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Author Topic: Bit diving when doing tabs  (Read 5746 times)

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Bit diving when doing tabs
« on: March 05, 2012, 07:50:25 PM »
Hello folks,
I am having an issue whilst adding tabs to a job. A "standard" scenario would be simply cutting out say, a 2" circle out of 3/4 MDF. I add the tabs via LazyCam, usually 4 of them at .4" wide and .125" high. With a 1/4" bit, the tabs are left just a bit wider than 1/8" (.15) which seems to be about right. In a "just chunk it out" cut, I would be doing the cut as (3) 1/4" deep passes.

The issue is that, during the first pass at cutting the hole out (first pass, at 1/4" deep) the machine "dives" down to cut the tab. After passing the tab, the bit is raised back to the 1/4" depth and the cut of the circle continues. As the next tab is reached, the cycle repeats. So far, in MDF and with a fairly slow feed rate, the bit and router have handled this sudden 5/8" deep cut. I would like to remedy the issue however.

My machine and build updates can be found here:
https://sites.google.com/a/rocketbrandstudios.com/rocket-brand-studios/cnc-project

I appreciate, in advance, your time.
Re: Bit diving when doing tabs
« Reply #1 on: March 05, 2012, 08:22:27 PM »
 :)
Check the "Plunge Speed" for your selected tool.
Adjust if necessary.
Russ
Re: Bit diving when doing tabs
« Reply #2 on: March 05, 2012, 08:35:15 PM »
Alas, it is not the speed at which the "dive" happens that is the problem. It is the fact that the machine is not waiting until it gets down to the level of the tabs before milling them. The tabs should be milled during the last pass of the cut --During the pass that, when finished, will release the part from the stock.
Re: Bit diving when doing tabs
« Reply #3 on: March 05, 2012, 08:58:27 PM »
Oh, I see.
So, do you have the "Max Cut p/pass" set correctly ?
Re: Bit diving when doing tabs
« Reply #4 on: March 05, 2012, 09:08:56 PM »


The issue is that, during the first pass at cutting the hole out (first pass, at 1/4" deep) the machine "dives" down to cut the tab. After passing the tab, the bit is raised back to the 1/4" depth and the cut of the circle continues.   

This is a bit confusing as the TAB process actually LEAVES the tab, doesn't CUT the tab.
You should get 3 passes similar to the attached pic.
Russ
Re: Bit diving when doing tabs
« Reply #5 on: March 05, 2012, 09:28:11 PM »
Yes, the tab is indeed being left, but the material above it must be removed. The issue is that this material (all of it, down to the top of the tab) is being removed during the first pass resulting in the "dive". Enclosed is the tool path that will explain a lot, I think.

--I am just getting used to the in's and out's of this forum. The photo is hopefully attached properly, if not a direct link appears below.

https://picasaweb.google.com/101426164395172997809/March52012#5716604927190850690

Re: Bit diving when doing tabs
« Reply #6 on: March 05, 2012, 09:39:39 PM »
Hmmm .. that is weird. LCam might not be to blame for that, never saw that before, could be something in the DXF ? ? Care to post it ? Is it ACad VersionR12 ?
Did you CLEAN and Optimize the dxf after loading it ?

To attach files, use the REPLY button, not Quick reply.
Re: Bit diving when doing tabs
« Reply #7 on: March 05, 2012, 09:50:45 PM »
Gotta be coming from LazyCam. The original DXF is via InkScape and is designed as if it were 2D --Like you were going to run it through a laser cutter. All depths, pockets (if there were any), passes and tabs are all done in Lazy. I can post the DXF if you like, but there is nothing special there at all. I can draw a square with a circle in the middle and replicate this issue each time. Oh, and yes, the bit information is spot-on --Depth per pass, feed rate etc. all are correct during the normal milling process. This "dive" is at a depth greater than the "max cut" I have set for the bit.
Re: Bit diving when doing tabs
« Reply #8 on: March 05, 2012, 09:51:31 PM »
Oh, and yes --I do a clean right after the DXF import.
Re: Bit diving when doing tabs
« Reply #9 on: March 05, 2012, 10:00:43 PM »
Lazy Cam can be a real pita at times. I'm getting mixed results with a few simple files here now too. I agree, probably not your drawing.
After multiple attempts at various functions LC has been known to continiously get more and more out of whack.
Many have given up on it. I still love the challenge but it often beats me. RICH is expert at it, I hope he can help you.
He should be along. There is a good manual but doesnt go too deep into tabbing (like your bit does lol).
You might just try shutting down and restarting...for the heck of it.
Other than that, I wish you the best of luck , and will watch this post for the solution.
Wish I could help,
Russ