topic Re: Parts being milled have horrible chatter/rough cut in Machining Discussions Forum

Parts being milled have horrible chatter/rough cut

Anonymous — Wed, 27 Nov 2019 04:24:31 GMT

I’m running a 1/4” 2 flute flat end mill at 3000rpm and supposed to be 12in/min but at only 20% to not have it “chatter” it is contouring a part out of 1/4” aluminum cutting down 1/16” at a time. It makes horrible noises at full speed and looks like it’s tearing the aluminum rather than cutting it, I looked at chatter but that still looks smooth evenly spaced while this is uneven and torn looking. I cannot seem to figure out how to stop it. Please help. Full tool is what I’m hoping it is but any other ideas?

Re: Parts being milled have horrible chatter/rough cut

Anonymous — Wed, 27 Nov 2019 05:07:05 GMT

after pulling the tool and chuck out I notice they were both considerably hot, we are air blasting it(warm air). So could that be it, we are cutting aluminum.

Re: Parts being milled have horrible chatter/rough cut

lenny_1962 — Wed, 27 Nov 2019 13:36:38 GMT

What series of Aluminum are you cutting?

What is the cutter made of HSS, HSS Colbat or Carbide?

What type of CNC Milling Machine (table top or commercial) and its specks (max RPM and Feed Rates)

Are you using and coolants or machining oil besides air?

FYI, air should be ice cold.

Here is a website that will help you with speeds and feeds, calculates for production machinery, table tops usually aren't rigid enough for the numbers supplied. https://zero-divide.net/?page=fswizard# click the launch online tab.

I did it for HSS 1/4 2 flute

Re: Parts being milled have horrible chatter/rough cut

lenny_1962 — Wed, 27 Nov 2019 14:18:46 GMT

your setup looks like your part will be flopping around when taking the final cut and you may bend the pat if the cutter grabs the thicker section.

i would cut the end first then move the clamp to that spot the run the final cutout around the other 3 sides, rigid setups is the key, don't know home many times I've had to cut one area then reclamation over that to cut out the rest of the part.

I have a question where is the lab manager? He should be helping you with issues like this.

if you are going in when he isn't there you should stop by and ask him/her what and why you are getting these results and how to fix/resolve.

that is what I do in our student shop, answer questions and help make better parts.

Re: Parts being milled have horrible chatter/rough cut

Anonymous — Wed, 27 Nov 2019 17:51:11 GMT

You see I’m kinda the only one at my school who knows how to use that mill and the part is I don’t even know that well how to take advantage of it, yeah I’m gonna have to give my knowledge to the freshman and sophomores next year when I’m a senior, so yeah there is no lb manager, but thanks for the info, I will look into more clamps. Also I have it on a waste plate with tapped holes that have 2 screws per part and 2 clamps on the cut out, maybe that’s not enough?.

Re: Parts being milled have horrible chatter/rough cut

Anonymous — Wed, 27 Nov 2019 17:53:42 GMT

I think the combo of warm air, possibly shaky work, and incorrect feed rate. Also we have a commercial Bolton tools XQK9630Sits max spindle speed is 3000rpm, with a gsk980mda controller. I have no clue what type of aluminum... The tool is a Walden shaft hss flat end mill in a set screw collet. Also I forgot to mention that the shop room that the mill is placed in has kindly moved the mill so it has not been re-leveled.

Re: Parts being milled have horrible chatter/rough cut

lenny_1962 — Wed, 27 Nov 2019 21:13:26 GMT

this is what I would do....

Since 3k is your max RPM, 2 flute HSS cutter and not so rigid setup I would do the following.

Take a depth of cut @.03" and do an 2D contour with a finish pass of .01" at final depth.

Go buy some WD40 and spray it on the cutter and material and then also during the cutting, you should then be able to run fast passes @Anonymous ipm.

if you go deeper you'll have to lower the feed, which you have discovered.

How long are the flutes of the cutter, if over 1/2 that is also an issue, as the cutter is flexing too.