I'm designing a router and I'd appreciate a bit of input and comments. I'm using 2x3inch and 2x4 inch aluminium rectangular tube for the main structure and gantry. See the exploded view for how I intend to attach it. I'm using supported 16mm rail for the x and y axes, and a Thomson 511P35A1 linear bearing for the z axis (see here for the details: http://www.danahermotion.com/website...a_standard.php). I picked up 600mm of the Thomson rail along with two carriages on ebay a while back for very little. The plan is to chop off ~200mm of the rail and use one truck. It seems like very substantial stuff, but I'd appreciate any comments on using it like this.
Working area will be about 450x300mm.
The pulleys are GT2 3mm pitch, 9mm wide plastic from sdp-si.com.
The spindle is a Kress 1050. I plan to cut wood, plastic and aluminium.
Anyway, enough description - the pics are self explanatory. Comments appreciated!
Looks like it would be a very stiff machine with such short distances from the linear slides to the gantry, and the z-axis being in so close the slides on the y.
I am going to drive the screws on my machine belt drive very much like you are, and I think it just makes the machine more compact and less items sticking out to get broken.
Instead of cutting off part of the thompson rail, why not just make yor machine a little bigger? One thing I have seen on many machines is that cutting area becomes and issue after you have been using the machine for awhile. And then alot of people end up building a bigger machine.
Only issues I can see, is that the cutting area is going to small compaired to the size of the machine. Because, correct me If I am wrong, the cutting area is going to be really close the z-axis or down inside the frame on all for sides.
You've touched on the two issues I'm really wrestling with.
The idea is the work/material sits inside the machine. The catch (that only dawned on me yesterday) is this means I won't be able to load any stock larger the the machine's working area, which is something I regularly do with my current router. With that in mind I've now revised the design a little with a slot cut in the front to allow loading of longer pieces (see pic attached). (Obviously I'll only be able to cut within the machine's working area, but I regularly use bits of metal/wood/whatever that are larger to begin with, and I don't want to have to cut them down first to work on them.)
The other thing I'm trying to settle on is how the base/clamping system will work. What I'd really like is a piece of 10mm ali covering the entire base, which I'd drill and tap a grid of holes in to form a mounting/clamping system. Trouble is I don't have the facilities to machine this, and I don't want to pay to have it machined. So at the moment I'm imagining a piece of 18mm MDF slung across the corner brackets (see pic), which I'll then mount work on. But I'm really open to suggestions on this front...!
Incidentally at the moment z working area will be ~75mm, x & y - 450x300mm. Outside dimensions are 660x512.
A big consideration with this machine is making it simple enough that I can actually build it. I have an MDF router with the Kress that I can machine ali on pretty well, but thanks to the limitations of the machine it's SLOW! So I have to keep the amount of ali that I have to cut as small as possible to maintain my sanity, not to mention ensure I actually finish the thing. All the ali other than the box section is 10mm, btw.
The thompson rail is 600mm long - I don't really need that kind of z axis range! So I'm cutting it down to ~200 to get the range mentioned above.
One question someone may be able to help me with: sdp-si.com don't have the right length of gt2 3mm belt for my dual screw x-axis, so I'm thinking of using HTD 5mm (but may stick with gt2 3mm for the y & z). I know nothing of timing belts - does this sound like a sensible plan? Also on a related note, is it essential to allow adjustable tensioning of the belts? I.e. in solidworks I can specify my pulley diameters and let the belt length drive the position of the servo, creating a mount to match, which is what I've done. If I then buy said length belt, will everything work great, or should I make my servo position adjustable to allow adjustment of tension?
Comments and suggestions appreciated!
Instead of having your large Aluminum tubs forming a box. Why not have the Side pieces sitting on top of the end pieces. This will let you put any lenght of part thru the machine. Also instead of having to machine those special aluminum joining blocks you designed you could just bold them together directly. maybe with a flat reinforcement play, or right angle bolting plate. to make the joint stronger. This would also make it so that you do not have to create a mount for your lower servo. Again saving some work.
Speaking of belts. I dont know one way or another on the HTD 5mm. I am going to try some out to see if it has any issues. You do need to put in some way to adjust the tension of your belts. Without out that you will not be able to keep the belt tight, they will stretch very slowly over time.
Another thing about making the belts adjustable is that will make the belts much easier to install.
I figure making them adjustable would probably only help.
Something like this? I'd thought about it but dismissed the idea, but having done this version I'm now quite tempted...
I think the later is a much stronger design. That is basically how I did my first router. I used heavy guage steel angle iron on the bottom instead of tube. I used 2" heavy steel tube for the long direction. You could substitute channel for your long axis tube if you wanted. This would also make it much easier to bolt together. You would forgo having to cut the slots too. It would make it easier to maintain the screws as well.
Channel in this orientation won't allow much more debris than tube with slots.
If you already have the tubing, then I would go with the later design, but if you haven't bought it yet, consider steel angle and aluminum channel.
Yes, I've been working at it since my last post and have discovered a number of knock on benefits, including shortening the outside x dimension by 60mm without losing any working area. So I think this (or something like it) is what I'm going with.
One question is how I make the right-angle brackets that hold everything together. I could do it as per the attached pic, and I'm sure it would be very strong. But it would be easier if I could buy something ready made. Anyone know of someplace I could get something like this? Preferably in the UK. Can't be larger than 2" width, 3" height, and ~2-3" in depth.
You would not need any brackets if you used angle iron instead of tube. One thing I can tell you is that the design you just drew is not very strong. That is in relation to much larger fasteners on something like angle iron.
It would be okay for your size machine though I think. Just one heck of a lot more work for no return in structural strength.
Leeway, I don't think I really understand what kind of angle iron you're proposing - could you point me to a picture illustrating the kind of thing you mean?
Here is a link to my router build.
http://www.cnczone.com/forums/showth...2&page=1&pp=40 (Cutty Shark I)
In particular, here is an image that shows how I built my frame.