Need more documentation for getting started!

06 Oct 2010 17:53 #4537 by rggrieger
EMC2 docs explain each cmd, etc. but need either more examples or documentation on how to get started and what to expect from CNC machine. With some help from Probotix I was able to get Stepconf Wizard to set the parameters and move all three axises. Now I am trying to ascertain that the limits work and to home the axises. I am working by myself (DIY) and have no one to ask or show me how to run the machine. I searched the forums and the web and did not see applicable info.

An example in the docs to show how to verify the limits work will help newbies. For example, in StepConf I activated test run and manually click the limit switch to open and the machine does not stop. Same with the E-stop. Is the Stepconf ignoring the limit switches or is the limit circuit not working. There is no documentation to indicate how to test these switches and what might be wrong is they do not work.

I ran the AXIS program with the default program and tried to home the switches. None of the axes move and again there does not seem to be any documentation on how to handle this situation.


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06 Oct 2010 18:48 #4539 by BigJohnT
Did you read the Getting Started Guide that is installed when you install EMC2?

As I recall the "Test this Axis" screen warns that no limit switches are honored when testing an axis.

The Integrator Manual contains information on setting up your homing switches as well as the Stepconf section in the Getting Started Guide.

Did you release the E-Stop and power up EMC before trying to home an axis?


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09 Dec 2010 08:52 #5933 by vincent
Hey, rggrieger

I think u have found a good start here. I start EMC2 one year ago. and now I'm gona to seek a job for this. but I still think I know too little to get a job about this.

anyway, let's get down to work!!

good luck.

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09 Dec 2010 15:19 #5940 by rggrieger
I used the StepConfig to set the pins. At first I used only the axis pins 2, 3 4, 5, 6 and 7. I then used Test This Axis to see how the axis moved being careful to set the travel of the table for each axis to within safe table and spindle travel limits. A disadvantage of this travel setting is that you need to set it each time you turn Test This Axis or you may over run the safe travel limits and smash into the ends of the travel. After seeing how the axis ran I clicked the run button to continually run back and forth along the x and y axises and up and down for the z-axis. I begin testing the velocity first by setting it low, e.g.-, 0.4 in/sec and gradually increased it to 0.8 in/sec where the stepping motor sounded like it was missing steps. I set the velocity back to 0.7 ips and gradually increased the acceleration until it seemed to run smoothly. I now use 7 in sq/sec. There are more accurate testing methods in the docs but this will get you started.

I made a simple CNC table out of wood, 1/4-20 drive screws and 1/2" rd CRS bars. It has a cutting volume of 5"x13"x13" and uses a Dremel motor. It has a big advantage for beginners like myself in that it bends some and recovers nicely without damaging the table, etc. I made several mistakes like driving the the tips too hard into the homing device and over running the limit stops before I got them working, etc. Although 0.7 ips seems slow it is awfully fast when something is going wrong or I am just slow in seeing and reacting to crashes.

I had installed limit switches in a series circuit, an E-stop switch, homing switch and a probe switch.

The homing switch is a small right angle bracket for x and y and an aluminum plate for z fastened to a block of wood. I mounted it in the zero corner of the cutting table. I clipped an alligator clip to the probe tip or the tool tip to home the 3 axises. I had the usual difficulties in understanding how homing worked and settled on setting the axis offset to zero since the tip or tool was constrained to the plus side of the axises, i.e.-, tool or probe could not pass by home and back through the home position. It hit home and immediately had to backup and do another approach to home to set the final home position. It does the z-axis home OK but it may take two or three tries to set the x and z axises. If it does not seem to home I restart EMC2 and try again.

I made a simple probe switch by using two 1/4" rd CRS rods set into nylon bearings and mounted on the 1/8"x1"x6" Dremel mounting plates on the z-axis. This probe is a learning and testing tool and not really for accurate probing measurements but it does make a mesh using the rectangular probe EMC2 probing example.

After setting the pin functions in StepConfig I was able to test the E-stop and limit switches. They all work as intended.

I used the probe to test how "level" the table is relation to the x and y axis table movement. I think it is within 0.005" +- 0.004". I used the EMC2 DRO to make these measurements. I used pieces of aluminum can as shims under the table guide bars to adjust the table. I think a dial gauge would have been better as it is a measurement independent of the table.

I used a cake of soap to drill 6 holes in circle and a 0.3"x1"x1" pocket.

Hope this helps, Bob :)

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