Buildlog.net Open Source Laser

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Belt Clamps

Postby bdring » Wed Mar 03, 2010 4:12 am

I drilled and tapped my belt clamps. Tapping acrylic is a little tricky, but the threads are quite strong. You just need to back out the drill and the tap many times to clear the material otherwise it gets hot and gummy and the crack the material. The tap can get stuck too if you are not careful.

Oh...and don't center punch :oops:

belt_clamps.jpg
Belt Clamps


I also updated a few drawings with some assembly and fabrication notes.
Bart
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Bearing Brackets

Postby bdring » Thu Mar 04, 2010 5:29 pm

I built and mounted one of the bearing bracket assemblies. These are the assemblies that hold the rear idler pulleys for the Y axis belts.

I made some changes to the way the bearing is held in place. I used two truss head screws with undersized washers and nuts on the other side. This gives clearance for the hex nuts without any spacers. I used a 3" piece of #1/4-20 threaded rod. This is bolted to the bearing before installing into the plate. This assembly has no load pulling on the bearings, so it works fine. The only load is trying to twist the bearing out. Using two bearings spaced apart by 40mm prevents this.
Updated drawings coming soon.
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bearing_brkts.jpg
CAD Model

rod_nuts.jpg

installed_bearing_brkt.jpg
Installed
Bart
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New Gantry Assembly

Postby bdring » Fri Mar 05, 2010 3:55 am

I completed the basic assembly of the new gantry. No problems so far. I will assemble it to the Y axis next. Tensioning the belt went pretty well. I made it pretty tight to start with and only had to use about 25% of the tensioning range.

Here is the process I followed.

The laser "car assembly" is built with the middle wheel loose. It is then put on the gantry. The middle wheel is then pushed against the v rail with the adjuster screw. The wheel will cock a little when loose, so you don't need to push it too tight. It will get tighter against the rail when the screw is tightened. Try tightening the wheel bolt to see where the compression ends up. You want it to have zero play. The car should barely hold itself in place and not slide down the gantry when held vertically. Make sure there is not so much conpression that the plate is visibly bent.

Attach one of the belt clamps to the end of the belt. Mount both belt clamps to the car assembly. They should be mounted as far apart as possible to leave the maximum amount of adjustment. Wrap the belt around the pulleys and cut to length. Attach the second belt clamp. Lightly attach the belt clamp so they still slide when the tensioner screw is adjusted. Tension the belt. If you run out of adjustment range, trim about 1/4" off the belt and try again.


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gantry2.jpg

gantry_motor_end.jpg
Motor End

gantry_bottom.jpg
bottom View
Bart
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Post Assembly Nuts

Postby bdring » Fri Mar 05, 2010 5:08 pm

Post Assembly T Nuts

I got these in the mail today from Misumi. These can be dropped into the frame slot after the ends are not accessible. They are worth their weight in gold if you have ever worked with T-Slot extrusions. Some have little spring loaded balls that hold them still on vertical sections. They are about $0.40 - $0.50 each.
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post_assy_nuts.jpg
Post Assembly Nuts (2 flavors)
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Re: Buildlog.net Open Source Laser

Postby Robert Williams » Fri Mar 05, 2010 6:15 pm

New gantry assembly... just the kind of information I need! Are your NEMA 17's double shaft? Shaft diameter 3/16?
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Re: Buildlog.net Open Source Laser

Postby bdring » Fri Mar 05, 2010 6:36 pm

Comment From Buildlog Author

I bought 2 of these from Keling Technology.

http://www.kelinginc.net/KL17H147-1684B.pdf

It is double shaft, but it does not need to be. EDIT: Y must be double shaft. The drawing says 5mm shaft, but 1/4" shaft was sent to me. That worked for me because I had pulleys for them. I think pulleys are available for both sizes. You should make sure to match them.
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Re: Buildlog.net Open Source Laser

Postby bdring » Sat Mar 06, 2010 6:08 pm

Comment From Buildlog Author

Oops...My last comment was wrong. Double shaft IS important for the Y axis motor.
Bart
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Gantry Installed

Postby bdring » Sun Mar 07, 2010 12:30 am

I got the gantry installed.

The first thing I did was make sure the Y axis rails were as parallel as possible. I made a measuring jig out of an extra piece of Misumi extrusion. I then loosened both end plates on the gantry so the gantry could be twisted to make sure it is exactly 90 degrees to the Y axis rails. I used a large carpenters square to do this. I then tightened the motor end plate to the v-rail. After that was tight and square I did the same to the other end.
gantry_in.jpg
Gantry Installed

I need to install the belt and pulleys next. I think I am going to connect the two sides with threaded 1/4-20 rod. I made a coupler to the motor with a coupling nut I had. I think I got it at the hardware store a while back. I drilled out the threads on one end and left the threads in the other end. I put two set screw spots on the motor end. I hope this will allow me to do fine rotation adjustments to do the final squaring of the gantry. I will use the laser to draw an angle. If the angle is not perfect, I will twist one side forward and re-tighten the lock nut.
y_shaft.jpg
Shaft Coupler
Bart
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Gantry runs

Postby bdring » Tue Mar 09, 2010 2:32 am

I hooked up the power to the X Axis motor and gave it a try.
  • 2500 in/min
  • 750 in/min/min
  • 1000 step/in
[*]10 in move shown

I could get it up to over 3500 ips, but it lost steps with an accel around 1000, so I backed it down.

I am waiting for some new pulleys for the Y axis.

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Re: Gantry runs

Postby lasersafe1 » Wed Mar 10, 2010 3:05 am

bdring wrote:
I could get it up to over 3500 ips, but it lost steps with an accel around 1000, so I backed it down.



You didn't really mean ips did you? That's 17,500 feet per minute! It looks great!
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