[ofcsilencer]

i have looked at building one of these machines for a while, but i am hung up on a few questions i came up with. bare with me i know they are probably very easy questions......

resolution - what actually sets the resolution of the router. something has to know the conversion to how many rotations of the servo/stepper are required to move the axis one inch. i used one of the preassmebled units from denver very briefly but i didn't see how it actually knew how big an inch was. is this preset in the software, set in the controller, or some specific gear ratio with the drive screws.

anti-backlash nuts - my understanding how ever wrong it may be is that these are used to stop shock forces from tearing up the machine, wouldn't this degrade the accuracy of the servo?

connections - do any of these machines / interfaces connect with anything newer than parallel or serial?

stepper/servo size - how do you determine the size of the servo needed. i noticed harbor freight has a few small cnc machines for a few hundred bucks. i also looked into buying the parts to assemble one but i wasn't sure what size servos i would want or how to determine the necessary size.

stepper/servo speed - this isn't really important since i really just have to watch but im assuming the motors have a higher chance of error at the higher rates of speed depending on the material.

well those are my questions im sure i have the idea all wrong but im hoping someone will point me in the right direction

[BobF]

i have looked at building one of these machines for a while, but i am hung up on a few questions i came up with. bare with me i know they are probably very easy questions......

resolution - what actually sets the resolution of the router. something has to know the conversion to how many rotations of the servo/stepper are required to move the axis one inch. i used one of the preassmebled units from denver very briefly but i didn't see how it actually knew how big an inch was. is this preset in the software, set in the controller, or some specific gear ratio with the drive screws.

anti-backlash nuts - my understanding how ever wrong it may be is that these are used to stop shock forces from tearing up the machine, wouldn't this degrade the accuracy of the servo?

connections - do any of these machines / interfaces connect with anything newer than parallel or serial?

stepper/servo size - how do you determine the size of the servo needed. i noticed harbor freight has a few small cnc machines for a few hundred bucks. i also looked into buying the parts to assemble one but i wasn't sure what size servos i would want or how to determine the necessary size.

stepper/servo speed - this isn't really important since i really just have to watch but im assuming the motors have a higher chance of error at the higher rates of speed depending on the material.

well those are my questions im sure i have the idea all wrong but im hoping someone will point me in the right direction

resolution - This is set in the controller software. Most here use Mach3 and there is a place to set steps per inch the config. I used 1/2" 8 two start screws so I have an effective pitch of 4 tpi. The steppers are 200 steps / revolution, and I set my board for 1/2 steps so I have 4 x 200 x 2 = 1600 steps per inch.

anti-backlash nuts - backlash is the amount of play between the screw and the drive nut. Anti backlash nuts have some built-in method of reducing that play as much as possible.

connections - parallel is the port of choice since you have both input and output pins and many of them. Typical connection will have step and direction outputs for each motor (6 or 8 is typical). Many machines also have some inputs for limit/home switches, emergency stop, zero set etc. Stepper motor technology development was greatly influenced by early printers and they used steppers to move things.

stepper/servo size - you will find as many answers to this question as there are members on the board. You need enough power to move the machine loads. The bigger and heavier your machine, the bigger motors you need to move things. Many first machines work with 200-300 oz in steppers.

stepper/servo speed - depends. steppers have high low speed torque and a fairly low max speed. They are usually connected direct drive and speed is limited by the drive method and max rpm. A stepper setup with a 4 tpi screw and a max speed of 1000 rpm would have a limit of about 250 ipm (inches per minute) for example. Servos have higher max speed and lower low speed torque. They are usually connected with some sort of gear reduction for these reasons.

Pick one of the machines others have built and have a go. You can find lots of build threads with most of the info you need. You will learn enought building your first to help design the next. You can even reuse many of the parts.

[Verfur]

resolution is set by the angle of each step on the motor and the gear raito and or thread pitch of screw.

You have to tell the software how many steps = an inch

anti backlash takes the end play out of the nut on the lead screw by jamming the nuts together this takes the clearance out of the nut so as the screw dos not have any play in the nut.

Ah connections go like this, The small and more cost effective setups use just a single PC to controll and with more money you can get a control for the machine and a computer together like say Funac, Seimens .... but they usely come with a big machine attached and or lots $$$$$$ needed to purchase.

Stepper size is a product of speed and torq needed to both hold and move an axis while working. Gearing has a great effect on this.

most of the small machines run on a nema 23 size motor with around 250 oz stepper motors avrg.. one reason is as the motor size goes up so does the drive/ amp size as well as the cost of.

and yes a stepper motor is less torq at high RPM and a servo is greater at high RPM and the oppisite at low RPM

[ger21]

There is a usb device and another on the way shortly.

http://ncpod.oemtech.com/
http://www.warp9td.com/

[ofcsilencer]

thanks for the help that has helped me understand what im actually lookin at. i try to over-research everything before i jump in but those were just some questions i couldnt figure out.