2-axis Sharp knee mill revival - Now with 50% more axes!!

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Dan M
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Re: 2-axis Sharp knee mill revival

Post by Dan M »

martyscncgarage wrote: Mon Apr 08, 2019 1:26 pm Is the plan to use one switch and two trippers on each axis?
If so, I think you will have to rely on using the one switch to home the machine on the far end of the travel and use soft limits on the other end.
Because, using one switch, the control will not know which end of the axis tripped and won't allow you to back off of the switch.

Marty
You actually can back off the switch Marty you just have to push the limit switch defeat button. I run a similar set up on my router but with proximity sensors.

I have them set to home/limit and it works fine, but honestly it's not really needed since the soft limit's work perfect and the first thing I do is home the machine.

It is nice though to have the extra safety in case for some reason I wanted to jog the machine around prior to homing it.

You are 💯 correct that it doesn't distinguish between + or- but it still works just doesn't show the correct side of travel on the one side when it trips. It would be very nice if the option could be added to one of the updates if possible.

Edit:
Try it out it works (delete),

Dan
Last edited by Dan M on Tue Apr 09, 2019 6:23 pm, edited 1 time in total.
Gary Campbell
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Re: 2-axis Sharp knee mill revival

Post by Gary Campbell »

Try it out it works good,
In my opinion not true, it can work, but nowhere near as good as it could be. Actually, its a "kludge" used in the low dollar hobby controller world to save a few bucks. Reason is that higher end controllers with discreet messaging will, along with displaying a message saying that an axis' limit is tripped, it will say whether it is positive or negative. Motion is then prohibited further into the switch direction. That's what "good" is.
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Dan M
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Re: 2-axis Sharp knee mill revival

Post by Dan M »

Gary, I completely agree and you are in a position to make it better. Please ask for the option to have sensors at each end of the travel, right now it's not a option. So what I'm doing is the only way I'm aware of having a sensor stop the travel at both ends. Even if I added 3 more sensors the software wouldn't support them to work any different than using trigger blocks. Maybe I'm not understanding your argument with out knowing what you currently do that is a better solution.

Is using home all and having no limit switches better. Or is there some trick to wiring it up to get both+ and - limit switches on each axis? I spent a solid day when I first built my router trying every option available and settled on home/limit.

Any info would be great Gary thank you as always for your help.

Dan
Gary Campbell
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Re: 2-axis Sharp knee mill revival

Post by Gary Campbell »

Dan...
Its already in there. You have the option to set an input as "HomeLimit" (lets call it negative) and then set another for Axis# Limit Plus. Of course this takes 2 sensors and 2 inputs, but it's in there.

What's not there is the ability to use a single sensor that will work on both the negative and positive ends of travel. Nor should it be.

Don't get me started on the "HomeAll". Other than being hamburger helper for not having enough IO, I see no other viable reason for it to even exist.
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Dan M
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Re: 2-axis Sharp knee mill revival

Post by Dan M »

Gary Campbell wrote: Tue Apr 09, 2019 9:01 pm Dan...
Its already in there. You have the option to set an input as "HomeLimit" (lets call it negative) and then set another for Axis# Limit Plus. Of course this takes 2 sensors and 2 inputs, but it's in there.

What's not there is the ability to use a single sensor that will work on both the negative and positive ends of travel. Nor should it be.

Don't get me started on the "HomeAll". Other than being hamburger helper for not having enough IO, I see no other viable reason for it to even exist.
Thanks Gary, I have a bunch of extra proximity sensors. I can easily add them to the machine, I just didn't think it would support them.

Right now I don't think I have enough inputs since I would use up 6 of the inputs for the limits correct? Or is there a different way to do it with them sharing a input or using a plc? I think I need to look at it some more when I'm actually at the machine. I don't remember how many inputs I'm using.

Thanks again Gary and sorry for all the questions.

Dan
Gary Campbell
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Re: 2-axis Sharp knee mill revival

Post by Gary Campbell »

Right now I don't think I have enough inputs since I would use up 6 of the inputs for the limits correct?
Yes, one for each sensor

Or is there a different way to do it with them sharing a input or using a plc?
No, if you are going to share inputs, you might as well put them all on one. Discreet actions and messaging is the real way to go.


Hang in there, Keith just posted today that the ETH1616 expansion board is on the horizon
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Dan M
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Re: 2-axis Sharp knee mill revival

Post by Dan M »

Gary Campbell wrote: Tue Apr 09, 2019 10:41 pm

Hang in there, Keith just posted today that the ETH1616 expansion board is on the horizon
Perfect, thank you very much Gary!!

Dan
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Re: 2-axis Sharp knee mill revival

Post by FlySox »

Made a bit more progress on the machine this weekend, starting with the control box. Since I’m reusing the original, fairly small cabinet, I’m utilizing not just the back, but also the side panels. Most of the electronics will be on the main back panel, while the side panels will be used for the rather large Dugong drives (as per my cardboard mockups in an earlier post).

I cut all three panels from .08" 5052 aluminum (I have this alloy on hand because it bends nicely and doesn’t crack at the bends like 6061 or 7075, not that that’s required here; just an FYI for those not familiar…). Lots of drilling and tapping with a 6/32 combo drill/tap later…

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…I was able to begin the actual mounting and wiring of the main panel:

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I put some thermal paste on the bottom of the drives to more efficiently use the side panels as a heat sink.

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I then soldered wires to the braking resistors:

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…and mounted them to the panels:

IMG_1147.jpg

Here’s a test fit in the cabinet. Don’t judge just yet. I plan to channel my inner Gary Campbell and make this mess look a bit tidier (panduit covers can hide a lot of sins):

IMG_1150.jpg

I eventually got it all wired up, including limit switches, an e-stop and a three position switch, one position of which activates the relay that powers the main toroidal supply (it’s also dependent on NoFaultOut, thanks to suggestions of others on this forum).

IMG_1171.jpg

The idea here is that I can keep the mill in “manual” mode for quick jobs. With no power to the motors, I can still turn the handles on X & Y. I was secretly hoping that the Acorn would report encoder counts when in “manual” mode, but there is no feedback loop from driver to Acorn, so this is not the case. Turns out, there’s no such thing as a free DRO. I might eventually get a set of scales (they seem pretty affordable these days), but perhaps I’ll learn to like “electronic” milling (the step between manual and full CNC control).

With all that done, I was finally able to go back and tune the servos using CNCDrives Servoconfigurator software. I’ve been involved in a couple of PID tunings in the past and the saying is true for all of them, including this one: tuning PIDs is a PITA. I spent at least 2 hours zeroing in on good values. Here’s a graph of one set fairly close to the final result. Good news is with belts connected, there is no latent buzzing or ringing. I take this as mission accomplished.

IMG_1168.jpg

Sadly, the sun set on my weekend. I can at least confirm that I can jog via the touch panel, but I won’t be able to really dive in to getting CNC12 tweaked until next weekend (configuring home/limits/axis travel, working on the homing sequence, etc). After that, I'll need to familiarize myself with its actual use making parts, and will get to more advanced things like spindle control, turning on coolant (mist only for me), and getting my recently purchased CWP-4 wireless pendant working. So much more fun in store!
Dan M
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Re: 2-axis Sharp knee mill revival

Post by Dan M »

Looks good!! I use 5052 sheet alot also, usually .063 though that's what I used for my enclosure too. Looks like you'll be running parts in no time going to be a nice mill when you're done.

PS. If you don't already have the drill tap's, check out Greenlee they work really well.

Dan
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Re: 2-axis Sharp knee mill revival

Post by FlySox »

Haven’t posted in a while, but do have a few updates. X & Y are all set up and working correctly. This was not quite as simple as it could have been, since my X-axis motor was missing a mounting plate. To remedy, I laser cut a hole template, marked hole centers on a square plate of 6061…
IMG_1174.jpg

…bored out the center hole for the motor shaft…
IMG_1175.jpg

…and drilled the rest, tapping where required.
IMG_1176.jpg

Simple project that turned out fine.
IMG_1178.jpg

With X & Y now under CNC control, I won’t need to use the laser template method for such things: I can use Intercon.

Of course, Intercon or gcode is much easier if you can set part zero quickly and accurately, so I bought a passive probe—the Hallmark ITTP—sold by Cliff Hallmark, a one-man operation out of New Zealand. This probe’s differentiator is that it is tolerant of unintended impacts — they won’t harm the probe (within reason; ITTP stands for Impact Tolerant Touch Probe). Not cheap, but reviews have been good and I like supporting the little guy, so I pulled the trigger. It arrived to my house in California in just four days.

To keep the probe’s internal electro-conductive gel in place, it is meant to be stored upright. Drilling a hole in a piece of scrap wood would have been the quick and easy option here, but the probe's final resting place next to my mill will land it in the "chip zone", so I wanted a cover in addition to a stand. Here is my solution, aided by a 3D printer and a laser cutter. What the photo doesn't show are the four rare-earth magnets press fit into the bottom of the base to keep it in place as the probe is removed and replaced.
probe_case.jpg

I upgraded my free CNC12 software to Digitizing version to get the complete set of probing cycles. Installed the license, wired the probe to input 7 and common, and was soon probing away! I’ve got no probe detect circuit, so I can’t take advantage of CNC12’s probe protect features, but it’s an impact tolerant probe, so as long as I don’t turn the spindle on, I think I’ll be OK. You might be thinking I can’t use all of the probe routines on a two axis machine. Well, once you get familiar with them, you can manually raise and lower the quill during what should be a Z up/down move. Takes some attention, but it works.
IMG_1205.jpg

I also ordered a CWP-4 MPG pendant and got that installed and working, too. I didn’t hit the issue others have reported with the MPG not working after unplugging a probe, simply because I keep my probe plugged in. I was a little taken aback thinking my VCP was “broken” with the MPG on, since it seems stuck in Turtle mode, but this was just me not thinking clearly: When the MPG is active, it determines speed, not the VCP, which makes sense, since a change on VCP can’t physically move the switches on the pendant (cnckeith mentions this elsewhere in the forum, too).

Another small change: I wasn’t happy with the plastic housing for the estop and manual/CNC selector, so I transferred the switches to a more rugged and official looking aluminum housing. Probably won’t make any practical difference, but I feel better about mashing the big red button on this set-up over the plastic one.
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Still haven’t gotten my VFD under Acorn control, so that’s still on the short list. However, this weekend I spent most of my time wiring up a drive and motor for the Z-axis. Yep, more than three months later, I finally took delivery of an Elrod Machine Z kit (now sold by Servo Products). Apparently they were out of ball screws(?).

Future updates will chronicle Z-axis fun…
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