Thread: New CNC Mill on the horizon
yeah thanks for the heads up I had taken that into account with the mounts one of the other reasons for making the descision so I could finalise those.
3KW version now ordered so getting on boring out the mounts!
Managed to get a bunch done today which was great!
Earlier this week I had some deliveries in the form of a 3kw spindle and inverter, some west system epoxy and extra slow hardener, some more aluminium plate and a few more essentials to move this project along a bit more.
I started out today machining up a mount for the x axis drive motor which is going to be driving 2 screws with one motor so needed a good mount and also space for a good tensioning system. The parts for the tensioners only arrived this afternoon so I have not had a chance to add those yet but they will be going on the taller part of the mount that the nema 34 motor is attached to.
I have managed to get some heat into the workshop so on sunday I am going to get the epoxy resin poured. Any tips? I have read most of the builds using this and I am sure if I follow those steps everything will work out fine! (heres hoping)
Finally I did not order enough aluminium for the spindle mount so mocked 2 plates up out of polycarbonate I had lying around and fitted that on to make sure I could get at everything for adjusting etc. So far so good all looking great, just need to spend saturday on the X axis mounting blocks and the timing pulleys and should be about there ready to pour the epoxy.
One last thing do people recommend drilling the x axis rail mounting holes before or after pouring the epoxy?
One word of warning with the epoxy and this cold weather.? I've just done a pour using 206 hardener which is faster curing and in a thermasticly heated workshop and after being left 5 days I still got a little sinkage after fastening rails. Nothing major but still enough to need a slight shim to avoid putting bind on the bearings.
Using the 209 I wouldn't touch yours for at least 10days. If you have any spare epoxy pour a little into something to simulate the width and depth your doing and then wait until it's gone hard so snaps when trying to bend. If it bends and doesn't break it's not ready. The surface will feel hard to touch but it won't be cured all way thru.
Cheers Dean! very helpful as ever :)
The plan is to pour it on sunday and then leave it for probably near on 3 weeks as I will be away with work so cannot do anything on it anyway so figured this would be the best option. I am planning on making a sort of tent around the machine and using a 3kw oil radiator style heater on a thermostat to try and keep the temp up. I prefer these to the fan type as at least they are sealed and there is no exposed heating element. This way i am happy to leave it on for extended periods and not worry too much.
I will pour a couple of samples of any remaining material as tests as well so thanks for that. I will look out for the "Snap" test once I am back.
Any suggestions on where is a good place to have a made to order length timing belt? I have yet to find one
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 :)
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:
YOU can addust it if necessary.
Also here's some info on fixing those bearings; http://www.mycncuk.com/threads/6565-...6128#post56128
Last edited by EddyCurrent; 03-02-2015 at 09:19 AM.Spelling mistakes are not intentional, I only seem to see them some time after I've posted
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.
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 :)
FOR SALE: Emco mill 50 cnc mill like Denford TriacBy gavztheouch in forum Items For SaleReplies: 0Last Post: 18-05-2014, 09:19 AM
By Richard in forum Machine DiscussionReplies: 2Last Post: 18-02-2014, 03:18 PM