Hard limit Switches

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sdumond
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Joined: Sun Feb 01, 2015 1:12 am

Hard limit Switches

Post by sdumond » Tue Mar 10, 2015 1:26 pm

I have installed limit switches and if I am facing the spindle, and run the the -X axis goes to the right and the -Y axis goes closer to me. When I run G28.2 x0 command, x axis runs to the right. If I give the G28.2 y0 command the Y axis comes toward me. If I give the G28.2 z0 command the z axis goes down. How do I correct this problem?

According to what I have read all the axis are supposed to move opposite of this.

Thank you for your time

khauser24
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Joined: Mon Dec 01, 2014 12:41 am

Re: Hard limit Switches

Post by khauser24 » Tue Mar 10, 2015 5:22 pm

This suggests you have the polarity reversed. You can correct the issue in the wiring, by switching ONE of the pairs for the stepper motors you want to change, or with the TinyG you can also change this in the configuration. See https://github.com/synthetos/TinyG/wiki ... --polarity

sdumond
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Re: Hard limit Switches

Post by sdumond » Thu Mar 12, 2015 4:52 pm

I wired the tinyg according to the color scheme off of the wiki. If I was to change the polarity at the tinyg with the stepper motor wiring, what color schematic would I use. I do not know which wires to change. If anybody knows I would appreciate it.

khauser24
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Re: Hard limit Switches

Post by khauser24 » Thu Mar 12, 2015 9:37 pm

By the way,in re-reading your post I think only the X axis is reversed. Y should go positive away from you, and I believe it is. Z should go positive upwards, and again I think it is.

The X-axis is the two motor setup. Depending on how you wired the motors, you either reversed one side and connected both to a single output on the TinyG, or you wired each to a separate output and set one to be inverse polarity.

If you did the first, you simply flipped the wrong pair, and if you did the latter you set the wrong output to inverse.

You can fix it either way, as I said.

cmcgrath5035
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Re: Hard limit Switches

Post by cmcgrath5035 » Thu Mar 12, 2015 11:20 pm

A couple thoughts:
Context here is a ShapeOko machine, which is uber flexible. Other machines might have a more rigid concept of X and Y.
1. There is no color coding standard for NEMA steppers. You can probably assume that a batch of motors from a particular manufacturer purchased at the same time are wired consistently, but that is about it.
2. Typical documentation from Synthetos will have one X motor, one or two Y motors and a Z motor. But your can decide to have one Y and two X motors, if that better fits your typical design and use patterms. Some folks like to design 'squarish' projects, Xmax =~ Ymax. But others perfer 'Landscape' designs, Xmax >Ymax, while some prefer 'Portrait' designs, Ymax > Xmax.
3. Z+ is up
4. X + and Y+ really depend on how you want to load your machine and run it - so what is + and what is - is up to you.
5. Once you decide what is + and what is -, the X=0, Y=0 is at the end of travel in the - direction.
6 Then wire your limit switches accordingly. The X0, Y0 and Z0 switches are the 'Home" switches.

Confusing? Perhaops, but that comes from the great flexibility of the basic design.
ShapeOko (V1) SN 1462
Dual 820mm Y, Double X, ACMEZ. V2 Motor Plates
TinyG V7 Controller; DUE and tinyGV9 test bed for tinyG2

cvoinescu
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Re: Hard limit Switches

Post by cvoinescu » Fri Mar 13, 2015 12:35 am

cmcgrath5035 wrote:A couple thoughts:
Context here is a ShapeOko machine, which is uber flexible. Other machines might have a more rigid concept of X and Y.
1. There is no color coding standard for NEMA steppers. You can probably assume that a batch of motors from a particular manufacturer purchased at the same time are wired consistently, but that is about it.
2. Typical documentation from Synthetos will have one X motor, one or two Y motors and a Z motor. But your can decide to have one Y and two X motors, if that better fits your typical design and use patterms. Some folks like to design 'squarish' projects, Xmax =~ Ymax. But others perfer 'Landscape' designs, Xmax >Ymax, while some prefer 'Portrait' designs, Ymax > Xmax.
3. Z+ is up
4. X + and Y+ really depend on how you want to load your machine and run it - so what is + and what is - is up to you.
5. Once you decide what is + and what is -, the X=0, Y=0 is at the end of travel in the - direction.
6 Then wire your limit switches accordingly. The X0, Y0 and Z0 switches are the 'Home" switches.

Confusing? Perhaops, but that comes from the great flexibility of the basic design.
I disagree with a lot of that.

1. There are three color codings for 4-wire bipolar stepper motors, and one of them is used much more than the other two. If your wires are red, blue, green and black, then red and blue are a pair and green and black are another pair. (The other codings are brown, orange, red, yellow; and red, red with white stripe, green, green with white stripe.)
2. All Shapeoko documentation will refer to the axis that runs along the gantry as X, and the one with two motors as Y. As you face the machine with the spindle facing you, X+ is to the right and Y+ away from you. You can change that, of course. Universally, the Z axis is the one parallel to the spindle axis, so vertical in our case (it would be left-right in a lathe, for example).
3. Agree.
4. Yes, but not quite. Y+ must always be 90 degrees counter-clockwise from X+, as viewed with Z+ pointing toward you (i.e., from above). If you do it the other way, you will mill mirror images of what you design in CAD. 3D coordinates have handedness: with your index finger straight out and middle finger bent 90 degrees, point thumb toward X+, index finger toward Y+, and middle finger toward Z+. If you can do this with your right hand, you have right-handed coordinates. Conversely, left-handed. CAD uses right-handed coordinates exclusively.
5. Homing toward X+, Y+ and Z+ is much more common. Many industrial machines do it that way, and it's the default in GRBL 0.9 too. With the maximum X, Y and Z coordinate being 0, all three components of machine coordinates are going to be negative. You'll see that referred to as "negative space" (or "negative octant"). You can home the other way, of course, but it may confuse your machinist friends.
khauser24 wrote:The X-axis is the two motor setup.
That's usually the Y, for most Shapeoko users. (But, of course, you can orient your machine however you please.)
Proud owner of ShapeOko #709, eShapeOko #0, and of store.amberspyglass.co.uk

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