Auto Tool Changer Realization...

[rb99]

I think everyone who owns a CNC router probably has dreamed of an auto tool changer for their machine. But I thought about something...
If you have an 8 tool changer, every time you level the spoil board you have to re-zero all the tools. At least all the tools you are using. So if you are not a heavy user of multiple bits, you could wind up zeroing more than if you didn't have the tool changer.

Is this correct?

[kubotaman]

No you are incorrect. The table has nothing to do with zeroing the bits. The bits are calculated to each other. In other words all bits are calculated and zeroed off a spot on the table that is not moved or cut when the table is surfaced. It is set below the table surface. All bits are then calculated from that spot in relation to each other. When you want to cut something you then only have to zero as normal. The program then knows where all bits are in relation to each other. On the 8 bit holder you can easily make it into a 10 bit holder. I have done this 3 years ago or so. It is an expensive add on but it is nice.

[rb99]

So you zero the first bit (after the initial zeroing of all bits as you say) then all the other bits zero internally to the set zero from the first one?

What about bit wear or does that not factor into it?

How much are they?

[gundog]

My machine starts with a homing routine at start up it will not do anything until this homing routine is ran. The homing routine uses the limit switches on all 3 axis. This gives the machine an absolute measurement that it refers to for all the offsets. You can set zero on all 3 axis anywhere on the table within the travel of the machine everything is relative to that absolute position the machine uses off the limit switches. You only need to zero to when changing one of the axis locations but it stores the tool offsets relative that homing position at start up. There is a tool height switch that you pickup the tools one at a time and it touches off with a tool height command my machine has a 10 tool changer and it stores these tool offsets until you run the tool height command again for that tool. You do not need to set the tool offsets each time you use the machine unless you change tool bits. My machine is not a shopbot but I believe they all work pretty similar with just small differences.

The tool changer is great compared to changing tools and has less chance for error so to me it is better for not just speed but accuracy.

Mike

[Brady Watson]

...The homing routine uses the limit switches on all 3 axis...My machine is not a shopbot but I believe they all work pretty similar with just small differences.


Pretty much the same for SB ATCs.

ATCs are great if you need them for production. They pay for themselves in short order.

I prefer a non-ATC for my day to day work and don't mind changing tools.

I believe it's roughly $15k to upgrade to a toolchanger if you A) own a PRS and B) own an Alpha model.

-B

[Gary Campbell]

"If you have an 8 tool changer, every time you level the spoil board you have to re-zero all the tools."

Not true. The tools are measured to the tool measure device, which is usually a conductive plate, mechanical switch or inductive device. The measurement is taken from the highest point of Z travel (Table Coords Z zero) and stored for each tool. The distance from the tool measure device to the table surface is also stored and needs to be changed each time the table is surfaced. Tools need not be measured unless they are changed.

If you have an ATC and have a few extra minutes you can add code to the surfacing routine that adjusts the tool measure offset after each surfacing. This assumes the surfacing bit is a measured numbered tool.

Assuming you design with Z zero plane at the table surface (bottom of material), you NEVER have to use a ZZero plate to zero any tool. This is the preferred and most common methods with experianced ATC users. IF by chance you need to run a file with ZZero on the material surface you need to zero only one (any) tool. This material offset is applied to all tool lengths.

The tool measure device can be above or below the table surface, doesn't matter.