cncak
New Member
Posts: 1
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Post by cncak on Sept 16, 2022 21:25:09 GMT
Lou, I would love to see a video about the laser! How you set it up as far as wiring to the millright control box, air setup, etc.
Thanks!
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Post by bLouChip on Sept 17, 2022 13:42:48 GMT
see the video 'MVP bC NejeA40640 install.mp4'
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Post by bLouChip on Oct 1, 2022 14:28:39 GMT
Update re. the THC Z STEP Suppressor Circuit and info that I posted on 7/30:
subtle but important improvement to the circuit concerning how the Z motor is enabled/disabled; the original design has the circuit output connected to the +ENA signal of the Z motor driver unit. Since performing some maintenance recently on the Z axis lead screw and anti-backlash bearing, I've discovered that using the +ENA signal to disable Z also removes the voltage from the motor windings which means the motor position is not held during moments of Z being disabled, thus Z position can be lost due to any force acting up or down on the lead screw, such as gravity acting on the Z plate. This is independent of the grbl config $1=255 or not.
So the corrected solution is to not use +ENA input of the Z motor driver, leave it unused as factory configured. Rather, take the output of the THC Z STEP Suppressor Circuit, invert it, then AND it with Z STEP signal from the THC (rerouted from Z motor STEP input); now send that AND output to the Z motor STEP input. Done. There is an extra 3 input AND gate available in the UC4 chip already in the circuit, just pull one input of the gate high and you have a 2 input AND gate.
I'll update the circuit diagram later today and re-post in the shared google drive folder linked in the reference post.
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Post by bLouChip on Jan 9, 2023 0:26:12 GMT
I added the rotary A (4th) axis to my machine this week. Its working great.
I also use LightBurn sw and my first use of the rotary axis was a laser test. Eventually I intend to laser etch some YETI tumblers. Although the Mega V XL Tri-CAM is working great with the new axis, I discovered a major bug in LB as it concerns G94 G1 XA and XAZ cutting moves. The bug is that LB is calculating/coding the feedrate incorrectly. A problem report has been opened and is being worked by LB. More info here: forum.lightburnsoftware.com/t/seeking-to-verify-rotary-setup-is-correct/87208Update 1/25/2023: If you read the LightBurn forum link above but not in its entirety, then you may have missed that a second bug was discovered, this one in Mega V 4th Axis grbl, MR-grbl as I refer to it.
Cheers, Lou
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Post by bLouChip on Feb 15, 2023 19:18:10 GMT
re. the G94 G1 XA Feedrate bugs, both the LightBurn bug and the MR-grbl bug have been fixed.
LB fix is in the next release, V1.3.02
MR-grbl fix is available from me for now, from MR Support at some point going forward.
Cheers, Lou
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Post by bLouChip on Mar 4, 2023 5:29:25 GMT
I made an interesting discovery this past week with Mega V series grbl controller, MR-grbl as I've referred to it in other posts. A random post in another forum drew my attention to the grbl code that sets the spindle PWM frequency, and how its not necessarily always set to 1kHz. I believe a J-Tech 2.8W laser that I have on my CarveKing 1 machine actually requires 1kHz PWM, which it has from the Atmega328p controller. Anyway, I assumed the Mega V controller (Atmega2560) was set to 1kHz also but its not, its default setting for spindle PWM freq is 1.9kHz. The Neje A40640 laser that I use on my MegaV doesn't mind, in fact that higher freq can facilitate more dots/inch when doing fine graphics and/or gray scale, so that's a good thing. And another discovery was noticing that the PWM duty cycle scale for the Mega V (and any Atmeg2560 grbl controller) is 0-499 steps rather than 0-255 as it is in the 328p controllers.
The Ah-Ha moment I had was how this doubling of PWM frequency effected the THC Z STEP Suppressor Circuit I made as a Z THC anti-dive measure during plasma cutting process, necessary when XY is performing a sharp cornering motion. Although the circuit worked seeming fine, it did have unexplained Z cut-Off and cut-On PWM duty cycle thresholds on the MegaV since the get go but I just chalked it up to using +/-10% tolerance capacitor/resistor components. (I had debugged and bench tested the circuit using a 328p MCU at 1kHz PWM). However, component tolerances were not the issue, there were adjustments needed due to doubling of PWM freq; basically a change to both the Accel and Decel NE555 timer Threshold input capacitor/resistor bridges. In doing so, I also adjusted the Decel and Accel duty cycles to <85% (Z STEP cut-Off) and >95% (Z STEP cut-On) respectively, and used a 10K POT in the Decel timer to fine tune the Threshold voltage and duty cycle on that leg to ensure it had good separation from the Accel Z cut-On threshold.
By coincidence and related to the Z THC anti-dive measure, earlier in the week I needed to cut 88 (count) 0.517" holes at +/-0.005" into 0.250" steel plate for a welding table I was making. This required even more THC anti-dive measures than I had in the circuit and related gcode (for plasma pierce/lead-in and M7 command to enable the circuit). So I set out to modify my SheetCAM post processor to allow on-demand per-cut disabling of the THC altogether. I did this by planting, during the pierce phase, a Spindle PWM (S200 for 20%) command which is well below the 85% Z cut-Off duty cycle threshold and an obvious "marker" for me in the gcode to know the THC is in fact disabled. An M7 command after pierce and Z plunge to ITH is what finally enables the THC anti-dive circuit, and thus will also disable it immediately when PWM <85% duty cycle as is this case. So I expected absolutely NO THC Z error during the hole cuts since it should have been disabled, however I kept getting 0.2mm to 0.4mm of Z error after making 1 or 2 practice/test hole cuts. I traced this down to a race condition at the end of each shape cut in that I had the post-processor script coding the M5 (torch off) and M9 (THC Z STEP enable) on the same line in the gcode files, followed by a dwell of 0.5secs to wait for the plasma cutter relays to react and actually turn off the torch before attempting to retract Z. Well, as soon as M9 was processed, it took nano-seconds with TTL logic gates to enable the THC while it took hundreds of milli-seconds for the plasma arc to cease, all the while the THC now being enabled to control Z was sending STEPs to raise it because it saw a dropping arc voltage as it went to zero. Hence the errant few tenths of mm "Z error" on each cut. This explains a lot since the circuit was put into service last summer. Holy Cow! Although the Z error went way down after the circuit was put in service, the accumulated error for 30+ pierce/cut jobs was still more than I liked but I again attributed it to NE555 timer cap/resistor tolerances. Well, after separating the M5 / M9 with the dwell time, and changing the NE555 timers (Decel and Accel) Threshold bridges to work within a 1.9kHz (t=500us) cycle, the Z error is finally absolutely zero. All good.
And one more thing, I added a 1 quart sized dessicant dryer to my air compressor last week also, and holy cow what a difference that made to what I already thought was very dry air. After 50 pierces and hole cuts, my Tecmo PTM60 torch consumables still looked and worked like new! Dry air once again makes a huge difference in plasma cut quality and consumable life. Btw, I still have the condenser on the air compressor before the tank, and that was a huge leap last summer in achieving seemingly dry air ( millrightcnc.proboards.com/post/25454/thread ). This is another equally huge leap. The observation that drove me to add this 1 quart dessicant dryer and replace the ~ 1/4 cup dessicant dryer was that during laser process cutting, I noticed the dessicant beads going from blue to pink in just a few compressor cycles, and laser air flow is 1/10 the volume of plasma air flow. So it dawned on me that the ratio of dessicant bead volume to air flow volume needed to be very high in order to thoroughly dry the air, so the 1 quart dryer does just that for plasma air flow volume.
Cheers, Lou
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Post by bLouChip on Apr 15, 2023 13:06:49 GMT
Good Morning.
I have been reading various welding and plasma process references online the past 3 years and found it odd that although such articles mention "using dry compressed air is important..." to the plasma cutting process, there is nary a mention of 'to what degree of dryness' the air needs to be. Also, most recommendations to attain 'dry air' include expensive equipment of $1,000++, in excess of the cost of the air supply system. Through incremental improvements and some trial and error, I believe I have finally attained 'dry air' from my air supply system, at a cost of < $350, and I believe I have a few tried and true methods of monitoring the appropriate 'dryness' of air for the purpose of plasma cutting process. And third, the importance of using 'dry air' in the plasma cutting process can only be appreciated, I believe, as one transitions from using 'moist air' to 'dry air' or visa versa. So I thought I'd write a paper on the topic to share with others. Enjoy.
Cheers, Lou
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Post by bLouChip on Jul 30, 2023 17:36:34 GMT
I updated the photo gallery with annotated photos of my Mega V build; I had some users contact me recently for more details and thought this was the best way to handle for all.
I also tested a new plasma torch recently and posted photos in a new sub-folder of the gallery. The torch is the new UPM105 model from Tecmo, previously I was using the Tecmo PTM60. The UPM105 uses Hypertherm consumables and holy cow those are excellent design and function. Its no wonder that Hypertherm is the gold standard for plasma power sources and torches, but $$$$$.
Photos of both UPM105 and PTM60 torch nozzles as well as cut parts are in the shared folder photo gallery with annotated details.
Cheers, Lou
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Post by bLouChip on Jan 8, 2024 22:41:30 GMT
Recent updates to my Mega V XL include:
* Neje E80 24W Quad Diode Laser Unit.
* SheetCAM GRBL Plasma post processor with Rotary Support -
* updated THC Z Anti-Dive circuit -
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Post by bLouChip on Mar 3, 2024 16:44:02 GMT
I've been doing some research, tweaking, and testing on my THC Z Anti-Dive Circuit (ADC), and the controlling gcode, for the past week or so, testing its operation during live plasma cutting, and in conjunction with the Proma THC SD, as well as testing and comparing performance to the Proma unit standalone in autonomous operation without the aid of the ADC. Several things learned throughout the whole ordeal. Just sharing results in case anyone else is use the Proma THC SD. plasmaspider.com/viewtopic.php?p=234235#p234235
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