|Martyn Edwards 2||10/05/2021 01:22:58|
|12 forum posts|
Same kit but slightly different approach on the Y and Z Axis.
|James Hall 3||13/05/2021 07:13:27|
|40 forum posts|
Thanks Martyn - interesting photos and another good looking installation. See that you have gone for fixed Y-axis read head and scale on saddle, but wondered what Mike Donnerstag's reasoning was behind doing it the other way round.
How did you cut the magnetic strip to length?
I still like the neatness of hiding the Z-axis gubbins in the column, but am hoping to pick Mike's brains on that.
20637 forum posts
If you get a longet scale extrusion for the Z then you can just mount that at either end and no need for the extra backing plate shown in Martyn's photo. I'd also fit the bracket to the casting rather than the sheet metal cover, you can make use of the existing screw hole in the top of the column.
|Mike Donnerstag||13/05/2021 12:15:12|
201 forum posts
Apologies for the delayed reply.
In response to James' questions:
The magnetic strips are easily cut to length. I think I just used tin snips. The aluminium extrusions obviously need to be cut with a hacksaw.
The mounting for the display is fixed to a thick aluminium plate behind the pressed-steel cover. This reinforces the mounting substantially.
Regarding my thinking behind how I mounted the scales and readers, it was all about future-proofing. Specifically, my objectives were:
1) To leave each of the three scales as long as possible to potentially mount them to a different machine in the future
2) To ensure the ends of the table are completely clear of mounting brackets, etc., to allow a power feed or even CNC motors to be mounted in the future.
I think this answers your questions so far.
I am still not too happy with my Z-axis readings. I think this is due to the 'spring' in the machine between the movement of the leadscrew nut and the head movement. I haven't investigated whether this is the gib adjustment, which may be a little tight, or whether it is fundamentally the fact that the reader is some way from the head. The travel of the feedscrew nut, to which the reader is fixed, doesn't perfectly follow the height (Z-position) of the head. The movement also seems to be too juddery to rely on for accurate height settings, hence why I use the quill for accurate height settings.
Jason: I'd be very interested in your thoughts on this. Specifically, would you expect to be able to set the head height just as accurately as the quill? Also, do you have any hints on how best to set the head gib so that it's not too tight or too loose? (Perhaps this is one for Ketan?)
20637 forum posts
As I have an X3 without the readout on the quill all my settings are done with the head and don't seem to suffer with judder or stickyness. Have not touched the gib in years but it's just a bit of trial and error to find the fine line between too tight and sloppy
|534 forum posts|
I don't have Jason's experience but yesterday I took a stab at adjusting my Z gib.
I first tried using a dti mounted on the top of the head to the column about 3" up. Using some wooden blocks and a leaver lifted the head via the quill. This resulted in about 10-20thou DTI reading and a sloping noise as the oil was forced in and out of the dovetail. Definitely proved I had a loose dovetail.
I tightened the gib about 4-6 turns before the noise stopped. I then tried raising and lowering the head. I found it got tight about 3" from the top of the column. When lowering the head from the top I could feel I was driving the head down. Then it went through a short distance of sticking/jumping and finally ran free. I used a very fine diamond hone on the column to smooth out the machining roughness to match how it had worn lower down. This improved it a little, but not much.
I then tried a second approach. I mounted the DTI under the head and measured the change in height when the head/gib was locked. I knew from past experience the head moved up a lot when locked, but after the above adjustment, I only saw 0.5thou movement. I loosened the gib till I was getting about 1 - 1.5thou over the normal working heights. After this, I found I could raise and lower the head all the way to the top without tightness or any juddering.
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