Thanks Irving thats what I meant but I pharsed the question wrong. I seem to have a problem getting the thoughts in my head to paper lol
is that 20N a worst case or would it be better to up it a little? Have you got any info for other materials or a table maybe?
I'm starting to see what you mean, this aint going to easy........efficient design isnt easy to build and requires good machining, sounds like the chicken and egg situation I'm in at the moment :heehee:
With regard to the design is space an Issue? ie. overall size. Because I cant help but think that this needs to be a fixed gantry design. The frame could then be as heavy as required and just move the table underneath. This would mean its twice as long tho.
Kip always said "router for routing and a Mill for Milling" or something along those lines.
Ok I been having thinking about this and was wondering if Aliminium U channel is the answer? The only problem is that it would need welding. Steel would be easier but is quite a bit heavier and seems to cost more at the mo.
The idea is use 2 u channels vertical and the fix one top and bottom. This would provide a channel for the ball screw and should be plenty strong enough for dremel, trim router. but if more strength is required then the top and bottom cavity could be filled with concrete and rebar(could be threaded bar that then bolts the uprights to the beam)
Done a few rough shetches to get an idea, I know theres a few mistakes and will probably need some bracing in the webs of the channel (more welding) and the x axis is probably overkill........
Any imediate or obvious problems before I go any further? 100x 50 ali is about £10 a meter so with the 4 bars on an 800mm y axis it would be £30 ish
At first glance the design seems to ba all wrong, there is no lateral support for the x-axis and when the head moves it will move in the direction of the movement.
I think some form of twin track stacked one above the other would be better to control lateral movement.
Thats my 2p.
Sorry not sure I understand, do you mean because to X axis rails arnt connected? I did say it wasnt finnished yet mainly concentrating on the Z and y axis :whistling:
Any sketches or pics on the twin track Idea?
In the drawing shown 2 bars each side and and 8 bearings each side the bar at top pulls the 2 sides together and will give lateral support.
Not shown attachement of bearings but this arrangement will allow spacers to be used between rods.
I would like to have a router using this method were the base fixed to a wall as per the saws in B&Q as I am running out of floor space!
Still not sure where the problem is? The bearing blocks can take loads in all directions, (slightly reduced where the rail is supported maybe, but thats why I put them vertical rather than on their side)
I see what you mean In your diagram but not sure how that relates to the one I've drawn, dose that use skate bearings and unsupported rail?
I could put another rail underneath like in your sketch but this will add to the cost, And in that case Id rather use linear rails as they would be the same cost as 2 supported rails but are 4 way loading and much much stronger.
If Ive made a mistake I want to known, but at the moment I dont understand......
I have thought about the wall mount option but not sure how easy it would be to use.... Im sure I remember a design that could be stored on a wall tho.
Its just that I dont think that the sitting of the moving part on 2 rails just like a train then there would appear to be very little stopping it rising up unless you intend to use expensive ball slides which grips on their hollowed sides.
I thought the skate bearing system is a cheaper option plus use of unsuported rails although I am unsure myself how to fix them to supports without drilling right through them.
Ross, that's an interesting concept using off-the shelf alu sections. What about using one of the slotted alu sections like kev is doing at the moment (ITEM, or similar).
I was buying some router bits the other day from trend, and saw this video. If in doubt, copy the professionals! :) (have you seen the price of these machines from trend!!)
One interesting part of this machine (well, to me anyway!) is the relatively small Z travel, allowing a simple frame.
The vid may also contribute to the bearing discussion. I can't make out the bearing system on this machine (about 1min in is where the machining starts). Are they v bearings?
[ame="http://www.youtube.com/watch?v=Ue5PcqTwihM&feature=player_embedded"]YouTube- Trend CNC Machining Centres[/ame]
Hi Tom, Yes I have looked at the Al sections and i do have some of the item ones, It just seems an expensive route (espessially if you go for the heavy range) once you get all the connectors fixings ect. If budget allows then use it. It sure is much easier and dose look very proffessional.
Cheers for the link that looks good, not sure on the bearings tho, they look similar to pnematic actuators but could just be a low profile rail. with that design the forces will be small so could be similar to the igus stuff.
The small z axis definetley helps as it reduces the loadings. I think the main point here is that it is being used as a router for fairly low precision work. which is much easier than the breif of this project to cut Al.
I only thought of the u channel as it can be accuratley drilled by an MDF machine and then bolted/welded together to make a strong frame.
I was pricing up the large uprights in 15mm Al and realised how expensive they are to buy and get machined. I figured that they only need to be that thick because they are 2 dimensional, if there was some bracing in the 3rd dimension then they could be a lot thinner, hence the 3.175mm U channel. I maybe wrong and someone else has already tried and failled.
Is it worth Re-clarifiing the goal, As I understand its a 2"x4" (cutting area?) mid range with Al frame(that can be made on an MDF machine if required) and uses supported round rail or linear bearings with ballscrews to cut Al.????? Probably £500 for frame and rails (ballscrews vs lead screw and motors/drivers optional)
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