Precision washers were causing slop: what I did to fix it

discussion of design changes / improvements / suggestions
daveczrn
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Re: Precision washers were causing slop: what I did to fix i

Post by daveczrn » Tue Oct 23, 2012 3:49 pm

Is the steel v wheel the answer though? With two bearings in a v wheel you are able to shim it to remove some of the play. Or use higher quality bearings. I would think making a metal version of our current v wheel would be the best option for removing the most amount of play. It could be something as easy to machine as brass and I don't think we would have any problems. I've also machined some parts our of a bronze/aluminum mixture that was very light And had most of the bronze characteristics. Oddly enough it was a acme thread nut that I made out of it last.

SnapFracturePop
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Re: Precision washers were causing slop: what I did to fix i

Post by SnapFracturePop » Tue Oct 23, 2012 3:54 pm

I'd never noticed this problem till 12 hours ago, and here's a thread on the topic! The superglue idea sounds like it's worth a shot on my X carriage.
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roberlin
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Re: Precision washers were causing slop: what I did to fix i

Post by roberlin » Tue Oct 23, 2012 3:55 pm

I keep toying with the idea of trying the steel wheels (I know you would need custom plates, and eventually they will wear out the makerslide (I think that problem may be overstated with average hobbyist use))
http://store.makerslide.com/index.php?m ... ucts_id=75
Does anybody know for sure if they are completely absent of slop?
It sort of seems like a bearing race is built into the wheel itself, so at least part of the problems go away. But I know nothing about this type of thing -- anybody more knowledgeable want to weigh in?

EDIT: I just saw daveczrn is posting about this simultaneously

ejs
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Re: Precision washers were causing slop: what I did to fix i

Post by ejs » Sat Oct 27, 2012 3:31 am

I love the idea of using a copper alloy for their ease of cutting and relatively soft characteristics. That's why I decided to use one for the upgraded spacers. What I hugely dislike about them, though, is the cost. Copper is so pricey these days that a full set of 16 would be prohibitive.

But still, the thought of redoing the entire bearing is something that I considered before just thinking in terms of the spacer. And if Improbable Construct is correct about their deformable nature, then it's something that needs reconsidered. So I reconsidered it.

Before the precision washers, the goal was to come up with a metal clone of the Delrin wheel, and that's where I was getting hung up. There's no method that I was comfortable with plunge/undercutting using a 2.5D machine that would yield a satisfactory result. Cutting one side, flipping it, and then cutting the other is always risky. I wanted a one part, one bit, one cut operation. I always want a one part, one bit, one cut operation. Back then I came back with nothing, but now the discussion is cresting. So I went back and decided to set the cogs whirling that way once again. This time, the cogs responded with a workable solution.

I'll start a new thread on this, but I wanted to touch on it here. Instead of one piece, this has become two--which has turned out to be advantageous in a few big ways.

UPDATE: New thread is here: Is it time for a metal v-wheel? http://www.shapeoko.com/forum/viewtopic.php?f=11&t=919

Image
Last edited by ejs on Sat Oct 27, 2012 10:32 pm, edited 1 time in total.
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daveczrn
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Re: Precision washers were causing slop: what I did to fix i

Post by daveczrn » Sat Oct 27, 2012 6:51 pm

Now that's an idea i can get behind. unfortunately it's not an identical part for both sides. For production purposes it might be easier if it were the same on both sides, think there is anything that can be done here? I understand the need for the screws, maybe two screws as through holes and two as tapped holes so that it is the same? will there be room for the screws with bearings in there without increasing the wheel diameter? maybe there is a way of not using the screws and using some other way to fasten the two sides together?

ejs
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Re: Precision washers were causing slop: what I did to fix i

Post by ejs » Sat Oct 27, 2012 10:45 pm

daveczrn wrote:Now that's an idea i can get behind. unfortunately it's not an identical part for both sides. For production purposes it might be easier if it were the same on both sides, think there is anything that can be done here? I understand the need for the screws, maybe two screws as through holes and two as tapped holes so that it is the same? will there be room for the screws with bearings in there without increasing the wheel diameter? maybe there is a way of not using the screws and using some other way to fasten the two sides together?
Dave, I understand exactly what you are getting at. When I first thought of this solution I began with wanting to use two identical pieces and put hollow threaded rod between them, tapping each side. That idea was stopped by a lack of such hollow thread at the needed size. Once I started picturing leaving threadable extra material on one side, the door was opened to using differing sized stock for components.

I thought of backpedaling and implementing what you suggest: four holes, two through-holes and two tapped in each. I gravitate to doing the minimal amount of cutting for the sake of the tools used. The issue with the stock I found is that it would require either leaving too large a lip pressing in on the bearings (which would interfere with the plate), or, with the shorter stock, not create nearly enough surface area since the gap between sides of the "V" would be much wider.

The solution I pictured has one large advantage which I discuss in the new post. Since one bearing is completely sunk into the taller half of the wheel, the second bearing has a half millimeter recess it can register into when it nestles against the first bearing. This will create bearings that are given to acting as one solid part, rather than two individual pieces.

I think it is the most ideal solution regarding time, materials, tools, and the reuse of the existing parts.
Build it better than it was built for you. And give permission for the next guy to do the same. That's how Open Source works.
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northbear
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Re: Precision washers were causing slop: what I did to fix i

Post by northbear » Fri Nov 02, 2012 3:06 pm

ejs,

Quick question. To measure the inside lip of the delrin v-wheel, did you measure the overall thickness and then subtract the depth of the counter-bores on each side? This is how I would think to do it, but I thought maybe you had a more direct method.

Thanks
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daveczrn
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Re: Precision washers were causing slop: what I did to fix i

Post by daveczrn » Fri Nov 02, 2012 6:19 pm

A more direct way would be to use a micrometer. I just measured three of mine. Measuring the flange thickness at .0375" thick.

northbear
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Re: Precision washers were causing slop: what I did to fix i

Post by northbear » Fri Nov 02, 2012 6:51 pm

daveczrn wrote:A more direct way would be to use a micrometer. I just measured three of mine. Measuring the flange thickness at .0375" thick.
Ah that makes sense. I was thinking of my caliper which will not fit on the inside. If / when I measure I will have to see if I can borrow a micrometer

Thanks
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WillAdams
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Re: Precision washers were causing slop: what I did to fix i

Post by WillAdams » Sat Feb 23, 2013 11:05 pm

Would simply getting some extra precision washers, measuring them, discarding the under sized ones and stoning down the oversized ones work?

Also, what are the tolerances for the bearings? Could it be a classic case of only the people who wind up w/ a set of parts which are all under or oversize have problems?
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