Educa's BigFoot

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Re: Educa's BigFoot

Postby TLHarrell » Tue Jan 03, 2012 1:43 am

Sounds to me like you've got plenty of pull. Make sure your belts can handle that amount of tension. Those linear rails, unless they have a major preload on them, are fairly close to frictionless. The bigger number to deal with will be mass calculations for acceleration.
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Re: Educa's BigFoot

Postby educa » Tue Jan 03, 2012 8:58 pm

Ok here we go again.

Today my X axis rail arrived from Germany.

Man this thing is HUGE. It weighs about 8 kilograms and is very very heavy.
Also, the linear ball bearing slide has (unfortunately) mechanical artifacts in the rail which make it not run very smooth.


So..... I allready settled with the ebay seller and the rail goes back. Meanwhile I allready bought another rail (this time 1400mm long) of the type THK RSR12WZM
This rail is a lot lichter (only 24mm wide and 8.5mm heigh) and the carriages only weigh <70grams

Still they are top quality (I allready have some of those here which measure about 30 cm, but its the same rail and carriages and I can really make them fly)

So its waiting again for that rail to arrive.


In the meantime, I have discovered http://www.beltingonline.com/ to be a site to bookmark.

I found there that they have T2.5 AND T5 belt. I really wonder if T2.5 wouldn't be a good solution for me instead of T5, but that largely depends on some stuff I'll have to ask to beltingonline (mainly the fact that I don't have the tools to accurately make my own bore + grubscrew holes.

If I use 2.5T 20Tooth pulleys, then 1 rotation of my motor in full step would be 50mm.

The motor is 200 steps motor, so 1 full step would be 50/200 = 0.25mm

The driver (a CW5045 microstepping driver) can do 1/10 , 1/25 , 1/50 step to the 3.1Nm stepper so theoretically that would give me a resolution of 0.025 , 0.01 or 0.005 millimeter (where 0.025 is the default resolution of HPGL files which only work upto 1/40th of a mm)



Life looks nice again.

Unfortunately I also got the idea to begin to draw my machine in sketchup and that is not so easy at all :)
Therefore, the first thing I'm going to do now is read a good sketchup book :)
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Re: Educa's BigFoot

Postby BenJackson » Tue Jan 03, 2012 9:23 pm

Just buy Alibre Design Standard.
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Re: Educa's BigFoot

Postby educa » Tue Jan 03, 2012 9:57 pm

Well not to act stupid, but its $199 and I don't want to spend that much on this part of the job :)

The design is more like a proof of concept try.
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Re: Educa's BigFoot

Postby BenJackson » Tue Jan 03, 2012 10:27 pm

But it's a vastly superior tool if you want to make mechanical designs. Perhaps HeeksCAD has caught up enough to get you by if you really need free.

I have also used SketchUp to do what you're doing and it's night and day. Alibre (and other parametric solid modelers like SolidWorks) really capture the intent of what you want to do ("put a hole 3mm from the edge" or "align this notch with this other part") and everything ripples through when you change the original constraints. Just try to resize a hole in SketchUp... Plus when you're done with your design Alibre is ready to output design documents, 2D sections for machining (or direct connection to CAM), etc. I also output STL to directly 3D print designs.

Alibre could easily save you $199 by helping you find interferences that might otherwise lead to scrapped parts. Being able to actually build the assembly such that you can drag the laser carriage and gantry around and see where everything goes will save you a ton of time as well (and probably lead to simple tweaks that improve your cutting envelope).
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Re: Educa's BigFoot

Postby educa » Tue Jan 03, 2012 10:35 pm

I see.

I just found that there is a 30 day trial version available so its actually quite risk free.
If after 30 days I'm still not convinced you can always ask for another 30 days :)

Now even if I use alibre or sketchup, I need to be able to learn it.

Are there any ebooks on alibre you could advise ?
I'm going to look at the tutorials now
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Re: Educa's BigFoot

Postby BenJackson » Tue Jan 03, 2012 10:59 pm

There are tutorials and once you get the "idea" of parametric solid modelling it's pretty intuitive. Even if you don't know a function exists you will suspect it should so you'll know to look for it.

If you see any tutorials on: http://alibre.dk/training_support/freea ... aining.asp which are not free (grayed out) it may be that someone like me has had access to them via one of Alibre's renewal incentive programs and has... viewed them... permanently... and might be able to recall them in vivid detail in the form of a .mp4...

A few of us Alibre users have uploaded designs to Thinigverse you could look at. Another advantage of parametric CAD is that you can look at those designs and see just how we did everything.

Alibre also has decent forums and Bart might be willing to put up a CAD/CAM forum here.

BTW if you have not picked a 2D CAM you might consider CamBam -- there's a plugin that one of the users made that lets you transfer sketches (the 2D foundations of most parts in Alibre) directly into CamBam. It has a very, very generous free trial. In fact, it is so generous that I have 75% of it left and I really should just buy it.
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Re: Educa's BigFoot

Postby educa » Wed Jan 04, 2012 12:43 am

Ben. I'm currently downloading the alibre design user guide to study it.

a few questions to you:


1) did you design your machine in alibre design? care to share?

2) do you know if the personal edition is enough to simulate gantry movement when you turn the stepper motor axle in the assembly?

3) Can this software also easily design the timing belt somehow?

4) Any idea if there is a parts library somewhere which could contain usefull parts for our purposes, like alu extrusions, nema 23 steppers,....

5) Any idea if you can export the completed machine design to some kind of 3d format usable for rendering in for example blender?
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Re: Educa's BigFoot

Postby BenJackson » Wed Jan 04, 2012 1:30 am

educa wrote:1) did you design your machine in alibre design? care to share?

2) do you know if the personal edition is enough to simulate gantry movement when you turn the stepper motor axle in the assembly?

3) Can this software also easily design the timing belt somehow?

4) Any idea if there is a parts library somewhere which could contain usefull parts for our purposes, like alu extrusions, nema 23 steppers,....

5) Any idea if you can export the completed machine design to some kind of 3d format usable for rendering in for example blender?


1) Not the laser cutter. I built bdring's design.

2) I don't know if there's a rotary-to-linear constraint. I don't think the personal edition is missing any constraints at the assembly level, though.

3) I've never designed a belt. Bart (Dring, that is) would be a good person to answer this. He makes lots of renderings with belts. I'm assuming they're cosmetic. The software could definitely model a belt as an extruded section that reaches from A to B and update that dynamically, but you'd probably have to reason from that about overall belt length. I'm not sure.

4) McMaster has lots of their parts online. I imagine others do as well. Misumi and 80/20 make their profiles available via 3D warehouse 3rd party sites. Things like steppers aren't that hard to model yourself if you just want the right shape. If you want them to be "pretty" you can find STEP files with a lot of detail (but then motor body length varies so beware of that)

5) You can export to lots of 3D formats including STL and I think whatever that 3DStudio format is. The pro version has more import/export formats as well.
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Re: Educa's BigFoot

Postby mikegrundvig » Wed Jan 04, 2012 3:22 am

I can't speak to Alibre but in SolidWorks, belts and the like can be actually added as needed and it will properly handle gear reduction, etc. I use this to tell me needed belt lengths for instance. You can also use it to determine if there are collisions with moving components and the like.

-Mike
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