Homemade DRO...maybe...sort of...

[zeeprogrammer]

First off...I know next to nothing about a DRO. By that I mean, the features and usage of those boxes with the 7-segment displays, buttons, and nifty functions.

Second...this may not go anywhere but it has a better chance of making it if I post it. In any case, it will be slow going.

My hope is to build and install a DRO system for my X2 mini-mill and my mini-lathe.
There's been a few threads on this...so it's not new...but I hope someone finds this thread interesting and/or entertaining.

The system is based on the DRO-350... http://www.shumatech.com/

The 350 is obsolete but you can still get parts, and more importantly, PCBs.

I went to Mouser and Digi-Key and bought all the components except for the PIC processor, enclosures, cables, and of course, PCB. I also didn't get the required number of switches. I intend to use something I'm already familiar with or have access to because of my work. Initially I was going to use perfboard. But I found the costs for board, wirewrap wire, and wirewrap sockets have gone way up since I played with this stuff some years ago. I stayed awake all night thinking about all the hand wiring that would be required (I want to build two of these)...so I went ahead and bought the PCB(s) from a place that services these systems. I can connect my own processor to the PIC holes. I still need to think about cabling and enclosures.

As I mentioned, I'm building two of these. One for the mill and one for the lathe. They will not have all the nifty features of a real DRO system. I just want to be able to see the relative distance, be able to zero out, and perhaps change scale (mm/in). Having said that...the system can easily be added to. I suspect I'll keep a communication port to a PC so I can also do some software enhancing from there.

While you can simply look at the display on the caliper, I'm thinking that will be difficult to do in some cases. There's also the possibility of coolant and I need to ensure the system is covered. You can also get remote displays for the caliper but I didn't want to buy a bunch of these. Besides, I wanted the flexibility and potential that the DRO system affords.

The electronics and software will be a piece of cake for me. It's how I make my living. The rest of the system is a different story...

As many of you know, the system uses cheap digital calipers for inputs. So the real challenge for me is going to be modifying the caliper (metal-wise) and mounting them. The mill will need 3 and I'm thinking the lathe will also require 3 (one for the tailstock).

Here's a pic of the caliper we're talking about...

So it was time to play...

I started with an angle grinder to knock off the pointy bits. I've never used an angle grinder before. ;D And while it was somewhat successful...the cherry red glow should have been a clue. The scale bubbled up near the end.

So I went to the dremel. That went pretty easily! This shot shows the display pulled off. The caliper at top shows the back. You have to peel the label off and undo the screws.

And so I continued...

I knocked off the rest of the pointy bits with the dremel. I now need a new cutting wheel for the dremel...it got worn nearly down to the shaft. At this rate I'll need 5 more.

Here's a pic of what's left sitting on top of the tailstock.

Now I need to figure out how to mount it so that no damage will occur when in use. Also want to protect against coolant.

A couple of things I noticed...the display went a little nuts. Seemed to work fine in my hand...but not on the tailstock. It could be that it's too loose sitting there, it could be residue from the grinding, or it could be an electrical issue. I read somewhere that the electronics' positive is connected to the metal caliper itself...so some insulation may be required. (Note: The actual values on the scale - I cut both ends off - are not important. The electronics reads everything relatively.)

So there's the start...tips, suggestions, well-wishes are welcome.

I got tired of waiting for that guy who owes me beer (you know the one) and have procured a supply. Nor do any of you need to worry about your snacks...I got that too...and you can't have any. :big: Not even going to tell you what they are.

 

[Twmaster]

I've seen more than a few folks do similar things with a caliper. I have a similar caliper I bought at H-F for $10 on sale. I plan to hack it up.

I got lucky and scored a used 24" scale for very cheap at the last metalworker club flea market. It needs to be cut off too...

Also, I have the PCB and overlay for a DRO350 I'd like to sell. Contact me via PM or email if you have interest.

 

[Noitoen]

The problem with home made DRO for me is the scales. I can treat any signal and display it on a lcd using Pic micros but my lathe and mill are to big for the calliper type scales. I've installed a cheap calliper on my mill's Z axis but the travel is small.

Optimum Maschinnen have a magnetic strip type scale but I can't get any information about the pick-up for these.

 

[zeeprogrammer]

Thanks Mike.

Noitoen...yeah scale size could be an issue. I managed to find a very affordable 12" scale that I think will work perfectly for the mill's X. I have a set of 6" calipers that should work for the mill's Y, as well as the lathe's cross-slide and compound. They may even have to be shortened.

I have no plans to mount a scale for the lathe's carriage. But we'll see.

The bigger issue will be the mill's Z. I think the 6" is too short now that I extended the mill's travel.

 

[rudydubya]

... well-wishes are welcome ...

Zee, I wish you well. ;D Good luck and be assured I'll be following your progress with interest. What kind of cutoff disk or wheel did you use with your Dremel?

Rudy

 

[Noitoen]

The sensor I was talking about is from these guys http://www.sikoproducts.com/MS100_1/part/MS100/1

The magnetic tape is sold by the metre. I've installed a readout from Optimum on a machine and works fine. I've tried to capture the signals between the MS100/1 sensor and the readout display with no success. Tried to get an application note for an amplifier from Siko but no response. If you can get something from them it would be great. They have other sensors that give "treated" signals but the price is too high.

 

[zeeprogrammer]

... well-wishes are welcome ...

Zee, I wish you well.

Ha! I knew it would be someone. But from a home state...even better.

If I'm identifying the wheel correctly from the literature that came with the box...it's just called a 'cut-off wheel'. I can't remember the diameter now. But I have to admit to some confusion. I'm looking at the pictures of the cutting wheel and none of them match the thickness. But I can't find anything else that matches either. Cut well though.

I'm wondering if it was actually a grinding/sharpening wheel? No idea if this pamphlet shows all of the bits that you can get.

But thanks to you Rudy, I've been sitting here reading this thing and getting all excited. I think I'm going to like this tool. ;D

 

[zeeprogrammer]

Noitoen,

Looks like a pretty interesting sensor. Good for long distance or even odd shaped applications...but seems more work than the caliper since you have to make something to carry the sensor. Seems particularly interesting for measuring a round turning object.

I tried looking at some of the user documentation but when it takes more than a couple of minutes to transfer...especially from a vendor...I give up and move on. If they make it difficult to get information...then I'm less interested.

Thanks!

 

[Blogwitch]

Carl,

I went the route you are taking a few years ago on my previous mill.

Even though these digiverns are a cheapy variety, they do need to be treated with respect when it comes to chopping them about. Your problem might be on reassembly, and you haven't got the correct pressure on the phos bronze wiper strip that runs along the edge of the main scale bit. They can be a bit fiddly to get back into the correct position and adjusted up.

Over the years, I found this was the most common area for failure, especially when you were half way thru a job. You need to get that wiper adjusted so that it doesn't lock the unit up, but still allow a good clean contact. The other main area of failure is the carbon pick up strips on the back of the display itself, especially thru condensation, you will get spurious readouts on the display. That requires a rather delicate strip down job of the whole display unit and the tracks very carefully cleaned down with methylated spirits.

Using digiverns and read heads of this design is fine, but I found that were rather unreliable at the best of times, even when well protected. Eventually, after about 3 years, and having many spare heads to swap over at a couple of minutes notice, I gave up on them and went to glass scale versions. After spending copious amounts of money replacing the scales, it worked out cheaper and less frustrating in the long run to swap over.

Don't get me wrong, they are a relatively cheap method of getting a DRO system, and they do work accurately most of the time. But this type of scale, no matter what anyone tells you, is not designed to work in the environment you will be putting it into, especially if you use suds as well.
The only reason they manufacture the scales in all lengths is because people still think they can get a good working system from them, and the manufacturers will continue to produce anything if it makes them money, whether it is fit for purpose or not.

I do still use one of this type on the quill Z axis of my mill, but only because it is out of the way of all the nasties, plus I have done away with the battery problems (another thing that needs to be addressed) by running it on a small power supply that a friend very kindly made for me.

That is just the way it didn't really work for me, it just might be OK for yourself.

BTW, when mounting it onto the tailstock, you really need to get something on there to compensate for the twisting motion of the barrel. I would suggest a double ended ball joint available from most model shops.

Blogs

 

[black85vette]

Should be an interesting project Zee. I have looked at several approaches to this myself. I can't get my head around spending $350 for a mill and $750 for the dang DRO!!! I will chip in if I have anything to add.

 

[zeeprogrammer]

Blogs...thank you!

I did notice the wiper strip. At one point I was moving the display back and forth and it peeped out. I had meant to mention that in my post.

If they worked for you for 3 years...then given my own production rate...I should be good for 10 or 15. :big: But seriously, thanks for the heads up...it's not something I want to frustrate me and take away from the enjoyment.

As for the battery...yes...power will be provided by the main system...no batteries should be needed.

I'm looking for success...if this turns out to be a failure but teaches some one else...then it's still a success. Does that make sense?

Your warning about the twist of tailstock barrel....I didn't notice any twisting when I cranked either direction...but I can rotate the barrel by, call it 1/2 a mm, by hand. I don't understand the issue though. If you get the opportunity I'd appreciate any additional information. Thanks.

Thanks Rick! That's exactly it...half again as much for the equipment is just way too high.

 

[deere_x475guy]

Hey Zee I built one of these back about 2004 and sold it with the dove tail column mill I put it on. The calipers as scales are very touchy. You might want to think about going with the glass scales.

 

[1hand]

Whats up Zee.

The way I mounted mine scales with the angle iron really protects it from swarf and coolant. I'm really happy with the way they function.


Matt

 

[ozzie46]

Zee, on the twisting of the tailstock barrel. It will put the scale in a bind and give inaccurate readings. I've run into this on the Z axis of my drill/mill. I will be doing as Blogs suggest soon.

Ron

 

[zeeprogrammer]

Hey Bob...that's the 2nd...no..third reference to glass scales I've seen. Guess I need to find out what that means. ;D

Matt...yep...in fact I ordered some angle iron...er...aluminum...just for that reason.

Ron...I have to admit I still don't understand. I may have to wait and see what happens when/if I mount this thing. I don't even know what blogs meant by 'double ended ball joint'....I'm just a softie! But I/we will get there!

Thanks all. The gating factor will be when the PCBs get here. I had to send a check so the turn-around time is a little lengthy.

 

[1hand]

Zee,
I know you seen my thread, but for others: Here they are all covered up and protected from the nastys.

matt

 

[zeeprogrammer]

Yeah...I think it was your thread that got me ordering some angle.

Thanks.

Pssst...next time put a link in to your stuff! ;D

 

[ozzie46]

Zee, double ended ball joints are used on the rotor heads on RC helicopters for the control linkages for the pitch and collective. Look up a picture of a RC helicopter at Tower Hobbies.com and it should become clear.

As to the twisting problem I don't know any other way of saying it. Maybe Blogs will chime in tomorrow. As he is in Britain he's probably asleep now. I know he could give you a better answer.

Ron

 

[1hand]

http://www.homemodelenginemachinist.com/index.php?topic=7354.0

Heres a link to a homemade DRO set-up. I hear the author is a heck of a guy............ :

 

[cfellows]

Good Thread, Zee! I've been trying to justify some kind o DRO for my mill/drill but just can't see spending $500 or more for one. It's one of those things I'd really like to have, but at the prices they command, they're just not worth it to me. Funny, I've always kind of thought that any tool I really wanted was worth the price. Guess I just don't want it that bad. I'll be interested in seeing how yours turns out.

By the way, was it hard to cut the bits off that first caliper? I bought one for less than $10, including shipping, wanting to make a height gauge out of it, but it's so darn neat, I'm using it as my primary caliper now!

Chuck