Project Shapeoko HD

discussion of design changes / improvements / suggestions
LouisV
Posts: 316
Joined: Fri Dec 13, 2013 3:41 am

Re: Project Shapeoko HD

Post by LouisV » Fri Dec 19, 2014 7:55 pm

Kind of random but I have some stats from Openbuilds themselves regarding the strength of delrin dual v-wheels vs polycarbonate dual v-wheels. They wouldn't go into detail about their fabrication process but assured me that their polycarbonate wheels were stronger then their delrin wheels. If that's the case then I'm going to have to re-consider using polycarbonate wheels for the HDX kit. I don't think it'll affect the overall asking price of the HDX but I'll need to verify that as I get a real firm handle on my cost and supply chain. If it does increase the asking price I'll stay with delrin and leave it as an optional upgrade, if it doesn't I'll include it in the kit. Either case It will certainly be a nice little upgrade to have on the HDX. 8-)

OpenBuilds Delrin Wheel

Elongation at Break - 55%
Yield Stress - 62Mpa
Tensile strength - 65Mpa
Compressive Strength - 63Mpa
Flexural Strength - 75Mpa
Shear Strength - 60Mpa
Rockwell Hardness - M80


OpenBuilds Polycarbonate Wheel

Elongation at Break - 120%
Yield Stress - 90Mpa
Tensile strength - 80Mpa
Compressive Strength - 86Mpa
Flexural Strength - 93Mpa
Shear Strength - 70Mpa
Rockwell Hardness - M75

WillAdams
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Location: Pennsylvania --- south of the Turnpike, East of US-15
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Re: Project Shapeoko HD

Post by WillAdams » Fri Dec 19, 2014 8:05 pm

Interesting. Are those values derived from testing, or FEA?

It's odd to me 'cause my recollection is that based on the material data Delrin came out better.

William
Shapeoko 3XL #0006 w/Makita RT0701 Router w/0.125″ and ¼″ Elaire precision collets
Nomad 883 Pro #596 (bamboo)

Hans
Posts: 290
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Location: Connecticut, USA

Re: Project Shapeoko HD

Post by Hans » Fri Dec 19, 2014 8:45 pm

You wouldn't want to load them up anywhere near failure -- isn't the elastic modulus what should make the real difference?
Shapeoko #1,123

cvoinescu
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Location: Camberley, UK
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Re: Project Shapeoko HD

Post by cvoinescu » Fri Dec 19, 2014 9:24 pm

Hans wrote:You wouldn't want to load them up anywhere near failure -- isn't the elastic modulus what should make the real difference?
Yes it is -- you are very correct. None of the ultimate stresses are valuable as a comparison. All of them measure various failure modes (stretching, bending permanently, breaking by pulling, squeezing, bending and shearing, and denting with a pointy tool, respectively). All we need to know is how much the material deforms under stress that does not cause permanent damage, and that's the modulus of elasticity. The fact that they quote irrelevant parameters makes me suspect that the relevant one may paint a different picture.

There is one way for polycarbonate to have a better elastic modulus than Delrin, and that's using it as a matrix in a composite with a tough fiber (glass or Kevlar, for instance). Glass-filled polycarbonate is very stiff, but the quoted 120% elongation at break suggest this material isn't such a composite. (And, if I made something of glass-filled polycarbonate, I would not miss the opportunity to advertise that.)
WillAdams wrote:Interesting. Are those values derived from testing, or FEA?
They're all specific to the material and not to the shape, so you would not be able to use FEA to compute them. In fact, some of them require the material under test to be in a certain specific shape (e.g. a bar with eyelets at the ends), so they can't be specific to any geometry. All should be measured in the lab, using standardized tests.

You can then plug these characteristics of the material into FEA to predict the characteristics of the object. But, again, we're more interested in normal use, not failures, so the most important parameter is the elastic modulus, which we don't have.
Proud owner of ShapeOko #709, eShapeOko #0, and of store.amberspyglass.co.uk

LouisV
Posts: 316
Joined: Fri Dec 13, 2013 3:41 am

Re: Project Shapeoko HD

Post by LouisV » Fri Dec 19, 2014 9:48 pm

WillAdams wrote:Interesting. Are those values derived from testing, or FEA?

William
I'm not sure, they didn't go into too much detail in regards to that.

cvoinescu wrote: And, if I made something of glass-filled polycarbonate, I would not miss the opportunity to advertise that.)
I wouldn't either, so that does make me wonder. :? However they've assured me that from their internal testing their polycarbonate wheels are better suited for heavier loads over their delrin wheels. The thought of them trying to sell an inferior wheel at a higher price with the claim that it's better than their delrin wheels doesn't seem right to me. Why go through the trouble and even potentially tarnish your reputation with the Maker community?

I think there is something more to this then just the spec sheet that we're looking at, as they have been pretty tight lipped on how these wheels are actually made. I want to give their claims the benefit of the doubt (I'm too nice for my own good) but I think some testing of my own is in order to either validate or refute their claims.

I'll also go see if I can dig up some more information from them regarding these wheels.

cvoinescu
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Re: Project Shapeoko HD

Post by cvoinescu » Fri Dec 19, 2014 9:51 pm

Now I want to buy some to compare them!
Proud owner of ShapeOko #709, eShapeOko #0, and of store.amberspyglass.co.uk

LouisV
Posts: 316
Joined: Fri Dec 13, 2013 3:41 am

Re: Project Shapeoko HD

Post by LouisV » Tue Dec 23, 2014 10:30 pm

Hey everyone,

No major updates today but I did cut out some mockup plates for the HD today. I'll be cutting out the real plates for the HDX after Christmas sometime. As I said before I want to have the tweaked HDX running by mid January so I can focus my efforts in getting the HD up and running as well as fulfill any beta orders for the HDX.

I hope you guys have a great holiday week with friends and family. :)

~Louis

LouisV
Posts: 316
Joined: Fri Dec 13, 2013 3:41 am

Re: Project Shapeoko HD

Post by LouisV » Tue Dec 30, 2014 10:35 pm

Hey everyone,

I have a small update today. I cut out all the plates needed for the updated HDX. They came out quite nice and are ready to be primed and painted for assembly next month. The end plates will now accept up to two 4080 extrusions on each side for a really rigid y-axis. While the stock machine will only come with one 4080 extrusion for each side of the y-axis you can double it up to increase the length up to 2000mm unsupported, or 3000mm with mid-span supports. As I said previously, if you want to increase the length beyond 1500mm you'll need to butt the Openrail together which I've encountered no problems doing in my testing.

I'll be re-using the z-axis motor plate and secondary y-plates as they have been left unchanged, that's why you don't see them in the photo.

Also, before I forget I will be cutting out the prototype HD plates tomorrow. I hope to have the HD running by the end of Janurary, though hopefully sooner. *crosses fingers*

Image

azonin
Posts: 1
Joined: Fri Dec 26, 2014 2:06 am

Re: Project Shapeoko HD

Post by azonin » Wed Dec 31, 2014 3:47 am

Louis, I would like to sign up as a beta tester if there's still a spot for me. Please send me a PM, since I cannot send you one for some reason.

Thank you

LouisV
Posts: 316
Joined: Fri Dec 13, 2013 3:41 am

Re: Project Shapeoko HD

Post by LouisV » Fri Jan 02, 2015 9:46 pm

Hey guys, it's finally 2015! I expect this to be a great year for DIY/open source CNC machines. The Shapeoko 3 is definitely shaping up to be a great machine and I hope my contributions and my efforts will make an impact as well.

Down below are some prototype plates for the HD machine, already painted and everything. :) You'll also notice that I compared some HD parts to the HDX equivalent so you can see a size comparison. Now it's not so much that the HD parts are small as it's more that the HDX parts are just really big and beefy. ;) With that said the HD plates are super rigid and should be plenty for most people in the medium duty category. The HD plates will be made out of 9 gauge mild steel while the HDX plates will be made out of 0.25" thick 6061-T6 aluminum.

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As I've said before I'll be unveiling an official name for these machines within the next week or so and I hope to push my project to the point where I can start my Kickstarter campaign and take pre-orders within the next couple of months.

Last but not least I have a teaser announcement to make. It's in regards to a collaborative effort that I'm involved in, but it's still too early to really go into any details. What I will say however is that it involves Openbuilds and a possible new part. :) More about this later.

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