Z Axis Height question?

[redbaron]

Just getting some advice here.
What height is your Z- Axis?
4" , 6" , 10", 15", 15+"

What's the limit if any? (Torque, flex, etc.)

Is the actual height of a cut limited by the endmill length?
ie. If I am using a 6" end mill, then the maximum depth of cut I could make is 4-5" for fear of the router hitting the work - correct????

Thanks for your help. Total Noob here!!

[Ken_Shea]

RedBaron, lets get you started at least in filling in some of the blanks.

There are so many factors in your question it is hard to know where to start but here are a couple of points and hopefully others will add their 2CW.

Keep in mind that the higher your Z axis goes the greater the importance of building to insure that the Z axis is perfectly perpendicular to the table, if it is off at 1" height the error will multiply as it is raised.

The higher you go the more rigid the construction needs to be.

Depth of cut is the amount of material that is removed while cutting. I think you are referring to "Tool Length" which is something all CNC machines need to know prior to cutting, this is the distance from the tip of the cutter to the top of your part you are machining. I know from personal experience what it does when you overlook this step

You will have a great deal of trouble finding a 6" end mill in the sizes that will fit routers as the longer it is the larger the diameter it needs to be otherwise it will simply flex and break.

In reading so many of the post here at the CNCzone it seems that most Z axis heights are around 6" or so even less.

If I am using a 6" end mill, then the maximum depth of cut I could make is 4-5" for fear of the router hitting the work
While your terminology may be incorrect you are essentially correct, the length of the cutter itself, the tool holder size and how close the surrounding material's walls are to the above all play a role in how far the cutter can reach into your part.


Well here is a start for others to add to.

Hope it helps a little.

Ken

[High Seas]

redbaron
Take a quick peak at the advert at the top of the page (The 4x8 CNC Router Plans). Note the "height" of the gantry? In that design, the gantry rides on "High Rails." You'll note its is a pretty stout layout and should be plenty rigid all welded steel and all. With a similar design you could have even greater clearence below the gantry, but then need to get the tool to the working surface. This means a longer z axis and may add weight and cost to the system you may not need. (Although, this added height could be later filled in with a rotating axis - adding complexity and heaps of extra capability).

My second system is similar to the one I refered to, and has an honest 10 inches under the gantry and 7 inches more to raise it, if and when I need/want too. I am using a laminate trimmer (porter cable) and the z axis is plenty rigid, but am limited to 1/4 inch shank tools for now. Water any muddier? Maybe I've stirred it up a bit.
Jim

[buscht]

redbaron, I suggest you design your Z axis, even the entire machine around your anticipated usages. The advice given above is very good.

If you are cutting balsawood for RC airplanes, a Z axis of 1" may be alright. If you are carving fireplace mantles, you may need a Z axis of 8".

The cutting length of your router tool and the Z axis height aren't always dependant upon one another.

You should probably figure out what the range of thickness that you want to cut are, add in the maximum cutter length, and an inch or two for clearance and that's you Z height.

Personally, my machine has a Z of 6". I want to be able to clear a rotary indexer, but my parts are rarely over 2" thick.

Also, just becuase your router bit is only 1" long, doesn't mean that you can only cut 1" thick parts.

Imagine a bowl with a gentle curve. By working your way down the curve, you can cut the inside of the bowl with a 1" long router bit. But you may need a Z height of 4" to be able to reach the entire bowl.

T

[ger21]

I designed mine to have enough travel to reach the table with the shortest tool I would used, and to lift high enough that the longest tool I would use would clear the bottom of the gantry. Keep your gantry high enough to clear the tallest part you plan on cutting. This will let you cut thin sheets with small bits and still cut thick pieces with long bits.

Gerry