[bobeson]

I wanted to share my experiences with tramming my PCNC1100 back into position following a pretty bad crash I had a few months ago. The crash happened during a rapid z down, while the spindle was not rotating. This caused my 1.5" ktool insert mill body to strike a glancing blow off the top left side of my vise, and then continued downward after getting forced to the side of the vise, until the right side spindle shoulder bottomed out on the vise and stalled the Z axis motor. Ouch. This was thanks to a missing decimal point during MDI movement. D'oh!

Anyhow, the first thing I noticed after cleaning everything up and restarting was that I had a terrible surface finish problem. Eventually I realized this was happening because my machine had gottten thrown pretty badly out of tram by the crash.

At first, I tried the method advocated by Tormach where you simply place shims under the machine base, between the machine and the stand. This worked pretty well to put the machine in tram, or so it seemed, but I still had bad surface finish. When I went to re-measure the tram, I realized that I had tweaked my machine base into a helix, because I had pretty large shims under the machine. The result was that the machine was in tram when the table was in the middle of the Y and X travels, but then went out of tram when Y traversed, and also somewhat when X traversed. I think shimming under the machine base is a good bet for small errors, but it seems that the magnitude of my shimming was too much, and I was getting a twisted machine base as a result.

So, I switched to shimming under the column. I started by using a 4x12" cylinder square mounted on the y-axis ways, and using an indicator on the spindle to determine the angle of lean of the column wrt to the y-axis ways. Once I had measurements of the X and Y axis lean angles, I designed two shims, one for each side of the column base. Then I unbolted the column from the base, and used an engine hoist to lift the column while I put a scissor jack under the head near the spindle, and coordinated the lift of the two to make sure I pulled straight up. There are two locating dowels that connect the column to the base. I was careful not to pull the column off the locating dowels; rather I lifted it just enough to slip the shims underneath, and then it went back down easily.

Unfortunately, the results weren't so great. I was still out of tram. Then I realized that referencing the Y-axis ways was a mistake, and the actual table plane is all that matters W.R.T. the column angle. So, I pulled out the cylinder square again and measured the lean angle of the column with respect to the table for both X and Y axis directions. Then I made new shims to compensate for these angles, and installed them under the column after removing the first shims.

This time, the results were fantastic. My table is now square to the column within close tolerances for both X and Y, and my surface finishes have become better than when I first got the machine.

In summary, if you need to tram your PCNC1100, and the errors are relatively small, I would start by using small shims under the machine base front pads, as described by Tormach. If you need more than ~0.050" of shim, you're probably distorting your base excessively and you oughta try shimming the column instead. I'd be happy to walk anybody through it if they need help, or share photos I took of the process if anybody is interested.

[keithorr]

This was thanks to a missing decimal point during MDI movement. D'oh!

would soft limits have prevented the crash?

[LENS_CAD]

I have had a few minor crashes during MDI rapid moves. I know how it's easy to make a typing mistake.

I usually jog rapidly near the desired location with the jog/shuttle control and then use MDI with G01 to get the precise location.

Len <><

[bobeson]

would soft limits have prevented the crash?

Yes, I believe they would have, since the value entered was -03 instead of -0.3, which would have put the spindle through the table if it had completed.

[twocik]

"would soft limits have prevented the crash?"


How would this be setup or does Tormach sell this ?

[philbur]

Google - "soft limits" mach3 -

Phil

"would soft limits have prevented the crash?"


How would this be setup or does Tormach sell this ?

[keithorr]

"would soft limits have prevented the crash?"
How would this be setup or does Tormach sell this ?

Soft limits would have helped. I don't know what Tormach offers. I (and others) no longer use the locked down Tormach version of Mach. We use Mach3 with Tormach screens to get access to all the Mach features available. Soft limits being one of them. No warranties implied or otherwise.

[zephyr9900]

I don't see how soft limits could have prevented the crash. The vise is within the machining envelope. The crash was the toolholder, and ultimately the spindle nose, against the vise, not the machine running out of travel.

Randy

[keithorr]

I don't see how soft limits could have prevented the crash. The vise is within the machining envelope. The crash was the toolholder, and ultimately the spindle nose, against the vise, not the machine running out of travel.
Randy

Good point. I'm not in front of the mill to try. I assumed the machine would refuse the mdi input when the move endpoint was outside the envelope. I know the feature puts up an error message when pre processing a file with an out of bounds coordinate. Won't be able to try it until tomorrow.

[mactec54]

No soft limits would not of stopped the crash, unless you had set it for that tool

You could set your Z axes soft limit so that the tool could not hit the vice, But then you would have to set the Z axes soft limit every time you changed the length of of your tool.

The soft limits are normally set just in front of the hard limits

[zephyr9900]

I know the feature puts up an error message when pre processing a file with an out of bounds coordinate.

Now that I didn't know, Keith. Running the "open" Mach with softlimits enabled (the Tormach version has them configured, just not enabled) is fairly recent for me. But I run all my gcode through CutViewer before taking it down to the machine, so I've apparenly never sent Mach an out-of-bounds coordinate.

I did some testing tonight. Scary writing a gcode that said G1 X-50 F1 (I figured the F1 would give me some reaction time if things went awry...). That gave a popop box that said "Softlimit warning..continue?". Same thing when I replaced G1 with G0 (even more scary...)

When I typed G1 X-50 F1 into the MDI box, I got a message on the message line (not a popop box) that said "Softlimits System Movement Aborted" so the softlimit does proactively protect even MDI commands.

Given that there is a defined deceleration zone for the softlimits, I thought that they would be reactive (i.e. monitoring the DRO's) rather than proactive. So you've taught me a thing today, Keith. Thank you.

You could set your Z axes soft limit so that the tool could not hit the vice

I do a lot of machining down between the vise jaws, Mactec54. Maybe that's one reason I'm so paranoid about previewing my gcode... And when I'm engraving with the Proxxon on a workpiece clamped to the table, the spindle nose is sometimes within 1" of the table. Of course I have the forethought to remove the vise before I do that...thus far...

Randy

[mactec54]

Soft limits are active as soon as a machine is homed, IF they have been SET UP, It does not matter if you are in MDI, AUTO Etc, They are always active,

[keithorr]

When I typed G1 X-50 F1 into the MDI box, I got a message on the message line (not a popop box) that said "Softlimits System Movement Aborted" so the softlimit does proactively protect even MDI commands.

Thanks zephyr for checking that out. I was operating on a distant memory; hadn't had the situation for a long time.

No soft limits would not of stopped the crash, unless you had set it for that tool

If mach knew the tool was loaded and the tool table was current and the soft limits were set to protect the table, then the crash would have been avoided. The OP stated the move would have put the tool through the table, which would have been set at the lower z boundry. Yes I agree soft limits won't protect the vise while running g code if the vise is inside the soft limit envelope.

[mactec54]

keithorr most users are not using the tool table so Mach would not know if the number GCode you put in your program is outside the boundry, the soft limit would not help unless it had been set so the Zaxes can only go down so far & not crash the tool into the table it would of still hit the vice

[zephyr9900]

Given that there is a defined deceleration zone for the softlimits, I thought that they would be reactive (i.e. monitoring the DRO's) rather than proactive.

I did some more playing this morning--Shuttle-jogging full speed at the limit--and that is the reason for the deceleration zone. In another thread I wrote

With the top speed of 90 ipm (1.5 in/sec) and an acceleration of 9 in/sec^2, the distance to accelerate to the top speed is .125".

so Tormach's deceleration zone of 1" seems very generous even for new machines (my Series 1 is still 65 ipm rapids).

Update: I wrote some test gcode operating within the 1" deceleration zones, and the machine ran it unaffected. So having a large deceleration zone doesn't affect the actual machining envelope. /update

If mach knew the tool was loaded and the tool table was current and the soft limits were set to protect the table,

Now that would be a very cool feature, Keith--an automatic parametric lower Z softlimit based on the tool loaded. You would need to define an offset to cater for how you measure your tools (i.e. I measure with the TTS fixture, so my offset would subtract the height of the fixture itself to get the true distance from the spindle nose to tool nose). But then the mill would never gouge the table. Vises and tooling can be replaced--the table is kind of permanent to the machine.

It does not matter if you are in MDI, AUTO Etc, They are always active,

That is a nice feature, Mactec54. My caution comes from years of using a Sherline mill without even limit switches. After running the table off the end of the leadscrew a couple of times, I learned to be more careful in what I was doing. And fortunately for the learning curve, the Sherline vise was aluminum.

Randy

[zephyr9900]

keithorr most users are not using the tool table

?!? I would think that the vast majority of Tormach users are using the tooltable, Mactec54. I don't think I've ever seen a picture of a Tormach in operation that isn't using TTS holders...

Randy

[keithorr]

Now that would be a very cool feature, Keith--an automatic parametric lower Z softlimit based on the tool loaded. Randy

I think you might be misunderstanding my gist. I was suggesting if the OP had all the parameters updated, it would work. If you show a tool number in the little box (don't know the name, not in front of the machine) on your simple, complex, mdi or offset page, then the tool length is part of the equation when soft limits come into play.

And;

I agree everyone is using tool offsets unless they are very new and still setting up the machine for the first time. Anyone using tool changes would be foolish not to have things set up ahead of time.

[keithorr]

keithorr most users are not using the tool table so Mach would not know if the number GCode you put in your program is outside the boundry, the soft limit would not help unless it had been set so the Zaxes can only go down so far & not crash the tool into the table it would of still hit the vice

Even without a tool offset and/or work offset, the system would still protect the machine.
If I had no values entered for tool offset, nothing for work offset and was just using the machine in machine coordinates;

Workpiece is 2 inches off the table, mill in 1 inch in length. I would have to program the G code or MDI to Z3.0 to get the tool to touch the top surface of the workpiece. If the Gcode or MDI had Z-3.0 (3 inches below the table) the softlimits would throw an error and not allow the machine to begin the move.

In this particular instance. The OP entered a value below the table. I don't know if he had offsets or not. Never mentioned. Doesn't matter. If he had softlimits set up and had zeroed the machine at the beginning of the session, the crash would not have occured. Mach would have thrown an error message and not allowed the machine to move at all. No move, no vise crash, no nothing. It looks ahead; does not wait until it is at the limit to stop the machine. Proactive, not reactive. What can you say now, that nobody zeros their machines in the morning? If they don't, they've earned a crash.

And yes to zephyr, the one inch buffer decel zone is only in play during jog. You can mill right up to the soft limit at a rapid after which the limit switch comes into play. (assuming you zero the machine and do all the other things I know you already do)

Happy Holidays to all. I'm going sailing.

[zephyr9900]

If you show a tool number in the little box (don't know the name, not in front of the machine) on your simple, complex, mdi or offset page, then the tool length is part of the equation when soft limits come into play.

Are you certain of that, Keith? With no tool loaded I can jog the spindle nose to within ~.35" of the table. I defined a dummy tool in the table with a length of 15" and activated it. I can still jog the spindle nose to the same point (obviously no tool actually installed on the spindle!) so at least on my installation Mach isn't taking the tool length into account, either for jogging, MDI or gcode execution.

I'm running PCNC rev. 3.12b (unlocked, and with the XML tweaked for Series 1 stepper and spindle parameters). I have softlimits enabled, and the machine respects all softlimits for jogging, but the minus Z softlimit isn't respected for MDI or gcode. I can MDI the Z into the lower limit switch with no complaint from Mach. Interesting what I'm learning, now that I'm poking at the envelope...

The virgin install came with Z- softlimit set at -20.00", clearly wrong because the machine travel is only a nominal 16.25"--but since Tormach has the softlimits disabled, it doesn't make a difference in the stock installation. On my machine, Z home is with the spindle nose ~17.25" above the table, and the lower Z limit switch is at a machine coordinate of -16.93". I have the lower Z softlimit set at -16.92", with the stock deceleration zone of 1".

And no, I don't think I misunderstood your gist, Keith. I was taking your gist and running with it. I was just envisioning a situation where the software was aware of the tool tip in relation to the table, and never allowing a move that would gouge the table. That is a fixed physical lower Z limit, irrespective of tooling on the table. Just take into account the length of toolholder+tool relative to the spindle nose, and it could be done.

Randy

[zephyr9900]

Workpiece is 2 inches off the table, mill in 1 inch in length. I would have to program the G code or MDI to Z3.0 to get the tool to touch the top surface of the workpiece. If the Gcode or MDI had Z-3.0 (3 inches below the table) the softlimits would throw an error and not allow the machine to begin the move.

I dispute that, Keith. (I'm going to take the opportunity to pile on you while you're out on your boat. )

On the Tormach I observe that machine coordinates take Z0 to be at the upper limit switch, so in machine coordinates all Z is negative. It is just the magnintude of the negativeness that the softlimit is looking at. And, as I just posted, with Tormach's stock lower Z softlimit the spindle nose could be 3" below the table before the lower Z softlimit was triggered, if it were not for the limit switch.

Randy