Steel Framed Router

[luke11cnc]

hello first

If you are using 25mm supported rails you will need box of 60mm and over

plus two ballscrews as to stop the bed crabbing

this is just the advice I have received as I'm by no means a expert

you may want to look at Jonathan's and chips CNC machine
James and Luke

[GTJim]

If you are using 25mm supported rails you will need box of 60mm and over
plus two ballscrews as to stop the bed crabbing
James and Luke

Hi Luke,
I have details of a fully supported rail that has a 21mm dimension across the base. I hope it is still available.
As for the crabbing, I was hoping by spreading the lower bearings apart as far as I did this may be avoided, but I will take the comment on board.

Jim

[Ricardoco]

Hello. I am hoping to design and make a router for hobby use just like many have done previously on this site, and I am currently putting together a concept and these are my current thoughts.
I am aiming for a working area of 1000mm x 1300mm (approx 3’x4’) and a Z of 130mm (5’’).
The main frame and gantry is currently 50x50x4 steel square hollow section with 25x25x2.5 bracing for the bed. This will be bolted together unless I find a good welder.



The linear rails are 25mm dia for the Y axis and 20mm for the X and Z, and hoping to use a 2510 ballscrew for the Y a 1610 ballscrew for the X and 1404 ballscrew for the Z. (hope I haven’t confused the X and Y).





I would appreciate your comments and constructive criticism as the design is easily changed at this stage before any serious money is spent. This is only a hobby machine and its main use will be engraving hard wood panels and cutting out the odd speaker panel.

Hi Luke,
I have details of a fully supported rail that has a 21mm dimension across the base. I hope it is still available.
As for the crabbing, I was hoping by spreading the lower bearings apart as far as I did this may be avoided, but I will take the comment on board.

Jim

Hi Jim, the design looks cool, I notice that the side bracing for the gantry is biased towards the spindle side of the gantry is this by design, IE is the Z axis and spindle going to exert a greater downwood force than the upward force generated while cutting.

Ive seen the crabbing or twisting of the gantry avoided by framework being added to the opposite side of the gantry to the spindle as in the commercial machines.

These are just observations and are not supposed to imply any knowledge or special wisdom on my part.

Oh and what software did you used to produce the pictures?

Rick

[GTJim]

I notice that the side bracing for the gantry is biased towards the spindle side of the gantry is this by design, IE is the Z axis and spindle going to exert a greater downwood force than the upward force generated while cutting.

Ive seen the crabbing or twisting of the gantry avoided by framework being added to the opposite side of the gantry to the spindle as in the commercial machines.

Oh and what software did you used to produce the pictures?

Rick

Rick, I am unsure about cutting forces but I was hoping to prevent the gantry flexing back and forth while cutting. I may also add a plate to the back of the gantry between the X axis to further restrict right or left deflection.
I just used Google SketchUp for the drawings as its quick.

Jim

[Ricardoco]

Rick, I am unsure about cutting forces but I was hoping to prevent the gantry flexing back and forth while cutting. I may also add a plate to the back of the gantry between the X axis to further restrict right or left deflection.
I just used Google SketchUp for the drawings as its quick.

Jim

I know its cheeky but can you send me an editable version of drawing two and i can modify it to show you what i mean..

[GTJim]

Rick, I've attached a zipped copy and hopefully it has worked.

[Ricardoco]

Rick, I've attached a zipped copy and hopefully it has worked.

Magic it worked fine, Be back in a mo..

Rick

[Ricardoco]

Rick, I've attached a zipped copy and hopefully it has worked.

Ok ive just done enough tinkering to give you an idea, of where bracing could do with looking at.

It may also be an idea to widen up underneath the table on the gantry just enough to stop the diagonal flex when the spindle is working at the far reaches of the gantry axis.

I built a table router very similar to this one some time ago and that is the only real problem area i had to re-think..

I would have put a double row but unless your stepper was on top it wont fit.. Good luck with the project i will be interested to follow your progress, its always nice to see projects from concept through to completion..

All the best Rick

[Jonathan]

The plate on the gantry to stiffen it is an excellent plan. I think you need to consider more how you are joining the box section, and gantry sides to bearings. Currently you have drawn the box section attached on just one face which is a bit weak.

I have done a drawing for you to illustrate how I think it can be made stronger:




That way the sheet reinforces the joints in addition to the general structure. I would be inclined to weld it for good measure. If not put plates (say 20mm thick) in the ends of the box section and bolt into them.

[JAZZCNC]

Jonathans suggestion is a good one not just for strength but also it protects the ballscrew from flying debrie.
If you must go with 1 screw done the middle then I suggest you make the cross piece that the ballnut fastens to wide as possible. you need strong bracing and width to counteract racking with a single screw.
Something like the pics below will handle just about most jobs at this width with a single screw. A 16mm 10mm pitch would work nicely.

Edit: The sketchs are rough quick knock up's and I would add some more corner braces to the cross piece but it should give you an idea of what I mean.

It probably looks a bit extreme but honestly it's not and the extra work and slightly more expense would be worth every minute and penny spent belive me.
Dont under estimate the forces's even with steppers.!! . . The forces can be extreme when cutting Ali and hard materials and the torque produced by steppers and ballscrews can twist and mangle a gantry built like this in the blink of an eye when the stick stuff it's the fan. :surprised: