My CNC vibrates
From investigation to problem solution
I had a request to cut and engrave high pressure laminates. These are a lasagna of compressed paper and melamine resin, coated in a thin layer of (colored) melamine. HPL is really so durable that it’s even taken for facade planking. It is dishwasher safe and some variants can be heated to 200°C without taking any damage. You can find HPL as boards on playgrounds, garden tables, as panels in the tram etc. So I was like “cool stuff, let’s get started!”
I used the cutting data recommended by a couple of websites with values for “hard wood”.
2-flute upcut wood carbide endmill, speed of cut
450m/min
, 6mm
, Z+ 6,5mm
, S24000rpm
, F3500mm/min
, full slot, climb milling.
And I was alarmed by the way the cut looked when I was done. Here are the symptoms:
First, I checked the spindle. No overheating, still tightly clamped to the portal milling machine, no bearing clearance, endmill securely fastened. Then I thought “Maybe something is wrong with the portal? Can I bend it?” No, I couldn’t. Then I looked at the endmill.
It didn’t look good at all. The cutting edges were practically gone where they had touched the material. Strange. It was brand-new when I started the job and it didn’t even run for 20 minutes.
I did some more research on the internet. HPL is incredibly hard and tough. To compare some values (Brinell-hardness):
I have found some recommendations for cutting HPL like “Carbide endmills should have a cutting speed of up to 150m/min
” and “Use diamond-hardened cutters or 1-flute ones that are optimized for Aluminium”.
To correct things, I just did all cutouts again at finishing settings in CAM. With a fresh endmill and less aggressive feed rates of
F2500mm/min
and an updated depth per pass of Z+1,5mm
.
The result looks much better now.
Still, let’s recalculate cutting data to take material differences to hard wood into account. I’ll choose a 4mm
single flute (z=1
) carbide coated aluminium cutter and assume a cutting speed vc = 150m/min
for HPL at a feedrate per tooth fTooth = 0,025
similar to cutting mild steel.
Target RPM: \(n=\frac{v_c}{\pi d}=\frac{150000\frac{mm}{min}}{\pi \cdot 4mm}=12000\frac{1}{min}\)
Target feedrate: \(F=n \cdot f_{Tooth} \cdot z = 12000\frac{1}{min} \cdot 0,025mm \cdot min \cdot 1= 300\frac{mm}{min}\)
I chose a 4mm endmill because my router motor torque diminishes over-proportionally when I reduce RPM. With larger endmills, this effect would probably lead to insufficient cutting power. If you have a spindle with an asynchronous machine, your torque curve is essentially flat so that shouldn’t be a problem of yours then.
The feedrate seems so slow - I hope that this wouldn’t heat up the material so much that it melts. I’ll complete this post once I bought and tried the respective coated carbide endmill.
For your reference: Here is the related thread in the forum that I am visiting regularly (all in German).
From investigation to problem solution
From Pixel to Vector graphics
Symptoms of insufficient spindle power
Beginner CNC issue: Speeds/Feeds
Automatic Z-referencing, Tool length, Tool changes
EdingCNC Settings & Variables
Software/Hardware setup & kinematics
Assembling Sorotec’s Basicline 0607
Switch box setup
Entry-point and questions
Circuit & Application examples
USB-PD power supply explained
Can I use a Metabo/CAS battery for my system?
How to set protective voltage & current limits
Current inrush limiters explained
Electronics knowledge: TVS diodes
Or how to kill your circuits
How to properly talk to VideoLan’s VLC player
Prototype build, issues, improvement ideas for Revision2
How To: First steps with FreeCAD
Professionalizing circuits for AnywhereAmps
AnywhereAmp Alpha’s simple single-supply preamp
Design, folding, stability, amplifiers
Evolving the mobile, foldable instrument combo
Fix ‘ERROR: favicon not found’
Export the instructions from Markdown to PDF! but how?
Why some images display OK locally but won’t on Github
How to make ToC sticky
-incremental
option
How to solve issues with disappearing posts
Configure: landing page’s header image, Navigation