CNC Router V1.0 (For Cutting Multiple Materials)

[Lee Roberts]

Thanks for all the feedback guys. I think I'll go with Hiwin 20mm for the Z axis. What would be the "minimum" recommended centre distance between the two rails? I want to keep this as small as possible to maximise the effective Y axis length but without compromising rigidity. At the moment my whole Z axis assembly is 130mm wide..

Well generally I always suggest 250mm minimum, obviously this harder to achieve on smaller machine with smaller z assembles...

.Me

[routercnc]

My Z axis plate is 147mm wide and the Z rail centres are only 115mm apart. I did this to maximise Y travel and placed my Y axis bearings pretty much back-to-back.

This works fine for me, but it can give you more stability and less likely to rack if the Y bearings are spread further apart, but you are trading Y travel. If you do spread the Y axis bearings out further, closer to Lee's figure, then I don't think you need to follow suit with the Z rails and can keep them fairly compact.

[biketrialsdave]

Your machine looks great, thanks for all the advice.

I've increased the plate width to 170mm now. The z rail centres are 118mm apart at the moment. Do you think the carriages need to be separated more in the z axis? (They are 119mm centres) I'm trying to reduce this length as much as possible in order to reduce the total height of the z axis plate (if that makes sense.

Also, is it worthwhile pocketing the carriages slightly like I've done elsewhere?

[JAZZCNC]

My rear plates are between 180-200 wide which I find is good balance between strength and space saving for a small machine. On larger machine I will try to make wide has possible to get most ridgidty. Carriage separation I make wide has possible and take the bearings to the edges of plates. Vertical Separation is roughly half the rails length.

Regards the pockets then it depends on the material your using.? If your using Ground cast plate then no because it defeats the object of the plate being ground. If just rolled Plate then yes it needs to be machined because it's often not flat.
If using Ground plate and you want registers for the bearings then Mill some Aluminium blocks or dowels into the plate inline with the edge but slightly overhanging the bearing side then secure with loctite.
Then Machine away the overhanging part to give your reference edge but set cutting tool flush with ground surface so not cut away. In practice it's actually much quicker than buying rolled plate and machining away pockets and more accurate.
Personally I tell people not to bother unless they are sure the whole machine is accurate from base upwards because they make adjustment much harder and in flexible.
In an idle world then yes you'd have them but the reality is that building in your Man cave then in-accurecy is sure fire going to be there so any thing to help adjust error out is welcome.
Also in DIY setting then it's unlikely you'll be chasing Um accurecy and neither will you be stripping it down every other week. So provided you take care when setting up and use good quality fasteners, tighten them up properly and use retainer then you'll not have any troubles and chasing away error will be so much easier.


One potential Gotcha I spotted on your drawing. The holes in the Top and bottom plate which fasten them to the rear plate may interfear with the bolts on the Gantry bearings.? Easy done so check it.!

[biketrialsdave]

Some progress. Am I going in the right direction? My only concern is I've had to mill a channel to allow the BF12 mount to not interfere with the plate holding the motor. Where the slot is the thickness of the plate is down to 10mm. However, its quite a narrow channel...

[JAZZCNC]

Split the difference by machining both sides like this.

[biketrialsdave]

I've been busy all this week so not had time to work on this. However, I've sneakily booked Monday off so I can get some more time on it! Instead of constantly asking questions, I've tried to think of all the main concerns I have at the moment. I would be very greatful if anyone can answer a few!


1. I need to work out how I am going to attach the extrusion (bed) to the aluminium tooling plate. I think I have two options: a) Either drill the tooling plate and insert bolts from the underside which screw into t-nuts in the extrusion. b) Or use aluminium corner brackets on the inside of the extrusion?


2. I think I need to assess how I am connecting the extruded pieces to eachother (for the bed frame). The X axis extrusion is actually comprised of a 45x45 piece and a 45x90 piece ontop of eachother. Unfortunately I cant seem to find a single 45x135 piece? At the moment they are only attached together by the steel end plates. Do I also need some internal corner brackets? I was also wondering if to add some plates bolted to the side of the 2 extrusion pieces?


3. How should I re-inforce the steel end plates? Would it be a case of simply increasing the plate thickness from 5mm? The end plates don't hold the ballscrew bearing houses (these are attached to the extrusion). The plates at the back of the machine do, however, hold the stepper motors.


4. Is it possible/recommended to add a vaccum to the z axis for swarf? Is this only to be used for wood? I am also going to add brackets for a coolant hose.


5. I need to consider draining the coolant. Could this simply be a hole cut into the tooling plate with a pipe which goes through the table beneath into a bucket? My only concern is I don't have a "fall" for the water.




Hopefully those all make sense!


Thanks again,


Dave