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Author Topic: CNC Build Proceeding - Cheap Couplers...  (Read 4288 times)

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Offline Zig

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CNC Build Proceeding - Cheap Couplers...
« on: January 03, 2013, 05:48:16 PM »
Just working my way through this CNC machine build.  I like to tinker and converted some lead screw nuts to couplers with a cheap tap and die kit.  Works pretty well but I have cracked one bit. 

I usually make videos of my progress.  Here's a couple of the latest little YouTube videos.

I'm always open to suggestions.  Pro and con.  And as I work my way through this build I'm already planning the next machine.

https://www.youtube.com/watch?v=i0sTrSkoDs0&list=UU3RIdlSCWn1w0Quh6zm6M1A&index=1

https://www.youtube.com/watch?v=9pKzInAQ7Dc&list=UU3RIdlSCWn1w0Quh6zm6M1A&index=2

Zig


Offline Tweakie.CNC

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Re: CNC Build Proceeding - Cheap Couplers...
« Reply #1 on: January 04, 2013, 04:43:55 AM »
Excellent work Zig.  8)

Rigid couplings are not normally used, for various reasons. On my machine, try as I may, it was not possible to machine the motor mountings precisely square and parallel so proprietary flexible couplings allowed my steppers to run without stress.

One other point you may wish to consider is incorporating a thrust bearing between your motors and screws. The motors have dimensional tolerance during manufacture and this is usually taken care of (by the manufacturer) with the use of one or more crinkle type washers fitted behind the rear bearing. This will allow the shaft to move axially under load and may cause you problems with maintaining an accurate tool-path later on down the line.

These comments are in no way intended as a criticism, you are doing fine work with building your machine and I am sure your video’s will be of great help to others. Keep up the good work my friend.

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.

Offline Zig

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Re: CNC Build Proceeding - Cheap Couplers...
« Reply #2 on: January 04, 2013, 02:15:31 PM »
Thanks Tweakie.  You've been very kind with all responses.  Makes sense - I was wondering about any extra stress on the motors if the couplings were not spot on.  Perhaps the low-rent solution of gas lines and hose clamps is easier on the bearings in the steppers.  I like the look of the coupling nut though.  What would be your guess on the reduced lifespan of a stepper if the coupler was a little off?  I'm sure there is a wide variable range there though - the degree of off-ness, the quality of the motor, the speed at which it's run...

Anyhow, I'm learning a lot as I putter along here.  When I look back on past projects over the years, the first prototypes are almost always greatly inferior to subsequent builds.  With that said, I've spent a lot of time on this one, and when it's complete I'll pretty it up a bit with some stain, varnish, and assorted shiny bits.

Thanks again,
Zig

Offline Tweakie.CNC

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Re: CNC Build Proceeding - Cheap Couplers...
« Reply #3 on: January 05, 2013, 02:13:27 AM »
Hi Zig,

Any stress applied to the stepper will ultimately shorten its bearing life but that could well be after years and years of use.

Coupling miss-alignment will most likely show as a reduction in maximum axis speed (the motor will stall at a lower rpm due to the torque reducing with speed).

I am looking forward to seeing some more pictures of your build as you proceed.  ;)

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.

Offline Zig

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Re: CNC Build Proceeding - Cheap Couplers...
« Reply #4 on: January 06, 2013, 09:13:59 PM »
Thanks again Tweakie.  After thinking about it and reading your post I didn't like the extra vibration I was getting through the machine.  The vibration was somewhat slight, but none the less there.  So for the time being I went back to the gas line and hose clamps.  As you noted in your attempts I couldn't get the couplers exact enough to eliminate some vibration. 

I had some time this weekend and have finished the assembly of the x, y, and z axis.  This afternoon I temporarily wired in all the steppers to the control board with some scrap wire just to test them.  All function properly when jogged around.  It's actually fun just driving the motors around.  If I can find some time this week I'll wire the motors up neatly and drop in some basic test g-code and see what this thing can cut.  I've been playing around with a few cad and text programs and then mock running the cut in Mach3.  That's fun too. 

I'm sure I'll have a million questions as I proceed with this engaging hobby.  I'll try to get more videos and pictures up within the next week or so.

Thanks again,
Zig

Offline Zig

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Re: CNC Build Proceeding - Cheap Couplers...
« Reply #5 on: January 09, 2013, 09:56:33 AM »
Tweakie - The machine is mostly built.  A quick YouTube clip.

http://www.youtube.com/watch?v=AGYKe11JUVo&list=UU3RIdlSCWn1w0Quh6zm6M1A&index=1

Zig
Re: CNC Build Proceeding - Cheap Couplers...
« Reply #6 on: January 09, 2013, 10:31:23 AM »
Cheap Couplers

http://buildyourcnc.com/couplings.aspx

I'm looking at the lovejoys

John

Offline Tweakie.CNC

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Re: CNC Build Proceeding - Cheap Couplers...
« Reply #7 on: January 09, 2013, 11:17:01 AM »
Excellent work Zig.  8)

I wonder what the first CNC machined project will be ?

Tweakie.

Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.

Offline Zig

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Re: CNC Build Proceeding - Cheap Couplers...
« Reply #8 on: January 09, 2013, 11:24:05 AM »
Thanks Tweakie. 

I have a little time here and I'm trying to just make a first test cut.  Scary and exciting at the same time.

Here's what I've done so far and where I'm hanging up.

I typed out, "Hello World" in Deskengrave.  I made the DXF code and opened that up in Lazy Cam.  I've then sent the .tap file to Mach3.  The CNC machine will start doing a pretend cut all moving in the right direction.  Here's where I'm having trouble.  How to I set the depth of cut - Z axis? 

If I touch the tip of the bit to the work surface Mach3 will pull up and the actual "cutting" is happening about an inch above the wood.

Thanks again for all the help,
Getting closer here to actually seeing some cut action...
Zig

Offline Tweakie.CNC

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Re: CNC Build Proceeding - Cheap Couplers...
« Reply #9 on: January 09, 2013, 11:30:56 AM »
Hi Zig,

In LazyCam you need to select the Layers Tab to set the depth and set layer etc.

The LazyCam manual can be found in Members Documents http://www.machsupport.com/forum/index.php/topic,12078.0.html

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.