Steel Framed Router

[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

[GTJim]

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.

All the best Rick

If I was to mount a plate (as shown in pic) to the back of the axis with many fixings would that stiffen up the gantry sufficiently?



The current design supported round rail, but this was down to cost and if available I would use profiled rail.
I also think the 25mm ballscrew is OTT but now that it has been mentioned I'll look at 20mm with 5mm pitch with pulleys and belts. I am concerned about whip in the 16mm screws, but again it could be a saving.
I am hoping to use a single ballscrew on each axis but if I find problems I think it would be easy enough to add an additional one, so I'll look out for a 4 motor and driver package.
Never thought about resonance, but kiln dry'd sand could be a good solution.

Thanks for all your input and please feel free to continue.
Jim


I can see this becoming a bit of a monster and it has to fit in my garage with all my junk.

[GTJim]

Just a couple of more sketchs showing potential positions for ball screws and motors.




Keep the comments comming as I will be buying materials soon.

Jim

[Ricardoco]

:confused:

If I was to mount a plate (as shown in pic) to the back of the axis with many fixings would that stiffen up the gantry sufficiently?



The current design supported round rail, but this was down to cost and if available I would use profiled rail.
I also think the 25mm ballscrew is OTT but now that it has been mentioned I'll look at 20mm with 5mm pitch with pulleys and belts. I am concerned about whip in the 16mm screws, but again it could be a saving.
I am hoping to use a single ballscrew on each axis but if I find problems I think it would be easy enough to add an additional one, so I'll look out for a 4 motor and driver package.
Never thought about resonance, but kiln dry'd sand could be a good solution.

Thanks for all your input and please feel free to continue.
Jim


I can see this becoming a bit of a monster and it has to fit in my garage with all my junk.

Ok let me show some diagrams..


With no load and Spindle central this is the look of the machine from above.


Now cutting brings in to play these forces and consequences.

As the others have touched on instead of using 1 screw in the center if you use 1 on each side that will sort it out but at the end of the day it is all down to cost and accuracy. if you take the above examples and apply them to the other two axis you will see the weaknesses in your structure at the time of design not when you have spent the money, most of us on here have been through the building process and made the mistakes for you...:whistling:

BUT. my first attempt at building a machine was flawed and at the end it was not accurate but it was cool looking and i played for hours with it just amazed ide built it and to me for that split second it was PERFECT!!

then i took it to pieces and joined this forum... the rest is history...

""MOST"" of these guys on here really do know their stuff, but dont just settle for one opinion get lots of opinions and you will soon see the way or be extreamly confused :confused:


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.