Cheap DRO malfunctioning - Thoughts on cause or fixes?

dmcclosk531 · Dec 9, 2019

Hello,

I have an old bridge port with a cheap DRO installed. The x-axis scale has recently stopped working, in a strange way.

This is the installed unit: Amazon.com: iMeshbean 2 Axis Digital Readout Dro for Milling Lathe Machine with Precision Linear Scale (100mm-1000mm Options),you will receive Random Two Scales (500mm and 1000mm scales), if u did't leave a Note.: Home Improvement

I've done some trouble shooting and this is what I've found:

- Doesn't matter if I plug the scale into the x or y socket on the receiving unit - the problem persists (must the the scale itself)
- I've pulled the end caps off the scale - all looks good inside. The glass is intact, no debris are visible, I tried cleaning the scale with isopropyl alcohol and a cotton swab (this didn't change the symptoms at all, but everything looks good inside)
- inspected all connections, wires, solder joints (all looks good)

The scale operates perfectly on one end, for about 10". Then it hits the "spot" and the reading just freezes and jitters back and forth plus or minus 0.0005 on the readout. The "spot" is the same every time. Every part of the scale on one side of the spot works, every part on the other side doesn't work.

Any ideas? This scale is pretty new, about a year. Has only been used a hand full of times. Worked great until it recently stopped. I've ordered a replacement, but want to know what's going on still. Could I have install the scale in some way that caused it to fail? How can I prevent this from happening again? Can it be fixed?

Thanks,
Dave

mTeryk · Dec 9, 2019

I'd say your best bet to keep it from happening again is to not buy the cheapest thing you can find. Buy quality components from reputable manufacturers that stand behind their products.

Either that or buy three for every one you need and continue to fill landfills with crap that never should have been made in the first place.

Sent from my XT1710-02 using Tapatalk

gustafson · Dec 9, 2019

could be alignment between the reader head and the scale. Check if the gap between the scale body and the reader head is consistent end to end

or because China

Pathogen · Dec 9, 2019

Got hit hard enough to damage

Was installed with uneven force on supports and damaged by hit or temperature changes

Absorbed a chemical that deteriorated it caused the damage

I would not hesitate to buy inexpensive products from China, I do not buy the USA made crap made by some scumbag outfit that cuts corners to save 13 cents.

eKretz · Dec 9, 2019

"Because China import" probably sums it up. It sounds like a manufacturer's defect to me. No warranty? Otherwise you're going to have to have the tools to actually monitor the output if you want to do much in the way of diagnosing the problem. Got oscilloscope?

Newman109 · Dec 9, 2019

I have a Mitutoyo KA 2 axis DRO on my mill. I've had zero problems with it. It's extremely accurate and stable. I can't fault it anywhere. It wasn't cheap, though.

On the other hand, I tried to save some money and installed a Sino 2 axis on my 13 X 40 lathe. I had to replace the scale on the compound within a year of purchase due to an internal short. CDCO refused warranty replacement and accused me of using it with coolant. (No coolant) I finally got one from them at cost ($70). Their one year warranty is a joke.

Later the long scale (Z?) would freeze now and then. This was cured by readjusting the scale closer to the read head. It's working now but I've learned my lesson. No more cheap items. I buy the best that I can now in both tooling and accessories.

MrWhoopee · Dec 9, 2019

Since it reads fine up to a point, it sounds like there might be an alignment problem between scale and table, causing the read head to drift up or down far enough to affect the ability to read.

Milland · Dec 9, 2019

MrWhoopee said:
Since it reads fine up to a point, it sounds like there might be an alignment problem between scale and table, causing the read head to drift up or down far enough to affect the ability to read.

I'd agree with you, except that it seems to hit an "exact" spot each time it flakes, which to me points to damage to the scale at that section such that the reader gets confused. But it can't hurt to double-check alignment before scrapping the scale.

Bill Simmons · Dec 9, 2019

I have used a cheap DRO as well and received a display unit that became intermittent. I believe the failure to be an internal trace failure on the printed circuit board. I was sent an additonal display for a fee that saved shipping both ways and a long delay. Quality is sketchy on these. You take your chances.

Now as how to prevent your future scales from failing. Impossible to say with out knowing the cause of the failure. But speculating I question the wisdom of using the mounting brackets supplied with these units. They resemble components of an old erector set (shows my age). They are light weight with excessively slotted holes. Any impact could cause damage to the scale as the brackets flex. I even question stability of readings using these brackets. I recommend machining custom brackets for your application. The scales will be better protected, readings more trustworthy and the installation will look much better. You may have already done this. If so, ignore.

HWElecRepair · Dec 10, 2019

Two things I would want to bring up/ask...

1. How flat, from end to end, is the scale?
2. In your original post, you said that you plugged it into X and Y and the problem persists. To be clear, do you mean that the issue follows the scale no matter where the scale is plugged into? Or that the problem persists on the same DRO axis no matter what is plugged in? From your gripe, I am assuming that you meant the problem follows the scale. But just wanted to clarify.

Sounds to me like what mrwhoopee and gustagfon are saying... I am leaning towards misalignment. It could go either way, but this is indicative of the scale not being mounted flat within the manufacturers tolerence. Either the reader head is getting too far away from the scale and the signal cant bounce off the glass and be read by the reader head or the reader head is being compressed up against the glass and has damaged the glass.

Typically when glass is damaged in just one spot from a crash or something hitting it, the scale will pick back up once it gets passed the degraded part of the glass.

Jon
H&W Machine Repair

jz79 · Dec 10, 2019

Heidenhain scales have a "floating" read head, it is tethered to the moving part you bolt down, floating head has rollers that track on the glass scale itself, holding the head in proper position

I'm not 100% sure about all cheap scales, but the ones I've taken apart, had the same general design, not as refined as Heidenhains, simplified to make manufacturing easier, but still the head was "floating", and it would quite difficult to pull it out of position, unless the aluminum housing would be bent, but that would probably mean broken glass as well, which isn't the case here according to OPs description

maybe the readout is doing something weird with reference marks on the scale, maybe someone played around with the settings and turned it on or off, I'd check readouts manual for that setting (if there is one), other than that, without at least a scope to look at the signal, it will quite difficult to figure out what the problem is exactly

Mtndew · Dec 10, 2019

Gotta love the marketing towards idiots. Just put an "i" in front of our product name and people will buy the shit out of it no matter the quality.
An idogturd would sell millions!

g-coder05 · Dec 10, 2019

Mtndew said:
Gotta love the marketing towards idiots. Just put an "i" in front of our product name and people will buy the shit out of it no matter the quality.
An idogturd would sell millions!

Did ya check out their iGaging DRO kit for $39.95?

Mtndew · Dec 11, 2019

g-coder05 said:
Did ya check out their iGaging DRO kit for $39.95?

lol no. The name alone pisses me off.

mike 44 · Dec 12, 2019

IGauging scales are not DRO's. They work very well for what they are intended for. I am a home shop machinist and have 5 scales installed. One is on a drill press Z axis. Two on a mill and two on a lathe.
I have been using them for 7 years with no problems except for battery life.

Joe Gwinn · Dec 12, 2019

dmcclosk531 said:
Hello,

I have an old bridge port with a cheap DRO installed. The x-axis scale has recently stopped working, in a strange way.

This is the installed unit: Amazon.com: iMeshbean 2 Axis Digital Readout Dro for Milling Lathe Machine with Precision Linear Scale (100mm-1000mm Options),you will receive Random Two Scales (500mm and 1000mm scales), if u did't leave a Note.: Home Improvement

I've done some trouble shooting and this is what I've found:

- Doesn't matter if I plug the scale into the x or y socket on the receiving unit - the problem persists (must the the scale itself)
- I've pulled the end caps off the scale - all looks good inside. The glass is intact, no debris are visible, I tried cleaning the scale with isopropyl alcohol and a cotton swab (this didn't change the symptoms at all, but everything looks good inside)
- inspected all connections, wires, solder joints (all looks good)

The scale operates perfectly on one end, for about 10". Then it hits the "spot" and the reading just freezes and jitters back and forth plus or minus 0.0005 on the readout. The "spot" is the same every time. Every part of the scale on one side of the spot works, every part on the other side doesn't work.

Any ideas? This scale is pretty new, about a year. Has only been used a hand full of times. Worked great until it recently stopped. I've ordered a replacement, but want to know what's going on still. Could I have install the scale in some way that caused it to fail? How can I prevent this from happening again? Can it be fixed?

This set of symptoms point to a bad glass scale. Perhaps some coolant or way oil got on the glass. This cannot be determined by inspecting from the ends. You will need to disassemble things enough to inspect the full scale face on.

I have a Jenix glass scale on the vertical mill, and I do use coolant, and no problems. But I did carefully install all the provided splash guards to protect the DRO components.

markz528 · Dec 12, 2019

Joe Gwinn said:
This set of symptoms point to a bad glass scale. Perhaps some coolant or way oil got on the glass. This cannot be determined by inspecting from the ends. You will need to disassemble things enough to inspect the full scale face on.

I have a Jenix glass scale on the vertical mill, and I do use coolant, and no problems. But I did carefully install all the provided splash guards to protect the DRO components.

Totally agree. Contamination will cause that. That is why I won't run glass scales anymore.

CarbideBob · Dec 12, 2019

If it always fails in one spot within one count it is not alignment. Generally scale alignment fails in a varying amount of counts around the same area.
It could be dirt but if you cleaned the entire length and it is still there it is a damaged or missing line. You can't fix that.
Once this error detected no readout should pick and continue without a clearing and new zero point.
If you pass this bug spot and power down or clear are further movements ok? Past this point working?
These things are also easily damaged at install. This is not the spot the head/slide was in when bolted on is it?
Bob

GregSY · Dec 12, 2019

Part of cheap junk is you have to go into it understanding that when it breaks, you throw it out. No customer support, no warranty, no nothing. You don't get to have your cake and eat it, too. Sometimes you don't even get your cake.

DanLinsch · Dec 12, 2019

Mtndew said:
lol no. The name alone pisses me off.

Agree 100%. Anything with an 'i' in front of it draws sheeple like flies to S**t.

Dan

Cheap DRO malfunctioning - Thoughts on cause or fixes?

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