Author Topic: Mini-mill DRO and swarf shields  (Read 1581 times)

Online bent

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Mini-mill DRO and swarf shields
« on: April 12, 2018, 09:10:04 PM »
Don't want people thinking I've been slacking.  I installed some cheap magnetic DRO's on the mini mill, these kind:

 https://www.amazon.com/iGaging-Digital-Readout-DRO-Set/dp/B01G5SUZEG/ref=cm_cr_arp_d_product_top?ie=UTF8

Yeah, they aren't up to Jo's standards (etched glass, .001mm resolution) but hey, they are about half the price of the cheapest glass ones.  I'm not gonna post a lot of detail, mounting them is no really big deal, and there is a lot of how-to stuff out there on the web.  I did want to show my read head brackets though.  Pic #1 below shows the bracket connect the read head to the vertical mill head (Z axis).  I used a piece of .018" stainless shim stock, to allow for flex in the lateral direction (perpendicular to the fat face of the read head/beam).  It's the one dimension that is affected by irregularites in the cast surface I bolted the DRO to, and rather than fuss with shims, I decided to use these "flexures".  Seem to work pretty good.

I tried to take a picture of the displays, but it came out blurry.  The only reason to show that photo, was that I bought the AC adapter to feed power to the units, rather than fuss with the little coin type batteries they come with (if anybody wants the batteries, pm me, I have no use for them).  But yes, one ac adapter at $18, and another few dollars for the 3.5mm x 1.3mm solderable power jack plugs to split the power cable up to feed all 3 units.  Works pretty good.  The amazon link for the plugs is below, I still have 7 left if anybody wants them, same deal as the batteries :)

https://www.amazon.com/uxcell-10Pcs-3-5mmx1-3mm-Solder-Connector/dp/B01BTWXFVS/ref=sr_1_13?ie=UTF8&qid=1523564038&sr=8-13&keywords=3.5mm+power+jack

Pic #2 shows my other neat idea, marking the positive reading directions for the various dro's on the mill stand, so I will have to work to screw up my dimensions.  ;)

Pic #3 shows some bits of delrin that I turned on the lathe.  A groove sized to fit sheets of acrylic I have lying around from another project, a set screw to clamp the sheet in place, and a pocket bored on the other side to hold a cheap ceramic magnet.  Pic #4 shows a pair of the finished products sticking to the bed of the mill, and doing a decent job of keeping aluminum chips from flying off to the far corners of the garage.

So, now I'm ready to machine!  Just gotta find time...

« Last Edit: April 12, 2018, 09:16:23 PM by bent »

Online b.lindsey

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Re: Mini-mill DRO and swarf shields
« Reply #1 on: April 12, 2018, 11:45:41 PM »
Those scales are working well for me bent. I used on on the Z axis of the cowells lathe. Very pleased with it so far.

Bill

Online zeeprogrammer

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Re: Mini-mill DRO and swarf shields
« Reply #2 on: April 13, 2018, 12:23:04 AM »
I'm thinking of that for the lathe. It would be very helpful.
Carl (aka Zee) Will sometimes respond to 'hey' but never 'hey you'.
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Online Jo

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Re: Mini-mill DRO and swarf shields
« Reply #3 on: April 13, 2018, 04:10:53 AM »
Yeah, they aren't up to Jo's standards (etched glass, .001mm resolution) but hey, they are about half the price of the cheapest glass ones. 

Oh dear she's getting the blame again  :facepalm:

Yes she started out with a set of those and they proved that having DROs on a lathe (despite what those who do not have DROs on their lathes say  :disappointed: ) is actually a good thing.  And an AC adapter would make using those displays even better  :ThumbsUp:

The down side of that type is the small LCD displays which can be difficult to see especially in sunlight and the small buttons

Jo
Usus est optimum magister

Offline Firebird

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Re: Mini-mill DRO and swarf shields
« Reply #4 on: April 13, 2018, 01:37:10 PM »
Hi Bent

I have those scales on my milling machines. They are the better type, I gaging.

If you fancy upgrading them again they are the ones you need to blutooth them to any android device, I use a 7" tablet.

I started a topic a while ago here

http://www.modelenginemaker.com/index.php/topic,2865.0.html

Unfortunately photosuckit have stolen the photos but there are a few links

Cheers

Rich

Online bent

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Re: Mini-mill DRO and swarf shields
« Reply #5 on: April 13, 2018, 10:41:27 PM »
No slur intended, Jo.  I just figured that, having a cheap mill with spindle tolerances and bed flatness no better than about .0005 and .001, no point in getting too fancy.  And I think seeing them on your home mill helped me make a decision, Bill.

I hear you about the tiny displays, and they are kinda slow to update, and the mounting arm is flimsy (its a little better when I stuck a piece of metal banding to the magnets on the backs of the displays, it acts to help stiffen up the stack a bit).

Bluetooth and a tablet...in a shop.  Hmm.  There's a bluetooth and display screen in the MX-5 I park near the mill, but it might be a trick to reach out the window to turn the knobs.  :lolb:  Seriously, I like the idea, but my eyes are getting a bit old to do the detail solder work that the diy approach seems to entail.  Unless Julian has ready-made boxes for sale and I missed that?

Offline Firebird

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Re: Mini-mill DRO and swarf shields
« Reply #6 on: April 14, 2018, 09:00:19 PM »
Hi Bent

I have given Julian a nudge, he should be in touch.

Send him a PM as well

Cheers

Rich

Online bent

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Re: Mini-mill DRO and swarf shields
« Reply #7 on: April 16, 2018, 05:51:24 PM »
Cool, thanks!

Online bent

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Re: Mini-mill DRO and swarf shields
« Reply #8 on: April 18, 2018, 06:09:57 PM »
Hmm.  Did some more machining last night, and was called to dinner in the middle of a setup, also sat and watched Jeopardy, so about 45 minutes elapsed until I returned to the mill.  It was quickly apparent that the dro's had drifted in the interim, and not a little, but a lot (like over an inch).  Looks like I have found the drawback to the un-shielded data cables (and my bundling them in loops to tidy up the extra slack probably is not helping either) of these low cost indicators.  Any suggestions or similar experiences?   
:headscratch:

Offline Les#053

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Re: Mini-mill DRO and swarf shields
« Reply #9 on: April 18, 2018, 08:10:14 PM »
Hi Bill,

I built the Bluetooth of Yuri's using the TI MSP430 Launchpad board and have just noticed that my Z axis seems to have bouts of jumping 2 or 3 inches.

It seems to be happening if you zero the readout and then switch the motor on, so I'm wondering if it's a surge in the EMF from the motor interfering with the Bluetooth signal?

I've tried zeroing by touching the chuck jaws, then winding the saddle back and forth 20 times and it stays spot on zero, as soon as I switch the motor on the readout jumps nearly every time.

I need to do some more tests, but would be interested if anyone else has noticed anything similar.


Les

Offline MJM460

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Re: Mini-mill DRO and swarf shields
« Reply #10 on: April 19, 2018, 09:34:20 AM »
I have installed those cheap dro's on my lathe and wouldn't be without them.  So far, I only have them on the long travel and tail stock quill.  Haven't worked out how to put them on the cross feed.  My 5c collet adaptor fits almost flush into the MT5 taper of the headstock, and making small parts requires the saddle to be at the limit of its travel and the tail stock right against it.  Even then, the compound slide has to be in the right position.  So no obvious room for the reader housing and cover.

I don't have trouble with the readings jumping as described, perhaps it is because I am still running them on batteries.  A bit frustrating, having to replace them, but so far I have had no real difficulty.  I do find, when the batteries are near flat, that the reading drifts a bit over time.  As soon as I notice any inconsistency, I replace the batteries and seems to solve the problem.  It is frustrating though, if the drift occurs as you near the final dimension, and as a result cut too deep.  Have to admit loosing one or two parts, but nothing big so far, I usually pick it up in time, by keeping a check that the wheel graduations make sense in terms of the movement I want.

I have found that the more expensive silver oxide cells do live up to the description, and do seem to maintain a more stable voltage than the cheaper alternative chemistry.  They seem to be worth the cost for measuring applications.

If the problem seems to be caused by a voltage spike through the power supply, it might be worth obtaining some split ferrite rings that can be fitted around the wire to suppress sharp spikes.  Put them around the motor end of the motor wiring and the instrument end of the readout power supply. No guarantees, but very cheap to try.

MJM460
The more I learn, the more I find that I still have to learn!

Online bent

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Re: Mini-mill DRO and swarf shields
« Reply #11 on: April 19, 2018, 04:11:32 PM »
Did a test yesterday - left the machine plugged in with dro's zeroed for an hour or two, no movement/jumping.  Motor on/off transients didn't seem to matter, nor lights in garage or other equipment (lathe, drill) on same circuit.  Not quite sure what to make of it, but did spend some time cleaning swarf off the x-axis beam and reader, and fitting a quick and dirty swarf shield for it (a piece of overhead transparency sheet, cut and folded).  Something to keep my eye on I guess.
:noidea:

Offline Barneydog

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Re: Mini-mill DRO and swarf shields
« Reply #12 on: April 19, 2018, 07:54:26 PM »
Hi guys,
Running on batteries wont make any difference as the  working voltage is exactly the same.
Rich has the same problem with one of the dro boxes i built for him. Replacement box does the same. I am going to solder some capacitors onto the board and that should help. The interference is almost certainly the on/off switch on the mill which is slightly worn and arcing across the contacts. It is a sign that the contacts inside the switch are electrically dirty. If rich leaves the switch on and does the on and off with the wall socket it works perfectly.
I have a similar problem in my workshop. When i turn on a certain spotlight the computer for the cnc mill starts up!!!!!!
It wont matter what sheilding you have. It will probably not have any effect.
Will let you know what the results are


Julian

Offline Les#053

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Re: Mini-mill DRO and swarf shields
« Reply #13 on: April 20, 2018, 09:37:11 AM »
Hi Bill,

I found this page on Yuri's forum which has couple of links which look interesting, I've only had a quick look at the moment,

will try to find some more time at the weekend.

https://forum.yuriystoys.com/showthread.php?tid=298


Les

Online Bluechip

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Re: Mini-mill DRO and swarf shields
« Reply #14 on: April 20, 2018, 10:34:49 AM »
Does the PSU for the DROs have any sort of RF filtering on the mains input?

Something along the lines of this?

http://cpc.farnell.com/roxburgh/cmv40/choke-com-mode-2x2-4mh-4a/dp/FT00013

Together with a couple of ( maybe ) correctly rated 10 nF caps. to earth. ( Can't remember whether they should be X1 or X2  )
There should be one ( or a canned filter ) on the mill to go some way to stopping all the shytte getting out onto the ring main   :thinking:

The ferrites that MJM suggests would be my first call. They may just do the job.  :ThumbsUp:

Dave

« Last Edit: April 20, 2018, 10:53:07 AM by Bluechip »