New CNC Mill on the horizon

[fvfdrums]

Another good weekends work out of the way...

So a slight change of plan, after heeding the warnings of laying out resin in the cold and the temp around here steadily dropping it was decided that we would attempt to see how level we could make the machine using various measuring methods and after an hour or so of painstakingly shimming and adjusting the base the top was where we wanted it to be.

A few cups of tea and staring later the straight edge I ordered arrived and from this we could see using feeler gauges there was a pretty consistent shallow curve from one end of the steel to the other mainly due to the welding around the middle of the machine as this was within 0.05mm at the same point on either side of the machine.

As the difference was not all that large we decided to embark on shims and the possibility of using epoxy putty if needed. All I can say is dont be put off by having to shim rails! Initially I did not even think I would be able to get it near close what we needed however a couple of hours of filing high spots and then measuring using a feeler and inserting the correct piece of shim steel and we had the rails matching the straight edge.

The gantry moves smoothly from one end of the machine to the other no tight spots and I just need to get hold of a DTi in order to do some final checks however all in all I am very happy with the results.

Fitting the x axis screws however was a PITA....

The first one went on fine, no binding alignment was great everything slid in place.

The second one is really bent :( I thought it was a bit bent when it came from Chai - i registered a complaint but heard nothing back after 2 emails. However with one end bolted down and the ball screw holding it steady one rotation of the thread results in the loose bearing mount the other end moving up and down about 2-3mm dependant on what part of the thread you are on.

Does anyone know anywhere I might be able to get this straightened? I have no access to a hydraulic press or anything precision enough to make this good? any suggestions?

This aside its all on and screwed in place and a few turns of ballscrews here and there results in a pleasing movement across the machine. The only other issue is there seems to be a large amount of end float coming from the bk bearings I have either end so I am going to disassemble them and see if they need shimming in the middle!

All in all a successful weekend :)

[EddyCurrent]

The second one is really bent :( I thought it was a bit bent when it came from Chai - i registered a complaint but heard nothing back after 2 emails. However with one end bolted down and the ball screw holding it steady one rotation of the thread results in the loose bearing mount the other end moving up and down about 2-3mm dependant on what part of the thread you are on.

Does anyone know anywhere I might be able to get this straightened? I have no access to a hydraulic press or anything precision enough to make this good? any suggestions?

This was Chai's response to my bent screw;

Before shipping, we tested the ballscrews VERY SERIOUSLY as the following standard:
The ballscrew assembly (Ballnut and Spindle assembled) Precision rolled, class 7 accuracy; JIS (0.050/300mm) (0.002"/12")
Ballnut: Single ballnut with zero backlash (<0.015mm) (0.0006")
Please refer to the link:
http://www.roton.com/screw_shaft.aspx
YOU can addust it if necessary.


Also here's some info on fixing those bearings; http://www.mycncuk.com/threads/6565-...6128#post56128

[JAZZCNC]

If you identify the bend location you can make a fair job of straightening these screws using a vice and 3 blocks of wood. You'll be surprised how much bend the screws will tolerate before becoming a problem. Obviously any bend will have a little impact on the life of the screw/nut but IME even moderate bends won't affect machine performance to much and last years without any problems. I doubt you'd still have machine before it became a problem and when it does you'll be ready for changes and upgrades.

Regards the BK bearings then check the bearings are not in wrong way around which often happens. I strip every bearing to clean/re-grease then shim and every other one the bearings are in wrong way around.

[fvfdrums]

I have had a play around with the bearing blocks, all of them had both bearings facing the same way round rather than back to back, also there was a larger amount of slop in at least 4 of them so I have ordered some alternative bearings to replace with as I was getting 0.4mm of end float once everything was tightened up.

So whilst I am waiting for bits to arrive I am trying to source some bits I was wondeing if people could let me know if they have any suggestions for the following?

e Chain? - have found a reasonable supplier on eBay for it so might just go down this route about £10-15 for a metre

Breakout board combination: Can someone tell me if I go down the PMDX or smooth stepper route what I would need. I did not order a BOB when I bought my stepper drivers as I had heard so many people knocking the cheap BOBs. So my question really is which of the two do I go for SS/PMDX and if so what do I need as well as this to connect to mach 3 (I am not talking limit switches etc I just mean between stepper driver and PC)

Finally now I have the rails levelled using shims I have a litre of WS resin and 209 hardener I dont use I would be willing to let go for a good price if people are interested please IM me :)

[JAZZCNC]

First I'll take the resin if you still got it.!! I'll PM you

[routercnc]

Looking really good now well done. I wasn't happy with my 2 X-axis ballscrews so sent the worst one away to be straightened using a hydraulic press. My original post is here:
http://www.mycncuk.com/threads/7160-...bent+ballscrew

Looks like I never followed up this post but it came back really straight and ran sweetly in the bearings.

I decided not to send out the ballscrew which was only slightly bent and fitted it to the machine instead. As Jazz mentioned there were no noticeable problems.

I know your spindle mounts are only temporary perspex parts, but I assume the real parts will be much thicker (my first ones were 20mm aluminium and worked well).

[fvfdrums]

Thanks it's nice to be finally getting somewhere!

It just so happens I have justified a 12 ton press this week as my van needs all it's bushes replacing and for the cost of the bushes and a press I've saved a heap on garage costs so I may well set up some v blocks and have a go at that.

Running them up and down I have noticed the bent one is considerably more noisy than the straight one