Messages

281

General Mach Discussion / Re: Am I loosing Steps, and what should I do

« on: July 22, 2016, 03:00:29 PM »

Gas springs are usually a fixed beginning force rating.  You must apply that amount of force to move it off the stop, then it increases about 10% over the full stroke.  Because it uses a fluid it also acts as a damper keeping quick motions from happening as well.  Some are adjustable, they come fully pressurized, but a bleed screw lets you reduce the force.  So one that was too strong also might damp motion too much and cause lost steps.  I'd lower the head on a bathroom scale and see what it weighs, then push the gas spring against the scale and see how that matches.  If it is too far off it may very well be the problem.

I added a gas spring on my machine when the new spindle motor cause the head to drift downwards when powered off.

282

General Mach Discussion / Re: Z plunging deeper after each retraction. Not mechanical

« on: July 22, 2016, 02:47:36 PM »

Gravity in on your side going up, and against you on the way down?

283

General Mach Discussion / Re: Z plunging deeper after each retraction. Not mechanical

« on: July 22, 2016, 09:44:09 AM »

I'd be looking at the Z motor encoder. Loose coupling or defective

284

General Mach Discussion / Re: How do you make a manual tool change then re zero the Z?

« on: July 19, 2016, 10:23:50 PM »

Bite the bullet and get some TTS tool holders for when you want to do tool changing. My spindle is manual R8 and I use a cheap right angle style 1/4" hex battery powered impact wrench to loosen and tighten the draw bar. I have a couple setscrew end mill holders, a collet holder and range of collets, and a drill chuck. That about does it and I still have the R8 stuff. R8 collet holders and setscrew end mill holders should repeat fairly well, but not as well as TTS.

285

General Mach Discussion / Re: skipping around a g-code file

« on: July 16, 2016, 02:07:07 PM »

Rick,
I thought you wanted to run or adjust say a feature of your part, say a pocket. So I was suggesting you run entire subroutine, not part of one.

286

General Mach Discussion / Re: skipping around a g-code file

« on: July 16, 2016, 12:23:15 AM »

I'd build the program using subroutines for each of the pieces of program that you'd like to run separately. The top of the program would be a list of subroutine calls in the order you want them executed. Each subroutine should contain all the usual prep stuff, like canceling tool offsets, canceling modal drill routines, starting the spindle etc. If you then use run from here at the appropriate subroutine it'll skip all earlier ones. This makes building a complex program easier too, build it in pieces and then load them all into one file.

287

General Mach Discussion / Re: Why Not The Same

« on: July 11, 2016, 09:51:13 PM »

Rich,
You bring up a good point, some things are modal and once changed stay that way. So a subsequent run of a program that left something modal in effect could cause the program to work differently during the next run.

288

General Mach Discussion / Re: Ref All Home & Auto Square Not Working

« on: July 11, 2016, 09:45:15 PM »

Gerry,
I wasn't suggesting running with reduced microstepping.  I was simply suggesting that the mechanical linkages be adjusted with a full step holding everything stationary. If the gantry is square at a full step then I think it might tend to stay that way. When my drives power up they always seem to jump to some position. Might be an initial full step? If two drives power up and they had be aligned by microstepping might they not be out when that initial step happens?  As I said just a suggestion, based on lots of people seeming to have an issue when two motors are involved.  Comes up frequently on the 3D printer forums too.

289

General Mach Discussion / Re: Ref All Home & Auto Square Not Working

« on: July 10, 2016, 08:02:13 PM »

Proximity sensors don't have anywhere near the accuracy and repeatabilty you are looking for, at least not at a price you'd be willing to pay! Really accurate limit switches are available, and they will likely be normally and forced open as that is generally more repeatable. In thinking about this issue I would be concerned about setting the squareness using microstepping. I think I would set the drives for full step and mechanically adjust the motor to screw or belt position to be perfectly square at full step. I believe they would then be much more likely to move together accurately.

290

General Mach Discussion / Re: Why Not The Same

« on: July 10, 2016, 07:53:29 PM »

Unless the G-code got executed in reverse I can't see that happening. Put single block on and strep through the start of the program to see where it goes. If you created the program in a Cam program and told it to make a pattern of multiple instances then it might start the next part at a different place, but you would see the part starting out in the middle of the program not the beginning.