How Much Chatter Is Acceptable?

M

Metalshop

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I am new to machining. I ran a few parts and was getting help on the Fusion 360 Cam forum to improve the bottom finish.

Someone with lots of experience noted that my parts seemed to show chatter on the edges. Is this amount of chatter normal for a PM-833? The person who commented has very high-end machines. They thought that my spindle bearings may be no good. Please let me know your thoughts as this is the first part I have ever made and have absolutely no previous experience.

20221231_083104.jpg

Thanks… Richard
 
Thanks... This is all new to me so I have no benchmark. I think I will try this with a 1/2" end mill as opposed to a 3/8" next time.
 
Welcome aboard!
It would be easier to evaluate and suggest changes to your setup if we knew the work piece material (looks like aluminum) and size, spindle rpm, feed rate, end mill type and number of flutes, cutting fluid if any and how the work piece was held for machining. Details matter. ;)

Tom
 
Thanks Tom. This was machined on a PM-833TV that I just finished converting to CNC. It is the first part completed on the machine. The material is 6061 aluminums. It was machined with a 3/8" x 1 x 3" 3-flute YG1 Alupower end mill in an ER20 collet. I used a Fog Buster with Durakut. The piece was held in a 6" vise. The part measures approx. 2 x 4 x .75" thick. The contour was machined at 3000 RPM and 7 inches per minute. I calculated the feeds and speeds fusing the G-Wizard calculator since I have no previous experience. For what it is worth, I machined this piece as part of a 10 pieces online course "Titans Of CNC Learning Block Series" so I could learn CAM.

Here is a link to the Fusion 360 file if needed:

Dropbox - File Deleted - Simplify your life

www.dropbox.com www.dropbox.com


Thanks.... Richard
 
Metalshop said:
Thanks Tom. This was machined on a PM-833TV that I just finished converting to CNC. It is the first part completed on the machine. The material is 6061 aluminums. It was machined with a 3/8" x 1 x 3" 3-flute YG1 Alupower end mill in an ER20 collet. I used a Fog Buster with Durakut. The piece was held in a 6" vise. The part measures approx. 2 x 4 x .75" thick. The contour was machined at 3000 RPM and 7 inches per minute. I calculated the feeds and speeds fusing the G-Wizard calculator since I have no previous experience. For what it is worth, I machined this piece as part of a 10 pieces online course "Titans Of CNC Learning Block Series" so I could learn CAM.

Here is a link to the Fusion 360 file if needed:

Dropbox - File Deleted - Simplify your life

www.dropbox.com www.dropbox.com


Thanks.... Richard
Click to expand...
What did you do to convert it to CNC? I was planning on doing this but then Heavy Metal CNC had the tragedy and closed shop days before I placed an order. I have not found a replacement (and while I am willing to try building most of the stuff myself it would be nice to have some pointers).
 
I have seen some pretty amazing things accomplished by some of the members here. It's impressive to see some of the cnc conversions. It hurts to hear someone try to compare them to a hundred and fifty thousand new milling center. Anyone can make good parts off of that. It take talent to make good parts off a less expensive set up. The same as as good machinist making good parts off of old manual machines. Would like to see pictures of your set up.
 
First part? Rriiiggghhhht. Have you other (sans-CNC) machining experience?

Looks good to me. I'd be proud and I've been doing this since 1972.
 
I would be very proud of that part if it were mine. The interior contours look perfect. That little bit of chatter on the outside certainly looks like a feed/speed/cutter "issue," although it is nearly perfect.
I think it might just be a matter of adjusting your feed see what happens. I am not sure that going down in cutter size is going to help.
 
Thanks for the kind words & encouragement.... Very much appreciated :). I really have no reference point to know exactly what these parts should look like.

In response to your questions:

Rodneyk: I sadly purchased the last CNC conversion kit from Heavy Metal CNC. Trust me, you should be glad that you did NOT. The kit was a total mess. Here are the details and hassles of my conversion: https://forum.drdflo.com/t/another-pm-833tv-conversion/307
The good news is that Dave Clements from Arizona CNC kits is just about ready to release a kit for the PM-833. His kits are of far better quality. here is a quick video about the new kit:
Dave really knows the fine details of these machines. If you do this conversion, I made dozens of 3D printed parts for this conversion and I would be happy to share them with you. Please feel free to reach out.

Nutfarmer: I don't think the gentlemen on the Fusion 360 CAM forum was putting down the part in any way. He was very helpful with my toolpaths. He noticed the surface finish and was concerned that my spindle bearings may be bad. I don't think he has any experience with smaller mills. Thanks for your complements! I have included an image of the mill with this part in the vice.

T Bredehoft: I never touched a milling machine in my life before converting this machine. I spent most of my life doing woodworking as a hobby. Two years ago, I gave up my woodworking due to shoulder issues (4 surgeries in the past 40 years). I watched a YouTube video of a CNC conversion and thought.... Great....Let those stepper motors do the work so my shoulders don't have to... I spent the last two years researching and building this conversion and learning CAD and G-Code. Thanks for you compliments.

7milesup: The contour of the part was machined with a 3/8" end mill. I was thinking of using a 1/2" end mill in the future to possibly decrease chatter. The online class I am following used a 1/2" end mill, I just happened to have a 3/8 on hand.

Again... thanks for all your nice words. The Titans Of CNC building block series is a free online class. I think it has been extremely helpful for someone starting from nothing. They have several other classes as well. The only challenge I have is that it is aimed at teaching someone to become an apprentice machinist at a large shop. For this reason, all the speeds and feeds are targeted at large production machines. I am doing my best to use the GWizard calculator to adjust my speeds and feeds for a 2HP machine.

20221222_125010.jpg



Here is my second part. Just finished it yesterday.
20221230_202831.jpg




Thanks again... Richard


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