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03-02-2020 #1
The requirement is a large work area, so a moving gantry design and making it as good as possible is my goal. This of course means that it wont be as rigid and as effective for aluminium / very light steel. This is a trade-off I need to make, as I don't have the budget or space to build 2 machines right now.[/QUOTE]
That's a good solution and one I'd take if building for my self with your requirements.
#1 Cannot tell you this because I've never used iit myself, I only built it, and the owner only cuts woods with it as far I know.
#2 No this is a design I build and Sell.
#3 Z-clearance = 250mm Cutting dims Y1300 x X800
#4 Yes it's a much stronger design than a single piece of profile. It's my own design that I've used for years and it's well-proven on lots of machines.
#5 The surfaces are made flat and on the same plane by coating with a fine spread of Epoxy metal (not epoxy resin) and then machine frame is turned upside down and placed on precision Granite surface table.
#6 The fronted mounted rail is to give maximum clearance under the gantry and the top-mounted rail is to give greater spacing between rails and support the Z-axis rear plate.
#7 Yes 120x80. They are mounted by bolting into the lower flat profile from the top. The top profile is bolted to the flat profile from the underside, there are also aluminum keys inserted into the slots to stop any movement.
#8 It's difficult to align the rails parallel to each other when side-mounted. It's also much more difficult in regards to them being on perfectly horizontal and vertical planes. If the surface the rails mount on is not perfectly vertical then the gantry sides will form a V if viewed from front plane, likewise, if the surfaces are not parallel to each other they will form a V if viewed from Top plane.
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03-02-2020 #2
#4. Makes sense. It basically becomes an incomplete 120x200 profile shaped as an L, which has way more moment of inertia compared to a 90x180 profile. How are they mounted together? And what about using something like a 100x200 profile? I guess that would be of similar strength as the L-shape made by 80x120, but easier to use.
#5. This is interesting. So without a flat surface to rely on, you probably woulf have to go with epoxy resin levelling?
#6. Of course, why did I not think of that immediately. Oh well, it makes sense now. Is it much more difficult to get it aligned like that, compared to mounting both on the front?
#7. So you are drilling holes through the profiles for the bolts?
Bonus question: How much approximately do you sell this type of machine for? It looks really good and it sounds like a lot of fun to be making money building CNC machines!
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03-02-2020 #3
They are bolted together from the bottom as mentioned in the last post and end plates are machined with L-shape pockets to match the profile then bolted to the ends to support the ends.
Yes, the first version I made used epoxy leveling until I aquired the large surface plate. Epoxy works ok it's just more work and takes a lot longer. The method I use now is dry within hours and can be drilled tapped the next day and rails fitted. You cannot fit rails on epoxy for at least 2 weeks.
Yes and no. Yes because the rails are not on the same plane so a little more work with a dial gauge to get parallel etc. However, it does offer other advantages regards setting up the Z-axis vertical tram because you can slide the rails back n forth ever so slightly if needed, plus you the X-axis top plate which can have a little adjustment in it. More adjustments the better when it comes to building a CNC machine but Obviously within limits so as not to put a binding on the linear bearings.
Where if you have both rails on the same plane and the Vertical tram is out then you have to mess around with shims or tilting the gantry etc. Worse still if the gantry as got any twist in it because then it's not so easy to get twist out. With rails on top you can take the twist out easier.
Yes, counterbore the slots to make a flat area for bolt head and then drill and tap into matching profile. Depending on profile type depends on how far into the profile I drill and counterbore.
Yes, it's a lot of fun and frustration at times. As for making money that's a different matter... Not so sure I really do at times...
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04-02-2020 #4
Can you specify or maybe give me a link for the epoxy metal that dries so fast? I'd like to try that.
From where/how did you aquire the large surface plate and how much did it cost? I am thinking if it would be possible to make one DIY with epoxy resin, hehe.
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04-02-2020 #5
They have many suppliers around the world I believe but this the company and the type I use.
https://www.belzona.com/en/products/1000/1111.aspx
It was gifted to me by a Friend. It's a massive 10" thick piece of fine-grained Granite that is precision ground to a calibrated tolerance and not something that could be replicated with epoxy.
You can buy them from any good tool supplier or meteorological supplier. However, they are expensive and very very heavy.
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