This is my first CNC build and it works pretty well in my opinion. Thanks Ryan for this awesom machine!
Data of my build:
Newest version from dezember 2018
25mm conduit with 2mm wall thickness (very stiff!)
600x800x110mm workarea (with this thick tubes it is still very stiff!)
Belt tension looks good (no bass-guitar-string and not loose)
everything is quare and snug tight
Katsu (Makita clone) router with massive mount (https://www.thingiverse.com/thing:1652878/files)
CNC shield with arduino uno and Estlcam Software
https://www.thingiverse.com/thing:1652878/files
First cuts where pretty nice. good sizes and good "roundness" in normal plywood with a 4 flute 4mm cutter. A bit gets a bit hot but I think its normal because of the low X/Y Speeds and the high RPM.
First I checked some other videos and posts from people who cutted PC with goo results. Many of them did this job with a 1flute cutter, low spindle speeds, low Z axis and high X/Y speeds (up to 1000mm/min).
I tried a first cut in a sheet of PC with 800mm/min, 1,5mm Z Axis and 10000rpm and it get a nightmare! The whole machine was shaking and nearly my router bit broke appart. The router bit (4mm) made a hole with nearly 20mm diameter!
I tried a second cut with PC. 200mm/min, 0,4mm Z Axis and 12000rpm. It gets better but not good - the machine was still shaking a bit and the 4mm line of the router was about 4,5-5mm in some areas.
I tried a third cut with PC. 200mm/min, 0,4mm Z Axis and 14000rpm. It gets better but still not good. The machine was still vibrating a bit but the result was ok.
Why is my machine vibrating this hard with a standard 1 flute mill? All bearings are on the rails and everything looks and feels fine - but if I push the machine to more X/Y speeds the machine vibrates so hard that I have the fear that something gets loose...
You went from 13.3mm/s to 3.3mm/s I bet the speed you want is in between those two numbers. Your router looks to have variable speed, start it in the middle, use 6mm/s and vary the RPM to try and get a good cut, start with 2-3mm DOC you should be able to go much deeper when you get it right. Too fast RPM (or too slow travel) and the chips will fuse melt and make a mess, too slow RPM (or too fast travel) you will break your bit or material.
Poly and acrylic are almost as speed sensitive as aluminum numbers need to be spot on. Do you have any HDPE or any other softer plastics you can get some cuts in first?
thanks for your fast help. I tried soft plywood with the single flute and the shaking happend as well…
I will try to get some deeper cuts into the PC with 2mm DOC and start with high rpm - if it works i will slowly reduce the rpm till it “whobbles” / I feel some vibrations.
A couple of minutes ago I tried to go with 5mm/s, 1,5mm DOC and higher RPM. I used a 4 flute/6mm. In my opinion I had a good result… (see picture attached)
but why does it shake so hard with a 1flute and „softer“ settings?
I never had any luck with those 1 flute cutters either, they were always vibrating a lot. But other people had good experiences with them so I never assumed they were the problem, it was definitely an issue with my machine or my feeds.
My guess at the time was that my Z axis wasn’t square to the work surface, maybe you should check that.
Single flute is great, maybe that one is a bit funky. I use these with great success. It is amazing just how good these are for $1.50. I have cut pounds and pounds of aluminum with these on a different machine. And by piles I mean production run style jobs so hours of cutting day after day. Granted that performance is only achieved with a mist.
My guess at the time was that my Z axis wasn’t square to the work surface, maybe you should check that.
I measured the Z axis and I have a angle of 89,05° instead of 90. But could this be the reason? How can I adjust the angle of the z axis?
Single flute is great, maybe that one is a bit funky. I use these with great success. It is amazing just how good these are for $1.50. I have cut pounds and pounds of aluminum with these on a different machine. And by piles I mean production run style jobs so hours of cutting day after day. Granted that performance is only achieved with a mist.
These look really different to my single flute... I have the theory, that my single flute is not that well for a machine with flexibility like the MPCNC. My single flute has its edge on one side and the rest of the tool is way smaller than the diameter of 4mm at the cutting edge... This means, that the cutting edge cant shore up on the rest of the material of the miller 180° behind the cutting edge. This can cause vibrations with flexible machines. What do you think of this theory? (hope you understand what I mean?)
The single flute miller in your link have materials behind the cutting edge so this will shore up the force from the cutter…
Ahh, I see now. That’s a drill bit, not an end mill. Look down at the questions and answers, the seller says it’s not for cnc machines. Try something like these.
Where I work we cut PVC it’s similar cutting and we have on occasion done pc. Single flat wood bits are not the same as single flute plastic bits. Two flute are often nicer cuts. Amana makes a good variety of plastic bits. I’m sure there are others but their quality is good. Most of the time they have recommended speeds and feeds for various plastic for a particular bit.
Ahh, I see now. That’s a drill bit, not an end mill. Look down at the questions and answers, the seller says it’s not for cnc machines. Try something like these.
i tried a new bit and it worked the same way as before...hard vibrations and i dont know what to do next...
I made video - take a look at it and you will hear the vibrations.
Every machine is slightly different. Different plastic, different tubes, different router, different sizes. That’s why you can’t really share gcode for cutting. Use the settings as a good starting point, but you’ll need to adjust them to your machine. Plastics, especially acrylics are hard to mill. As you’re seeing, they’re grabby. That’s why I suggested trochiodal cutting. It lessens the forces on the end mill, and makes the slots larger to allow better chip clearing.
Also note that that you are doing 50% faster moves and 20% faster bit spinning. In order to match his you need to slow down to 20% less than 800mm/min, or 740mm/min.
