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I've never used or seen a rack and pinion linear motion system myself. What particular vendor/model are you using? What would be the backlash of the rack and pinion itself?

Mapping the axis...

My rule of thumb is to look at your accuracy/velocity requirements and choose your counts base on a factor of 10-20 from those. I.e. if you want positioning to 1um choose your encoder to be...

"only" 20 bits? 20 bits is a lot. (By the way a 16 million count is 24 bits). If you look at the angular accuracy of the highest end rotary encoders from Heidenhein and Renishaw you'll it's a lot...

Just FYI I've worked on the design team of several commercial machines with servo drives and have designed servo systems myself so I think I can say I understand what a servo system is. How about 2G...

The Galil would normally close the position and velocity loops with the servo amp closing the current (kind of torque) loop.

Copely, Parker, Kollmorgen, Baldor (and I guess Yaskawa) all make very...

I'd look at the servo drive manual. The servo drive may have an encoder input and output in which case you'd want to connect the encoder to the drive and another cable from the output to the Galil. ...

Hey Rob,

Most modern drives *can* be controllers or they can be used with external controllers such as the Galil. The drive's controller features aren't applicable when using an external...

I'm feeling like I'm intruding on your private conversation here... ;-)

Many modern servo drives are also servo controllers. That is they implement velocity and or position control loops, not...

I think spoiledbrat was going to use a Galil controller in both situations. I.e. he wouldn't be using the Yaskawa as a controller.

:-)

With regard to locking a gantry design, the challenge would be to find a method of locking that makes a large enough difference in stiffness. A fixed bridge machine would generally have a...

How about this?

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From a performance perspective two servo motors with the same (or close spec) should perform the same. Do the motors have a similar torque constant? Voltage constant? Coil resistance? Inductance?...

My bet is that a simple, comparator based system, will not work. Especially not with your laser pointer style, low power lasers, where the ambient light will swamp the laser. Note how in all the...

I think the OP was thinking of digitizing the analog signal from the photo-diode and processing it in software on a micro-controller. Should be doable.

It wouldn't surprise if commercial...

OK. So you could do this by mechanically gearing off the same motor or you can use something called electronic gearing to synch one motor to the other. Most commercial servo controllers support...

Not sure about the rest of it but A/D at 400Khz is not a problem - 1Mhz, 8 bit, $3 in Digikey (you can go into the 100's of Mhz and probably much further today, I'm not up to date...)

How about a...

Also worthwhile taking a look at some commercial CNC machines...

There's also the question of whether or not you're looking at this as a fun/learning project or looking for the fastest way to get...

The CAM software takes in your 3D model and spits out G-code. G-code is fairly simple. There's a wide range of CAM software with different capabilities and prices. If you're a software person you...

I don't know too much about crankshaft design but if you're 10mm off the axis of the motor your force would be x100 the N-m rating (1N at 1m is 100N at 10mm). So for 2000N you need a motor rated at...

Well, motors are rated in torque, you need to convert this torque into force... With a screw you could have a huge mechanical advantage but you'd also have more mass to move. With a crankshaft you...

How long is your stroke and what are those accuracy requirements again?

Moving something at 15Hz any significant distance/angle/load sounds like a challenge to either servo or stepper motors. ...

My 2 cents:
- As you are cutting foam your cutting forces should be very light which is a big help.
- The 0.03" accuracy spec is almost 1mm which is really not that accurate at all. So that one is...

Steppers can be very accurate. It's just that they run in open loop, not closed loop.
Just to give you an example, one stepper system I worked on had an accuracy of about 5um (0.0002") over 3m of...

You really should do a search of the forums and also look at some other people's design...

These above mentioned linear rails are designed to be mounted on machined surfaces and some of them have...

Hmmm... They're not always interchangeable, the profile is generally different, event the rail mounting holes can be different.

I think THK are the biggest but all make high quality linear rails...

The problem with measuring to the "earth" pin is that there could be a very large series resistance and you wouldn't see it. It's not necessarily meaningful. V- is most likely not connected to the...

Ah. So I guess it *is* a 48V supply. Not a 36V/-12V supply. It's really hard to figure out the specs for this model on your web site.

By the way, how did you figure out it's -12v and +36V? It may simply be floating relative to the earth ground. Do you have three outputs? (0, -12V and 48V?)

I took a look at the g251 and it doesn't look like it's optically isolated. I couldn't find your exact supply on keling's web site and their specs for the others seem fairly sketchy. I can't say...

I'm not familiar with this particular drive but if all the inputs are optically isolated you should be able to use the power supply. If the inputs are not isolated and the input grounds are...