Multiple Routers?

[GalaticDan]

Hi,

I've seen that many commerical routers have auto. tool changers and that most peoples DIY CNC router has one head. I know shopbot offer the choice of a second head, if you selected there router option that would be 2 routers. Is there any big reason against say having 4 routers on my y axa with seperate z's ofcourse? (I know cost so don't mention it). I assume that theres no real neg's against have four and that most people have one because they're not concerned about time, bit changes and so fouth?

Dan

[diarmaid]

Im a complete noob at the cnc stuff so thats why Im asking this.

Will you need different software to be capable of running 4 routers simultaneously on the same machine, and is this the extra cost you mention? Sounds like the programming and entire setup would be much more complicated to be able to interface the 4 routers so they turn on and off, and move up/down as required, and also so that the computer can relocate the 'home' or 'zero' position repeatedly as required for each specific spindle when its switching between using the different routers?

Just a thought but maybe they are irrelevant, I dont know.

I think using even 2 routers mounted on the one machine would be a huge production bonus (Like maybe 100%!...400% for 4 routers etc etc ), but would be great to have.

[RASPNC]

I used to work with a cnc router that had 3 routers side by side. I think it was a Reichenbacher (German machine).

It was only a small machine aprox 1m x 1m table.
If I remember correctly the machine had its own operating system and there was an option to use more than 1 router at a time.

It could be used to machine 1 - 3 parts at the same time.
Alternatively it could be used with different bits in each spindle.

When a router was engaged it would move down the z axis, if one was not engaged it would sit at the top of its z axis but would still move in the x and y axis following the engaged router/s.

I did run into a problem with this machine, the leftmost router could not reach over to the far right of the table and same thing with the right hand router not reaching the far left of the table.

If you were to use 4 routers you may run out of room to mount them in the x or y axis.
You may also find that they can't all reach the whole surface of the table.

[GalaticDan]

Hi,

Thanks for your replies.

I was thinking that I'd use one router at a time and even use the same drive circuit and home/end switch circuit by adding a circuit to switch over the only set of position switch inputs and drive circuit using relays. Then have software control the state of those relays (4 TTL lines say) and ofcourse the servo/stepper drive disable line so to make a safe switch between any of the four router motors. Sorry guys I should have said because I mentioned that commerical cnc use auto tool changers, all I want to do is save time switching router bits and then leveling them. I counted 4 types of bits would do every job I wanted over a normal day and thought it would be great to see a multi headed router, just upload my GCODE and away.

You're right about the table area and routers not reaching the full table dimensions.

I've asked in the GCode forum if theres a specific GCode used to switch router heads. If this comes back with a negative then I still think that maybe a combination of Gcodes to move the Z axis in place and any other axis for centre alignment would be possible? Maybe some sort of simple GCode macro...

Dan

[datacop]

Ohhh...

4 routers ... in a revolver type mechanisim...

Tool change, spin the revolver on the Z axis to get the router in position for the tool you want to use..

that would be trick

[diarmaid]

That revolving mechanism would work great, no need to worry about positioning as when each router rotates into the 'in use' position the spindle should be precisely located where the previous one was.....but what about variations in the bit shapes and sizes...

I was thinking have the four in a line with the gantry large enough that it protrudes the width of the 4 routers out either side of the table. That way you keep your full table working area.

But the software would have to know how far exactly the four routers are from each other so that when switching from one router to the other it could move the new one into the perfect position to continue cutting. It would also thus have to be able to allow for different shapes and widths of bits on the different routers. Depending upon your tolerances these measurements would have to be pretty accurate, and the router clamps not allow any variation over time...unless you re-measured and set up the software each time b4 cutting. And of course as already said, each router would have to be moved up/down on its own z axis so they dont start cutting where they're not supposed to.

I just think it all sounds very complicated. But thats just me.

[ger21]

Shopbots don't use g-code, so they probably have some special codes to switch, or each router is it's own axis.

That's the easiest way, have one be the Z-axis, and one be the W axis for instance. The problem might be writing g-code, though.

Another option, if you use Mach3, is a function that Mach3 has that will swap the axis. So do as the previous example, and when you need to switch routers, have Mach swap the Z for the W. Then swap them back to switch again. All your g-code would use the Z axis, but you'd have to add the swap code in there somehow. You'll also need to do a work offset when you switch.

Our router at work has 2 independant routers, and one has a tool changer as well. It uses it's own special g-codes. Each router has a tool #, Tool 41 and tool 42. Tool 41 uses the changer, and is called tool 41/1, 41/2, 41/3 and so on to specify which tool.

[CNC Pro]

Depending on the size routers you plan to use, (i.e. laminate trimmer vs. 3-1/4 hp porter cable) the weight on the gantry might be an issue.

If the weight is not a problem, one solution if going with laminate trimmers might be something along the lines of turret type design like on a CNC drill & tap machine (Robodrill). A turret mount holding 4 (or more) laminate trimmers should only need 1 addition drive to control for indexing the turret, and pneumatics to disengage and engage the turret during indexing. This design eliminates additional linear rails and pneumatics (and the “work/head offsets”) typically seen on multiple head gantry set-ups, while still allowing full travel/access to the table. Also, you could design it to power only the router staged in the “down” position, thus simplifying controlling the multiple routers.

You’d still need to allow for tool length offsets, or make sure all tools were set at the same length.

[GalaticDan]

All sound good ideas. With regard to tool offsets, assuming the router is fixed firmly in position and doesn't move, can I just set these up once? Each new bit is simply a radus off center from each router so for arguments sake each router is on the y axis and spaced 1000steps apart (center to center), couldn't I issue a code to move that axis 1000 steps left or right to select said router?

I'll looking into that Mach function to swap an axis...

Also thought about router life and as my router has a duty cycle so while it's cooling down another could be in use?

Axis weight. Yes this might be a problem, I'm thinking of using some rails I've collected over the years, German made star linear 25mm which are simlar to THK HSR 25's for the y axis. However for my X axis I only have 3metre lenths of THK SSR15's which would have to support the huge Y axis. Do you think this a problem?

Dan

[Rance]

Originally Posted by GalaticDan Each new bit is simply a radus off center from each router so for arguments sake each router is on the y axis and spaced 1000steps apart (center to center), couldn't I issue a code to move that axis 1000 steps left or right to select said router?

Probably what you are referring to above... Get lots of table space and just move your work (1000 steps over) to a different router which contains a different router bit. To combat gantry weight, make it a moving table. Unfortunately, the above makes your table 3x a normal table (for the 'Y') and 2x a moving gantry (for the 'X'). If you can live with that, then build it. Design & build to YOUR needs.

[CNC Pro]

All of the multi-head machines I’ve worked with allow for adjustment of the head spacing. While this should be a “one-time” event, my experience has shown (especially with multiple operators) that adjustments are sometimes necessary (i.e. crashes).
One benefit to the spacing adjustments is the ability to space the heads to accommodate cutting with multiple heads at once on smaller parts, in essence “ganging” the heads.

The weight issue can sneak up on you. Once you start looking into the main Z- plate, and the extra linear slides and pneumatic cylinders for each individual head. Typically a counter-weight of some sort is used to ease the burden on the z-axis motor lifting the additional mass (again, additional weight).

[GalaticDan]

Not possible because of space and machining dimension requirements. I was really hoping for a fixed table with moving gantry - maybe I'll have to think again.

Dan