Thread: My 1st homebrew CNC.
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!
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.
JeffNothing is foolproof......to a sufficiently talented fool!
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
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.
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.Nothing is foolproof......to a sufficiently talented fool!
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!"
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:
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.
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..Me
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.
By epninety in forum Electronic Project BuildingReplies: 0Last Post: 06-09-2011, 10:11 PM