3 Attachment(s)
Re: David A's New 2x3 Bench Top CNC
SIDE TO SIDE:
Place something straight on
the table.Here, a 1515 will do:
Attachment 415476
Place one dial on one end of the
straight and note the reading. Start
sliding the dial towards the other end:
Attachment 415478
Compare with the reading at the other end:
Attachment 415480
2 Attachment(s)
Re: David A's New 2x3 Bench Top CNC
Adjust the straight with paper underneath
so that both ends read the same on the dial:
Attachment 415482
Place both dials on the straight and see if the axis is
off. Side to side was right on the money in this case:
Attachment 415484
4 Attachment(s)
Re: David A's New 2x3 Bench Top CNC
FRONT TO BACK:
Do the same with the straight
in the other direction. This time
the Z-axis was off as the weight
of the slide has skewed the axis
during installation:
Attachment 415486
By pulling the plates towards/away from linear blocks:
Attachment 415488
Attachment 415490
Tram can be adjusted quite accurately:
Attachment 415492
Re: David A's New 2x3 Bench Top CNC
Do you relly only on friction to keep tram or you have some kind of exentric shoulder screw?
Re: David A's New 2x3 Bench Top CNC
Excentric shoulder screw where?
Just at the front portion of the X-carriage,
where the Z-axis is bolted to, are 48 bolts
to keep tram. And another 16 at the back.
It's really not something you do often like
a belt tensioner.
Re: David A's New 2x3 Bench Top CNC
Not complaining at all, just asking, this buld is fantastic, i guess that 64 bolts will be more than enough to prevent any slippage!
Re: David A's New 2x3 Bench Top CNC
No problem, just keep asking.
Personally don't know of any
excentrics for tram on a DIY.
Re: David A's New 2x3 Bench Top CNC
.
X-AXIS POWER NUT DRIVE:
X-axis power nut is installed.
Break-in for about 10 min.
Starting with one inch per minute.
Very slight jerkiness, probably
due to too short of a break-in.
More videos tomorrow:
https://youtu.be/PiEyv528mxA
Re: David A's New 2x3 Bench Top CNC
Ok, more random thoughts from my 150 mile drive home tonight...
First, now that I see the belt size, I retract my questions about stretch or adjustment. I guess I didn't have a good perspective from your pics before and thought you were only using one of those 1/4 inch belts.
Second, unless I missed it before, have you already accounted for any twist that could be present in your ways on the X and Y axes?
Re: David A's New 2x3 Bench Top CNC
Outlawtaz, where do you think twist could
occur as I don't have any traditional ways per se?
The only place I could imagine it occurring would
be the ball screw itself. And I don't think that is
going to happen at loads we have when cutting.
Re: David A's New 2x3 Bench Top CNC
Let me start by saying that I typically WAY over engineer my stuff, so take it with a grain of salt...
Twist would be along the linear rails from one end to the other in both X and Y. And not along one rail but the surface of the pair of rails in relation to each other. It only occurred to me when you trammed in the spindle and you used a piece of paper to level your straight edge. Typically, paper is 0.004-0.005" thick (I always used 0.005 as a reference and a "round" number). It appears that the piece of 1515 was around a foot long so this could possibly induce a difference of 0.015" over the length of your machine. Even if you skimmed your base plate, it would just make a curved surface that would come out if you made parts that filled the entire machine. I hope this is making sense... It makes sense in my head but I can't always type my thoughts exactly...
What I was always taught was to level the table / base first and remove any twist. Then, if I was concerned about X and Y being perpendicular, I would throw a granite angle on it to adjust one or the other. Next, came verifying Z to the table / base (if needed) again using the granite. Tramming the spindle would be the last step.
Again, this is probably overkill. Also, I just happen to have all the precision tooling for this since I averaged doing this a couple times a month over 6 years when I was a field tech.
I'm just impressed with your design and I think with a little playing around, you could have fairly precise machine with good repeatability.
Re: David A's New 2x3 Bench Top CNC
Quote:
Break-in for about 10 min.
Starting with one inch per minute.
We need more speed :D
In particular to see the effect of the rotating mass. I think inertia increases by something like the square of diameter increase ?
I don't know the exact formula and as they say the proof is in the pudding.
This design is as light as possible with 2 flanged ball nuts, I hope this works as good as it looks.