X and Y sliders using skate bearings

Re: X and Y sliders using skate bearings

BodgeIt — Fri, 21 Aug 2009 20:08:18 -0400

Some conclusions from my tests on Method 3 & Method 2...

After testing method 3 with Bike chain I found that you must use method 2 for bike chain.

Its a bit of a catch 22 ~ toothed belt runs great with method 3 and method 3 is the closest to a printed Darwin.

However with bike chain the extra weight causes too much friction and method 3 with the skate bearings is needed. that was easy.. as I have both.. versions on two repstrap darwins so I swaped the belt for chain..

Skate bearings and bike chain are cheaper ;-) but in the long run you will need to buy toothed belt ;-(.

I will continue to look for an inexpensive reliable method of making ball chaine drive pulles as this solves the catch 22 by eliminating toothed belt.

Oh since I said I would not try cable I bought 3 meters of 1.5 mm steel cable to try an idea out.. as this would also be cheaper than using method 3... it could just be a bad design idea .. bit like my steep learning curve delta robot attempt see Delta robot post..

Re: X and Y sliders using skate bearings

sid — Sat, 15 Aug 2009 14:44:56 -0400

Now that's even more impressive.
I always wanted to know what those tiny little white zombies are made for at all,
I used to have them laying around in the drawers of my workbench.. until I sponsered a trip to the local dump.

Now I know I shouldn't.
Thank you bodgeit, I think I'll try that too someday

'sid

Re: X and Y sliders using skate bearings

BodgeIt — Sat, 15 Aug 2009 11:21:39 -0400

X&Y sliders method 3

I am total amazed by this one I expected this to have more friction than the skate bearings and for it to have a lot of play.. neither is the case it is also very very much lighter as it has not got 32 skate bearings. I cant belive how simple the X & Y mechanisims are now and its £16 cheaper to buy..

I just have to figure out an easily repeatable method for the Y axis next...

Re: X and Y sliders using skate bearings

BodgeIt — Fri, 14 Aug 2009 20:31:13 -0400

The X & Y Sliders method 2 is now posted on the blog ,.. sory the camera is auto focus and I am not too good at getting it right in the close up shots..

~Here is the link.. X & Y Sliders method 2

Re: X and Y sliders using skate bearings

philwaud — Fri, 14 Aug 2009 02:45:06 -0400

That is sweet!

I think I had already ruled out using the bearing as a horizonal slide bearing, especially on a screwed rod. I have some 15mm chromed copper pipe and Im going to use that as the "rail". I did think about using a pipe olive as the slider, surprisingly they are quite a loose fit - too loose in fact, the play is 1mm or so. My next idea was to use the 608 bearings as a wheel, similar to your idea.

Im still favouring screwed rods to move the X and Y stages and four screwed rods connected with a belt for the Z stage. I know its slower but it just seems so much more elegant!

Phil

PS, is the auto focus turned off on your camera? Lots of the pics are a little less than sharp!

Re: X and Y sliders using skate bearings

sid — Thu, 13 Aug 2009 20:02:12 -0400

Now THAT looks promising :D

what a nice idea...

'sid

Re: X and Y sliders using skate bearings

BodgeIt — Thu, 13 Aug 2009 15:22:51 -0400

Here is a picture of method two..

Im making the drawings for the chopping board parts once made and checked by using the drawings I will add to my blog.

Re: X and Y sliders using skate bearings

BodgeIt — Thu, 13 Aug 2009 14:51:36 -0400

Hold off on copying this method I have a much better one for X and Y I am making drawings for it you will need.

32 skate bearings some plain ASDA chopping boards they are £1 for a large and a small one in one pack or just a sheet of 6mm mdf, chopping boards look better thou.
A pack of 100 Nylon blocks £6 at B&Q £5 at Wicks. I have 3 of my daughtesrs visiting so I have not had much time this week.

Once I finalize the full set of instructions with those 100 Nylon block you can make the whole Darwin cartesean bot. With the minimal effort / mechanical enginering and a few nuts and bolts.
I had these ideas several months ago but no time to do it letalone make drawings.

I am still calculating a total cost for this method of making a Dawin cartesean bot at the moment however the ball park without steppers extruder and controll electronics is around £60 an the build time I think would be just one long weekend or less.

I am working on these other areas like cheaper electronics and motors and an easy way to make an extruder. The whole construction will not need any printed parts. I will supply the drawings as I draw them and blog each part all parts made will need a saw, drill and a vice.

Im not a mechanical enginner so the design has evolved by testing many many ideas and experimentation.
My aim all along has been to get the total cost of a Darwin down to < £200 its looking very much like I might have ahived that target price area now.

I am an Electronics development enginner who has been lost in software development for a little while.

Re: X and Y sliders using skate bearings

philwaud — Thu, 13 Aug 2009 09:21:27 -0400

Ive just bought two sets of skate bearings (16 in total) for 12 quid, so I dont think the cost is an issue!

Im thinking of using the 608 bearings as a slider on some 8mm threaded rod - am I asking for trouble or do you think it would work?

Re: X and Y sliders using skate bearings

sid — Tue, 11 Aug 2009 07:39:34 -0400

Well polished steel on polished steel with a thin film of oil works well, true.
But it's rather a pain as soon as the oil is poluted by dust.

Since there are very very cheap linearbearings (steel, ptfe coated) that cost less than a skatebearing (that is if you don't have the skatebearing laying around of course)
I would not encourage to do so.

Also a skatebearing is not meant to stand lateral forces so you have to make sure that it doesn't jam

'sid

Re: X and Y sliders using skate bearings

BodgeIt — Mon, 10 Aug 2009 11:51:25 -0400

They slide very well with just a little 3 in one oil ~ I have another method that I am trying that looks more promising I will blog it shortly in fact I think the new method is the one I will use.

Re: X and Y sliders using skate bearings

sid — Mon, 10 Aug 2009 08:34:36 -0400

uhhhh don't!

It may work, if greased well.
But any piece of hdpe (from an old chopping board maybe) drilled to fit the rods would be a much better scenario here i guess ;)

'sid

Re: X and Y sliders using skate bearings

joaz — Mon, 10 Aug 2009 06:06:53 -0400

Using these bearings to act as linear bearings doesn't seem very efficient to me. However, it'll be fine if you keep your rods to greased.

X and Y sliders using skate bearings

BodgeIt — Sun, 09 Aug 2009 05:49:15 -0400

Repstrap Dawin X and Y sliders using skate bearings.

[repstrapdarwin.blogspot.com]