Thread: Installing a DRO scale on front of table HM50/52

Hi Dave,

Beautiful work, (like the way you managed to work a bit of red into the project).

What are the advantages of having the scale at the front?
Do you get a little more Y axis travel perhaps?

That method of holding cap screws for turning the head, is now filed away in memory, nice and simple.

Regards
Ray

Thanks Ray,
Yes you don't loose the 40mm travel out of it. I was able to extent the Y axis out with a few other mods to 280mm travel, 300mm is possible if I put a longer scale on it.

I used the nut on the bolt in the on the tail stock end to give the centre something to sit in. It was the easiest way to do it because I had a few to do. It would work for philips head as well as others, just not the standard slot screw or it would slip out.
Dave.

Hi Dave,

That's a pretty significant increase over the standard 220mm, and they way you have done it, it looks neat, and it looks like it "belongs".

Maybe you can sell the design of the mods back to the manufacturer...

Been thinking about how you made the power feed stops, and my first thought was, that there must be an easier way than welding three pieces, but apart from a custom casting, I think, on reflection, your method is probably the simplest and best.

Well thought out and executed modification.

Regards
Ray

Hi Ray,
With the extension you need to make new sheet metal protection plates (3 instead of 2) under the saddle, I gave the cardboard templates to Retromilling from this forum.
I am sure if you wanted the sizes of them, he would tell you. I would have to pull the machine apart to get them. I can give you details of the travel extension if you want to do it to yours.
There is another way of doing the power feed stops if you don't have a welder. Just make extension blocks for you original stops, you will have to make new longer pins and add longer springs to reach around the bracket. It was the way I was going to do it in the first place.
My wife blames me for being a Virgo (perfectionist) for not doing things the simple way and fussing over small things that don't look right. A job that should take 1 day ends up being 2 or 3.LOL
The standard travel on my factory fitted DRO was 160mm stop to stop, though advertised as 220?

Dave

Hi Dave,

I'm thinking that this would be a good modification to do while I'm doing the CNC conversion. I didn't realize that the DRO option would reduce Y axis by 60mm!!, and they don't mention it at all in the specs.

Still, I want to keep the scales, so that I can do a ballscrew correction table at some stage in the future. I did think about using the scales for primary positional feedback, but everything I have read cautions against that approach, mainly, I think that you can get unstable oscillations caused by any backlash, so the primary feedback is better if it's the encoder directly coupled to the servo motor. There are ways of introducing the linear scale encoders in a secondary control loop, but that would be a whole other can of worms.

Can't wait for my HM52(B) to arrive, I've pretty much got the workshop sorted. Insulation, lined the wall, new 15A power points.. Might get the roof insulation completed before the machine arrives...

Regards
Ray

Hi Ray,
They tap holes on the knee and put 2 stops on there, and one in the saddle to stop the travel. Why they do this I don't know, because my Y scale is a 270mm one.
When I was having all the troubles, I asked the Syd manager about the 160mm travel instead of 220mm and the 560mm table travel instead of 600mm, he said it was possible to get those travels out of it with a few modifications?
The Y axis travel used to be advertised as 180mm then changed to 220mm for the same machine. The advertised weights also seems to fluctuate from 850kg to 1050kg.

The way I figure scales and a DRO is it fights itself for position and it always backing up unless there is no backlash at all, which is pretty hard to do. The large manufacturers have it worked out, but it's out of our money range for a home shop.

Your shed sounds like it is coming along. If it's like your sheet rack I think it will be a good job, and the insulation will make it more comfortable to work in and keep the condensation of the machine.

Dave