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Topics - mbele

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Tangent Corner / Machining Al-7075 and deformations
« on: September 08, 2015, 08:08:53 AM »

can someone please suggest proper way to machine Al-7075-T651 alloy to minimize/avoid deformation?

Stock ~1000x70x25mm, was clamped to the 6 standoffs using one M6 screw per standoff, which were then clamped to the table. When I machined one side and released it from the table, the part was bent (~4mm about the middle of the part lengthwise).
I've attached some pics illustrating machining strategy and the result.
1. profile part using 6mm single flute carbide endmill, flute length 25mm (6/1/25 cem): DOC0.5mm, F3000mm/min, S13800rpm
2. clear ~550x70x8-10mm area in zig-zag pattern, using 6/1/17 cem, DOC8-10mm, WOC1mm, F875mm/min, S12000rpm
3. rough using 6/1/17 cem, climb only, waterline: DOC2-17mm, WOC,Feed and Speed variable too keep relatively constant MRR and the machine happy
4. finish using 6/3/18 cem, waterline climb in X direction + contour in Y direction combined, max DOC/WOC 2mm, step-over 0.1mm, F4000mm/min, S24000rpm
Material was never too hot to touch - it was warmest after #2 (and I suspect that was the problem). I used some WD40 on all cuts.

I've done similar parts in Al-6082-T6 ~800x80x25 and Al-6060-? ~800x70x20, using different roughing strategy (waterline 0.5mm DOC), different clamping method (normal clamps on top) and the parts turned out straight.


General Mach Discussion / Start Mach3 with gcode line numbers displayed
« on: November 28, 2014, 04:20:22 PM »
Is this possible ?


General Mach Discussion / Mach and VFD, modbus or pwm
« on: May 06, 2014, 02:32:35 AM »

I'm upgrading spindle on my machine with VFD controled one, I'm total noob in that area, and I would appreciate any info. I have two options, Toshiba Tosvert VF-nC3 or VF-S15 - I really dont understand the difference between these two models and will probably go with cheaper one (VF-nC3).
I want to control spindle start/stop and speed from gcode. If I could perform tapping operation it would be absolutely great (is this called semi-rigid tapping in this case?) . It would be nice if I could read current/actual speed from drive, so I know when the spindle has reached commanded speed.

VFDs can be controled via Modbus-RTU / RS-485 and vendor offers USB(serial) to RS-485 interface for that. VFD speed can be controled with PWM, and for that vendor offers gizmo for interfacing parallel port output to VFD PWM input.

If I go with PWM option, i'll have to use relay+contactor for starting/stopping spindle - that's two extra ouputs, one for PWM speed control and one for the relay, right ?
I think I can save some money if I make my own serial to RS-485 interface using AM26LS31CN line driver - providing diferential TxD/RxD signals.

What do you think is better solution for Mach?


General Mach Discussion / Testing salvaged AC servos
« on: April 22, 2014, 09:45:10 AM »

I've salvaged some parts from 2 inkjet printers:
Fuji Faldic-w driver RYC201DC3 VVT2 + motor GYS201DC2 T2C w/ 17bit encoder (200W, input 200-230V@3.4A)
Fotek SSR-25 DA (25A/250V) input:3-32VDC, output: 24-380VAC
Panasonic Minas driver MSDA043A1A + motor MSMA042A1G w/ 2500 P/r encoder (400W, input 200-230V@1.8A)
Delta Electronics 20DBAG5 EMI filter (250V/20A 250V/16AHPF)
Delta Electronics 06GEEG3E line filter (6A)

I'd like to test if they work, but I'm not sure if I should power them on without other required components in the power supply chain.
Fuji requires circuit breaker/Earth leakage circuit breaker, AC reactor and power filter. Panasonic requires "Non-Fuse Breaker" (probably simple automatic circuit breaker), noise filter, magnetic contactor (probably relay), and reactor. I've found all the missing components on ebay, but price is too high if it turns out that motors/drives do not work.

Can I connect drives directly to 220V AC power supply, and check if they work without burning them?



I'm using Mach3 42.20 and it seems that in this version, the CV mode makes smooth transition from G1 to G0 move (eg. tool retract move). This may be less obvious on setups with high acceleration.
N1 G1 Z0 F100 (plunge)
N2 G1 X100 F4000 (cut)
N3 G0 Z100 (retract)
This may present a problem (especially when engraving) on line 2, because G1 move is not completed on Z axis/level. CV smoothes the transition between lines 2 and 3 and starts retracting the tool before the end of G1 move.
Workaround for this is to check "CV stop at angles" option in General settings (89 degrees worked for me in this particular example, but since this option is used for transitions on all axes, exact value depends on desired behavior on all axes and acceleration/feed settings).
Attached picture shows the example engraving with "CV stop on angles" option unchecked (left, notice 2 unfinished lines) and checked->89(right) done with 0.1g@4m/min. It also shows for 90 deg angles CV radius to be:
radius = (feed^2)/(2*acceleration)
distance between engraved lines is 2.5mm, calculated CV radius for 0.1g@4m/min is 2.2mm (with 0.3g, radius is 0.7mm - which is much less noticeable)


Others / Rhino: 2D path to g-code
« on: April 19, 2013, 03:53:13 PM »

I've attached few scripts that I use to generate g-code from curves drawn in Rhino. Supported curves are lines, arcs and circles, so before executing scripts, paths should be converted to lines/arcs.

SegmentsIO - import/export paths (evaluation version does not alow but 25 saves)

2DPath2GCode - creates gode from planar lines,arcs and circles. One polycurve (joined lines/arcs) is treated as one continous feature. If you're getting weird paths from polycurves that overlap at subcurve start/end points, try turning off "simplify" option.

Holes2GCode - creates gcode for drilling holes from circles and/or points (other curves will be filtered out after selection)

disclamer: use at your own risk :)

ps. if you find bugs, please post seg files here

General Mach Discussion / Is my PC too slow or...?
« on: April 18, 2013, 04:14:35 PM »

I've noticed some time ago that when I increase feed rate via feed rate override in mach3 mill it looks like CV mode turns off (moves are not smooth any more). I'm able to reproduce this behavior now, so I'm posting my g-code and xml file. When program is running at 4000mm/min it runs fine, but when the feed rate is set to 5000mm/min or above (via feed rate override or in g-code program) moves are not smooth any more. What's more interesting is that, at raised feed, the first pass is smoother that the following passes :) I haven't noticed lost steps.

PC is based on AMD Athlon 2400+ 2GHz CPU with 1GB RAM running XP SP3 (Standard PC install). It takes one minute for the attached g-code to initialize (I've always experienced very slow initialization when program is based on arcs).

I get peak power from steppers at ~4000mm/min (~200RPM x 20mm lead direct drive 2.7Nm steppers 1/8 micro-stepping). Kernel runs on 25kHz.

I'd really like to be able to feed faster since my spindle is not very strong and I have to take light cuts.


General Mach Discussion / How to customize keyboard shortcuts
« on: August 05, 2012, 08:48:37 AM »

is there a way to disable all Mach3 keyboard shortcuts, and define smaller set of custom ones ?


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