Hi I am a software engineer by profession. I also studied some electronics in my graduation. I can do lot of stuff in a Comp, few stuff with Microchip PICs, but mechanics is a new world for me .
Only Last week I got introduced to fascinating world of Home Made CNC by visiting http://www.mr-bean.co.uk. Though first I though “It’s not my cup of tea”, after visiting http://www.cnconabudget.com and http://www.crankorgan.com/brute.htm I though of building one on the same design. But I have some basic questions which you senior people need to answer.. be patient to read till end..:
1. Since a stepper motor is Open Loop motor, how computer (or the CNC controlling software) knows that a command is successfully completed by the machine? For example if the controller asks the CNC machine to move the spindle down to drill 0.5” deep hole how it knows that its finished? What is stepper stalls because the job material is very hard?
2. In all the designs I have visited I could see a limit switch and a home switch but none say anything about the wiring part. If steppers are controlled by stepper motor controller where these switches will go? What happens when these switches are closed? If it simple stops the stepper from rotating further or it even informs the computer that the job table reached the extreme end? If it only stops then what happens if I try to mill a job of say 8” (in X axis) but my machine supports only 6” movement, so when the x axis tries to move behind 6” it closes limit switch. What will be the response from the controller?
3. As per my understanding movement of the table along the leaner guide depends on pitch of the guide screw. And its thickness as well. So the distance the table moves/revolution of stepper is a variable. How does that taken in to account? Is it at the controller hardware or we have some thing to configure in the CNC software?
Don’t blame me for such a long set of questions.. be patient once I get answers for these I have few more… actually for the last few days I am getting dreams of my own CNC, al that I could see is a PCB milled by my machine.. but I was so happy in that dream that I could not notice much info about the machine so I have to ask you guy’s only..
Note: Mods.. I am not very sure whether this the right place to ask these questions, if not then please move this thread to proper location (other than Trash Bin )