MakerSlide, Max Usable Lengths

Extrusions/Tubing/Hinges/Etc.

MakerSlide, Max Usable Lengths

Postby Patrick34 » Sun Feb 05, 2012 8:57 pm

What is the maximum unsupported length that can be achieved with the MakerSlide if the design is very similar to the Laser 2.X?

At some point there will be unwanted bouncing and flex with the cross-section of the MakerSlide being approx. 7/8" x 1.5".

For my application I am going to modify the 2.X so the gantry is along the y-axis and extend the x-axis to have a 48" cutting width. By turning the gantry I am able to keep the length and weight to a minimum of the moving parts. My concern is for the two MakerSlide rails along the x-axis.

I am not just simply extending the y-axis to have the 48" length because I am incorporating a slot on the front and back of the machine enclosure to have infinite y-axis material length. The electronics on the right side of the machine get in the way to make the x-axis infinite. Think CAD "plotter," except I will have a 24" y-axis bed that I can slide full sheets of plywood or acrylic through.

How much can I expect the rails to sag when the gantry is in the middle assuming that the length will be around 56" to get the desired 48" of cutting? Will I just have to add a say, 20 x 60mm, support beam to mount the rails on (those supports cost about $40 each)?

I am looking for ideas here because the my first frame design is approximately $480.00 just for the skeleton extrusions and gussets with hardware. I need to reduce this cost.

Plus I'm sure others are wondering the same thing about how rigid the MakerSlide is at length.
Attachments
Asm_Laser_Top2.SLDASM.pdf
Iso view of initial frame design
(156.41 KiB) Downloaded 1301 times
Asm_Laser_Top.SLDASM.pdf
x-section of MakerSlide against support
(813.14 KiB) Downloaded 1324 times
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Re: MakerSlide, Max Usable Lengths

Postby Patrick34 » Sun Feb 05, 2012 11:27 pm

I have made some revisions to the design based on a suggestion by a friend. I moved the supporting corners in to the work area. This effectively makes the area for the laser tube and the electronics as an add-on to the main enclosure. By doing this I am able to reduce the number of larger support members and reduce the cost. The only side effect is that the legs will be inset which I can deal with. Overall this new rev reduced the frame cost from $480 to $403.

If the MakerSlide can span 57" without any deflection I could further reduce the cost by another $60 by removing the 20 x 60mm supports along the x-axis.

What lengths are you guys using unsupported?
Attachments
Asm_Laser_Top.SLDASM3.pdf
rev2 frame
(734.11 KiB) Downloaded 1324 times
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Re: MakerSlide, Max Usable Lengths

Postby twehr » Sun Feb 05, 2012 11:50 pm

Not sure what you are planning to use for a controller or what you want to do with the laser, but you may want to consider...

If doing engraving (filled vectors or photos) and you are going with the DSP, there is no y-axis bi-directional engraving available. It is either x-unilateral, y-unilateral, or x-swing (bi-directional). I don't know what Retina does, but I suspect it is also X and maybe X only engraving.
tim
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Re: MakerSlide, Max Usable Lengths

Postby Patrick34 » Mon Feb 06, 2012 12:42 am

I am planning on using a DSP to start, but I am mostly interested in cutting. I will play with engraving, but that is not my intended use.

As far as the x or y direction, this is fairly arbitrary. I used the 2.X directions as a reference to help visualize what I am trying to accomplish. Which direction is x or y in the machine solely depends on how it is wired up. If it makes more sense to swap the axis and have x run the other direction to work better with the controller, then so be it. The parts will just machine "sideways" when viewing them.

The infinite axis length is my planning ahead on its use. I know at some point I will need to slap a 4' x 8' sheet on this thing to cut something. This way I can slide the sheet 24" at a time (reference pins used of course) and accomplish a large cut with a small machine. The only caveat is that one axis needs to have 48" of cutting length.

I am interested in finding the extreme maximum unsupported length condition of the MakerSlide to determine how much support, if any, I need along my longest axis.
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Re: MakerSlide, Max Usable Lengths

Postby twehr » Mon Feb 06, 2012 2:16 am

I agree with what you say about the axis designation. I just want to bring it up so you could factor it into your thinking.
tim
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Re: MakerSlide, Max Usable Lengths

Postby Patrick34 » Fri Feb 10, 2012 4:39 am

So, anyway, back to the original question...

MakerSlide Deflection: How long is the MakerSlide usable at length unsupported?

I did some theoretical analysis using Solidworks COSMOSWorks on the MakerSlide up to 2000mm in length @ 5#, 2#, and 1# loads in the center of a beam with unfixed ends (worst case). Here are the results:
Length (mm), Deflection (mm) @ 5lb
400, 0.007
600, 0.024
800, 0.057
1000, 0.11
1200, 0.191
1400, 0.303
1600, 0.452
1800, 0.644
2000, 0.883

Length (mm), Deflection (mm) @ 2lb
400, 0.003
600, 0.01
800, 0.023
1000, 0.044
1200, 0.076
1400, 0.121
1600, 0.181
1800, 0.258
2000, 0.353

Length (mm), Deflection (mm) @ 1lb
400, 0.001
600, 0.005
800, 0.011
1000, 0.022
1200, 0.038
1400, 0.061
1600, 0.09
1800, 0.129
2000, 0.177

Sorry for the mixed English(IPS) and Metric values. It was just what I happened to enter in the analysis program because I estimated the weight of the gantry to be no more than 5lb, and didn't feel like dealing with the decimal equivalent in Newtons. The unit conversions were taken into account in the calculations by the software.

Basically what this means is that the MakerSlide should not deflect more than 1mm when 5lb is in the center of a rail up to 2000mm in length.

This calculation actually would be useful for a gantry weight of up to 10lb because during by setup of the problem I had forgotten the fact that the axis requires two rails (one at each end of the gantry).

I would like to know how close these numbers are to reality.

**IMPORTANT** These values are calculated for the MakerSlide standing on edge NOT flat.**

If this is accurate, these numbers could be useful to those using the MakerSlide in other design situations.

Please add to this info as possible.
-Patrick-

"Measure twice, cut once."
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Re: MakerSlide, Max Usable Lengths

Postby bdring » Fri Feb 10, 2012 1:10 pm

I measured very similar results with the camera slider. I don't have the numbers in from of me, but is was just under 2mm deflection with an 8 pound load at 2 meters.

This was with the extrusion set on round rods at the ends. You get a lot of stiffness added by providing a firm support at the ends.

MakerSlide was not intended for long extended length unsupported. It was design to be the bearing and support for small to medium sized machines. When you get large you should add additional support.
Bart
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Re: MakerSlide, Max Usable Lengths

Postby iGull » Fri Feb 10, 2012 7:31 pm

FWIW, on my Blackhole laser, the span is about 1500mm. The section is vertical (as you would expect for a beam).
I actually tested the deflection when I was building the X axis - with a 5Kg load on the centre, the deflection was about 1.5mm in Z

However :D one thing I hadn't taken into consideration was the tension applied via the toothed belt - I had allowed for plenty of tension in the pulleys, but not the pull across the span - consequently, the centre of the axis was out by more than 1mm in Y :oops: I added a shortish piece of 12mm aluminium angle and that seemed to cure it.

Cheers

Neil
EMOs are a sign of weakness ...
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Re: MakerSlide, Max Usable Lengths

Postby Patrick34 » Fri Feb 10, 2012 7:50 pm

Wonderful input guys. This is what I'm looking for.

I too have not thought of the extra tension from the belts. This could be used as an advantage in a case where the belt pulley axles are below the center of the rail. The tension would tend the deflection upward, pre-loading the beam to some extent. In a gantry cnc design using the tension method is not precise enough to obtain accuracy, but for projects similar to the camera slider it may be a viable means to stabilize the design.

I have decided, as I had originally assumed, that I will need to add a support rail along my Makerslide rail to avoid z-axis deflection.

It's also satisfying to see my calcs seem to be in the ballpark and could be useful to others.

Please continue to post actual observed deflections, length of the rail, and load on the rail. The bigger the data sample the more useful, and accurate, it will be.

P.S. Bart> I have this topic also posted in the General Discussion for the MakerSlide, but here it has gotten more response. It may be helpful to put this information there as well.
-Patrick-

"Measure twice, cut once."
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Re: MakerSlide, Max Usable Lengths

Postby SSW » Sun Feb 12, 2012 4:05 am

Hello,

Noticed this thread because I'm planning a 2' x 4' wood router table. Sounds like all good news here.

I'm wondering if you've considered the twisting/flexing of your base framework? I've seen many router table designs incorporating a "torsion box" that stay very flat. I'm not that familiar with lasers, so I'm interested as to how you will stiffen up the machine to keep it from twisting at this larger size.

Thanks.
-- Bernie
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