Linear Bearing Idea

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Linear Bearing Idea

Postby bdring » Wed Sep 08, 2010 6:02 pm

I have this idea for a linear bearing . It would basically be a 20mm x 40mm extrusion with the v rails already formed in place. I was thinking about trying to get it funded via the Kickstarter program. The extrusion die would then be paid for and the material would be dependent on the production costs only.

ms1.JPG

ms2.JPG


The v rail / v wheel bearing is a proven system. Shopbot for example uses this slide system. I have used it on my large wood router for years. It is used on my laser cutter. It holds firmly in all planes except the plane of movement. It even holds strong against rotation.

The current fabrication method is a lot of work. It takes a lot of time to accurately layout the holes, drill and tap them. Any slight misalignment can cause the v track to not be perfectly straight. Also, the thickness of the tapped area is only about 2mm which at best case yields only 3 or 4 threads. Most design standards require 1.5 times the diameter of the fastener.

The goal is to be able to sell the extrusion for less than $3 per foot (I have quotes to support this). The wheels can be expensive, but in qty they are quite cheap. I have quotes in reasonable qty's in the $3-$4 dollar range. That puts a robust 4ft slide in the low $20 range. There are existing designs like this, but they are 5 times the cost and do not work perfectly with the millimeter based extrusions.

I think the open source community could use a cheap high quality standardized linear bearing. I know you can find cheap deals on eBay for some decent linear slides, but it is difficult to base a new open source design on lucky eBay finds. Even those slides require a lot of accurate drilling. A typical maker/hacker could keep 10-20feet of this on hand for quick project

There would be several options
  • Anodized alum with Steel wheels
  • Anodized aluminum with nylon wheels. Very smooth and quiet, but lighter duty.
  • Hard Anodized Aluminum with steel wheels. Hard anodize is extremely hard and would provide years of service in a dirty environment. Rockwell hardness of C60-70.

Here are some ideas that went into the design.
  • V-rail does not interfere with standard angle brackets (does now)
  • V-Rail center is aligned with the edge for easier designs
  • V rail could mount a rail for a rack and pinion drive
  • A few extra drill center grooves have been added.
  • Fully compatible with Misumi Extrusions and accessories.

I know some of the KickStarter programs have had mixed results, but I think my buildlog.net cred would do a lot to reduce that feeling. My public Internet reputation is worth way more than this little project.

Any thoughts, ideas, suggestions?
Attachments
makerslide.pdf
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Re: Linear Bearing Idea

Postby thechoochman528 » Thu Sep 09, 2010 12:00 am

I saw something similar to this on makergear's website recently:

http://www.makergear.com/blogs/frontpage/1951022-the-road-to-maker-faire-nyc
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Re: Linear Bearing Idea

Postby bdring » Thu Sep 09, 2010 2:38 am

Yes, I saw that before. Something like that is actually quite a bit of work to fabricate and align. For probably about half the cost and a 1/3 the fab time you would be ready to go. That design probably does not have any load on it, but with an extruded profile, it could have a lot of load.
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Re: Linear Bearing Idea

Postby mpeele » Thu Sep 09, 2010 2:58 am

It's a great idea. How much funding would you need?

I have looked at PBCs Integral-V™ Technology (IVT) which I think Epson uses on there large format printers. They have a structural version and a bolt on which we am conserding for another project. There prices are much higher and I was having a problem finding a source for small quanities
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Re: Linear Bearing Idea

Postby macona » Thu Sep 09, 2010 3:11 am

It wouldnt have a good life, it will wear out fast. Possibly better if it was hard anodized. Or better yet have it extruded so commercially available track will mount into it. I have some massive aluminum slides I have saved for a router table. It uses hardened steel strips that slide into a channel that the bearings run on. A small version of that would be probably better in the long run.

Bosch and I think 80/20 both make a linear system that works with their extrusions but its a slide system so it probably will have quite a bit of stiction.

Have you ever gotten a quote for an extrusion die set?
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Re: Linear Bearing Idea

Postby bdring » Thu Sep 09, 2010 3:25 am

The 80/20 system is not for CNC. I have seen it and played with it. It has a lot of play and wobble. It is made for sliding things around like tools supported from overhead and sliding panels.

Sure it would have some wear, but I think it would be fine for the duty we would subject it to. I, along with thousands of users built a wood router based on pipe/conduit and skate bearings. They do wear relatively quickly but it really has little affect on the performance. This system would have a higher contact area, less pressure per unit area. Hard coat is tough stuff. They coat race car pistons with it.
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Re: Linear Bearing Idea

Postby Tweakie » Thu Sep 09, 2010 11:45 am

"Hard coat is tough stuff. They coat race car pistons with it."

The aluminum cylinder blocks for chain saws and other lightweight engines have the bore hard anodized. Tough stuff indeed.
However, I think that the cost for production of a specialist extrusion is going to be mega.

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Re: Linear Bearing Idea

Postby bdring » Thu Sep 09, 2010 1:30 pm

Costs: Extrusion dies are about the cheapest tooling of any process. I have quotes from two suppliers right now. For a couple thousand dollars I can get the tool and about a thousand feet of the extrusion. I need to figure out the best way to run the Kickstarter program. I think each sponsor will get a nice laser marked piece (Chotchkie). Any sponsor over say $20 will get the balance in $3-$4/foot of extrusion.

Kickstarter sponsors typically are not trying to get a deal. They are just firm supporters of the cause (open source hardware) and get some cool stuff in return. In this case they probably will get a decent deal.

Wear: I think I will setup a test. I can use a piece of aluminum square stock to simulate the wear surfaces. I will write some G-code to simulate laser cutter mode (long slowish moves with a few rapids), makerbot mode (a lot of mid speed movement confined to a small area), laser engrave mode (fast movement confined to a medium sized area). I can run it continuously in a loop. I can also periodically change the load angle. I don't know what a life expectancy goal should be. If you want several thousand hours of maintenance free use, you would invest in a more expensive solution. The rapid development DIY'er probably does not need that much wear free life.
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Re: Linear Bearing Idea

Postby Tweakie » Thu Sep 09, 2010 3:33 pm

Looking forward to seeing how this turns out.

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Re: Linear Bearing Idea

Postby macona » Thu Sep 09, 2010 7:57 pm

Dies alone are about $1200 to $2000. Have you got any quotes on price per pound on the extrusion? How many cubis inches per foot in your drawn prototype?

One issue with this design and something you need to look for when running you tests is wear will probably accumulate in one area near the home switches. So you really cant adjust the bearings to take up the slop. And when you do need to replace parts from wear you are removing and scrapping large chunks of material.

Have you ever gotten a quote on the smaller round rail recirculating assemblies from china?
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