Messages

311

General Mach Discussion / Re: Selecting the right equipment for a Bridgeport BOSS retrofit

« on: May 25, 2016, 07:31:34 AM »

Bruce,
I used to build pneumatic operated packaging machinery, 25 to 40 strokes per minute on about 10 cylinders all day long. We stopped using lubricators because they mostly make a mess where the air goes back and forth to a cylinder. We just put a couple drops of oil in both ports of a cylinder at installation. The cylinders would typically go  up to 7 million operations before replacement.

312

General Mach Discussion / Re: soldering iron info, please

« on: May 16, 2016, 11:18:00 PM »

Surprisingly a small wattage iron is likely to do more heat damage than a small one. When the iron is too small it cools down the instant it touches the joint. Then you are waiting for the joint to heat up and heat is traveling where you don't want it. A larger iron holds more heat and brings the joint to temperature instantly, you touch the solder and you are done.

313

General Mach Discussion / Re: Multimeter info

« on: May 14, 2016, 03:32:11 PM »

Yeah I've been hunting test equipment on Ebay. Got a Fluke 289, 773, and a 789, real pricey if new. We have a real use for it all though, not just collecting nice toys.

314

G-Code, CAD, and CAM discussions / Re: Tool paths

« on: May 12, 2016, 08:33:31 PM »

A couple of possibilities. Look at the g-code for the Y move in the Mach 3 editor and change it to a different value. However it is possible you won't find Y value that is doing but instead a G-code that could be say homing the Y axis or something like that.  The cam program is doing a post processing step that may be for the wrong machine, or it may have defaults that insert the big Y move.

315

General Mach Discussion / Re: Bridgeport Knee Mill Conversion?

« on: May 12, 2016, 11:20:12 AM »

You can't compare torques of steppers with Servos at all.
750w servo 2:1 would be fine I would think, 1 Kw definitely. Have heard people saying 400w but I am sceptical about that small.
They will be much more expensive than steppers but once you have had good servos on a machine you will probably not want steppers again
I put 1.3Kw Allen Bradley MPL servos on my Series 1 CNC after I took the steppers off and it was probably way more than needed but I had them sitting there anyway.

Hood

Hood,
This part of what you wrote is critical "They will be much more expensive than steppers"  Everyone compares undersized steppers to  properly sized servos.  Spend the same money on steppers as servos and the results will be much different.  In fact a stepper closer to the ideal driver for machinery than a servo is. A steppers torque is maximized at the bottom end of the speed range, as if you had  a gear box reduction.  A servos torque is lowest at the slow speeds where most of the cutting is done, so you need bigger servos to drive the same load that the steppers would do.  Properly sized steppers do not lose position.  Stalls during cutting are simply a result of steppers too small.  My home built Minimill has 960 in/oz steppers, 80 volt drives with a 1500 watt 68 volt linear power supply and the performance is really very good. I have 18" travels in all directions and easily do 300 ipm even cutting.

316

General Mach Discussion / Re: Bridgeport Knee Mill Conversion?

« on: May 11, 2016, 10:26:14 PM »

$.02 more...

i ran my 10 x 50 Acra knee mill, knee driven, pc controlled and built by CNC Automation here in NH USA, for 11 years, with NO problems related to the knee driven part.  in fact having the spindle free was the best part.  position over a hole, and mdi hand tap holes small as #2-56 with the tap held in a drill chuck.  or lift the spindle and watch the program run with cutter above part.  also enables you to use a quick change tooling like ultron snapchange, or a power drawbar and TTS type tooling.  no its not a bed mill, but with high positive insert cutters, moderate cut depths and fairly high feed & speed, you can move metal, including steel, at a pretty impressive rate.  if i was doing a lot of tiny short move work, or engraving, id like the quill driven.  otherwise, no.  my acra has 15"+ of cnc Z

it has ballscrews, fat ones at that.  so i dont have to deal with a cnc with old acme screws.  but having said that, i worked with a company for years that only employed big clunky worn out machines.  one of these they retro'ed with an old clunky cnc system.  despite the large amounts of backlash and way slop, this machine never sat empty.  they found ways to program so the looseness wouldnt crash the machine.  of course it could not machine a 30" dia +/- .001 hole, but folks lined up to have that hole put in at +/- .015 tolerance.

and im lucky to have dc brush servo motors already mounted.  but i think 50 ipm of stepper bridgeport would be great, when hand cranking is the alternative.

i did say my acra has 15"+ of Z.  well no it doesnt.  it is electronically brain dead. old like me heh. but im working on it now with the help of a forum member, in a year or less i hope to see it uccnc guided, and using Mach too, and a better machine than when i bought it.  i did a lot of great stuff on her, hope to have her ready when i retire from working for the man which ive been doing for 6 yrs or so, the man has been kind enough, but working for me i like the boss a lot better.

then, after all this fun, theres the lathe in the corner.........
 

You are right about the loose quill being very nice. Which is why I said bed mill as they typically have a quill. Since you are only moving the head, with a counterweight up and down instead of the entire knee, table and part you do things like peck drilling a lot better.  I peck drill all the time.  Can't see the point of CNC if you have to stand there watching for chips to wrap around the drill all the time and possibly causing a crash.

317

General Mach Discussion / Re: Bridgeport Knee Mill Conversion?

« on: May 10, 2016, 06:48:09 PM »

When you get all done it is still a knee mill, with a really short Z axis. A short Z axis just plain sucks. You wind up spending time and money trying to find a combination of tools all about the same length. I worked on a CNC knee mill for four years. We now have a bed mill with a 21.5" travel Z and we use all kinds of tools without a second thought.

318

General Mach Discussion / Re: Turret macro is giving me issues

« on: May 09, 2016, 01:56:13 PM »

If this is a stepper motor and you back up against a pawl solidly how are you preventing the stepper motor from loosing steps from doing that, because it definitely will? The only way I can see to make this work is to zero the stepper motor position after the back up motion, then calculate the steps to subsequent positions from there.

319

G-Code, CAD, and CAM discussions / Re: Make M-Code

« on: May 05, 2016, 10:47:02 PM »

Ben,
This may be a silly question, but what are you doing that you need looping?  I used to be quite good with looping and macros, but never bother anymore. Two reasons, almost no program size limits for PC based CNC, and inexpensive PC cam programs that do a much faster and more reliable job than I can. I use CamBam for $149 on my Mach3 homebuilt CNC and on the Servo 5000 bed mill at work. Programs take only minutes to write and you can use scripts and plug-ins to automate things still further. 40 free sessions before you pay, an awesome user forum, how can you beat that?

320

General Mach Discussion / Re: Dust Collector blowing fuses...

« on: April 28, 2016, 10:36:59 PM »

Relay damage doesn't happen on start. No current flows until the contacts actually touch. No gap no arc. When the relay opens and the magnetic field collapses it generates a huge inductive surge voltage that arcs across the contacts. Hence motor rated mechanical relays have double break contacts to break the arc faster. In the early days of digital meters I blew a couple up before I realized what was happening!