Are the proximity switches really accurate?

[knight_toolworks]

Maybe I am way off base but I was thinking using them to zero the x and the y then find out the measurements from them to the actual home I want then make a file to do that and give me a accurate home. A good idea?

[fleinbach]

Steve,

You are so on base here. That is exactly one of the uses of the prox switches. The shopbot software has a homing file just for zeroing the X and Y position and it is dead on acurate. After you get the measurement from the x and y axis you put it into the homing file and that's it.

[knight_toolworks]

great I will ge it set up today.

[knight_toolworks]

I forgot to ask whats the name of the homing file I need to modify?

[fleinbach]

It is located in the SBPARTS folder and is called s_home. The instuctions for setting it up are in the file.

[jhicks]

Just remember that if you rely on one switch to find home on each axis,(lets say ox/oy your other end (lets say 0x/48Y or 96x/48y)) can still be out of square if it has no absolute registration target/switch/ stop block(s) or whatever you use to calibrate and confirm square.
Getting back to home 0/0 is one step but not much good if out of square

[dray]

Yeah the squaring thing is a problem even with the new prs alpha.

I think the limit switches cost around $35 for another $35 you can add a second on the y axis and add a routine to HOME then SQUARE HOME.

wouldnt be a big deal I dont believe for the shopbot people to offer that but im not a programmer.

[fleinbach]

When you fire up your machine there are 2 steps that need to be done in there proper order to assure you are working with a properly tuned tool. The first step is dependant on your making sure your Y axis is squared to the X axis. There may be other methods to squaring the 2 axis's but none works better, nor is easier then pulling the Y car against properly squared stop blocks while activating the control box.

So step one is to pull the Y car against your squared stop blocks and turn on the control box. At this point the Shopbots X and Y axis's are square.

Step 2 is to run the X/Y homeing routine.

If you repeat these steps in this order you will find you can repeatedly cut in the exact same path even after shuting down and restarting, as long as you repeat the whole process over again.

As far as I know even though there has been a recent thread discussing the use of an extra prox switch to be used for squaring to my knowledge no one has actualy done this yet. One of the complications is software would have to be written that would allow independant control of the X motors. Anyone please correct me if I'm wrong and you have knowledge of software availiable that will square the axis's.

[jay_p]

Steve,

Take a look at the "tool setup" menu item under Tools in the ShopBot window. It gives you the opportunity to define multiple parameters and automatically setup things like the s_home file that Frank is talking about.
There are two options for the proximity switches. One allows to to input the distance from 0,0 to the switches. The other has you position the tool at 0,0 and it does the distancing for you.

Jay

[denver]

Frank, I understand the part about correctly setting the hard X stops, then holding the X car against the stops when powering up. I do that now.

At this point the X car is against the hard stop at the zero end of it's travel, and it's beyond the limit switch. Whenever I've run the "home xy using prox switch" routine (C3), it moves towards zero, not away. So if I run C3 at this point it's going to go in the wrong direction and stall against the hard stops. Or am I missing something?

What I do now is use the keyboard to move X & Y close to the 0,0 corner, but over the table surface. Then I use an XY zero routine I found somewhere else on this forum along with a piece of aluminum angle held on the corner. This is a variation on the Z zero process. It works, but what you are describing sounds much simpler.

Thanks,

Denver

[denver]

I have a PRS Alpha, and I don't have s_home.sbp, but I do have XYzero.sbp. That's what gets called from the C3 command - Custom3.sbp just contains:
FP, c:\SbParts\XYzero.sbp

This one moves the carriage towards zero. If I'm starting from the zero hard stop, it would have to move the other direction, past the limit switch, then back towards zero till it hits the switch again, from the plus side. Does that sound reasonable? Or do you just use the keyboard to move the carriage to the plus side of the switch after powering up?

Thanks,

Denver

[fleinbach]

Denver,

You are right I guess I should have added that step in between step 1 and 2. Step 2 should be to move the tool manualy from behind the prox switch. I usualy just watch the led on the prox switch until it goes out then run the x/y home routine.

As for the software I believe it is the same for all machines at least the ones after the prts. And yes I believe they changed the file from s_home to one of the custom files in one of the later versions of the Shopbot software but I'm not sure exactly which one it was. I set mine up nearly 6 months ago and am not sure which version I am running. I will check it out when I get out to the shop.

[beacon14]

You can easily add the commands

SR
JX, 5
SA

near the beginning of the xyzero file. Instead of the number 5 use whatever distance your machine needs to move to get past the limit switch. Then the machine will move over that distance before beginning the zeroing routine, saving a step.

[denver]

Thanks Frank, David. I'll try those commands. That will simplify things a bit. I always had to turn limits off in VN to get past the switches. Now maybe I won't have to do that.

Thanks again,

Denver