Messages

551

General Mach Discussion / Re: Rigid Tapping

« on: January 04, 2014, 05:30:33 PM »

 I did some ridgid tapping on Fadal 6030 once.  Scary watching a 5/8-11 tap accelerate towards a big cast iron part and plunge right in to a depth of 2 inches and stop, then accelerate back out again!

I've also done tapping with tension compression tool holders on an old knee mill with a Bandit cnc and no encoders and it actually worked quite well.  I just started shallow and watched if the tap was extending or retracting on the way in.  If it was extending the feed was too slow, if it was retracting the feed was too high.

I got lucky recently and picked up two Tormach auto-reversing tapping heads for a very nice price. One is up to 1/4", the other is 1/4" to 1/2".  They look pretty good, I hope they work well.

552

General Mach Discussion / Re: Removed EMI, but still need debounce?

« on: January 03, 2014, 06:51:43 PM »

I used to work with a microprocessor driven product.  It is surprising how much mechanical switches can bounce on closing. I always wire limits, float switches, etc. to operate by opening, less bounce.  A broken wire looks like the limit is hit warning you that it isn't working. Otherwise you could crash into a non-functioning switch. A broken wire indicates a tank is full, warning you that it isn't working before you over fill it.  It pays to always think failsafe.

553

Share Your GCode / Re: lego block just for kicks.

« on: December 26, 2013, 05:59:34 PM »

.nc is a G-code file, just plain text.

554

General Mach Discussion / Re: CNC router power supply question

« on: December 26, 2013, 05:57:24 PM »

When running multiple steppers from a single power supply the unregulated power supply is preferred because energy produced by the steppers when slowing down can be stored by the capacitors and used by the other axis.  A switcher won't do that and could give you an over current condition.  Your caps have to be large enough to absorb the power and also have a high enough voltage rating as the voltage rises when storing the braking energy.  You also need to be careful that you don't exceed the voltage rating on your drives during braking as well. I have some zener diodes on my power supply output to clamp an overvoltage condition.

555

General Mach Discussion / Re: Z Axis issue with RUN FROM HERE

« on: December 24, 2013, 09:38:44 PM »

Hah!
I've seen this same thing and wondered why it happened.  Now I know.

Thanks Hood,

556

Show"N"Tell ( Your Machines) / Re: Zero gravity Z

« on: December 10, 2013, 05:57:47 PM »

If you have really good quality ball screws (efficient) then they backdrive very well once you overcome detent torque on your motors if they are steppers.  My Z never moved with a Sherline spindle mounted.  When I changed to a mini mill R8 spindle with a treadmill motor it always drifts slowly down when the motor is off.  A 50 lb gas spring has it in almost perfect balance now.

557

Show"N"Tell ( Your Machines) / Re: Zero gravity Z

« on: December 02, 2013, 05:13:29 PM »

Lifespan is qouted at about 100,000 full strokes.  Mounting position should be shaft end down so seal gets oil. One of mine is up and one is down, and my arrangement puts some side load on the shaft. So I expect the life of one of them to be quite short. So we'll see, but a replace once a year or so wouldn't be too awful.

I used to build pneumatic packaging machinery using cylinders like you used.  I did away with lubricators because they made more mess than they did good. However I always shot a bit of air lube oil in both ports on the cylinders before attaching the lines.  You can get 3 to 5 million stokes on those cylinders. We easily put 5 million strokes on in a year.

558

Show"N"Tell ( Your Machines) / Re: Zero gravity Z

« on: December 02, 2013, 09:47:35 AM »

I had a similar problem on my home built mill. With the new spindle and the Y axis mounted to the Z the total weight is about 50 lbs and the Z started slowly drifting down. I just installed 2 50 lb gas springs hose clamped together to give an 18" stroke. About $40 total from Mcmaster Carr.

Gas springs have about 2000 psi of nitrogen in them. It takes the rated load to start compressing them. Then the load increases by only about 10% over the full stroke. So the 50 lb cylinders put out 55 lbs of force at the bottom of my Z stroke. They are also filled with oil so provide damping too.

559

General Mach Discussion / Re: How do you Connect the Metal Braiding of a Cable?

« on: December 01, 2013, 09:45:35 PM »

Forgot to mention, Home Depot has them

560

General Mach Discussion / Re: How do you Connect the Metal Braiding of a Cable?

« on: December 01, 2013, 01:32:12 PM »

I've used the heat shrink solder type butt splices for this. Just put the two ends into the splice and heat with a heat gun. Solder melts and tube shrinks at the same time. It looks very neat.