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Joints and step time configuration for open loop stepper system

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01 Jul 2019 14:58 - 01 Jul 2019 15:09 #138303 by richard123
Hello everyone,

So currently I am working on my project which is an open loop laser engraving machine. So, after doing several researches, I can implement the desired custom kinematics to my system. What I realize is, for the forward kinematics formula which I have derived, the inputs should be the angle for each of my motor and also the radius. But, after following the example from trivkins kinematic (trivkins.c), I saw that apparently this angle and radius are being replaced by joints in array (joints [0], joints [1]... etc). Since this is an openloop system which uses steppermotors, I would like to know how the linuxcnc get the angle and radius as the input so the system can move to the desired position either in X, Y or Z axis (or in other words, how these joints [0] and so on get the values). I believe that the "joints" contains the calculation of the angle and radius, but I still cannot find which file contains this declaration. Please correct me if I am wrong, and I really hope that someone can give a better explanation about this case.

Other than that, I also would like to know how linuxcnc gives pulses to my stepper motors. Since at the beginning of the stepconfiguration, users have to fulfill some requirements such as Step time and step space, I believe that there is a file that give this instruction to the steppermotors, but I still couldn't find which one. In my understanding, the step time and step space is the same as delay if we want to move our stepper motor by using arduino programming. Therefore, I would like to know which file is responsible to recieve the numbers of step time and step space which we give as an input in the stepconfiguration, and how do they control the motors using those numbers. Again, please correct me if I am wrong, and I really hope that someone can give a better explanation about this case.

Thankyou.
Last edit: 01 Jul 2019 15:09 by richard123.

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01 Jul 2019 17:57 #138316 by pl7i92
hi
for a laser system // timing belt you only need a small Driver you can go with a 3D printer system at 25Euros
the timing and stepepr are limited at this system
but you got no force
you need speed

so it is quite up to 200mm/sec

that means a Nema17 stepper at 0,8A per phase

at 12V woudt be best
the Z axis is not needed
you can also go with a low cost setup at 10meters /min
with a low cost china Breakoutboard and some DRV8825 or the a4988

this woudt fit your need if you are a elektronik man that can put togeter 4cables

there are also finished boards at Ramps 1.6 search that only nneed to ad g-code

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01 Jul 2019 22:57 #138343 by tommylight
There are some " tree_something" or "something_tree" version 1.3 boards with 32bit processor's and everything included for 3D printers, just add the drives and an LCD if you want. The board is 21$ US on banggood.com or nearly 30 on eBay. With drives 35 on eBay.
Thinking of getting some to mess with, already have plenty of arduinos and ESP32 . Wasted a lot of time with them, a lot! But nice for some automation for sure.

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02 Jul 2019 22:34 #138447 by andypugh

richard123 wrote: I believe that the "joints" contains the calculation of the angle and radius, but I still cannot find which file contains this declaration.


You haven't given us much to guess on, but it sounds like, in your case, the joint positions are the motor angles.
You then need to use the radii in the kinematics module to calculate XYZ from the angles and radii, and then the reverse for the other kinematics.

Scarakins might prove to be a more useful file to look at.

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