Pivot jig, WCS and touch plate example

Discussion about Tooling and Fixtures. End Mills, Router Bits, Hold Downs, Fixtures, Etc.
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swhillier
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Pivot jig, WCS and touch plate example

Post by swhillier » Thu Oct 01, 2015 8:04 pm

I saw a couple of questions about the need for limit switches and touch plates and my answer is YES. Life is much simpler with them and I thought I'd give an example where they are helping me out...

I'm making a Thien dust separator for my dust collector. I have a Dust Deputy for my shop vacuum and it works great. I want a similar solution for my dust collector but I don't want to pay the big dollars for the big Dust Deputy. After some looking I decided to go with the top hat style version of the Thien Separator. Cutting out the circular pieces using a band saw circle jig is quick and easy but the Thien separator needs a 1 1/4" inch slot around the edge of the baffle in the separator. I could have cut it with a jig saw or a scroll saw but I have an SO3 so why not use it. Not to mention that the SO3 does a much better job than I would on a scroll saw.

The separator pieces fit into the SO3 but the cutting required by the pieces pushes right up against the maximum cutting dimensions of the SO3. I was worried that I might trigger the limit switches mid job if I tried to cut things as a single job. The solution is the break the cuts up into smaller areas that easily fit into the SO3's cutting dimensions. Since the separator pieces are round I embedded a piece of UHMW plastic in my waste board with 1/4" tapped pivot point. Using the homing ability that limit switches give you along with setting the pivot point as the X0Y0 for the work coordinate system mapped to G56 allows me rotate through several aligned and accurate cuts. Using a touch plate just speeds the process for setting zero on Z axis.

Here's a video of me using the jig to cut the baffle slot. Ultimately I'm only making a simple circular piece of 1/8" hard board with a slot in it but hopefully it shows how limit switches, a touch plate and figuring out WCS should be high on your list of things to do after assembling your SO3.



I've decided to use the same method to make all the other internal cuts that Ill need on the rest of the Thien separator pieces.

TomDChi
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Re: Pivot jig, WCS and touch plate example

Post by TomDChi » Fri Oct 02, 2015 6:38 pm

Cool! I think actually seeing someone use a WCS helps a lot in understanding how they're useful.

Am I right in understanding that to do this, you ran a homing cycle, then switched into a specific WCS (#56 in this case) then positioned the router in X and Y where you wanted that 0,0, and zeroed out X and Y, and that the controller stores those X and Y zero points until they are actively changed (in other words, they are retained even when the system is powered off)?

When you generate the g code, you're using that X0/Y0 position. Does the g code need anything to tell the system to use G56, or is the controller simply "still in G56" when you send the code?

Which g code sender are you using?

twforeman
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Re: Pivot jig, WCS and touch plate example

Post by twforeman » Fri Oct 02, 2015 7:27 pm

I use WCS very extensively, so I can answer some of these questions.
TomDChi wrote:Am I right in understanding that to do this, you ran a homing cycle, then switched into a specific WCS (#56 in this case) then positioned the router in X and Y where you wanted that 0,0, and zeroed out X and Y, and that the controller stores those X and Y zero points until they are actively changed (in other words, they are retained even when the system is powered off)?
You don't have to do the steps in quite that order.

1. Home the machine. This sets machine zero. All WCS systems are referenced from here.

2. Move the machine - by jogging or entering G commands, not by moving it by hand - to where you want to set WCS zero. You can set zero for each axis one at a time (which is what I usually do) or you can do them all at once. You do not need to select the WCS before you set it. The P option to the G10 command determines which WCS you set.

3. Set the chosen WCS using the G10 command. You can specify an offset and set each axis individually. To set the X axis using WCS G56 and a .125" offset (if you indicated in with a .250" endmill) you would use G10 P3 L20 X0.125

Yes, the offsets are stored in NVRAM, so they persist between uses and power cycles.
TomDChi wrote:When you generate the g code, you're using that X0/Y0 position. Does the g code need anything to tell the system to use G56, or is the controller simply "still in G56" when you send the code?
I usually set the WCS by hand by entering the commands. But it would not be a bad idea to do it by adding them to the start line in the file.

More details on the WCS here: http://www.shapeoko.com/wiki/index.php/ ... te_Systems
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swhillier
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Re: Pivot jig, WCS and touch plate example

Post by swhillier » Sat Oct 03, 2015 12:37 am

Yes, as @twforeman has indicated I usually set up the WCS manually. First I home the router and then I use jogging to move the router to where I want to have my WCS defined. So far I've set up two WCS reference points and they're both for jigs that allow me to find a repeatable X0 Y0 point. I've set mine using no offset since I like to use them with different diameter bits and just use them as a well defined X0 Y0. I can then take the bit diameter into account when I design the part or create the gcode. I also usually set the Z0 for my WCS's to be the same as the Z0 from homing since you need to set your Z0 each time any way.

Once you have your WCS then each time you use it you just need to home your machine, enter G56 (for WCS 3) then G0 X0 Y0 to go to the WCS zero point. Then set the Z0 using your touch plate or some other method. Note that you should only use the jogging controls once you start using a WCS. If you move the machine manually then you need to home it again.

I don't think you want to put the WCS command (G55, G56 etc...) in your code since it will overwrite the Z0 that you've set manually using the touch plate.

I also have G28 defined to be the front center of my machine so I can just enter G28 and the router goes to the front so I can do tool changes. Just note that G28 moves all axes at the same time so keep an eye out for Z height clearance issues.

twforeman
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Re: Pivot jig, WCS and touch plate example

Post by twforeman » Sat Oct 03, 2015 2:39 am

swhillier wrote:I don't think you want to put the WCS command (G55, G56 etc...) in your code since it will overwrite the Z0 that you've set manually using the touch plate.
Well, no. If you set the Z in your WCS (using the G10 command) then it will remember that when you enter G56, etc. I'm not sure how else you would set Z zero.
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swhillier
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Re: Pivot jig, WCS and touch plate example

Post by swhillier » Sat Oct 03, 2015 12:58 pm

I'm just using the ChiliPeppr touch plate button to set Z0 so it overwrites the current Z0 but doesn't set the G56 Z0. I guess the probe, G38.2, command and the G10 command could be combined to set Z0 using the touch plate and then set the WCS Z0.

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