Build Thread- 4 Axis DRO Fitout to Hafco HM52

[DMBGO]

I've had my HM52 for a few years now and have been keen to follow in the footsteps of Chic2's CNC conversion of the same mill. Unfortunately I have realised that I am unlikely to have the time or money to do a full cnc conversion in the short term, so a couple of weeks ago I started to research DROs. I was impressed by the Easson 3 axis DRO, carried by Hare and Forbes,

https://www.machineryhouse.com.au/Pr...stockCode=D701

-but the cost seemed too high, so I widened my search and found the identical DRO for sale on Ebay, with the seller located in mainland China.

For under $900.00 (less than 1/2 the best price locally) I purchased an ES10 DRO and 4 Easson scales. I know it is only a 3 axis DRO, but I am planning to fit a scale to both the knee and the quill, so I will use an old PC serial port switch to swap between the Knee and the quill for the Z axis readout.
I paid via paypal and then held my breath, hoping that what I ordered would be what I got.

Yesterday morning at 7:15 am there was a knock at the door, and to my surprise, the postie handed me a hessian bag from china. It took only 5 days from despatch to delivery! I cant say much good about the packaging, the boxes containing the scales and the DRO had just been dumped in the bag and then the bag was tied shut with a couple of bindings around the bag.

When I opened the bag I understood how it had arrived so quickly, it had obviously been the payload on one of North Korea's ICBMs. There is probaly a crater outside customs in Sydney where it landed.

I am exagerating a bit, but the fuse holder on the back of the DRO was broken on impact, otherwise everything survived. I have replaced the broken fuseholder, which was a simple 5 minute job.
Here are some photos of the condition of the parcels from the bag.
I will have started the fitout and will post again tomorrow with progress details.

[chich2]

Dave,
Did the Eason DRO come with good instructions?

Chich

[DMBGO]

It depends what you call good, It came with instructions, and I guess if you are the sort of person that feels capable of accurately installing a DRO and scales, and have had some experience of mills etc then you would probably understand them. They certainly weren't for beginners and were full of the usual errors in translation, and just plain mistakes with the diagram of one axis labelled X at one end and Y at the other.

[DMBGO]

The first thing I did was unpack the boxes and lay the contents out on the workbench.



Everything seemed to be there, except the X axis scale did not have a backing plate like the others did. Since the back of the table was ma machined surface I thought I probably didn't need one, but then again perhaps I did? I spent the next couple of hours making a new backing plate for the X scale



Once this was made I mounted the new backing plate onto the back of the bed, which required the drilling and tapping of two 6mm threads to hold the backing plate onto the bed. There are 2 grub screws at each end of the backing plates, to adjust the parallelism of the scale when mounting on a non machined surface. On the X axis it was dead parallel straight away, so I really didn't need to make the backing plate at all the scale could have been screwed straight onto the bed.

The next step was to was to mount the scale to the backing plate and check for parallel and straightness with a dial gauge. Once this was done I drilled and tapped the 2 holes for the swarth cover.



With the swarth cover done, it was time to make a bracket to mount the index head, in order to drill and tap the holes for this I had to swing the bed around 40 degrees to get the drill in there.

When making brackets for and mounting these scales it is very important to make sure things are square and parallel at all times, there is only a small tolerance in the scales for misalignment.

With the bracket made and installed it was time for a test (once I replaced the broken fuse holder on the DRO). With the DRO none the worse for it's accident I plugged it in, connected the serial port lead for X and voila! I had numbers.
I had also spent the best part of a day, so I will continue with my next post on the Y axis

[chich2]

Nice work mate! Be sure to add a mechanical stopper to your Y axis so you don't accidently crush your scale against the column.

Chich

[DMBGO]

Thanks for the feedback Chich, I did think of that, but discovered that the concertina swarth cover over the y axis bed at the back of the table doesn't allow the scale to hit the column. Good thought though! I have now done X Y and the Z Knee, I will post details soon, but I've been so busy working on the mill, that I haven't had time .
I have run into an issue with the quill, however. When I tried to align the scale after mouting, I found that the quill column is deflecting radially when it gets wound down. While this doesn't affect accuracy, it wont be good for the scale, since it is meant to stay very parallel. I am in the process of designing a bushed guide to stop the quill from turning when being woud down (sigh).

[DMBGO]

With the X axis operational, it is time to go to work on the Y axis This is a little more difficult than the X axis, since there is not a nice machined surface to mount the scale on. It is definitely necessary to use the supplied adjustable backing plate here.



The backing plate just fits below the Y axis bed on the left hand side of the mill, just above the cast bulge that houses the winder for the knee and hard up against the column.



After working out where the backing plate fits, it's time to drill and tap the holes and mount the backing plate and scale to the mill. Dont drill the hole at the column end of the backing plate too deep, or you will hit the slideways, see below.



Once again we need to adjust the backing plate and scale for alignment - use the 4 grub screws to adjust the backing plate so that it sits away from the uneven surface casting and adjust the scale so that it is parallel with the Y axis travel, using a dial guage.



Now it is time to fit the Y axis scale cover to protect the scale from coolant and crud. Due to the snug fit of the scale in this location, there was nowhere to mount the cover in its original incarnation, so I used the angle grinder to cut the mounting flange off the cover and instead drilled 2 3.5mm holes in the top of the backing plate and screwed the cover directly onto the backing plate, using 2 x 4mm self tapping machine screws, that I had salvaged from an old photocopier. You can tell the self tapping variety of these screws from normal ones, because the shaft of the screw looks slightly triangular, when viewed from the end of the thread. The screws tapped themselves easily into the soft alloy of the backing plate.

Ready to cut...


Drill here, and at the other end


With the cover installed all that remains is to make a bracket and attach it to the scale reader and to the Y axis, sounds easy, but this is the most time consuming part of the job so far, the bracket needs to be very square and takes a bit of setting up.



So that's the Y axis done, Now we can mount the DRO display arm on the other side of the column and drape the X and y cables over the mill. This way we can use the DRO to make the next lot of brackets etc. Next post we will continue with the Z axis.

I almost forgot to mention that I had help with all of this, here is a photo of my helper. If you are looking for that missing frisbee he will find it for you

Cheers
Dave

[DMBGO]

I hope someone is reading this thread! please feel free to make any comments, critical or positive, but best of all would be to make some constructive ones like Chich's posts

anyway on with the story.

The Z axis is basically a repeat of the Y axis, so there is not so much to say here. I installed both the Y and Z scales on the Left of the mill, since the right side has the locking handles for the Gibs etc. I have faced the reader side away from the cutting action to minimise chips etc getting into the scale.

The brackets I used are the ones supplied with the scales, I am not sure what Easson was thinking with with the supplied brackets, since none of the holes in the brackets line up with any of the holes in the scales??? This is the first time I have used their brackets in this job.

I think the photos are self explanatory, my only other comment is that I will need to put a better cover on the top of the existing scale cover to stop coolant from running down the scale from the top.

[chich2]

Looking good Dave,
Funny thing that the bracket's don't match the scales?????? Wonder what's going on there?

I am interested to see where you are going to attach the Display arm.

Chich

[DMBGO]

Thanks Chich, the display arm is next, but didn't present much of a problem. The interesting bit is the quill, there was a weeks work in that!