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So the extra strength is really coming from the fact it's steel vs aluminium?
If I can find a suitable steel channel section I might go down this route... I need to keep the sides (the long axis) about 4"/100mm in height. I'll phone my local metal supplier tomorrow.
I think the added strength is really in the much larger fasteners. Bigger bolts provide a lot more holding power and shear strength. My machine has never gotten out of square since I squared it up the first time.
The strength aside, it is cheaper to do it with these extrusions rather than aluminum tube and easier to fabricate and bolt together.
Really no reason to complicate things for yourself.
I'm looking into the steel vs ali thing. Basically it's going to come down to cost. Perversely it's might be cheaper to go with ali than steel because I can buy aluminium extrusion in shorter lengths.
Anyway, while I investigate that I'm trying to design a bed for the machine. How's this? It's lengths of 1.5"x0.5"x1/8" aluminium channel. It'll be easy to make and it'll be cheap. Can anyone offer any insight into whether it'd do the job?
Incidentally all the suggestions and comments so far are really appreciated!
Hi, nice design.
IMHO, your belts are kind of light duty.
It is not that much more to buy belts that are 25mm wide vs 9mm wide. As far as 5mm pitch, it is ok, but can deflect under strong loads. I know this sounds like overkill, but if you can fit it on, consider a 10mm pitch belt x 25mm wide. Example Brecoflex AT10 x 25mm.
The reason I suggested using steel angle is because here it is a bit cheaper than aluminum.
I understand issues from a point of supply. It is nice to be able to get drops. I have a local aluminum fabricator that I sometimes get some stuff from. He is extremely reasonable.
Aluminum would be strong enough for this size machine. I don't think you will have strength issues with either for a machine this size.
I like the channel for the table too. That should work out nice for both strength and work holding.
Hi, there is a rather dramatic benefit to go to slightly thicker Al tube walls.
At 1/8th inch (3mm) thick, it is pretty flimsy and can easily be flexed in your hand. Once you hit 1/4 in thick / 6mm it is almost like a different material altogether, with the added bonus that you can drill and tap a 5mm screw thread into it.
As Lee points out, steel is going to be stiffer and stronger (intrinsic property). So far, I am staying with Al as it is just easier for me since I have mostly hand tools, a (wood) chop saw, and a small borrowed drill press. BTW, these are great for Al.
Last edited by harryn; 03-25-2009 at 09:29 AM.
Hi Harry. I think his table will only be about 12" wide. If that is the case, then perhaps this would suffice, but I like to overbuild everything.
Some good T-track might work pretty well too. The slots might fill up, but could be vacuumed out easy enough. They would have the added bonus of being able to use T-Bolts. No drilling needed for work holding then. TYhey are also slightly stouter than normal channel.
I'm limited to some extent by what the on-line retailer I intend to buy the aluminium (or 'aluminum'!) has available, and I think they only have 1/8" channel. (Here in the UK everything is sold in metric but is clearly derived from imperial fractions, hence the mix of units!) But I'm making a trip Thursday to see what offcuts my local metal yard has available. While their per-unit prices seem to be higher I may be able to pick up exactly what I need, and therefore save a bit of cash - this will affect the choices of materials in terms of steel vs ali etc and hopefully resolve those elements of the design.
Which is a long way of saying I'll see if they do 1/4" thick channel, or maybe steel channel the right size.
Looking at your last picture, won't your gussets get in the way of the material or are they outside of your intended cutting area.
They're outside the cutting area, but they will reduce the width of the stock that I can load if the stock is longer than the cutting area, if you see what I mean. In practice I don't think it'll be a problem. That said, I'm still trying to find a better solution. The obvious thing would be to have the lower tubes longer so I put the gusset on the outside. But this'll increase the footprint of the machine which I don't want.Originally Posted by rowbare
Way overkill. 9mm belts should be fine for this application. Sorry Harry.
Gerry
Mach3 2010 Screenset
http://home.comcast.net/~cncwoodworker/2010.html
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)
I don't actually think gussets would even be needed on such a design, but if they were wanted, it would be just as easy to place them on the outside leaving a smooth inside table.
The narrow end rails would need extended in this case.
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