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Kammo1
03-11-2008, 11:55 PM
Hi guys, after many months in fact it seems more like years I have finally started my 1st CNC build consisting of 20mm MDF,Oilite bushings and ground linear rails.
Well have to admit given the chance to start again and recommending what I have learnt and messsed up I certaily would not use the oilite bushings ever again, they are most unforgiving and if you think that you can drill 2 holes a said distance apart like I did and get it right 1st time "WRONG!" literally every piece of the build I had to make 2-3 times very frustrating and very annoying, to be honest if I had taken the angle and skatebearing approach this machine would have been finished as regading all the linear motions working ie X Y and Z.
I started with 2 X 1 metre long 20mm OD ground steel rods for the X axis ie forward and backward motion, 2 X 600mm long 20mm OD ground steel rods for the Y axis left to right motion and 2 x 16mm OD for the Z axis, I thought I would have a generous size machine capable of cutting a good size of work when it comes to showtime.
I started the machine on Monday and have built the main gantry as well as the Z axis and again without alot of frustration with the bushings have now got the machine moving by hand very smoothly and there is virtually very,very little play and should eventually once its showtime cut and produce some accurate results, although I will only cut wood parts it should be more than adequate but again we will see as mister "sods law" hasn't reared his ugly head again. The Z axis should have a range of between 3"-4" inches of travel more than I need.
I will use for the X axis motion the skatebearing/angle approach as I cannot for the life of me go through with the problems that I had with the rest of the build and I am almost 100% positive this will produce a beautiful smooth motion for quite a reasonably heavy gantry. I will try and get some pics up tomorrow so I can show you all how its turned out and have to say its quite a thrill to be making my own CNC as I have trawled this forum endlessly searching for tips,plans etc,etc although I have quite honestly not worked from any plans but built and measured as I have gone along and have enjoyed it very much.
I will be starting to think about leadscrews and the drive components so would like any help I can get in what would be reasonable components to use. I have thought about using 8mm threaded rod which I can get here in the UK from my local Screwfix or B&Q depot and using a skate bearing to hold the rod in place as its a perfect fit "BUT" for the life of me I cannot think how to fix it in place ? I know that when the stepper motors are fitted I will use an adapter from 1/4 inch or 6.35mm to 8mm but how do I fix it at the ends of the rods to keep it spinning freely and keep it in place without moving ? I have tried to look at other builds but cannot for the life of me see any pictures of what I need to do. I thought I would ask here as I do not want to drill any unecessary holes and risk making errors as I do not want to go about making what I have got moving perfectly again which I know will present me with problems, any help and advice will be greatly appreciated.
I guess the main thrill for me is learning what to do and not to do and have this machine build me my next one which will be an awesomme task and more accurate and I have loads more other questions but I'll save them for later.

irving2008
04-11-2008, 02:29 AM
Hi Kammo,

Read this post and had a sense of deja-vue! I hope my reply on CNCZone was helpful...

Kammo1
05-11-2008, 11:12 AM
Many thanks Irving and yes it was very helpful indeed.

Kammo1
05-11-2008, 07:53 PM
Bro I couldn't agree more and have to admit I am pretty good at manufacturing things but this CNC is very trying at times I nearly threw the damn thing across the workshop. Most of the build in all honesty has been enjoyable but like I say its my 1st so the next one should be easier as I can machine the parts more accurately.
Kip do you have your machine running yet ?? I am still toying with the idea about using the 8mm threaded rods but may still do as I am on a budget and would like to try the trapezoidal leadscrews that so many are using, where is the best place for them ? What size would you recommend ? my machine will eventually have a cutting area of about 28 inches X 17 inches X 3-4 inches. I know its alot of questions but I could do with some expert advice. If I was to stick with the 8mm threaded rod from B&Q what sort of backlash nuts should I use or maybe make, has anyone on here made there own for this type of threaded rod ?

Kammo1
21-02-2009, 07:04 PM
Hi guys managed to fit my main carrier bearings on my machine on the X axis, now would like some opinions if this is a good way or bad ? I haven't yet seen a machine with the bearings fitted in this configuration but it was easy and I also have scope to support the 20mm round rails without the chance of any impedemnet from the bearings if I choose to do so. Hope you enjoy the pics and any comments please advise. Laz
http://img.photobucket.com/albums/v111/Kammo1/MyCNC3.jpg
http://img.photobucket.com/albums/v111/Kammo1/MyCNC1.jpg
http://img.photobucket.com/albums/v111/Kammo1/MyCNC4.jpg
http://img.photobucket.com/albums/v111/Kammo1/MyCNC2.jpg

John S
22-02-2009, 12:00 AM
What stops it lifting ?

JS

Kammo1
22-02-2009, 01:20 AM
At the moment nothing is stopping the whole gantry from lifting up and it will only have a worktop/surface spanning the 2 uprights holding the X axis rails, so in actual fact the only thing that will hold it from lifting will be the threaded rod when its connected to the bottom of the gantry and obviously this will be connected to the stepper motor one ened and the other end will float within the bearing at the other end. At the moment it is bothering me but I might even fit a fixture which will hold a bearing so it rides under the table but also be pressing down on the gantry which will stop the lifting if it occurs.
John sure could use your expertise on this one bro ?

Lee Roberts
22-02-2009, 03:44 AM
I think i would be bothered as well kammo !

Smiler
22-02-2009, 01:07 PM
I would just make two more trucks and extend the bolts you are using for bearing axles to attach the new truck at 90 degrees. With a bit of shimming the bearing which will now be underneath the tube can be made to contact it quite securely. So hard to describe this in words:mad:

Basically, keep the truck as you have it but bolt on another identical truck using the axle bolts from the first then shim. This will also allow you to support the rail with no interference. This will do what you want. You only need one extra truck per side so two new trucks to make Kammo, shouldn't take more than 15 mins so get cracking!
;)
Jeff.

progomez
22-02-2009, 05:36 PM
Id mount the bearings on the inside of the gantry on the left and right. Similar to joes cnc. That way you wouldnt have to redesign the x axis, although you may need to flip it over to give more clearance.

Kammo1
22-02-2009, 08:34 PM
Some good comments and I do think I need to revise this as I know it will cause some problems, is there any advantages of using this method I do think it is certainly better than mine as it would take an awful lot of cutting force to knock this off its rails
http://img.photobucket.com/albums/v111/Kammo1/CNCskatebearing.jpg
I may result to mounting these this way as its so much easier or to mount them on the inside of the gantry like the Joe CNC again comments or ideas welcome, good god this machine is proving to be hard going!

Smiler
22-02-2009, 10:14 PM
Some good comments and I do think I need to revise this as I know it will cause some problems, is there any advantages of using this method I do think it is certainly better than mine as it would take an awful lot of cutting force to knock this off its rails

I may result to mounting these this way as its so much easier or to mount them on the inside of the gantry like the Joe CNC again comments or ideas welcome, good god this machine is proving to be hard going!

Looks good to me Kammo, That's how the Solsylva router I based mine on uses its trucks and from what I hear, they work very well indeed.

If you think it's hard going now, just wait until you get it running! Learning curve is vertical with lots of expensive bits to break :)

Keep us posted on what you end up doing.

Jeff

John S
23-02-2009, 01:09 AM
Kammo,

PM sent.

John S.

Kammo1
23-02-2009, 10:55 AM
John PM sent CHEERS!
I can't imagine what I will be like when I get the thing actually cutting I'll probably die of shock!!!!!! Its a great project don't get me wrong but it is very trying at times and in all honesty I thought it would be a doddle "WRONG!" One good thing for sure is that John S who lives near me is a wizard when it comes to all things CNC. I met up with John about 1 1/2 ago and I must say was amazed at what he knows he is a legend in my book and with a little help and a steer in the right direction my little homebrew will soon have some life breathed into her fingers crossed. Again guys many thanks for all the help and advice it really is truly appreciated "CHEERS!" Laz

Kammo1
24-02-2009, 11:35 AM
Ok guys just have a quick one for you all. I have some 8mm threaded rod at the moment which I will be using for the machine to drive the X Y and Z axis as I have had it given to me for free so why not use it for the time being. I came up with an idea for the leadscrew nuts and that was to take a large washer which has a hole so that the 8mm threaded rod can pass through and then epoxying a 8mm nut to it and then when this is dried and firm thread it onto the threaded rod and then glue another nut on the top but just tightening it so it takes out the backlash and believe it or not there is very little if no play in it at all. I have made 2 so far and have fitted it to the Z axis and the Y axis but have ran out of some epoxy to make one for the X axis. So my question is to you all is what are you guys using that is better than this and works without any problems ?? Also I would like to eventually upgrade to some Trapezoidal leadscrews maybe some 1/2 10 which seems the most popular leadscrew that everyone is using but again I am a bit green on this issue so any help would be great and also other than Marchant Dice where is the best place to order this and what would the cost per meter be ?? sorry for all the questions guys. Laz.

Smiler
24-02-2009, 10:13 PM
Delrin nuts. Doesn't Lee make/sell them? Very easy to make yourself I would have thought, lump 'o delrin, 6.5mm drill, M8 tap.

I think by using M8 nuts and preloading them in the way you are doing will lead to wear on either the nuts or screw and quickly too. When using threads in this way, you really need to have the nuts to be of softer material than the thread. I think you will find the most likely scenario will be that your leadscrew will seize and scrap both the screw and the nut even with lube, BTW, don't even think of trying it with Stainless nuts/screws.

Make some delrin nuts!:p

That's what I'd do anyway, no doubt I'll get shot down now by everyone who's done it your way for years:D

Jeff.

Kammo1
24-02-2009, 10:19 PM
Jeff that makes perfect sense to me, I guess I just went the cheap ass route trying to save a few quid here and there but I know what you're saying as I cant imagine the machine cutting a beautiful piece of work only for it to splutter and fart and turn it into scrap, again thanks for a steer in the right direction "CHEERS!"

Lee Roberts
24-02-2009, 11:47 PM
Hi guys, sorry Kammo i ment to hit reply today but its been a busy day for me as its my little girls 3rd birthday today so i'v been busy putting things like trampolines together all day and maintaining order on the bouncy castle, mind you i never was one to share :D

coming back to the business end of things...

Jeff is right, steel on steel like that is not a good idea, go with delrin and you cant go wrong.

I do sell them for 4 each ready to go:



http://www.mycncuk.com/ebay/images/delrin_nuts/DSC05116.JPG

Each drive nut kit consists of the following parts:

M4 X 50mm Zinc Plated Pozi Pan Head Screws x 2
M4 Stainless Steel Nylon Insert Lock Nuts x 2
M4 Zinc Plated Flat Washer x 4
Delrin Drive Nut x 1 - 20mm X 40mm X 16mm

The mounting holes are 20mm from centers, countersunk 5mm. The threaded hole is 8mm on center, from the bottom.

This drive nut as been designed for use with standard UN (Unified Thread) M8 Threaded Rod.

If you want to grab some delrin from ebay 3-4 and make your own i would say "why not" its true it is easy if you'v got all the tools and so on.

You will need an M8x1.25 TAP also the pilot boring drill bit needs to be 6.8mm OD not 6.5mm. You can use over and under size bores but you will more then likely run into problems later on. Ending up with you needing to remake them, as you will find the thread will strip from the nut or it will be lose and so on. Other then that you shouldnt have any problems making them yourself.

Only other thing for me to add is I consider my drive nut on a machine to be properly the most important thing on the machine, think about what it does and how important it is for it to be reliable.

progomez
25-02-2009, 12:04 AM
Jeff that makes perfect sense to me, I guess I just went the cheap ass route trying to save a few quid here and there but I know what you're saying as I cant imagine the machine cutting a beautiful piece of work only for it to splutter and fart and turn it into scrap, again thanks for a steer in the right direction "CHEERS!"

Not only will the delrin nuts be the best 12 + del youve spent they will save you from hours of work trying to get the standard nuts to work. Also it will move your project very quickly into the finishing stages and let you get on learning cad and cam.

Kammo1
25-02-2009, 11:41 AM
Many thanks guys for all the tips. Just got off the phone to my mentor and CNC guru John S and has given me some excellent tips and a way to get X axis bearings aligned perfectly which I didn't know how to get around and his idea is almost foolproof and will guarantee they sit nice and snug against the rails without splaying or binding he is the man!!!!!!!!!!!!! I am hopefully going to get John to come round when he has a few spare minutes and we can go from there. Guys if you are ever stuck on anything CNC John will have certainly done it or will give some sound solid advice on how to get over a hurdle the man is a genius. Laz.

rinderpest
04-06-2009, 08:33 PM
If you ever use trapezoidal ACME thread Im told that a good low backlash nut can be made from that low melt point plastic called polycaprolactone (or PolyMorph, Shapelok, etc).
The way its done is to make a piece of it around the right size with a rough hole just larger than your ACME.
You then heat the ACME with boiling water etc then clamp the plastic onto the thread. The thread heats the plastic to the point where it will mould itself around the thread.
When its set or just about set you unscrew the ACME, job done.
Apparently it takes a few goes to get it exactly right but then its easy.
I've not tried it yet but I just ordered some polycaprolactone granules, 100g for 1.25ish.
Very handy stuff for other things too Im told. Provided its not paper thin its very tough stuff, have a Google for some of the interesting uses people have found for it.
When mine arrives I'll start a thread with photos and see what sort of results I get.

fasteddy
11-06-2009, 01:43 AM
Hi... Am just building my first one, inspired by a chap from the states and his wonderful set of videos of every stage of the build.. This one http://buildyourcnc.com/step8.aspx shows his quite clever (and very cheap) anti-backlash nut, also how to terminate the leadscrew with a skate bearing and couple of nuts...

Hope this helps..

HiltonSteve
11-06-2009, 01:48 AM
...., also how to terminate the leadscrew with a skate bearing and couple of nuts...

Hope this helps..

I can get hold of 12mm bore angular contact bearings for 2.00 each, much better than using skate bearings. Let me know if you need some as I will be ordering some tomorrow.

fasteddy
11-06-2009, 07:20 AM
http://buildyourcnc.com/yleadscrew.aspx

This one for terminal bearing on the leadscrew..