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[How do I?] G0704 CNC Need More Help - Please

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angelfj1

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#1
With help from many of you, I was able to complete the conversion of my G0704 mill. Thank you.
See http://www.hobby-machinist.com/posts/503343/ for more background.

I have been able to make some small parts to mount my home switches for x, y and z axis and I am ready to mount the switches and set up Mach3. However, I am totally confused how to actually do it!

At present, I have two of three switches mounted, the Y and the Z. Both are attached with brackets to the machine column, the Z near the top and the Y near the bottom. The Z axis switch will be triggered when the head travels to the top extreme. The Y axis switch will be triggered when the table travels toward the column, just before it touches, but with enough room for the way cover to fold. This distance is approximately 0.75 inches. I have not yet decided where to mount the X-axis switch, either to the extreme left or extreme right of the table. All of the switch brackets have slotted holes to allow for approx. 0.5 inches of adjustment.

Questions:
Is there a convention for homing switch location? If not is there a preferred location?
Is there a convention for positive and negative direction for X, Y, and Z travel?
I'm using a C10 BOB and have 5 input pins, 10, 11, 12, 13, 15 available. I'm not sure how to connect the switches. The switches have Normally Closed contacts, which open when tripped. Do I need to use 3 of the 5 inputs, or can I connect all three switches in series and only require one input.
After connecting the switches, how do I make the necessary changes in Mach3?

What about soft limits? Are these set after the home switches are set up?

Finally, I'm not sure how to connect my emergency stop switch.

I realize there are many articles and You Tube videos describing all of this, but I have seen lots of contradictions and the more I read or watch the more confused I get.

Any and all recommendations will be sincerely appreciated,

Best regards, Frank
 

Boswell

Hobby Machinist since 2010
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#2
On my mill the axis switches are mounted on the table (or head). In other words on the moving part. There are then "blocks" that trigger the switch mounted to the non-moving parts. This way you can get over travel protection in both directions. Left-Right, Up-Down and Front-Back for Z,X and Y. In fact my system has a second switch in all three axis with a "trigger blocks" at only one end for homing. The result is that Home position is less travel that the Over-travel protection and separate. I find that I almost never use the home switches because I just zero to the part each time I use the mill. No multi-day production runs.
 

TomS

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May 20, 2013
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#3
As an alternative to Boswell's limit switch installation I installed my switches on a stationary part of the mill and the activating ramps on the moving part. See pictures below. Both arrangements work well and achieve the same results.

X axis. There is another activating ramp on the left side of the table.
20150323_103336.jpg

Y axis.
20150319_135317.jpg

Z axis.
20150323_103402.jpg

As you can see I'm using three switches. They are wired in series and connected to one input pin of your choice. Setup Mach 3 by going to Config/Ports and Pins/Input Signals. The dialogue box is easy to follow but if you need specific help please ask. The Mach3 manual is also a good source.

I am by no means a Mach3 or CNC expert but I do believe you have to home your machine before you can set soft limits. Mach3 needs to know where it is before soft limits can be applied. Someone please correct me if I'm wrong.

In regards to the E-stop I connected mine to one of the available input pins. Your E-stop switch is configured just like your limit switches. Scroll down in the Input Signals dialogue box until you find E-stop. Input the appropriate info and you are good to go.

This is not the only way to install limit switches but it's the way I did my mill. Hope this helps. If you have any more questions ask away.
 

Boswell

Hobby Machinist since 2010
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#4
I would agree that soft limits only work correctly if you home the mill so it knows where it is.
 

Boswell

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#5
BTW, I can tell I am getting old in that I described the limit switch and block setup BACKWARDS :(. The switches are mounted on the non-moving part and the blocks are in short tracks that allow some adjustment on the moving parts. Like TomS described. I guess I was too lazy to walk out to the shop and check it.
 
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