Hi,
I repair welding equipment for a living. We support a brand of pickling machine which is a DC current source to a carbon fibre brush with an acid etchant
which is used to clean up stainless steel post weld. They work well and they need to, they are expensive. The Austrailian company that makes them is
a low volume manufacturer and they use 3D printed plastic handles and torch couplings. The problem is the plastic produced by a 3D printer is s*********t!
It lacks the density and strength of an injection moulded part.

3D printing may offer a few production wrinkles that cannot be matched by subtractive methods like milling but the quality/density/strength of the resultant
printed material means that they are for decorative purposes only. Maybe there are printers and print heads that can do a better job but they bloody well better
do a better job before I'd use any 3D printed part in a serious engineering application.

Craig

Hi,

Setting Limits, I find that when I hit a limit switch and it back off slightly I can then drive into again after pressing reset and the DRO number has increased from its original number by about 0.0300 on both "X" and "Y" on "Z" its less about 0.0020 to a higher number.

Also has I am slaving "X" with "A" when I do the same again the "A" motor wants to go a little further then the "X" motor and then comes back. Nema 17 "X/Y", Nema 23 "Z"

Lastly on "X" axis I get a negative number on the DRO when I move from Zero into the table how do I change to a + number.

Apart from that everything seems fine.

Regards John

Sorry for keep being a pest, I hate asking for help.

I think sorted most, Homing seems fine know, Z doesn't seem to come off limit switch at 0.000 even when I set set the Home offset to 0.500 the same as all the others, but that could be I use a Lead screw which may need a larger Number.

Only problem I am left with is the axis move in a negative direction from home / Machine zero, Z is fine and the "A" drive motor seems to sing a bit after Homing until I hit either reset or the "X" axis limit switch again.

Regards John

Hi John,
I think there is some confusion about limits and homes. Limit switches are at the end of each axis and the principle reason for them is to stop the machine
from banging into the endstop and wrecking itself. Home switches are to reference your machine at the start of your session.

It is quite common to use the limit switches as home switches temporarily at the beginning of the session while you reference your machine. During that time
the limit switches have to be ignored and treated differently. Once homing (referencing) is complete then they go back to being limit switches.
To be perfectly honest I think this idea of 'double duty switches' just to save a few bucks and/or a few Mach inputs is a disaster waiting to happen.

The common way to wire your limit switches is to have all six switches in series with normally closed contacts. If any one of the switches opens the machine
Estops. The machine can't tell which switch opened just that one has. You can then hit  <limit override> and back off the offending axis , remembering
that while you do so Mach can't stop you from making a mistake, if you go the wrong way you may make the situation worse. So while this method has its
disadvantages it does only require one Mach input pin.

If you wish to do the 'double duty' home switch thing....hit <ref axis> and that axis will drive in the nominated direction at the nominated speed until the limit
switch string goes open circuit, then it will back off until the switch closes and reset the machine co-ords commonly to zero but you can nominate any number,
the 'home offset', that you like. It does not mean that it drives to that location. So while homing the one input pin is treated differently and you have no limit
protection at all. This has caused innumerable crashes over the years.

I prefer to have three homes switches in addition to the six limit switches. I also prefer that each home switch have a dedicated input pin. Given that
a parallel port only has 5 input pins you are going to run out. You need a second port, now you can have not only another 5 inputs but you can assign
pins 2-9 as inputs also rather than their more normal use as outputs so the second port gives you an extra 13 inputs. Highly recommended. With all these
inputs you don't have to compromise, the limit switches ALWAYS are limits and HOMES are only ever home switches. Further than that it means you home
switches can be really nice microswitches which give repeatable and accurate homing which is a real boon to your machining operations.

If you are prepared to stump up the bucks for a PCI to parallel card and another breakout board you will make a big advance it what you can achieve and reduce
the chances of confusion which result in crashes.

Craig

Hi Craig,

Very grateful for your comments, I will certainly look at doing that, I have limit switches on all axis at moment using pins P12 P13 and P15 for X Y Z, P11 for Tool setting and P10 for E-Stop, they go via high when active which I know is wrong so will modify that so if wire breaks no damage is done.
I have another PCI Parallel card which I will use as you suggested, and I am looking at making another Breakout board from the schematic I put up on this thread, I am an electronics/Computer engineer so that makes things easy.

I was also looking at some YouTube videos on all these procedures and found that Roger Webb gave me an idea to try the Soft Limits similar to the milling table that he did.

I also think the "A" drive that was singing a bit once I homed my system, it only stopped when I hit Reset or a limit switch again, may stop with proper Homing.

Also got to set the table Soft Max and Soft Min, I presume as I have "A" slaved to "X" I set "X" axis settings in "A" settings the same.

Regards John

Hi John,

I have limit switches on all axis at moment using pins P12 P13 and P15 for X Y Z

so they are limits, that is three pairs, of two switches?

Soft limits are very useful ONLY if the machine is accurately and repeatablly referenced.

Craig