3 Axis CNC router

[JoeHarris]

Anyway don't complain too much because when you do have it cutting and wanting something to impress the Mrs you wont have to try remembering which post ya saw that Aztec calendar. . .Lol

Oh I'm not complaining, just a tad jealous - need to be patient!

[JoeHarris]

OK!

Finally got round to making some progress on the model of my machine. I have made a load of changes / developments based on your very helpful comments so far. I have uploaded some screen shots and an honest appraisal would be very much appreciated, together with any ways you can think of to make it cheaper!!

Thanks again to all who take a look at this.

Joe

p.s.for anyone who is interested this thread started at http://www.mycncuk.com/forums/showthread.php/4489-Hello

[Jonathan]

Currently the number of teeth on the X-axis motor pulley engaged with the belt is too small - it will slip. You should put an idler either side of the motor pulley to force the belt to wrap around it.

The travel on the Y-axis is limited by when the Z-axis makes contact with the X bearing block support, so there is a gap between the position of the Y bearing blocks at this limit and the gantry sides. Therefore you could space the Y-bearing blocks out further (with longer rails to match) to add strength without compromising travel.

The piece of aluminium extrusion underneath the gantry that links the two sides doesn't really add any strength since the gantry is well supported there by the ballnuts. I would get rid of that extrusion and clearly shorten the gantry sides where it was. The Z-motor mount can also be made narrower near the motor to save material.

[JoeHarris]

Man - I cannot believe how long it has taken for me to find the time to upload some more to this thread.

I have reworked the Z axis a little to take on some of the comments - images attached bellow and as usual comments more than welcome.

The main changes are double plates to attach the y axis uprights to the bearing blocks to allow for adjustment and an increase from 100mm from the bottom of the z axis mount to the top of the bed to 150, giving 132mm clear if an 18mm sacrificial board is used on top of the bed.

I am now quite close to saving up enough to buy the first batch of parts and could do with some guidance on ordering bespoke end machine for the ball screws to allow for the pulleys to be mounted. Jazz had mentioned having them machined longer than usual - would about 100mm extra suffice?? Also did you have the diameter machined down too to receive the pullies?? many thanks in advance

[JoeHarris]

As I have no way of machining the aluminium plate apart from drilling holes - I have had thought that I would like to float.
If I was to temporarily replace all of the alu plate for MDF which I could route by hand - would I be able to then use the machine itself to machine the aluminium parts or is MDF too unstable and flexible to make this worthwhile? Has anyone done this in the past or did you all have metal working mills and lathes in your garages and sheds?!

[JAZZCNC]

As I have no way of machining the aluminium plate apart from drilling holes - I have had thought that I would like to float.
If I was to temporarily replace all of the alu plate for MDF which I could route by hand - would I be able to then use the machine itself to machine the aluminium parts or is MDF too unstable and flexible to make this worthwhile? Has anyone done this in the past or did you all have metal working mills and lathes in your garages and sheds?!

It could be done but you would have to beef up the MDF parts considerably to cut aluminium and then take it careeful with the DOC.

I cut some of the parts for my first machine in Aluminium by hand using MDF templates and bearing guided cutter and very shallow pass's.!! . . .You need to be used to working with a powerfull router and have confidence and take it slow but it's do-able.! . . (scary as hell at first but soon settle down.)

[Jonathan]

I am now quite close to saving up enough to buy the first batch of parts and could do with some guidance on ordering bespoke end machine for the ball screws to allow for the pulleys to be mounted. Jazz had mentioned having them machined longer than usual - would about 100mm extra suffice?? Also did you have the diameter machined down too to receive the pullies?? many thanks in advance

To add pulleys you want to increase the length of the bit the pulley mounts on as on the standard drawings it's 15mm, so I always ask Ghai to 'increase dimension F on end machining to 25mm for pulley'. That makes it much easier to align the motor and screw pulley, but clearly you'll need to add 10mm to the length of screw to compensate...The standard diameter for that bit is 10mm, but you may want to consider having that 8mm (same as motors) you can easily swap the pulleys round if required.
This is the end-machining drawing Chai (linearmotionbearings2008) sent me:

Has anyone done this in the past or did you all have metal working mills and lathes in your garages and sheds?!

Yep, I got the mill first and used that to make the router. My milling machine was £320 on eBay from someone local, so if you can find a good deal I strongly advise getting one as they're so useful just in general. You might even be able to get one second hand, make the router, flog it and be in profit.

[JoeHarris]

Thanks Guys, Chai has given me a quote including 50mm extra machining - wanted to be on the safe side in case the design changes!

He seems pretty reasonable, I wanted to go with "proper" linear rails but when you can get change from £30 for a 1500mm long SBR20....

[JoeHarris]

I know you have all seen these bits and pieces a 1000 times before, but I'm excited so heres a picture of what arrived yesterday from china.
The BK/BF Support blocks seem a nice snug fit - any techniques for getting them on (and off!) - I don't want to set about them with a rubber mallet just yet. Also does anyone have any thoughts on lubricating ballnuts? how often and what to use...?

[JAZZCNC]

The BK/BF can be a tight fit so a light flick round the shaft with some fine emery is some times required. They can be pulled on/off with even pressure but some times you will need to give them a very very light tap evenly on either side with rubber mallet.

Thing to watch out for is the rubber bearing seal rubbing on the screw causing binding when butted up to the little spacer. Some times you'll need to either add another spacer or push the seal in further, just be careful not to push in so far it rubs on the bearings.
Also don't tighten the nut like nut and bolt just nip it up enough to take the play out then lock with grub screws. If you over tighten you'll cause binding and wear the bearings quickly. After a week or so running then re-check for any settle movement.


The ball-screws I just use light way oil pumped into the nuts every so often. You don't need much for every day use and it should just leave a very light film on the screw after running up & down it's length. If the screw is dripping or blatherd then thats too much.!! Every now and again I'll pump loads of oil thru the nut to flush any crap out.