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Diy Dro

I would like to get a DRO for my mill. Since I live in Canada the selection is poor. To get a Dropro 3 axis glass scale from the U.S.would cost me $1020 for the cheapest one. The exchange rate today was 1.46. Shooting star in Canada sells one but it costs even more. Someone at work showed me.
The remaining gauges have been attached to the DRO. There's now 3 gauges on the lathe and three on the mill. All of the gauge channels are now populated and attached:
Poor Man's DRO for Taig Lathe: I have a Taig lathe for some time. Expressburn exe. One of the things which annoys me is that the cross slide turning dial (as well as dials for the other axes) has a lot of backlash which means that it is tedious if not difficult to move the tool to a precise posit. Arduino Based DRO for GRBL CNC Machine: I started this project with a single goal in mind. I wanted a simple, yet effective way to view information about my CNC machine, while standing at the CNC machine, rather than craning my neck in almost contortionist positions, and squinting like a.

Each card has a PIC on it that converts from the gauge serial protocol to I2C. The main ARM processor then interrogates each of the relevant gauge channels over I2C and displays the values.
Each of the gauge channel PCBs is identical, the firmware is almost identical, the only difference is the I2C slave address, which is 0x30 and 0x40 for each pair of PCBs on the same I2C bus. There's three I2C busses.
The main DRO PCB has an ARM processor on a commercial LPExpresso card:

The TFT screen is a touch screen and there's a menu system running on it. The DRO can be set to display the lathe channels or the mill channels. The smaller OLED displays then show the appropriate axis tags. When running in lathe mode the two X axis values can be added together.
The gauges have been attached with 3D printed plastic mounts. I may re-make them in metal if they aren't rigid enough.
The gauges are held in clips that can have screws clamping them from the sides:


 I've removed the buttons from the gauges if they were pressed by the clips. The buttons aren't needed and you also don't need to read the displays as the DRO does that.

The batteries aren't needed either as the DRO channels all have a 1V5 power supply. The gauges run from that and are powered all the time the DRO is powered. The power down of the gauge display doesn't stop the serial data stream, either, which is nice.
 The mill X gauge is mounted in a similar way:

The Y as well:

And the Z gauge:

The lathe bed gauge was one of the more complicated mounting arrangements.

I've started to use the DRO and it certainly makes measuring things much easier. I need to check that the gauges are working correctly by comparing with a dial indicator.
 Re: DIY DRO Parallel Guide #sawsetup#diy
Touchdro App

#102728 

I wasn't suggesting it would eliminate parallax error, only that the best way to calibrate the DRO is to make it's readout match the measured distance of an off-cut. That said, the extension table he plans on using registers to the Prism on the edge of the slider and thus is square to the slider, and if his distance-stop arm is parallel to that extension table, there should be no parallax error.
David Best

toggle quoted messageShow quoted textOn Mar 8, 2020, at 4:11 PM, imranindiana via Groups.Io  wrote:


I agree with what you are saying but it only works if the guide arm is at 90 deg. You cannot remove parallax error just by this method. You will measure whatever width you cut and punch in the DRO correctly but when the arm is moved in or out, DRO will show arm length movement. If the arm is not moving at 90 deg path, DRO will not show the actual distance travelled towards or away from blade.
Imran 

On Mar 8, 2020, at 4:25 PM, 'david@..'  wrote:
The better method for calibration is to measure the actual width of cut produced and enter that value into the DRO. Pushing against the blade is not very precise. https://www.youtube.com/watch?v=qjqdmV4HBw0David Best

On Mar 8, 2020, at 11:48 AM, imranindiana via Groups.Io  wrote:


I would recommend calibrating the guide arm against the blade. If guide arm is 2 deg off from 90 then DRO set to 30' will be off by 0.018'.
Imran

On Mar 8, 2020, at 2:24 PM, Sang Luu  wrote:
Since the extension table is pretty square against the slider (specifically, the prism channel surface), I'm actually registering the guide to the slider and not the blade. The adjustment on the pivot is just enough since the arm stretches out about 30' there's actually quite a bit of movement. I don't plan on taking it off the table but do intend to move the whole table on the slider as the workpiece requires.
This wasn't a cheap DIY and if I had to outsource the machining it would be higher but not sure by how much -- maybe $100 for all the pieces? I don't really have a reference point though. The critical components could be made with standard tools with patience and good patterns. You could cut the Delrin with a sharp dovetail saw and the holes with a standard drill press. The 80/20 came in about $75 and the electronics about $523. Throw in another $25-30 on small parts, handles, etc. I debate including the aluminum table in the cost, but since I bought it for use in this scenario, it's another $350 or so - others may already have one. 
Working on this project I learned that the Felder's price for the DRO is actually not that far off in terms of value to me. All the machining, tooling and design of the cross cut stops, and the electronics would add up well beyond what they sell the things for. 

Each card has a PIC on it that converts from the gauge serial protocol to I2C. The main ARM processor then interrogates each of the relevant gauge channels over I2C and displays the values.
Each of the gauge channel PCBs is identical, the firmware is almost identical, the only difference is the I2C slave address, which is 0x30 and 0x40 for each pair of PCBs on the same I2C bus. There's three I2C busses.
The main DRO PCB has an ARM processor on a commercial LPExpresso card:

The TFT screen is a touch screen and there's a menu system running on it. The DRO can be set to display the lathe channels or the mill channels. The smaller OLED displays then show the appropriate axis tags. When running in lathe mode the two X axis values can be added together.
The gauges have been attached with 3D printed plastic mounts. I may re-make them in metal if they aren't rigid enough.
The gauges are held in clips that can have screws clamping them from the sides:


 I've removed the buttons from the gauges if they were pressed by the clips. The buttons aren't needed and you also don't need to read the displays as the DRO does that.

The batteries aren't needed either as the DRO channels all have a 1V5 power supply. The gauges run from that and are powered all the time the DRO is powered. The power down of the gauge display doesn't stop the serial data stream, either, which is nice.
 The mill X gauge is mounted in a similar way:

The Y as well:

And the Z gauge:

The lathe bed gauge was one of the more complicated mounting arrangements.

I've started to use the DRO and it certainly makes measuring things much easier. I need to check that the gauges are working correctly by comparing with a dial indicator.
 Re: DIY DRO Parallel Guide #sawsetup#diy
Touchdro App#102728 

I wasn't suggesting it would eliminate parallax error, only that the best way to calibrate the DRO is to make it's readout match the measured distance of an off-cut. That said, the extension table he plans on using registers to the Prism on the edge of the slider and thus is square to the slider, and if his distance-stop arm is parallel to that extension table, there should be no parallax error.
David Best

toggle quoted messageShow quoted textOn Mar 8, 2020, at 4:11 PM, imranindiana via Groups.Io  wrote:


I agree with what you are saying but it only works if the guide arm is at 90 deg. You cannot remove parallax error just by this method. You will measure whatever width you cut and punch in the DRO correctly but when the arm is moved in or out, DRO will show arm length movement. If the arm is not moving at 90 deg path, DRO will not show the actual distance travelled towards or away from blade.
Imran 

On Mar 8, 2020, at 4:25 PM, 'david@..'  wrote:
The better method for calibration is to measure the actual width of cut produced and enter that value into the DRO. Pushing against the blade is not very precise. https://www.youtube.com/watch?v=qjqdmV4HBw0David Best

On Mar 8, 2020, at 11:48 AM, imranindiana via Groups.Io  wrote:


I would recommend calibrating the guide arm against the blade. If guide arm is 2 deg off from 90 then DRO set to 30' will be off by 0.018'.
Imran

On Mar 8, 2020, at 2:24 PM, Sang Luu  wrote:
Since the extension table is pretty square against the slider (specifically, the prism channel surface), I'm actually registering the guide to the slider and not the blade. The adjustment on the pivot is just enough since the arm stretches out about 30' there's actually quite a bit of movement. I don't plan on taking it off the table but do intend to move the whole table on the slider as the workpiece requires.
This wasn't a cheap DIY and if I had to outsource the machining it would be higher but not sure by how much -- maybe $100 for all the pieces? I don't really have a reference point though. The critical components could be made with standard tools with patience and good patterns. You could cut the Delrin with a sharp dovetail saw and the holes with a standard drill press. The 80/20 came in about $75 and the electronics about $523. Throw in another $25-30 on small parts, handles, etc. I debate including the aluminum table in the cost, but since I bought it for use in this scenario, it's another $350 or so - others may already have one. 
Working on this project I learned that the Felder's price for the DRO is actually not that far off in terms of value to me. All the machining, tooling and design of the cross cut stops, and the electronics would add up well beyond what they sell the things for. 


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