Squaring ShopBot Gantry

[Toaster]

Hey all, I'm nearly done setting up my Acorn for a transplant into my ShopBot. The last thing I need to tackle is gantry squaring. This is how I do it right now using a relay and the ShopBot software:

https://youtu.be/LrSLWpKjLU8

It's essentially a method of unlocking one X axis motor, and using a second proximity switch to walk the gantry into square. (Thanks to Gary for helping me with this)

I learned from another thread here that a built in solution is coming to CNC12 really soon. I'm wondering if I should hold off on doing the swap until this new software update comes out? Or if it's going to be a while I'll just write the script again myself so I can start using the Acorn sooner rather than later.

In either case, I thought it would be helpful to share this so that anyone else thinking of doing a similar swap could use a similar method, it's worked great for me for a while now.

[Gary Campbell]

Do a search here for gantry squaring macro. One has been posted. That should get you by until the next release

[cnckeith]

I would wait for next release.. that macro posted requires a custom PLC program for it to work.. just manual square it for now..and when v4.14 is released Auto Squaring is supported in the wizard and will auto generate the macro and plc program for you. here is a link to the setup guide so you can get prepared. http://www.centroidcnc.com/centroid_diy ... _guide.pdf

for now start with the configuration shown on page 15 for software pairing this is supported in v4 .12, or page 5 for hardware pairing.

[gerald martin]

Following this because I'll want to set up the auto squaring on my retrofitted ShopBot too. Got the additional new proximity sensors and hoping to install on Saturday.

Gary, I noticed one difference in configuration - on my setup we were putting each prox sensor on its own input. However the user guide Keith has linked here shows 3 of the sensors wired in series and the 4th one (in my case, the X1 sensor probably) using a second input. This configuration conserves use of inputs. I don't know if the sensors I'm using can be wired in series? Or is it better to leave them each on their own input?

Gerald

[Gary Campbell]

I don't know if the sensors I'm using can be wired in series?

No, daisy chaining inductance sensors wont work well.

Or is it better to leave them each on their own input?

In my world yes. The daisy chaining of limit switches is an old school version of "hamburger helper" for not enough IO It works OK when using mechanical switches

I feel there is an advantage to having discreetly configured inputs and outputs, especially when they are configured hi and lo. If Acorn users require more IO, there is an add-on board coming in the future.

[gerald martin]

Makes sense. I have discovered there is usually a reason you do things a particular way.

Looking forward to getting the limit sensing and auto squaring set up.

Gerald

[Charlie.G]

hey guys,
I mean no disrespect just learning about other machines ....
is it a big issue ( a common thing) with the gantry being out of square for shop-bot
and others?
I use to have auto squaring on my machine with mach-3, quit using it
awhile back and just set my hard stops to square and I can pull the gantry
up to those stops manually and then turn on the power to the steppers and when it ingagued it
would lock it square.
then I quit using that method and just took the time and squared the gantry,
and once in awhile I will check it against the hard stops to make sure it is still square.
hasn't been an issue since.

thank you,
Charlie

[Dan M]

I don't know if the sensors I'm using can be wired in series?

No, daisy chaining inductance sensors wont work well.

Or is it better to leave them each on their own input?

In my world yes. The daisy chaining of limit switches is an old school version of "hamburger helper" for not enough IO It works OK when using mechanical switches

I feel there is an advantage to having discreetly configured inputs and outputs, especially when they are configured hi and lo. If Acorn users require more IO, there is an add-on board coming in the future.

Gary do you know if the new software update will allow for the sensors to be wired separately? It sounds like I have my proximity sensors wired how you do it. Each sensor having it's own input. I didn't see that option in the link either. I'm wondering if you will still need a custom macro to wire them that way? Any info would be great thanks.

[Toaster]

Charlie: ShopBots run on a V roller system. There's a stepper motor on each side of the gantry. When the machine is powered up, both steppers are locked. Unless you lose steps that gantry won't "rack" because it's being held in place by those two steppers.

When the machine is off, because of the V rollers, it's very easy to rack the gantry back and forth by hand. This is why ShopBot recommends that you pull the machine against the hard stops before you power it up. Those hard stops are adjustable, so it's on you to make sure they're in the right spot. When you power up against those hardstops (it they're square) your gantry will be square. See this video for my method for manually squaring: https://youtu.be/s2z9tTbTdcY

While this is a viable way to make it square, I like using the prox switches better. First of all, they're easier to adjust as you can very finely adjust them using a squaring script, so when you're checking for square you can "sneak up" up on perfect square. Also, those inductive prox switches are really accurate, so no matter what happens when the machine is powered off, or in a situation where I do lose steps I can run the squaring script again and get that machine back in position. Also, since it runs automatically with my warm up script there's less of a chance that I'll forget to square.

While I have most of my experience on large ShopBots, this problem isn't just a ShopBot problem. I'd guess just about any large format machine can experience this. Smaller machines probably have this issue to, but the problem would be so tiny on a 24" x 18" machine you'd never detect it.

Dan: As far as I know there's nothing better/worse about chaining sensors together VS having them on separate inputs. For squaring, you can have XY&Z all on one input, and your X2 (your second one on the X axis). The reason being is this:

When the machine is homing, it moves in one axis at a time. So when an input is triggered it knows that it hit the prox switch for that particular axis that it was moving on. So you can have 3 prox switches on one input. For squaring, you need to move the machine on X, and you need a sensor on each end of the gantry. So this means you need a second sensor on another input so that the software can distinguish both ends of the gantry. unlock one of the steppers, twist the gantry too that second sensor, and lock again.

Since all of those moves are happening in X, there has to be that second sensor. Does that make sense?

[mikes]

I would wait for next release.. that macro posted requires a custom PLC program for it to work.. just manual square it for now..and when v4.14 is released Auto Squaring is supported in the wizard and will auto generate the macro and plc program for you. here is a link to the setup guide so you can get prepared. http://www.centroidcnc.com/centroid_diy ... _guide.pdf

for now start with the configuration shown on page 15 for software pairing this is supported in v4 .12, or page 5 for hardware pairing.

@cnckeith, just an FYI the below sentence in the squaring doc needs a bit of help:

"This is especially important since when the axes are not paired it is possible to cause damage to the when jogging since only one motor on the paired axis will be responding to the axis jog button."