Thread: machine beds

  1. #1
    What do you guys do for your machine bed?

    I know alu profile is common, but I'm sure there are many other things people here have tried.

  2. #2
    Well since you mention it... my machine has just started cutting a bed out of 25.4mm aluminium plate, 50 worth of which will be turned into swarf after 20 hours machining! It's essentially a T-slotted bed with an array of roughly 300 M8 holes for additional mounting options.

    It all depends on what you want to cut? In my opinion aluminium profile should be avoided since a rigid bed made from this would be exceptionally expensive. If you want to machine aluminium regularly, then a bed made from strips of aluminium or a single plate is far superior. If aluminium is only occasionally going to be machined, then MDF is fine but for long runs it's not good due to it absorbing coolant.
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  3. #3
    Quote Originally Posted by Jonathan View Post
    Well since you mention it... my machine has just started cutting a bed out of 25.4mm aluminium plate,
    i wish i could Justify/afford a piece 750mm X 750mm X 25mm plate for the center of my new bed...Alas NO.....
    Always bear in mind that your own resolution to succeed is more important than any other - Abe Lincoln

  4. #4
    I have a 10mm aluminium plate bed, I then screw mdf on top of it. it's fine for wood plastic and small bits of aluminium, but it really does degrade in my shed.

    I plan to create some sort of make shift aluminium bed from lengths of aluminium stacked on top of each other.

  5. #5
    I've gone for 40mm x 40mm aluminium profile for the bed on my machine currently under construction. I considered 160mm x 16mm and 160mm x 28mm but thought it would not be stiff enough. I'd have thought a 10mm or even 20mm solid sheet would be rather flexible over large areas too, do you support it a lot?

    I guess I'll still need a sacrificial bed on top of that, and I'm not sure what to do since that will stop me being able to easily clamp stuff down on the profile.

  6. #6
    Quote Originally Posted by Tenson View Post
    I've gone for 40mm x 40mm aluminium profile for the bed on my machine currently under construction. I considered 160mm x 16mm and 160mm x 28mm but thought it would not be stiff enough. I'd have thought a 10mm or even 20mm solid sheet would be rather flexible over large areas too, do you support it a lot?
    How much 40x40 profile, what spacing etc? If you could post a rough drawing that would be ideal.
    If using 10mm sheet I would put steel box section arranged in a grid beneath the sheet and screw it into that. On it's own 10mm would not be much good.

    Quote Originally Posted by Tenson View Post
    I guess I'll still need a sacrificial bed on top of that, and I'm not sure what to do since that will stop me being able to easily clamp stuff down on the profile.
    If you're not using coolant than MDF is fine for the sacrificial bed so long as it is well supported (hence the question about spacing). You could make some plastic blocks to raise the part off the profile. HDPE will withstand coolant, but over the size of your machine the cost would be unreasonable. The good thing about MDF and HDPE is you can use standard wood screws to quickly clamp stuff down in any position and you can use any hole in the part for clamping so it's a lot less restrictive than T-slots. The compromise of course is a well supported aluminium bed will be a lot stronger. If you're serious about it I would go for strips of aluminium (http://www.aluminiumwarehouse.co.uk/...Bar/pages.html) bolted on to steel box section. Leaving a gap between strips gives slots which you can use like a T-slot for clamping. You should get as thick flat bar as you can afford, nothing is too much here really.
    There are many many ways to make a bed so look at other machines around the same size...
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  7. #7
    Hi Jonathan,

    I've gone for about 80mm spacing between each 40mm extrusion. There will be a cross brace at each end and in the middle.

    I think putting HDPE strips on either side of the extrusions seems a good idea. That way I can still use the T nuts and also move the extrusions about to support different size parts. Do you think there is any advantage in using Tufnol, it can be harder wearing I guess.

  8. #8
    Quote Originally Posted by Tenson View Post
    I think putting HDPE strips on either side ... Do you think there is any advantage in using Tufnol, it can be harder wearing I guess.
    Tufnol is stronger and has a higher coefficient of friction, which will both help with clamping. However, being a composite, it will cause *much* more wear to the cutters when it gets cut. There's some good data here:

    http://www.directplasticsonline.co.uk/graphs.html

    Acetal is good since it machines so easily (but it's more expensive). When the cutter breaks through it's unlikely to be going the correct speed or feedrate for cutting the bed material, so ideally you need something that cuts over a wide range of conditions.
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