Linear Bearing Idea

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Rapid RepRap Design

Postby bdring » Thu Sep 16, 2010 5:52 pm

I decided to do a rapid development of a design for a Makerbot clone. This was done in less than 1.5 hours. It is a simple RepRap concept that has about 75% more build area than a MakerBot. It uses standard Misumi 20mm extrusions shown in white and the slide extrusion shown in gold.

The Y axis rails are used as part of the frame structure. I did not model any motors, but my thought was belts for X and Y and a leadscrew for Z. The total cost of all framing and slide extrusions is $55.53 using standard Misumi pricing (no discount) plus $1 per 100mm pricing for the slide extrusion. Misumi brackets, screws, nuts etc should cost less than $30. It requires 13 v wheels which should cost less than $10 in nylon (fine for reprap load) or about $60 for stailess steel double row v-groove wheels. No cutting, drilling or tapping of any parts on the frame or rails is required.

That puts a ready to go frame and rail system at less than $100. Compare that to $200 for the Makerbot laser cut chassis alone (no slides).

This is just a demonstration of the rapid development possible with this bearing idea, not a real design to be critiqued.
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builder_bot.JPG

Edit: added a second image with motors.
builder_bot2.JPG
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Re: Linear Bearing Idea

Postby lasersafe1 » Thu Sep 16, 2010 6:52 pm

Not a critique because it looks great, but a question. Since it appears that the XY motion all occurs in the base, and Z motion is the only thing up top, then wouldn't a pyramid structure be the most stable and require fewer braces?
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Re: Linear Bearing Idea

Postby artwood_decor » Mon Nov 15, 2010 5:38 pm

Here is a proof the aluminum extrusion proposed by Bart would work...

RAIL:
http://www.drillspot.com/products/52923 ... file_guide

Very expensive for a 3 ft. extruded profile.

CARRIAGE:
http://www.drillspot.com/products/53791 ... e_carriage

and here are some other solutions, with prices, just to have an idea on how much DIY can save.

http://www.drillspot.com/power-transmis ... andid=4060
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Re: Linear Bearing Idea

Postby lasersafe1 » Mon Nov 22, 2010 3:56 pm

I thought about your first post on this subject again. Have you considered building a carraige that has no wheels at all? If you use Rulon or one of the other new advanced polymers, it will be quite slippery with only a small preload to remove the slop.

This is the idea behind the drylin W from IGUS. A bit expensive for the rail though compared to the numbers you are talking about for your own custom extrusions.

http://www.igus.co.uk/wpck/default.aspx?Pagename=DryLin_W_Einzelschiene_eckig&CL=US-en
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Re: Linear Bearing Idea

Postby bdring » Mon Nov 22, 2010 4:24 pm

I have seen various versions of those type of dry plastic sliders. I would be worried it would be difficult to get that right without a few iterations, so not a good candidate me. I would like buy a sample piece of that some day to get a feel for it.
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Re: Linear Bearing Idea

Postby r691175002 » Wed Dec 15, 2010 12:28 am

I agree that some form of cheap reliable linear slide would completely change the diy cnc game. Right now there is a major gap where you are either paying huge bucks or improvising.

Extruded aluminum v-rail doesn't have to last years of heavy use or be super rigid. For reprap/makerbot type stuff and this style of open-source project I think you have the right idea.

An extrusion will be cheap, super easy and work better than 90% of the stuff currently out there.
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Re: Linear Bearing Idea

Postby bdring » Wed Dec 15, 2010 1:44 am

I have a bunch of Delrin wheels on order. If the wheels work well on the existing setup, I may pursue the aluminum extrusion. Delrin is a very hard plastic and could easily last for years. It is also unlikely to cause to much wear on the aluminum too.

The wheels I have on order are machined and press on. I also have a quote from a good quality Chinese bearing house for molded on Delrin wheels.
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Re: Linear Bearing Idea

Postby thechoochman528 » Sun Feb 20, 2011 2:15 am

After doing some looking for alternatives to v-rails, for a large CNC machine I'm working on, I stumbled upon a vendor that already does integrated rail extrusions.

They also have bolt on parallel rails that you can add to extrusions so you wont have to drill another v-rail again.

unfortunately I haven't inquired about pricing yet, but I thought I'd share the link:

http://www.pbclinear.com/Integral-V-Linear-Guide-Technology
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Latest Thoughts

Postby bdring » Wed Mar 16, 2011 11:52 pm

This is the lastest profile I am considering for the linear rail. The configuration allows it to be compatible with the current wheels and brackets by maintaining the same v distance. This will allow people to mix in steel and hardened steel as required.

The V center is parallel with the extrusion edge which is a little different than the 2.x, but 2.x is designed to adjust in this direction. I did that to improve the stiffness.

The V rail feature no longer extends onto the 40mm side. This will allow 40mm extrusions to be attached (butted) to the side. The 2.x requires this and it adds more flexibility to it's use.

I was tempted to add slots to the front surface, but decided the extra stiffness to the load (compression) of the wheels was more desireable. There is a center mark which will simplify drilling and tapping if a bracket needs to be mounted to that surface.

The width of the v still allows a standard bracket to be mounted to the 20mm sides as shown in the rendering.

With this extrusion, you are now free from reliance on Misumi. Any 20mm based extrusion can be used to build the rest of the frame. Even inch based systems or other materials could be used.

maker_slide1.jpg

maker_slide2.jpg

maker_slide3.jpg
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Tougher Delrin V Wheel

Postby bdring » Mon Apr 18, 2011 6:13 pm

I am pretty sure I am going to go ahead with the linear bearing idea on Kickstarter. I have been hashing out a lot of alternative uses and I thought some might suffer from bearing pull out.

I have been super gluing in the bearings lately and they are really tough to push out. I added that method to the build instructions. With that said, the laser has inherent design feature that resists bearing pull out like the two rails on the Y and gravity on the X. Some designs might need serious pull out resistance like the Z on a CNC router.

Here is a new idea. I initially resisted pocketing the wheel on both sides due to cost, but my screw machine supplier gave me a decent quote of only about $0.50 more per wheel. This wheel has a ridge down the center of the wheel so bearings are pushed in from both sides. There is also a little spacer between bearings so there is no stress on the balls. When bolted in place this will not pull out under hundreds of pounds of force. It will also have increase rigidity like a dual v wheel

better_wheel.jpg
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