. .

Threaded View

Previous Post Previous Post   Next Post Next Post
  1. #11
    Now comes one of the last parts. I frankly admit i was quite indecisive there, from the beginning of the design. So it was time to sit on my arse and make some calculations and think the things clearly.

    The working area / table bed. May be it a theme for a whole new topic. i see many people are wondering how to do it differently than plywood, especially if they mean to cut aluminum and cool it.

    Now lets be clear i am not talking about the machine bed structure nor the sacrificial board. I am talking about the working bed/fixing area and method which is in between the frame and the sacrificial board and which is water/coolant resistant and is strong enough for moderate aluminum milling

    So lets see the options. prices are Spanish, but may be more or less the relations will keep in different countries. Some thickness prices are not known but can be extrapolated. 1kg of steel is ~1 euro, 1kg of aluminum 6082 is ~5euro,

    -phenolic 10mm thick 65euro/m2 so as i see it needs to be minimum 20mm best 30mm thick ...
    -marine ply wood 15mm thick ~36-50 euro per m2 , i see it needs to be at least 30mm thick.. so its good for a spoil board but expensive for top
    -marine ply wood with phenolic top for truck flooring, now this is a good one, but its even more expensive and the phenolic will be very thin to surface

    Now instead of writing here i have made some drawing with data for the better options:












    I have spent all morning in calculation and last days rethinking the things. So for me its clear:

    My choice will be UPN140. I have the bed clearance for it. It is cheap and very strong for the money. Like the last photo, 2 welded together, with T channel and DIY Tee nuts as per drawing. So i will drill a lot of holes and use them for fixture and big sheets will be fixed with clamps that will pass trough the channels. It will be screwed to the table with nuts that pass between the connection of 2 of the UPN. I will have to find a resistance welder from somewhere for clean job.



    Note: Moment of inertia is x axis cause its in C position when measures are given, so a bit misleading. Anyway, its in the good for us direction.

    last thing that i have not clear is if i will machine it both sides and machine the bed bellow, so all is flat when mounted and dismounted if needed. I am seriously starting to think to somehow mount a grinder on the Z or surface all using small bit, slow speed and coolant. i said before no steel work with that machine, but its quite tempting. And from what i have seen people have done it with much weaker designs.

    One thing i know is that on top of that UPN140 i will use then thin phenolic sheet or even better scrap pieces, for sacrificial board. At leats on some part of the machine. On other i will use cheap expanded PVC sheet.

    I hope that these calculations money/material/ strength will help people to evaluate properly what exactly bed they need.

    Notes
    -UPN profile can be cast filled with cement which will make things even better. Non crack cement for table tops and garage floors is enough for that.
    -aluminum T channels are damn expensive so i did not even consider them. Even steel channels are very expensive, crazy.


    PS2.
    One question . For the the threaded holes to be closed to keep them clean , what is the name of the screw that is like a grub screw but is for flat screw driver?
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	CNCsteel table top working bed 5.png 
Views:	2644 
Size:	80.9 KB 
ID:	15125   Click image for larger version. 

Name:	CNCsteel table top working bed.png 
Views:	2677 
Size:	78.8 KB 
ID:	15126   Click image for larger version. 

Name:	CNCsteel table top working bed 2.png 
Views:	2667 
Size:	92.4 KB 
ID:	15127   Click image for larger version. 

Name:	CNCsteel table top working bed 3.png 
Views:	2656 
Size:	55.1 KB 
ID:	15128   Click image for larger version. 

Name:	CNCsteel table top working bed 4.png 
Views:	2621 
Size:	60.2 KB 
ID:	15129  
    Last edited by Boyan Silyavski; 11-04-2015 at 02:51 PM.
    project 1 , 2, Dust Shoe ...

  2. The Following User Says Thank You to Boyan Silyavski For This Useful Post:


Thread Information

Users Browsing this Thread

There are currently 2 users browsing this thread. (0 members and 2 guests)

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •