CNC3018PRO - Speed Test / Milling Parameter

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** Experience for CNC3018PRO ** It depends. The following information is based on experience, not a guarantee! | 8000 RPM (24V) | 100 mm/min | Ø 1.00 mm | -0.1 mm | aluminium | | 8000 RPM (24V) | 300 mm/min | Ø 1.58 mm | -0.2 mm | wood | | 5000 RPM (15V) | 300 mm/min | Ø 3.17 mm | -0.4 mm | wood | | 4000 RPM (12V) | 400 mm/min | Ø 3.17 mm | -0.4 mm | plywood | The harder the material, the slower the feed and the lower the milling depth. WD-40 spray, for example, can be used as a coolant for hard materials. ** Work in Progress ** Yes, it's a milling machine! Of course, this is not a professional tool, but numerous reports on the Internet show that even aluminium can be machined with the inexpensive hobby cnc. I'm compiling theoretical and practical experience with this mill. For me, the question was how fast the spindle can rotate and what maximum feed rate is possible. ** The Test ** For me, the questions are: 1. What maximum feed rate is possible? 2. How accurate are the dimensions? 3. How fast the spindle can rotate? 4. How can I regulate the spindle? To measure the feed rate and accuracy, I created a 10 cm line and ran it ten times at different speeds and measured the length. You can download all the necessary files here. _Result: 800 mm/minute is realistic and the dimensions fit very well_ I measured the frequency of the spindle in Herz with the Spectroid app and converted it to RPM with calculate Hz x 60 seconds. I changed the speed via the voltage at the power supply unit and via USB cable and the GBRL Controller 0.5.2. _Result: 8000 RPM @ 24 V and 4000 RPM @ 12 volts_ ** How to control the spindle speed? ** Most CNC machines interpret the speed of the spindle in the GCODE linear from 0 to 1000 and reduce the speed with PWM. On my CNC3018PRO the speed setting works binary (2,4,8,...,256), where the speed is not reduced linear. The maximum speed can be halved via PWM. The speed can also be changed at the power supply by selecting the appropriate voltage. 24V * M3 S4 = 4020 RPM (67 Hz) * M3 S8 = 6000 RPM (100 Hz) * M3 S16 = 6300 RPM (105 Hz) * M3 S32 = 6480 RPM (108 Hz) * M3 S64 = 7020 RPM (117 Hz) * M3 S128 = 7920 RPM (132 Hz) * M3 S256 = 8280 RPM (138 Hz) 12V * M3 S4 = 1260 RPM (21 Hz) * M3 S8 = 2460 RPM (41 Hz) * M3 S16 = 3360 RPM (56 Hz) * M3 S32 = 3840 RPM (64 Hz) * M3 S64 = 4020 RPM (67 Hz) * M3 S128 = 4020 RPM (67 Hz) * M3 S256 = 4020 RPM (67 Hz) If possible, the speed should not be permanently below 50%, as otherwise the air cooling of the engine may not be sufficient. **Determination of the spindle speed** Without the right speed, the cutters become blunt or break off. The optimum cutting speed depends on the material to be milled. Theoretical reference values can be found on the internet. In practice, however, it also works at lower speeds with reduced infeed depth and feed. | m/min | Ø 1.00 | Ø 1.50 | Ø 2.00 | Ø 3.00 | material | | 450 | 0.050 | 0.060 | 0.070 | 0.100 | wood, MDF | | 500 | 0.025 | 0.027 | 0.030 | 0.035 | wood, soft | | 450 | 0.020 | 0.022 | 0.025 | 0.030 | wood, hard | | 600 | 0.025 | 0.027 | 0.030 | 0.035 | plastic, soft | | 550 | 0.015 | 0.017 | 0.020 | 0.025 | plastic, hard | | 365 | 0.015 | 0.017 | 0.020 | 0.025 | brass,bronze, copper | | 200 | 0.010 | 0.015 | 0.020 | 0.025 | aluminium | m/min = cutting speed of the mill through the material Ø 1.00 mm = diameter of the milling cutter 0.050 mm/tooth = cutting parameters for material hardness and diameter Alternative values vc + fz / 30-50% deeper with coated cutters (TiN, TiCn, TiAlN) | vc | Ø 2-4 mm | Ø 5-8 mm | Ø 9-12 mm | material | | 100 - 500 m/min | -0.04 mm | -0.05 mm | -0.10 mm | aluminium soft | | 100 - 200 m/min | -0.04 mm | -0.05 mm | -0.10 mm | aluminium hard | | 100 - 200 m/min | -0.04 mm | -0.05 mm | -0.10 mm | brass, bronze, copper | | 40 - 120 m/min | -0.02 mm | -0.03 mm | -0.06 mm | steel | | 50 - 150 m/min | -0.05 mm | -0.06 mm | -0.07 mm | thermoplastic | | 100 - 150 m/min | -0.04 mm | -0.08 mm | -0.10 mm | duroplastic, gfk | The spindle speed is calculated from the cutting speed and the perimeter of the cutter. _n = (vc x 1000) / (d x pi)_ The theoretically required speed of 62,995 RPM via the formula (200 m/min x 1000) / (Ø 3.175 mm x 3.1415) is far from what this CNC machine is capable of. With an external 36V power supply, a speed of 12000 RPM can be achieved with the 775 spindle. With low feed and low depth, aluminium 6061 can also be milled with 24V. _Result: 8,000 RPM speed and 24V power supply should work fine_ **Determination of the feed rate** If you drive slowly, you lose time unnecessarily. The feed rate depends on several parameters: spindle speed, number of cutting edges and tooth feed of the material. _vf = n x z x fz_ For aluminium, in our example, a maximum of 400 mm/min results from the formula 8000 rpm x 2 x 0.025 mm/tooth. The values apply to powerful CNC machines with strong stepper motors. The CNC3018PRO has about 15% of the power for the feed. _Result: 60 mm/min should work for aluminium (15% of 400 mm/min)_ **Determination of the mill depth** The depth depends on the material, the diameter and quality of the milling cutter. | D Ø | M Ø | Q Ø | Ø 1.00 | Ø 1.55 | Ø 3.17 | material | | 350% | 500% | 500% | -3.50 mm | -5.00 mm | -10.00 mm | depron | | 50% | 75% | 100% | -0.50 mm | -0.75 mm | -1.50 mm | wood | | 5% | 20% | 30% | -0.05 mm | -0.07 mm | -0.15 mm | aluminium | The recommendation for the CNC3018PRO is as follows: | Ø 1.00 | Ø 1.55 | Ø 3.17 | material | | -0.50 mm | -0.75 mm | -1.50 mm | depron | | -0.10 mm | -0.15 mm | -0.30 mm | wood | | -0.02 mm | -0.05 mm | -0.10 mm | aluminium | ** GBRL Settings ** [CTRL+X] < Grbl 0.9j ['$' for help] $$ < $0=10 (step pulse, usec) $1=25 (step idle delay, msec) $2=0 (step port invert mask:00000000) $3=0 (dir port invert mask:00000000) $4=0 (step enable invert, bool) $5=0 (limit pins invert, bool) $6=0 (probe pin invert, bool) $10=3 (status report mask:00000011) $11=0.010 (junction deviation, mm) $12=0.002 (arc tolerance, mm) $13=0 (report inches, bool) $20=0 (soft limits, bool) $21=0 (hard limits, bool) $22=0 (homing cycle, bool) $23=0 (homing dir invert mask:00000000) $24=25.000 (homing feed, mm/min) $25=500.000 (homing seek, mm/min) $26=250 (homing debounce, msec) $27=1.000 (homing pull-off, mm) $100=400.000 (x, step/mm) $101=400.000 (y, step/mm) $102=400.000 (z, step/mm) $110=1500.000 (x max rate, mm/min) $111=1500.000 (y max rate, mm/min) $112=1500.000 (z max rate, mm/min) $120=10.000 (x accel, mm/sec^2) $121=10.000 (y accel, mm/sec^2) $122=10.000 (z accel, mm/sec^2) $130=200.000 (x max travel, mm) $131=200.000 (y max travel, mm) $132=200.000 (z max travel, mm)