First Build - Yet Another Alu Profile Router - 900 x 800

[CaptainBarnacles]

Looks ok to me and will work fine. Thou I've got a few suggestions which will make it a little stronger and easier to setup etc.

The height of the gantry doesn't look very high so you could change it a little and gain some height while increasing the strength and making it easier to setup.
I would make the gantry and bearing plates two separate items. Make the Bearing plate and the drop bracket for ball-screw one part. Then use another plate bolted directly to the profile from the underside and into the shortened gantry sides, this will stiffen the gantry a little. Then bolt this to the bearing plate because how you have it now will make accessing the bearing bolts difficult. But also it allows you to square up the gantry without affecting the ball-screws.

As you have it drawn now then if you need to adjust the squareness all you can do is loosen the bearing plate and rotate the gantry as a whole. This then changes the alignment of the gantry sides so they are no longer parallel to the ball-screws, this, in turn, means your ball-nut mount unless shimmed, etc puts a twist on the ball-screws that causes binding and premature wear, etc.
If you do it as described above then you can just loosen the gantry without affecting the ball-nut alignment. The extra bearing plate also adds a little height to the gantry, It's also very easy to add extra height if ever needed.!

Simple changes which will make a big difference to the machine setup.

Edit: You could also gain back some of the lost travel by making the Gantry plate a little longer than the bearing plate and offsetting the gantry back a little.!

Thanks Jazz, some great suggestions. I am not sure that I understand 100%, do you mean something like this? (sorry, really crude drawings just modded from my originals so ignore hole placement etc.):




The red plate fixes to the gantry profile from below and the gantry plate, the gantry plate fixes to the gantry profile in the usual way (and also to the plates on the back of the gantry that carry the BF/BK blocks for the X axis ballscrew). The red plate can then be fixed to the bearing plate and if I either elongate or slightly oversize the clearance holes I can get some adjustment for squaring the gantry assembly.

Am I on the right lines with that?

[JAZZCNC]

Yes, that's exactly what I mean. Makes things a lot easier regards setting up and ball-screw alignment.
Getting the ball-screws aligned correctly makes a massive difference to performance and the life of the screws. Just a little off and you'll get binding which robs power and causes excess wear on the ball-nut.

[CaptainBarnacles]

Yes, that's exactly what I mean. Makes things a lot easier regards setting up and ball-screw alignment.
Getting the ball-screws aligned correctly makes a massive difference to performance and the life of the screws. Just a little off and you'll get binding which robs power and causes excess wear on the ball-nut.

Cheers for that Jazz

It's stuff like this where years of experience really show. It all looked good (to me) on my plan but the practicalities such as being able to access screws or adjust alignment etc just don't become apparent (again, to me) on a model. I would have been stuck into the build before having one of those "d'oh!" moments.

[AndyUK]

Cheers for that Jazz

It's stuff like this where years of experience really show. It all looked good (to me) on my plan but the practicalities such as being able to access screws or adjust alignment etc just don't become apparent (again, to me) on a model. I would have been stuck into the build before having one of those "d'oh!" moments.

One trick I used was once I had the design all sorted, I put it to one side and started the assembly from scratch, bringing in each component at a time and working out how to attach it, and zooming out to see what access I'd have at each stage.

Still doesn't totally work - but it helps a lot. There are still two bolts that I have no idea how to access under the gantry!

I wouldn't wait too long before adding bolts into your model - the heads can be large enough to change things, and then you might want to think about countersinking them. This ties in with the adjustment Jazz is referring to; there might be places like the Y axis ballnut connection where you want a bit more adjustment room. For example, here I used slots so I didn't have to be spot on on the height of the screw vs the rails. How would you adjust each connection in all three axis? How will you tighten the motor belts? etc.

It was all very overwhelming at the start, but now I'm looking back I regret not going that extra mile with the CAD and thinking of ingenious limit switch placements to hide them away from everything. Its a little irritating trying to retrofit them now. Obviously that's not a concern for right now, but I'd at least consider it before starting the build. The same goes for covering the screws and rails somehow - I'd prefer my build if they were protected from chips, and lubrication pipes to make everything easy to lube when its in place.

[JAZZCNC]

Cheers for that Jazz

It's stuff like this where years of experience really show. It all looked good (to me) on my plan but the practicalities such as being able to access screws or adjust alignment etc just don't become apparent (again, to me) on a model. I would have been stuck into the build before having one of those "d'oh!" moments.

It's common for the little details to get overlooked and it's the little details that can make a big difference to how the machine performs and ease of maintenance etc.

I model all the major mechanical components individually in CAD right down to the exact mm and with every hole for bolts etc in their correct locations. Then I build sub-assemblies with the components ie: Z-axis, Gantry, Ballscrews with end bearings and ball-nut mount, this lets me check for clashes with bolts, etc.
Then finally I build a full working assembly with the sub-assemblies all mated together accurately. This way I can check every detail and catch if any interference or if access is restricted etc. You'll be surprised just how easy it is to miss quite obvious details that would be major problem after parts are made.

My personal opinion is that making mock-up parts from MDF etc is a waste of time and provided you are accurate with the cad models then it's not required and defeats the purpose of CAD. Every machine I build is done solely in CAD with each part machined straight from the model and they fit together perfectly every time. (Unless I screw up the machining which never happens.!. .Honest.!!)

However for those who don't have good CAD skills or use lower-level packages that don't allow mating and assemblies etc then I agree it's a good and safe way to work.

The best advice I can give is to build in as much adjustment as possible and pay close attention to bolt hole locations/access to prevent clashes. Think about the little details right at the start like Limit switch locations, Energy chain mounting and paths, Cable routing and access to grease nipples, etc.

Break the machine down into segments and think about how each segment interacts with the next. ie: Z-axis and how it mounts to moving axis on the gantry and how the Energy chain runs along gantry and mounts to moving access does it clash with ball-screws or motors or limit SW etc when moving.?
These little details can be a right ball-ache if left until the machine is built only to find out there is no way to avoid clashing. Often the difference between something fitting or not is only mm's and can completely screw the job up or cause major part remake or big compromises on design.

The extra time in CAD is well worth the time and frustration it can save, not to mention expense if screw up big.!

[Kitwn]

However for those who don't have good CAD skills or use lower-level packages that don't allow mating and assemblies etc then I agree it's a good and safe way to work.

This probably applies to most of your readers.

MDF can be the old man's CAD. Perhaps we need a new acronym? MAD..... Model Aided Design

Either method will help you avoid creating a TURD... Totally Unbuildable Router Design