Hi Everyone, I had posted this question the other day and it seemed like I duplicated the post, but when I tried to delete one of the messages I then saw my original post disappear before my eyes. I am going to try this again and see if I can understand better. This has to do with changing endmills from one size to another, I already ruined two pieces of aluminum practicing and I still haven't figured it out. If I do a X,Y,Z probe test with a 3mm drill bit to drill some holes, then I change to a 6mm (actually 5.47mm) end mill to do the roughing and make bigger holes etc. my question is do I use the same X0, Y0 position, then just do a Zero probe to get the Z position again? I forgot who had answered the question but since the post is gone I don't remember the answer. Also, if your endmill is supposed to be 6mm and you measure it and only get 5.75 do you put that value into the probe location and not use a 6mm as the value. Hope I am explaining things correctly because I am actually confused just typing this out. This is what I am trying to cut, the piece that I am cutting from is about 3" wide and 12" long. The position how this image is being displayed is the same position that I have the aluminum laid out on my machine its just 12" long to the right. Probing is an issue because in the OpenBuilds software you have to use front left as the default and I wanted to probe from the rear left. Maybe I can change it to front left tomorrow and see if I succeed. What advice can someone give me to make this cut (this is all new to me). I drill my (4) 3mm holes which is one job, then I load up another gcode without the (4) 3mm holes and I use the larger endmill to finish up the rest. Appreciate any help. Thanks.
You only locate X and Y one time. That will not change on your work piece. Each time you change tools, you must re-zero the Z position. I would use the actual diameter. I probe with a very precise 6.35mm rod. I do not use an endmill to probe if I absolutely need an accurate XY position. The reason is that the endmills have different measurements across them depending upon where you measure. I use that same rod whether I am using a 3mm endmill, or an 8 mm endmill. I measure every endmill and use the actual dimensions for that tool in the CAM software. That ensures I get accurate cut sizes. I measure with a digital caliper at the narrowest diameter of the cutting surface and then slowly rotate the endmill so it opens the caliper up to the size of the widest part of the endmill cutting surface. I do this because depending on where you measure across the cutting surface, the distance will vary. I figured this out quickly when I cut my first aluminum plate and all the holes were slightly undersized. I then measured my endmill which was supposed to be 3.175mm in diameter. It was only 3.12mm in diameter. It was a cheap Chinese endmill so I should have known to measure ahead of time.
Awesome information, thank you very much Giarc I am going to make a note of this so I will always have it on hand.
I should add that I will measure each endmill a couple times to be sure I didn't drink too much coffee and shaky hands gave me an inaccurate measurement while turning them in the caliper.
hahaha. I tried this last night with the endmill and it works pretty good, the measurements I can work with now. I will definitely be giving this a test again today and see what happens.
Giarc, I wanted to point out that what was confusing me and I just couldn't get it was if you change end mills to different diameters how in the world would your X and Y be the same distance. But once you explained that its all compensated for in the CAM program, now that makes sense to me and I totally get it. Thank you.
Thus - also remember: Be sure to use the actual endmill diameter in your CAM too to ensure the compensation (called the OFFSET) is correct - if you tell the CAM you're using a 6mm endmill, and its actually a 5mm, then centerline will be 0.5mm off the mark - resulting cut sized incorrectly too
