problem with thread bolt with pictures

[freddean2006]

On the picture could someone tell me what they think is the problem and is it related to the threaded rod end bolt and bearing slipping?

If so how do I stop the bolt from loosening?

my thread is like this

motor coupling > rubber > threadcoupling > bolt>skatebearing(sb)>gantry delrin bolt> sb > bolt.

The last bolt keeps spinning off.

[Kammo1]

Hi bro are you the guy I spoke to a while back who lives just off Junction 28 near Nottingham ??? nice to see you have the old boy up and running I think you could have some backlash problems there but am not 100% sure but it does seem quite severe ! check all components are tight and no issues of material slipping under the cutter load as its cutting. I am still on the construction side of things and hopefully will get there in the end. Post some pics of the finished machine as I would love to see it

[freddean2006]

Originally Posted by Kammo1 Hi bro are you the guy I spoke to a while back who lives just off Junction 28 near Nottingham ??? nice to see you have the old boy up and running I think you could have some backlash problems there but am not 100% sure but it does seem quite severe ! check all components are tight and no issues of material slipping under the cutter load as its cutting. I am still on the construction side of things and hopefully will get there in the end. Post some pics of the finished machine as I would love to see it

I think its to do with the last bolt slipping on the threaded rod. Need a way to stop it from moving. Are lock nuts what others use for this.

yes I am the junction 28 chap. this is my third try at a cnc with this one using buildyourcncs' directions and some delrin nuts from mycncuk. 1st two were moving table types using a dremel whereas this uses a moving gantry and 1000w plunge router. Noisy though.

Quite amazed at how well it works. just need to iron out some of the minor problems so I can get to cutting out a joes cnc + buildyourcnc hybrid.

Maybe I will post pictures of my forth cnc cut machine when its done

[freddean2006]

ive fixed the bolt problem and its now cutting quite well except everything it does seems to be out exactly 1mm, in the x and y (havent checked the z)?

tried adjusting the backlash and this corrected the x but sent the y out by 2mm.

but the threaded rod is 1.25mm as it is m8? any ideas?

[Kammo1]

Hey Bro, although I'm no expert and can only go by the excellent info of this site I've heard a few things posted about final tweaking can be done in the Mach 3 menu under configuration I think, maybe this might solve or greatly reduce discrepancies that you have in a machine build. I'm sure some smore knowledgable folks here might have a better solution but generally what I have learnt is sometimes its something real small that can throw everything out,give it a try you have nothing to loose, sorry I can't suggest any more.

[freddean2006]

After further testing I dont understand how the machine can be 1mm out in the y and 2mm out in the x but when making circles its only 1mm? Surely it should make slightly oval shapes? As long as I make a circle pocket 1mm extra in diameter, ie bearing hole 23 instead of 22, then it makes a perfect circle?

odd this cnc thing?

What Im doing is using it to make another one so but adding 1mm or 2mm depending on the axis.

Any ideas?