Need a little guidance re: electronics

[adt2]

I'm getting ready to order the electronics for my 2' x 8' build and I need a little direction. I'm planning to order Ahren's 4-axis kit, which includes the Gecko G540 controller and 4 motors, plus the cabling. My intent is to use a single motor for the Z-axis, a single motor for the Y-axis, and two motors for the X-axis. My understanding is that the second X-axis motor will be slaved to the first. I'm planning to use Mach3 with the machine.

My questions mostly deal with limit switches and the E-stop. How many limit switches will I need? Do I need two on each X-axis (one at the left end and one at the right end of gantry travel), or just on one side? What about for homing/zeroing the machine? I think I remember from the Mach3 manual that the limit switches near 0,0 could be wired to do double-duty for both limits and zeroing the machine.

Do I need limit switch on the Z-axis? I wouldn't think so, but I'm not sure.

What is the easiest and/or best way to have Mach3 control the router power? I'm not so concerned about speed control, since I rarely change the machine speed, but I would like to be able to automate the on/off function. On a similar note, is there a way to make Mach3 control a dust collector/shop vac?

On the Gecko documentation, the sample wiring diagram shows a Relay Power Supply and a couple of Relay Coils; what are these for? What is a VFD drive?

Thanks in advance for your advice. I'm getting close to being able to fire it up for the first time, and I would really hate for the machine to explode and burn down my workshop...

[solodex2151]

Originally Posted by adt2 I'm getting ready to order the electronics for my 2' x 8' build and I need a little direction. I'm planning to order Ahren's 4-axis kit, which includes the Gecko G540 controller and 4 motors, plus the cabling. My intent is to use a single motor for the Z-axis, a single motor for the Y-axis, and two motors for the X-axis. My understanding is that the second X-axis motor will be slaved to the first. I'm planning to use Mach3 with the machine.

Correct. The setting for slaving motors in Mach 3 is just a checkbox. Slave axis in Mach3 is a really nice tutorial on how to do this.

Originally Posted by adt2 My questions mostly deal with limit switches and the E-stop. How many limit switches will I need? Do I need two on each X-axis (one at the left end and one at the right end of gantry travel), or just on one side? What about for homing/zeroing the machine? I think I remember from the Mach3 manual that the limit switches near 0,0 could be wired to do double-duty for both limits and zeroing the machine. Do I need limit switch on the Z-axis? I wouldn't think so, but I'm not sure.

You will want 2 Limit switches on each axis, one on each end. The Z-Axis limit switches are useful for preventing the router from running into your table top. You will need 2 homing switches on the X axis. The switches can be wired for double duty but you will have an easier go if you separate them. The limit switches for the X-Axis can be all on one side, but a homing switch needs to be on each side.

Originally Posted by adt2 What is the easiest and/or best way to have Mach3 control the router power? I'm not so concerned about speed control, since I rarely change the machine speed, but I would like to be able to automate the on/off function. On a similar note, is there a way to make Mach3 control a dust collector/shop vac? On the Gecko documentation, the sample wiring diagram shows a Relay Power Supply and a couple of Relay Coils; what are these for? What is a VFD drive? Thanks in advance for your advice. I'm getting close to being able to fire it up for the first time, and I would really hate for the machine to explode and burn down my workshop...

For both router and dust collector, you want to use relays controlled by the output pins on the G540. http://www.homanndesigns.com/pdfs/EN010_V8.pdf should get you started with how to hook up a relay. If you need a source for the relays and the outlets, I can provide them.

To turn on the relays in Mach 3, you need to look in the 'Spindle Setup' tab in Ports&Pins under 'Relay Control'. Set the Output number to the logical output you want triggered when the spindle is told to turn on in the forward and reverse direction. For example set M3 to Output #1, and M4 to Output #2. Now go to the 'Outputs' tab and set 'Output #1' and 'Output #2' to the proper port and pin numbers.

The VFD is for higher end spindles like the 80mm ones you see floating around Ebay. If you are using a router you don't need to worry about this. The VFD controls not only turn the spindle on and off but also controls speed. You can convert your router from the relay control to a VFD control using the SuperPID module (www.SuperPID.com - Super-PID Closed-loop Router Speed Controller), but it's not necessary.

Hope this helps.

Regards,

Nate

[ssutton]

I remember not so long ago that I too was concerned about burning down my shop with a bad CNC router start-up experience.

Nate is spot on, I have almost the identical setup as you will as far as controls go. I am using a total of 6 limit switches all wired into 1 input on my G540. I am using 3 separate hall effect sensors for my homing sensors and they are very repeatable from run to run. The homing sensors are also wired so that they all go to 1 more input on my G540. I have 2 motors on my X and they are slaved together. On that note: when you are setting up Mach with the slave have your motors disengaged from the drives so that they turn but do not actually move the machine. The reason for this is is that you are going to have to set up your motors to turn in the appropriate directions to work together as a team. I crashed several times during the configuration until I had this worked out. Mach will control your router with an output that will turn on another output on the G540, that output is routed to an external relay that can handle the current for the router. On my machine, I have 3 relays that turn on, one for the router, one for dust collection, and the other to open an air valve for bit cooling with compressed air. Only the first relay is powered by the G540, the other relays are slaved off of the first. Your estop is a direct input to the G540.

Good Luck!

ask lots of questions

Scott

[adt2]

Whoa, Scott....that all sounds....complex. I don't even know what a "hall effect sensor" is. Good warning on the slaved X-motor, though - I never would've thought of having to reverse one of them, and I don't think I've seen that written anywhere else.

My guess is that I'll go the simple route first, make sure everything is working, and then upgrade little things later as I learn what I'm doing (and, no doubt, get fed up with stuff). The two of you have given me some things to research, some things to think about, and a case of twitchy fingers waiting for my parts to arrive....

[ssutton]

"Sounds complex" but no really. If you decide to use hall effects for your home sensors then I or many others can give you part numbers, where to get and how to hook them up. All of this is just a series of small steps that add up to a very complex operation, but taken one step at a time you will get it done.

A Hall effect sensor is an electronic sensor that reacts to the presents of a magnetic field, it can sense the field and then give an output that is fed into a control circuit (input on your G540). The advantage of a hall effect verses a contact switch is that there are no moving parts and the repeatability of a hall effect will always be more accurate that a mechanical switch.

In practice, you fasten magnets at key locations on you machine and when a hall effect comes into proximity with it it gives an output that signals Mach it has reached a "home" position of an axis. If you go this way, I can draw a schematic for you to follow.

[DonFrambach]

I learned the hard way that limit switches are very important when I only put them on two of my three axes. After 200 or so hours of flawless performance, I had a totally unnecessary crash that damaged the one axis that wasn't protected. Yes I recovered but the limit switches were immediately installed.

Relays to control my spindle and vacuum are extremely convenient. I used 48v relays so that I didn't have to fool around with different voltages or power supplies. You probably know this anyway but the G-code commands I use are:
M03 (Spindle ON)
M05 (Spindle OFF)
M08 (Vacuum ON)
M09 (Vacuum OFF)
also:
G04 P3000 (Pause 3 seconds for the spindle to come up to speed)

I have not worked out a "home" system because I have been zeroing to my workpiece.

[adt2]

Originally Posted by DonFrambach ...You probably know this anyway but the G-code commands I use are...

Don, you are a funny man. Seriously.

In all honesty, I haven't spent any time fooling with Mach3 yet because a) I don't have the computer to run it on (picking that up Sunday - a coupla-year-old desktop my mother no longer uses) and b) I don't have a machine to test it on yet. I can honestly say I knew there were commands to be entered, but you are speaking Klingon as far as I can tell...

I'm sure I'll look back on this post and laugh in a few months. I hope.

[DonFrambach]

Originally Posted by adt2 I'm sure I'll look back on this post and laugh in a few months. I hope.

Hopefully in a few months you'll be too busy making stuff with your router to look back and read this post!

Don

[brtech]

There are a lot of choices on how you wire the home/limit switches. The problem needed to be solved is the Gecko has 4 inputs. You really, really want to reserve one for auto set (height or 3 axis), so you have 3 inputs left.

For a 4 drive, 3 axis machines (dual drives on Y), you typically want to have separate home switches on the X drives (although with only a 2' X, this may not be an issue).

So, what to do?

First of all, there is little point in separating home from limit. You CAN have separate switches, but for these kinds of routers, there isn't any advantage in doing that. So, that means you have 6 switches for 3 inputs, and you know you want the X and A home on different inputs.

An observation you can make is that with the default configuration, Mach homes each axis independently. That means you don't get anything out of using different inputs for different axis. Another observation is that it doesn't matter which switch trips on a limit switch, the system halts.

So one way to do it is put all of the switches except A home on one input, and A home on another, and leave another input free.

Another is to put X and Z home on one input, Y and A home on another, and all the limits on the 3rd.

Any other arrangement works as long as X home and A home are on different inputs also works.

[ssutton]

Just to further muddy the water on this issue. I have recently rewired my machine's limit and homes to work as such;

I took all of my limits and wired them in series with the estop input, any over travel will result in an estop condition. 3 of my 4 home switches go into 1 input on the G540, my Z, my Y and my X. A is a slave off of X and it has its own input into the G540. That way, I square my gantry ( gantry is over 60 inches wide) when I home the machine. I have my homing routine in Mach set up so that they home independently but then A is a slave of X. I found that Mach ignores the limit switches when it is homing. This caused a series of ugly crashes when setting up my machine. Now, because it is a part of the estop the G540 will stop in the event of an over travel no matter what Mach is doing at the time. Much better. I have to respectfully disagree with brtech, I do find that having home switches are an advantage. My machine machine homes to a repeatability within a few thousands of an inch on every axis. This assures that my gantry is square every time I start up and home. I also have another input used for my zero tools that I use with the Big Tex blue screen. I have found these to be super useful! I use a plexiglass sight with cross hairs machined into and an aluminum tube on that. I also have a corner touch off and a Z gauge plate.

[ger21]

G04 P3000 (Pause 3 seconds for the spindle to come up to speed)

Why don't you use Mach3's built in spindle delays? Much easier than adding it into your g-code.

[Mountaincraft]

I use three switches.. one on each axis at the negative end.. this is for homing... and it is also the negative direction limit.. for the positive direction, I just use Mach 3's built in soft limit system..

You'll want a limit on the 'up' end of your Z axis for homing...

Once you get your homing system in and working, you'll want gerry's 2010 screenset.. best $20 I ever spent!

Only thing I would do different on mine, is to install a second home switch on the X axis for the slaved motor, then once adjusted the table will always perfectly re-square the gantry when it is homed.. Will remove one more maintenance item...

I will do that at some point...

Right now I'm using Ahren's cheapo mechanical limit switches and they work fine... But when I rebuild my table in steel, I want to switch to opitcal limits that I can set up with fine adjusters... and with opticals if I need to run past them, I can disable the limit system and do so.. with mechanical switches you can't do that... I imagine you can do the same with Hall sensors too, depending on how you mount them...