RepRap的X_STEPS_PER_MM參數(shù)

背景介紹：
參數(shù)Steps per mm：這個(gè)參數(shù)是決定了工作臺(tái)每運(yùn)動(dòng)1mm，步進(jìn)電機(jī)需要多少個(gè)脈沖。
計(jì)算方法(公式)=(步進(jìn)電機(jī)旋轉(zhuǎn)1圈的標(biāo)準(zhǔn)脈沖數(shù)*驅(qū)動(dòng)器細(xì)分?jǐn)?shù))/絲杠導(dǎo)程(導(dǎo)程也就是螺距，如果絲杠不是直接連接電機(jī)而是通過(guò)減速后連接則計(jì)算結(jié)果還需要再乘以減速比)
例如：1.8度/脈沖的步進(jìn)電機(jī)旋轉(zhuǎn)1圈需要360/1.8度=200個(gè)脈沖。驅(qū)動(dòng)器使用8細(xì)分，絲杠導(dǎo)程為2.5mm。
Steps per=200*8/2.5=640個(gè)脈沖
http://reprap.org/wiki/Arduino_GCode_Interpreter
Usage
Firmware Configuration
In order for the firmware to operate properly, you must configure the proper variables in the firmware and then upload the firmware to your Arduino. The values are stored in the file _init.pde. An example version is included in the distribution called _init.pde.dist.
We'll cover each of the variables below:
X_STEPS_PER_INCH
This variable stores how many steps to take to move the X axis 1 inch. You will need to set this as accurately as possible if you want your machine to be accurate. There are two ways to set it:
Move and Measure - slap a pen or marker on as a toolhead and draw a 1000 step line. Measure it and divide 1000 by the length in inches.
Calculate Step Size - this one is the preferred way of doing things. Its rather easy to calculate step size based on your drive mechanism.
For threaded rod drive systems:
Find your TPI (threads per inch). for example, 1/4"-20 threaded rod means that there are 20 threads per inch (aka 20 turns = 1 inch.) Simply take that number and multiply it by the steps in a revolution. With a 400 step motor, it would be 8000 steps per inch.
For belt/pulley systems:
Find the circumference of your drive pulley. (remember circumference = 2*pi*r) (say: 2.75")
Calculate step size (ie: circumference / steps per revolution) (say: 2.75" / 400 = 0.00625")
Divide 1 inch by step size (1" / 0.00625" = 160 steps/inch)
X_STEPS_PER_MM
This variable stores how many steps to take to move the X axis 1mm. You can either calculate it independently, or take the number above and divide by 25.4.
實(shí)際設(shè)置:
在用雕刻機(jī)改裝成RepRap的過(guò)程中，遇到問(wèn)題。電腦上面發(fā)指令走100mm，機(jī)器實(shí)際上只走了25mm。查閱資料無(wú)數(shù)，始終不得要領(lǐng)。
根據(jù)上面的知識(shí)，理論上X_STEPS_PER_MM的設(shè)置應(yīng)該是160（雕刻機(jī)原來(lái)是8細(xì)分，320 steps per mm,絲杠導(dǎo)程為5mm）。RepRap默認(rèn)是4細(xì)分的。
可是實(shí)際上，當(dāng)設(shè)置超過(guò)18以后，就走不動(dòng)了。A3977的電流、細(xì)分都調(diào)過(guò)。始終無(wú)法解決。
在“process_g_code.pde”里面，把收到的GCode都加大4倍，可以暫時(shí)解決這個(gè)問(wèn)題