Welcome, Guest. Please login or register.
Did you miss your activation email?
October 30, 2014, 10:10:28 AM

Login with username, password and session length
Search:     Advanced search
* Home Help Search Calendar Links Login Register
  Show Posts
Pages: « 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 »
381  General CNC Chat / Show"N"Tell ( Your Machines) / Re: 9x20 Chinese Lathe Conversion on: March 14, 2012, 12:55:28 PM
Here is the bearing housing for the X axis:


I went for a needle thrust bearings arrangement here. It is two needle thrust bearings closed from either side of a step inside the bore. They are combined with a deep groove ball bearing at the end to provide axial support for the belt tension. Here is the section of the arrangement:


The reason for this over angular contact ball bearings is that angular contacts at that size are pretty limited in the axial loads they can take. The needle thrust bearings on the other hand can handle axial loads several orders of magnitude higher than the angular contacts. Preloading is fairly easy too. And as a bonus they are only a fraction of the price of angular contacts Smiley

The bearing housing will be mounted on the back of the carriage (as the motor is going to sit on the back). There are M6 mounting holes on the back of the carriage seen on the carriage picture.

The two bosses on the bearing housing are for mounting the motor mounting plate.

By the way, it's not shiny in the picture as it got treated with a light solution of phosphatic acid to prevent corrosion. Works well.

Dan
382  General CNC Chat / Show"N"Tell ( Your Machines) / Re: 9x20 Chinese Lathe Conversion on: March 14, 2012, 11:43:58 AM
Hi,

I am going to keep it flat. I have sheet metal guards designed to cover the screws so should be no problem there.

Thanks for the picture. I like your collet addition. Might consider it on my Emco C5 as I usually use bar stock there. Where did you get yours?

Dan
383  General CNC Chat / Show"N"Tell ( Your Machines) / Re: 9x20 Chinese Lathe Conversion on: March 12, 2012, 08:28:22 AM
Thanks Russ.

For the Z axis I have a 14mm diameter, ground NSK ball screw I got from eBay. It's used but it looks in a very good shape. For the X, I got a Hiwin 12mm diameter C5 rolled ball screw from 1aballscrew.co.uk who tend to offer good pricing and also do the end machining.

Dan

384  General CNC Chat / Show"N"Tell ( Your Machines) / Re: 9x20 Chinese Lathe Conversion on: March 11, 2012, 01:19:58 PM
The front gib was more tricky in terms of mounting and size to prevent interference with the Z ball nut underneath. This is what I ended up with:


Again it's two pieces for the same reason, base being steel and the sliding bar cast iron. The two M6 holes at either end match up with the original holes on the carriage two bolts there will be used for adjustment. The 3 larger holes match with the 3 holes I bored in the carriage (bottom view photo in the previous post). These will have dowel pins.

It's hard to see on the picture, but there are M4 holes on the sides perpendicular to the M6 ones. They are for M4 locking set screws.

Dan
385  Tangent Corner / Tangent Corner / Re: MY NEW MAN CAVE! on: March 11, 2012, 01:05:06 PM
Love it!

Very impressive, 8 days from scratch to something like this!

Dan
386  G-Code, CAD, and CAM / G-Code, CAD, and CAM discussions / Re: Milling alloy on: March 09, 2012, 01:57:41 PM
Looks like 5052 or some other soft alloy. They don't machine well. Only way to successfully machine this stuff is using heavy flood coolant with fair oil concentration or Tapmatic cutting oil .

Aluminium alloys with excellent machinability are 6061, 2024, 7075. 6061 being the most common. Also, your feed is way too low. Assuming a 3-flute end mill you'd want to feed it around 350mm/min at that spindle speed.

Dan
387  General CNC Chat / Show"N"Tell ( Your Machines) / Re: 9x20 Chinese Lathe Conversion on: March 08, 2012, 05:00:52 AM
The original carriage gibs weren't satisfactory for me. I wanted something more substantial and something that can be easily adjusted and locked. The original ones had the gibs mounted on screws which could be tightened for to adjust, but nothing to lock those screws themselves from unlocking.

I designed new gibs to replace the original ones. Here is my rear gib:


Couldn't find cast iron stock large enough to make it so made it two parts. The base is mild steel and the slide is cast iron. The slide bar sits on a step and is bolted to the base. It has the lub channel milled.

The 3 holes on the base match with the original bolt locations and will be used to tighten it against the slide for adjustment. The slots on the back flange will have bolts to secure it in place once adjustment has been completed.

Dan
388  General CNC Chat / Show"N"Tell ( Your Machines) / Re: 9x20 Chinese Lathe Conversion on: March 08, 2012, 04:35:15 AM
There was no enough room to put a substantial ball screw in place of the poor leadscrew, so I decided I to put the cross slide on linear guides to have a bit more clearance for the ball nut. On the other hand though, I didn't want to significantly reduce the clearance over the cross slide. I had very low profile Bosch Rexroth preloaded linear guides (10mm high) and I decided to you them, but also had to mill a bit into the cross slide as well as the carriage to achieve the required clearance.

Here is the carriage after milling the recess and drilling the holes for the linear blocks:


Going to mount the linear slides upside down as I figured it would be more convenient, so the carriage will have the linear blocks and guides will be mounted on the cross slide. The mounting holes for the linear blocks got counter-bored from the back:


Also, in the above photo, a lub channel has been milled into the flat sliding surface. The V-groove won't need that as it has a slightly smaller angle than 90 and there is always some clearance between the top of it and the V-guide.

On the left side, milled flat the surface for the Z ball nut assembly to be mounted.


This is the cross slide after milling the recess and drilling and tapping M3 holes for the guides:


Here's a top view, mounting holes for the X ball nut assembly have been drilled and counter-bored:


Will fill the unused holes with epoxy later.

Dan

389  General CNC Chat / Show"N"Tell ( Your Machines) / 9x20 Chinese Lathe Conversion on: March 07, 2012, 09:23:57 AM
Hi,

I have this little lathe which hasn't really been used in the last couple of years, so I decided I'd better convert it to CNC which I could really use.



It is a Chinese conventional 9x20 lathe. They make them on several factories in China with different quality. This particular one was quite poorly made. The good thing in these lathes is usually their heavy cast bed and headstock and that's why it qualified as a good candidate for a conversion Smiley

Going to strip off everything and fit ball screws to both axes, with stepper motors to drive them and make up a new tray with appropriate guards. The plan is also to replace the AC induction motor driving the spindle with an AC servo motor. Quite some rework is needed to make all I want.

First, stripped off everything:


Headstock got new bearings installed and after mounting it back I checked for alignment to the Z axis:


It was found to be around 0.1mm out over 150mm. Simply filing the V-groove on the headstock in the right spots brought it to within 0.02mm over 150mm, which is a satisfactory result. It was a long process: filing a bit, mounting it back and testing and then back dismantling and filing more based on the test result. Took quite a few iterations, but it paid off Smiley
390  General CNC Chat / Show"N"Tell ( Your Machines) / Re: Just got a lathe to retrofit on: March 04, 2012, 04:07:24 AM
Very well done, Hood! It's so much better than the original turret you had, which was stopping each station on its way.

Dan
Pages: « 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 »
Powered by MySQL Powered by PHP Powered by SMF 1.1.19 | SMF © 2013, Simple Machines Valid XHTML 1.0! Valid CSS!