Clamping question (photo attached)

[windcrest77]

I have a question on the photo attached... My job will be cutting 6 parts out of the 12 x 12 piece of .125 aluminum sheet. This sheet is crazy glued to masking tape applied to my spoil board and the underside of the aluminum plate. The spoil board is then clamped at each corner to the machine. The crazy glue with masking tape for clamping down aluminum is apparently all the rage with machinists these days. Assuming my job is working only within the confines of the 12 x 12 aluminum plate and assuming between tool changes the machine wont be bringing itself to machine home (that it will just leave the spindle where it last was or bring it back to "work" home).



Do you see any danger in the spindle hitting any of my 4 clamps here? they are well away from the work but I wanted to make sure before I run the tools (I will need 3 tool changes).

Attachments:

[Chad]

You should be fine...

Normally the machine would jog to the new location with the Z-axis elevated fairly high based upon internal safe heights.

Then when the job is done, again depending on settings in the controller...it should just shut down and raise up. It should not be going back HOME...by default they are not programmed this way, but it is an option.

[toddd]

Interesting, I was going to reply that he was safe because the machine returns home at the end of running each file as mine does this, I did not know this is not a regular feature

[johnb]

Aug 4, 2020 10:41:44 GMT -5 toddd said:

Interesting, I was going to reply that he was safe because the machine returns home at the end of running each file as mine does this, I did not know this is not a regular feature

My AR-16 Elite returns home after the job ends (by default) as well.
When starting the job from "Home", it slowly moves down to the programmed Safe-Z height as it travels to the start point of the job. If this height is lower than the top of the clamp, there could be a problem.
There have been times that I thought it was going to hit a clamp on the way there (but it didn't). I kept my hand poised on the e-stop button.
Presumably, if it doesn't hit the clamp on the way to the job, it won't hit it on the way "home" either, but I've never run a job where it finished cutting (very) far from where it started, so that may not be the case.
You might consider "running" the first part of the job with no bit, starting from "home", then place your clamp where you know it's completely out of the path from home.

[windcrest77]

Thanks guys/gals,

It turns out by default my Iconic 4 "forgets" "machine home" once you give it a "material home" and run all your tool paths which is good! At the end of each tool path my spindle simply stays where it last was x/y but raises the z up all the way and stops. I finally had time to cut this piece today so my son snapped a short video of two of the tools. Tool one was simply a 9/64 twist drill so the parts can be mounted with 6-32 hardware. And the second tool was a 1 flute .125 for-aluminum-helix angled end mill. The drill bit needs to be run slow I think it was around 3,000 but 2,000 would have probably been better. But I was getting curly cues and not chips of aluminum. I did find out that the Vectric software has a bug computing the Z depth when using twist drills. If you puck off a twist drill Z the very tip touches off, but a twist drill has a 135 degree point, so drill paths by nature must be set to drill way past the thickness of the material. Vetric has no parameter for the tip angle. Since the hole bottom is V shaped you have to drill past where just the tip pops through the other side. So as a tip when using twist drills just set your material thickness thicker, it will spoil your spoil board but drills are not flat like end mills are.

Here are some videos, I'm making eight aluminum mounting plates to mount some large motor run capacitors in a chassis out of this piece of .125 6061 aluminum: One video is the 9/64 hole drilling and the other is cutting out a part shape:

photos.app.goo.gl/MZAhxRrHLXtjDCiWA

photos.app.goo.gl/joYvCaU22D3VDBPi8

I'll post more videos if they are of interest. My next problem is I want to bend .125 aluminum plate at a perfect 90 degree angle, it is nearly impossible to bend .125 aluminum straight and clean without rupturing the surface, and no hope of getting it bent square and at exactly 90. So I was going to CNC a slot on the back side and chamfer it with a 90 degree bit, leaving only 1/32 of an inch of aluminum below the slot, then when I bend it it should both bend easily and at a perfect 90 degrees and also at exactly parallel to the other sides. Hope it works.

[johnb]

Chris

I don't know that I'd call what you have encountered regarding the twist drill bit depth a "bug"...it's just a consequence of using a tool (the twist drill bit) that was meant for something else (other than a CNC machine) for a "different purpose". Many people have commented here and there that they get "better holes" by using an end mill with a diameter smaller than the desired hole and ramping it in to "spiral cut" the hole from the inside out. You'll still need a little over-depth to clear the burrs at the bottom of a through-hole, but nothing like what you need with a 135 degree tip on a twist drill...and the twist drill has too many flutes to work effectively in aluminum or brass.

[windcrest77]

Aug 10, 2020 19:33:12 GMT -5 johnb said:

Chris

I don't know that I'd call what you have encountered regarding the twist drill bit depth a "bug"...it's just a consequence of using a tool (the twist drill bit) that was meant for something else (other than a CNC machine) for a "different purpose". Many people have commented here and there that they get "better holes" by using an end mill with a diameter smaller than the desired hole and ramping it in to "spiral cut" the hole from the inside out. You'll still need a little over-depth to clear the burrs at the bottom of a through-hole, but nothing like what you need with a 135 degree tip on a twist drill...and the twist drill has too many flutes to work effectively in aluminum or brass.

For all holes under 1/4 inch in aluminum I'm using newer Cobalt twist drills with 135 degree point. A guy on ebay sells these by the dozen per size, great bits (ebay drill hog). For all those small screw mounting holes the quality is better than an end mill and the time to drill out 30 or 40 screw mounting holes is reduced by a factor of 30 or more over using a small end mill with 3 passes! That alone is worth it, not to mention less wear and tear on the machine as its just a Z plunge at 2400 RPM or thereabouts. Twist drills are a perfectly normal tool for a CNC of any type, but you do have to account for the tip angle because Vetric forgot to do that.