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MiKro

cnc rebuild

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Even if it costs the same as a kit off the 'Bay, you'll be building it every step of the way and will therefore have reassurance that it's more solid where you want it to be. The 3020 is probably a good one to burn the idea into your head.

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That's what I figure too. I've been quite happy with the 3020 for the price, and with the various upgrades I've done to it it's been a solid performer. But like Mike I've found I've milled a few things recently that would've been easier if I could do it in one shot rather than tiled in sections. I was looking at the 6040 kits, but there appear to have been more mixed reviews of them when compared to the smaller units - more flex in the frame, unsupported rails over long distances causing sag, so-so electronics.

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BTW I think I am going ahead with the spindle/vfd so if you know anyone that would be interested in a SuperPID V2 controller and precise bits for Porter Cable collet set 1/8", 1/4", 3/8" 1/2" set let  me know. will make someone a good deal on that.

update: I have ordered my spindle and vdf :)

MK

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My VFD and Spindle came in. I programmed the VFD and made the spindle cable. Tested it on the bench. Damn I never realized how quite these are now. :)

MK

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8 hours ago, Prostheta said:

Till you grab hold of the spindle as it's winding down in which case they aren't loud enough....!

yep and my VFD will not support a braking resistor. :(  I may have to look into another VFD sometime

mk

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How can it not support one? Is it designed to destroy the vicinity with back EMF and generate voltage to mash your electronics?

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Reminds me of a post that Konrad Sauer posted about a huge old bandsaw he bought which had no brake, so when the power was cut the motor turned into a generator. I believe that he fried the hair dryer hooked up as a braking load, the generated current was so excessive.

Rotational energy is an amazingly easy thing to underestimate.

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4 hours ago, Prostheta said:

Reminds me of a post that Konrad Sauer posted about a huge old bandsaw he bought which had no brake, so when the power was cut the motor turned into a generator. I believe that he fried the hair dryer hooked up as a braking load, the generated current was so excessive.

Rotational energy is an amazingly easy thing to underestimate.

I agree, but this Chinese VFD does not have a place to hook up a braking resistor.  While showing that the resistor for my spindle would be a 70amp 300 watt resistor in the manual. I am perplexed as well? I know it is weird but that is how it is setup. So the best way  I know to stop it is to use an S code to lower the speed with a dwell setting G4 P#before the m5 or m9 to stop, this way no over voltage should occur. They don't even address the issue and I am the one thinking about the S and M codes in my post processor footer.

something like this will work and then it will coast down without over voltage.

begin FOOTER

"[N]G00[ZH]"
"[N]G00[XH][YH]"
"[N]S 5000"
"[N]G4 P10"
"[N]M09"
"[N]M30"
%

 

Edited to add: Funny I just received an email about this resistor. and yes it does support one it just is not marked on the VFD for connections. LOL!! So I have one on order. I will most likely still use the s and m codes to slow down at end of job and then set the resistor voltage accordingly. Then again that may be a problem in the event of an Estop. Will have to think this through?

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49 minutes ago, Prostheta said:

Is it not just switched in parallel when the VFD is powered off?

edit: just read the edit

It has that option in the programming best I can tell.

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Is this the generic Huanyang VFD that's sold on Ebay and Aliexpress? I've just taken delivery of the 1.5kW version, and reading the manual it may be that the braking resistor is only applied after the spindle is ramped down to the stopping frequency (PD028, 10Hz max) for a period of time specified by PD030 (max 30sec).

As far as I can tell you'll still need to get the RPMs down somehow before the VFD will apply the braking resistor. To my thinking, that makes sense when trying to stop a motor. Dropping the anchors on something moving at 24000RPM is unlikely to do the bearings any good, so there must be a lower threshold level that the VFD will allow you to do so safely. Whether this works the same way when doing an E-stop is something that needs some investigation.

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39 minutes ago, curtisa said:

Is this the generic Huanyang VFD that's sold on Ebay and Aliexpress? I've just taken delivery of the 1.5kW version, and reading the manual it may be that the braking resistor is only applied after the spindle is ramped down to the stopping frequency (PD028, 10Hz max) for a period of time specified by PD030 (max 30sec).

As far as I can tell you'll still need to get the RPMs down somehow before the VFD will apply the braking resistor. To my thinking, that makes sense when trying to stop a motor. Dropping the anchors on something moving at 24000RPM is unlikely to do the bearings any good, so there must be a lower threshold level that the VFD will allow you to do so safely. Whether this works the same way when doing an E-stop is something that needs some investigation.

Well it is a HY VFD I got it through Amazon. Mine is a 2.2khz with the spindle. and yes it will still need to be slowed some before the BR will take effect. I am currently studying the 4 or 5 parameters that affect it and how they interact. If you have pd025 (ithink) set for 0 then anything to do with the BR is invalid for startup and PD026 set to 1 and it will coast down. That being said and overvoltage would occur if stopped at 24K rpm. so still the need to ramp down. I think my footer gcode will still work for that  no matter. :) I'm like you though what about the Estop? That is something I am trying to understand as well in the manual.

MK

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The other thing that seems to crop up in discussions about these VFDs is that some of the HY variants do not have the components installed on the PCB to perform the braking function, despite having terminals provided for connection of an external resistor. You may find that after connecting a braking resistor and programming the VFD appropriately will still result in the spindle freewheeling to a stop.

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OK, a little more reading on the subject reveals that there are two separate braking systems at play on these VFDs.

Dynamic braking is using an external resistor to slug the motor as it spins down by converting the back-EMF produced by the motor when the drive is ramping down into waste heat. It's 'dynamic' in the sense that more RPMs = bigger back EMF = harder braking action. In the Huanyang VFD it appears that dynamic braking can be applied as soon as the shutdown command is initiated, either by a manual stop or by the e-stop (if configured). Ramping down too quickly without a braking resistor (or using an improperly-sized resistor) will give you the over-voltage alarm/trip of the VFD.

DC braking (which is what settings PD029 - PD031 refer to) is an additional function in the VFD, where the drive applies a DC voltage to two of the motor windings to slug it into submission. DC braking requires more grunt on the VFD's side, and also stresses the rotor more than dynamic braking, so it makes sense that this should only be applied when the drive signal reaches a few hertz for a few seconds.

 

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Some more brain ideas to chew on, then I'm done for the day.

Just done some quick and dirty testing on my unit. There is a setting at PD118 that enables the Over-voltage Stall Prevention function. Setting this to 1 allows the VFD to detect when the motor back-EMF voltage becomes too high during ramp-down and halt the ramping process until the backfeed returns to an acceptable level.

The lowest I can reliably set the ramp-down speed from a 24000RPM (setting PD015) on my 1.5kW unit, without a braking resistor fitted is 1 second. Any quicker and the VFD trips on over-volts. Even at this deceleration rate I can hear the over-volt stall prevention kicking in multiple times as it ramps down (the spindle speed audibly goes down in spurts over the course of the complete deceleration period). A more forgiving setting for PD015 appears to be 5-7 seconds, which doesn't seem too unreasonable for a fast stop from 24K. It should also be noted that the time it takes to stop from a lower RPM is proportional to the ramp time, so with PD015 = 5 sec, a deceleration from 12K RPM takes 2.5sec.

I suspect that an e-stop function could probably be implemented by taking advantage of the multiple configurable ramp times this thing can apparently do. A normal stop could be set to ramp-down at 10sec (PD015) and an e-stop could be configured to ramp-down at 2 seconds, or quicker if you fit a braking resistor (PD017). Hitting the e-stop button could select the second quicker ramp time and command the VFD to shut down.

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So with my hands and wrists all boogered up, it is hard to get shit done. I have been slowly getting the new Table/platform built. Damn it is not easy using a circular saw with your left hand in a splint for cutting plywood as that is my good hand for now, My right hand is in a splint as well, A new splint on the way with abducted thumb isolation for my right hand. Whoopee!! :( I'm right handed. LOL!!  I feel like a 4 fingered monkey at a circle jerk. LMAO!!! More pictures to come on the table. It is all 2x4s and 2x6s planed, glued and screwed.

MK

 

table1.jpg

 

The splints I am wearing, Keeps the wrist immobilized well just not that good for the thumb. This sucks

 

splint.jpg

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4 minutes ago, Prostheta said:

Yeah, I couldn't allow myself to do that. Powertools and less than 100% control, no way man. I play to win.

Well I had already made a shooter table so, plywood on it and flat is not that bad. Just getting the start of the cut is the problem. :) Still have to be slower and more careful.

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I'd have my doubts, personally. I never like to assume that I can wing it or that the machine will do what I want it to in less than ideal circumstances. So far, I have had no major accidents. Almost a broken hand from table saw kickback, that's about it.

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Oh, and I shot a piece of wood across the room when it got trapped between the fence of a router table and the cutter!

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My parts, damn it, I want to get this thing back together, I have so many things I need and want to do. F Me Running. Like I said I feel like a two fisted, 4 fingered monkey in a circle jerk. LOL!!

Have a Great week end.

MK

cncparts1.jpg

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8 hours ago, MiKro said:

My parts, damn it,

For some reason I misread that as 'My pants, damn it'. Either way, I sympathise ;)

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