and Z
That's a biggie all by it's self. A machine that needs to go a meter in each of those can be "interesting".
With those inputs you can work out your aluminum budget and figure out how much that's all going to weigh. There are various drive approaches, screws and belts are the two main ones. Your accuracy budget will steer you to one or the other.
If one lead screw (or belt) does not get you to adequate positioning, you may need two (or three for interesting drive approaches).
Finally:
You can calculate the number of RPM you need to move your head a given distance. You can work out how fast you need to accelerate or decelerate. (right angle turn that is still fast enough). That will give you a torque at RPM number. That plus the friction and back force on your motor give you the likely torque range. I'd add at least 20% and probably 50% to whatever you come up with as a "first time I've done this" safety factor.
So now you run off and buy a bunch of aluminum straight piece parts, and all the fittings to rigidly attach them to each other. You come up with the drawings for your various mounting plates and send them off to the laser shop to have them cut. You order up a few (hundred) bearings. Out goes the order for belts or lead screws. If it's lead screws, they start at "expensive" and go up from there. Also get the traveler nuts for the lead screws from the same guy.
Figure that it all comes in and *something* isn't going to fit. Back for more mounting plates or some such thing.
Note that that the motors and electronics come in very late in the process. The other stuff needs to be worked out much earlier.
Bob