[njwtech]

I am not sure if this is the right forum for this, but I have a Grizzly 11x26 lathe and want to do a CNC conversion. Budget is an issue. I can't do the conversion right now, but I need to be making parts in my small shop. I didn't want to spend ~$600 for DRO cause that is money that could go toward CNC stuff, but DRO would help me make parts, especially on the cross-slide axis. I made several trips back and forth to Grizzly's showroom while pondering this over a week or two, and then when I was there one day I happened to look down and see their 8" digital scale in a display case. When I saw a $40 price tag a light bulb went off. I bought it and made a stop at the hardware store on my way home to pick up some 1 1/2" x 3/16" flat iron. Here is the result. I thought others on a budget might benefit. I would think the idea could be adapted to pretty much any of the small lathes from the mini to 11x26. I can make parts twice as fast now, and the repeatability is excellent. I made a plexi cover that keeps swarf and coolant off it (works very well). All I do is make sure I zero it before shutting it off so I don't have to recalibrate every day.









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Norm
http://www.wacparts.com

[twocik]

WOW that's too funny. I was just at harbor freight a week ago and thought to myself the same exact thing. Luckily they had a sale for there calipers,

4" - 10.00
6" - 16.00
8" - 24.00
12" - 36.00


I bought the 6" for my cross slide, but I'm mounting it in a way that can be adjusted for the 3" loss on my 9 x 20.



Very nice job BTW!!!!! :rainfro:

[in2steam]

Norm,
Looks nice, thanks for the post and this is the right area, its not entirely new but I am sure there are newer members looking for similiar short cuts.
I did the same as twocik, I got a bunch, several for my shaper, a couple for my atlas mill, and 3 more for one of the lathes, as an added bounus you can take off the cover on the side and if you want buy the DRO screen and cables for around $200 depending upon the style you by, from what I understand even the cheapos form HF work just dandy.


chris

[njwtech]

Thanks Chris. Can you elaborate a little on that last sentence? Are you saying it is possible to tap into the digital scale and feed the information to a DRO? If so, can you point me toward the information about how to do it? Thanks.

..
Norm

[acondit]

Thanks Chris. Can you elaborate a little on that last sentence? Are you saying it is possible to tap into the digital scale and feed the information to a DRO? If so, can you point me toward the information about how to do it? Thanks.

..
Norm

Norm,

There is a little removable door on most of the scales that covers a 4 pin pcb connection. The Shumatech DRO-350 (a user build item) can work with the chinese scales or with an adapter (QCC100) with quadrature scales.

I have a DRO-350 on my mill drill. Just google Shumatech DRO-350.

There are also remote readouts that you can buy to work with the digital chinese scales or calipers.

Alan

[Mr.Chips]

WOW that's too funny. I was just at harbor freight a week ago and thought to myself the same exact thing. Luckily they had a sale for there calipers,

4" - 10.00
6" - 16.00
8" - 24.00
12" - 36.00

I bought the 6" for my cross slide, but I'm mounting it in a way that can be adjusted for the 3" loss on my 9 x 20.

Very nice job BTW!!!!! :rainfro:

You have to watch the resolution, some of the less expensive ones had only a 0.01" resolution. Think you would want 0.001" at least I think for metal work.

[in2steam]

All the ones I got were .001 one was even reading tenths on the half(it was a 12" odd to the other three shorters). B&S they are not, but for the machines they are going on there bettter then what they have and thats nothing. Not to mention I have no problem drilling a hole in them.

chris

[njwtech]

Yes. The Grizzly one I got has really good resolution (.0005") and seems to be pretty accurate. I couldn't read any error at all with my dial caliper on the work I did today. Thanks for the info guys. I checked out Shumatech. Does anyone know the principal of operation of these units? I'm just wondering if they could be extended somehow so I could use the same thing on the Z axis.

..
Norm

[Mr.Chips]

Frequently the internet price of the HF items are cheaper than the store price. Print out the internet add and take it to the local HF store and they will honor it. You have to have the print out though, you can't just tell them.

They will even honor competors pricing if they are selling the same thing.

[under-dog]

Very cool.

I have seen an web article before of someone doing something of this nature.

I have wanted to do it for a few years since I saw the article but never gotten around to it.

Any insights into how you did it. Cost and time involved?


Thank you

[acondit]

Yes. The Grizzly one I got has really good resolution (.0005") and seems to be pretty accurate. I couldn't read any error at all with my dial caliper on the work I did today. Thanks for the info guys. I checked out Shumatech. Does anyone know the principal of operation of these units? I'm just wondering if they could be extended somehow so I could use the same thing on the Z axis.

..
Norm

Norm,

I have a 22" chinese scale on my mill drill and I have seen them up to 40" long on eBay. However, at that length it is almost as cheap (possibly cheaper) to actually go with a quadrature scale.

The chinese scales use a capacitive circuit printed on a pcb for distance readout. The quadrature encoders use optical scales and I believe that two optical readers are phase shifted to provide 4 counts for every mark on the optical scale. So a 500 count linear scale provides 2000 cpi at the readout. Check out the linear scales and quadrature encoders at US Digital.

Alan

[scubasteve_911]

Has anyone tried to create an interface for linear encoders to a display? You can pick up relatively inexpensive linear encoders precise to 1uM off of ebay. I have done quadrature decoding on a microcontroller in the past, it's extremely simple. Then, you could simply convert the count with a basic math routine, then display it on an LCD.

I have programmed similar things in the past in a matter of hours on a PSoC microcontroller. I plan on doing this for my soon to be arriving HF 8X12".

Steve

If anyone is interested, please send me a message and I will publish schematics and code.

[snoopy27]

I would like to see what you have done. I have played with this idea, but have never gotten serious with it. The problem I see on any machine tool is the mechanical mounting of the encoder and detecting a precise index pulse for homing.

Also linear encoders cannot compensate for thermal expansion along an axis, if mounted to a linear drive composed of belts, pulleys, and gearing, not to mention backlash angular displacement. Although on small machines many of these factors can be negligible. I am sure you already aware of what I am saying and I agree that this can still be a more cost effective solution than scales and other DRO's that are not as accurate.

My other question to you is why not just use MACH3 coding as your DRO if you already have it to drive your axis motion?

[njwtech]

I did the scale DRO quite a while ago. It worked for what I needed since the tolerances were not too tight on the parts I was making. In the end though, I converted the lathe to cnc and took off the DRO. I use Mach3 to drive a stepper system. I can make parts much faster now and accuracy is plenty good enough for the car parts I am making. You can see video of it in operation [ame="http://www.youtube.com/watch?v=vAOvWgBtCm0"]on Youtube[/ame].

[dareposte]

What's the purpose of the operation starting right around 3:45 in the video, where you start facing from the center for a 1/2" or so then go back and take a deeper cut and cut the first one off then keep going? I'm puzzled, please educate me.

[njwtech]

What's the purpose of the operation starting right around 3:45 in the video, where you start facing from the center for a 1/2" or so then go back and take a deeper cut and cut the first one off then keep going? I'm puzzled, please educate me.

Sure. Basically, I do it so the (thick and almost flat sided) carbide tool bit I am using can handle the small diameter close to the center of the face. Shallow cuts face fine, but when you are making a deeper cut near the center of the work, it is in effect the same as trying to do a boring job with a thick, flat faced tool. So it cuts fine even close to the center if you take light cuts (because of the front rake), but hits the work if you make deeper cuts until you get far enough out from the center. Thus I make two lighter cuts rather than one deeper cut until I am far enough away from the center so that the bottom part of the tool bit won't hit the work. If I was using a tool with more side rake I would not have to do this, but carbide tool bits are cheap and I don't make enough of these parts to worry about a little wasted motion (and time) on the cutter path. If I was doing larger production quantities I would use a thinner tool and optimize the path for time, dropping the (then) unnecessary step.

..
Norm

[gmac]

NOW - go to ratshack or otherwise and get an LM317 voltage regulator. use a couple of resistors to set it up and calibrate to the battery voltage of the digital caliper ( probly 1.5 volts if a single battery style). now solder a few wires in the battery compartment and run the LM317 power from the lathe control box ( pick a low DC voltage like 5v or 12V from a voltage controller output on the control board) and BOB's yer uncle- the dispay goes on and off with your machine switch and NO batteries to run out. use some hotglue or contact cement or dubleside tape to stick the LM317 into the control box ( the 2-3 resistors are soldered right onto tit) , and even fine little wires like telephone cable stuff will be OK since the currents are very low.