Messages

251

General Mach Discussion / Re: Z Axis Air Assist

« on: December 26, 2016, 02:36:57 PM »

The compressor tank can't be the accumulator tank because it is in front of the regulator. So if there is no tank after the regulator then it can be one of two things. It could be just using cylinder volume which is a poor way to do it. Or it has a relieving regulator that can dump air as the cylinder is compressed. Listen to the regulator as the axis moves. You can hear a relieving regulator when it vents off due to a rise in pressure. I dealt with a lot of this stuff when I was building pneumatic packaging machinery. So I'd be interested in what you actually have because I have seen lots of bad designs.

252

General Mach Discussion / Re: Learning Mach 3

« on: December 25, 2016, 12:39:36 PM »

CNC without a Cam program is starting back in the dark ages. I worked as a CNC programmer back before Cam became really common. We have a very nice nearly new (1996 with 100 hrs) bed mill because programming took way too much time unless you were going to run production, so it never got used. Now we have a seat of CamBam right on the mill computer. We don't bother manually writing code for anything. The fastest way to learn G-code is to have an expert help you. Having a Cam program showing you how to write code makes the learning go really fast. Get CamBam and use it for 40 sessions free. Get on the forum and get lots of help free. Then buy it for $150 or use what you have learned to get what you really need.

253

General Mach Discussion / Re: Z Axis Air Assist

« on: December 24, 2016, 08:07:29 PM »

If you have a check valve in the line then I believe the regulator only supplies air if the pressure drops below a minimum value. In that kind of system there is likely to be an accumulator tank. The ratio of the cylinder volume to the tank volume determines the pressure change during the full stroke. If the tank volume were 10 times the cylinder volume then the pressure change would only be about 10%, you don't need a perfect balance force.

254

General Mach Discussion / Re: Z Axis Air Assist

« on: December 24, 2016, 09:36:14 AM »

A pneumatic assist doesn't need to be connected to Mach 3. The pressure simply gets adjusted to make the force equal to the weight of the Z axis so the motors only supply the force for cutting not for lifting. Typically a pnuematic assist has a tank as well as a cylinder so the change in force as the cylinder extends and retracts is less. A regulator may supply air at a minimum pressure to refill from leaks.

255

Third party software and hardware support forums. / Re: Parallel port wiring

« on: November 03, 2016, 08:21:53 AM »

Actually my thinking is more along the line of driving an LED. They usually need a series resistor selected for the voltage you are using to limit the current otherwise they will burn up.  This would be simple if I had a wiring diagram!

256

General Mach Discussion / Re: Hybrid stepper motors from e bay

« on: November 02, 2016, 10:03:50 PM »

You built this, what does your wiring look like? Shielded cables? Twisted pairs? Power wires routed away frm signal wires and only crossing at right angles? One ground point, no daisy chain of ground wires? Noise problems can make you think you have mechanical problems very easily.

257

Third party software and hardware support forums. / Re: Parallel port wiring

« on: November 02, 2016, 02:25:02 PM »

I am trying not to hack the driver box, and only connect via the DB25 intended for a parallel port. That way if the box fails I can just replace it and move on.

The current limit resistors was just a thought about not putting 5 volt from a supply that might supply amps into a port that can only handle ma.

258

Third party software and hardware support forums. / Re: Parallel port wiring

« on: November 02, 2016, 10:25:01 AM »

Its called a TopCNC TC55H. The outputs have + and - terminals so I figure they are open collector and you supply whatever voltage your drives require. The CNC3020 driver box is blue in color (no part numbers) appears to have driver board for the four axis with the toshiba stepper driver chips. Don't have any wiring diagrams so this is way more complicated than necessary.  

What I am building is a waste water sampler. Use fourth axis to drive a peristaltic pump to pull a sample, move to test tube location, dose a sample into the test tube, reverse to pump out to clear out the sample tube, pause for a period of time, repeat.  All G0 moves in X,Y and maybe Z.

259

Third party software and hardware support forums. / Parallel port wiring

« on: November 01, 2016, 10:09:58 PM »

I bought a cnc 3020 for a specific task, not machining. It has a DB25 connector for connection to a parallel port and is set up for Mach 3. I am not using mach 3 for this task, I am using a dedicated controller. I don't want to blow out the driver box so I am wondering what input voltage and current it expects on the axis inputs?  I would guess 5 volts but I have only a 24 volt supply at the moment. If I had a 5 volt supply would I also need to use current limiting resistors in the circuit?
I am a power and industrial control guy not electronics so much.

Thanks,

260

General Mach Discussion / Re: Backlash...

« on: November 01, 2016, 08:34:42 PM »

Actually a gas spring is quite linear, which is why you use one instead of an ordinary spring.  A 90 lb gas spring with say a 10" stroke requires 90lbs of force to move it off the stop.  At full compression the force is only about 10% higher or about 100 lbs!  On my Z axis I have two gas springs back to back for a longer stroke because otherwise it drifts right down when the drives shut off.  The Z stroke is 18"