I have been trying to chase away the chatter I am facing with my machine for a while now but am having no luck. Posted are videos of the machine running and I will post my cut file in a follow up post as well. I am using Freud 76-102 bit, however this chatter and tearing is occurring with similar Amana DC bits, both both old and new bits alike.
I am cutting into Hickory in the above example but I am seeing this issue with walnut, oak, and even plywood (to a lesser extent). Parameters: 1/4" DC bit 12,000 rpm 0.125" DOC 2400 mm/min feed 600 mm/min plunge 0.1 mm chip load
Difficult to tell from the view angle of the video, but you seem to have a quite a lot of tool stick-out.Tool deflection will contribute to chatter. For slotting type situations, you will probably need to slow your feed rate down - Try 1200mm/min and 2mm DOC and see if it cuts more cleanly.
I will get it slowed down and see how it goes. I have the tool stick out where I do to reach the bottom of the bed.
I would do a finsih pass, slotting is always a problem since the cutt is cutting on both sides. For the roughing add 'radial stock to leave' (in Fusion360 terms) of about 0.2mm or whatever your software needs, you may have to lie to it about the cutter size. Then for the finishing pass I would try going the same direction (climb cut as you are now) and also going the other direction (conventional cut) and see what gives me what I want. in that segment where the bit is descending for the next pass, what is the finish like there?
Unsure on the finish in the desending area, I will cut a new part to test and report back. I use Vcarve for my cut files, I am running a seperate last pass of .003 inches (.08mm) for a finishing pass. Can you get chatter from a lack of engagement of the bit with the part? I can also test a seperate part with a conventional cut but in previous testing this tended to shift my chatter from the Y to the X axis.
I have been using ChatGPT 4.0 to help me setup speeds/feeds and it tends to push on the need to hit certain chip loads. ChatGPT is recommending I would need to run at 6000 RPM if I am running at 1200 mm/min which is impossible since the makita router only goes down to 10000. TLDR: My question, how much does chip load matter, and if so, does chatGPT's goal of .1mm make sense?
The curse of AI! It’s a starting point, but it clearly isn’t working for whatever reason, so you need to change something. It’s not a magic number - if your machine / tool bit isn’t stiff enough to take the load, then you need to reduce it. Different types of machining operations are limited by different factors - slotting, in particular is s demanding operation. Experimentation and building up experience with your machine and materials is the only way. Leave the RPM where it was, just reduce the feed rate and/or depth of cut. (Reducing the feed rate with constant RPM will reduce the chip load.) FWIW, my readyreckoner (based on my machine) suggested the figures I quoted above, based on 12000 RPM
I run the same doc and feed rate as you posted above but at about 16000 rpms and do not experience chatter. I do try to insert the endmills in as far as is reasonable for the material to minimize deflection. Because mine is not an industrial machine I use the recommended rpm/chip load as a starting point, but will manually adjust the rpms while listening to it cut. I can tell by the sound when I am getting chatter.
Thanks for the help. I just tested my machine at 12,000 rpm @ 1200 mm/min and at 17000 rpm @ 2400 mm/min, both of which eliminated my chatter and significantly improved my cut quality. Looks like the 0.1mm chip load was to high for the machine and it is better to shoot for 0.05 - 0.07 mm chip load. I have a few followup questions as well since I have figured out the issue. Giarc, I am sure this is something that will come with time, but is it possible for your describe what you are listening for when changing your RPM? I think I have a pretty good idea of what chatter sounds like at this point, but is it possible for the machine to not be cutting "enough" material? ChatGPT also mentioned watching for different chip formations, is this something I should be paying attention to and if so, are there any examples of what they should look like?
Glad to hear you're making progress Yes - you get things like scorch marks when cutting wood, or the cutter rubs and grabs intermittently. Always worth paying attention - as long as the chips look like chips (small curls rather than dust), then the cutter is actually cutting. The best thing to do is to spend an afternoon experimenting - push the feedrate; dial it right down; try deep and slow cuts vs shallow and fast, and home in on where your machine gives you the results you're looking for on the material you want to use.
