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Installing a magnetic DRO on my VM32L

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JasonB01/07/2020 20:24:05
18318 forum posts
2024 photos
1 articles

I would be tempted to make the X axis mounting bracket "t" shaped as viewed from the front which should allow the two vertical holes that the existing table stop screws into rather than tap another pair of holes. Or it could be a wider block but with two vertical holes.

Iain Downs01/07/2020 20:56:04
667 forum posts
594 photos

Jason. I agree. Also I'm near the end of my Motor Feed build and was planning to use the central position pointer to locate the optical sensor for my end stops - with the stops themselves holding a blade to interrupt the sensor.

Ian. Quite disturbing, really, I'm not quite sure what you mean by U channel on the Y axis. The strip is on the base on the sensor on the saddle so I can't see how to use a U there.

I'm going to have buy some stock to make the various brackets. I've get everything but what I need...


Ian P01/07/2020 21:42:06
2406 forum posts
101 photos

I will take a picture so I can post a sketch of what I was suggesting (probably in the morning).

I am not familiar with your machine but if I interpret what I see in the pictures I think their installation has the Y axis strip on the stationary base of the mill, and the sensor head as the moving part. Since the cable does not look particularly robust I would reverse the tape and sensor positions.

Their X axis sensor and cable also look to be vulnerable. There is no need to have the sensor dead in the middle, moving nearer to one end might allow much better routing of the cable.

Drilling and tapping holes in a machine (brand new or old ) would never bother me but I know some people are reluctant (to even paranoid) about making any modifications to a machine, In this case, unless you want to glue everything together, some holes are inevitable.

Ian P

Iain Downs01/07/2020 22:43:55
667 forum posts
594 photos

Ian - I get what you mean about the Y axis, but I think the travel may be greater than the depth of the saddle. I'll measure up tomorrow.

I'm cool with drilling holes!


Ian P02/07/2020 10:19:18
2406 forum posts
101 photos

Really crude sketch of what I was trying to suggest earlier.

Something like 3/4" x 3/4" x 1/8" aluminium channel will be 1/2" wide internally which I think will be wider than the sensor head.

I have shown the channel sticking out at the back of the machine only to show that once you know the overall length of channel required it can be positioned offset towards the rear so that the rear end of the extrusion projects no further than the back of the machine base.

Hope that makes sense

Ian P

scale mounting.jpg

Mike Crossfield02/07/2020 11:22:40
216 forum posts
19 photos

The arrangement Ian P describes is very similar to what I used on my mill, In my case the scale is mounted on a length of aluminium angle attached to the undeside of the carriage,, and there is also a swarf guard over it. The read head is mounted on an adjustable bracket attached to the base casting. Works very well.


Iain Downs02/07/2020 17:01:56
667 forum posts
594 photos

I'm having a think about the Y axis.

The saddle is 210 mm deep and the travel is about 230 mm.

With the length of the sensor around 40mm, I'd need about 310mm of channel which would leave 100mm sticking out the back.

The main advantage I can see with this approach is that I would be sticking the magnetic strip to a clean piece of metal and not to a suspect and rough painted surface.

I feel slightly uneasy about a 4 inch bit of 15mm channel sticking out of the saddle. Not sure if it's particularly justified!

Similarly, I've ordered some bar to replicate the Y axis mount in the pictures above - so I screw the bar to the column and stick the strip to the side of the bar.

I was thinking of spraying the strips with laquer after mounting to keep contaminants away from the sticky strips, but I'm not sure if the lacquer would survive the contaminants. Any thoughts on that.


ChrisB02/07/2020 18:37:42
497 forum posts
190 photos

This is how I installed mine, possibly the simplest way to do it! The mounting bracket is just a piece of 1.5mm sheet metal, bent to match the angle of the milling machine base (the base casting has a slight slant to it) The bracket is slotted to allow for the readhead hide height to be adjusted.

The surface finish of the base might not be the same as that of a machined surface, but it's certainly fine for the magnetic tape to be installed on to. Installed this way you will not have any issues of anything sticking out.

My readhead and tape might be considerably smaller than yours but the length should be approximately the same. Have had no issues with it yet - my only complaint would be that some chips do tend to stick to the tape occasionally, but it's easy to wipe off with a brush.


Iain Downs05/07/2020 19:16:52
667 forum posts
594 photos

Somewhat to my surprise, success!

Here's how I added a (supposedly) manufacturers DRO kit to my VM32L.

Firstly, I didn't rate the brackets provided. I didn't even see that they could work.

So I made my own.

dro x and y mounts.jpg

The X Axis was nice and easy. There's a 10mm slot which normally holds the scale. Rip the scale out (held in by pins), clean it up and stick the strip in there.

dro x strip and mount.jpg

At some point, I'm planning to adjust the end stops (round button on left) with a rod so they can intercept an optical sensor int the DRO mount and provide a limit for power drive. However, that can wait.

To set it up I just put a feeler gauge between the sensor on the strip and tightened up

dro x setting up.jpg

A word on cutting. I Kind of freaked about this. Is there some special way of cutting? Actually no. if it will cut metal just do it. I used tin snips, I drilled, I used a hacksaw. Careful though ,there seem to be some ridiculously fine splinters in the strip. Hacksaws aren't the best way!

I reckoned that the X axis in the slot would be fairly secure, but was less happy about the Y axis on the cheap paint of the body (meths seems to dissolve the paint. Ugh!).

So I drilled 3mm holes in the end of the strips.

dro y strip drilled.jpg

In this case I stuck the stainless fascia to the strip before mounting it. For the X I mounted the strip then stuck the tin bit on top afterwards.

With the Y I drilled and tapped one end and used that as a reference for the other (bolted one end to the base and the made sure it was aligned).

dro y strip screwed.jpg

You can see the bolts at each end in this picture.. I was happier doing this that using swarf covered magnets!

With this in place I hooked up the display and set it up and turned the handles. Whoo Whoo! The numbers changed!

dro powered up test.jpg

Finally, I tidied up the wiring. I've used sticky mounts here rather than bolting the cable to the mill. Let's see if that sticks and if not, out comes the frill!

dro wired.jpg

The DRO display is mounted on top of the motor control box. You can't really see it in this picture, But I think that's the best place for it.

I've not actually USED the thing yet, but I'm really looking forward to doing some real work with it!


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