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

[phill05]

I've been paying some attention to my X and Z Axes design this week and I'm starting to question whether I have built my gantry too high. The fully extended Z Axis looks like it could be vulnerable to excessive deflection given the amount of extension from the gantry.


What I realised is that most of the work I'll be doing will be on relatively thin material (12-40mm) so the router will be operating at full extension most of the time. I also realised that this must be a problem for a lot of machines; do most people raise the bed in order to minimise the deflection of the cutter? I would like to work material up to 100mm thick and I currently have about 120mm clear travel on my Z axis.

I have 120mm clearance under my gantry and have the rails fitted to the back plate on the Y axis and bearing blocks fitted to the plate holding the spindle and travels no lower than the gantry, if you lower your spindle housing to around 30mm of bottom of the plate you have the option then to cut 100mm high or lower the spindle in the housing to cut the smaller jobs, this is how I work mine with no problem cutting ally and have cut some steel with the correct cutters.

Phill

[AndyUK]

Yeah, I see what you mean about those rails being unsupported when the Z is lowered and yes, I have already got the ballscrew.

Three options then:

- Add more plate to lengthen the router mount plate.
- Consider shortening the whole linear travel by cutting the rails and ballscrew.
- Buy another ballscrew. (perhaps a 1605 would be sufficient?) Looks like I can get one for about £33 with the supports, nut bracket and coupler so that won't break the bank.

I had previously wondered about shortening the ballscrew using my ML7. I'm not a very accomplished machinist and my biggest concerns (apart from completely stuffing the job up!) were about the hardness of the ballscrew and whether the action of cutting into the thread might make the cut wander.

Nothing wrong with the ballscrew being that length; its just that you're not going to use its entire travel, so if the ballscrew hadn't been purchased you could save some money by getting a smaller one.

I'd argue the easiest option is just to extend the plate.

Second option is to swap the rails and carriages (as I think Phil suggests) but its quite nice to be able to remove the spindle plate in one go with just four screws on the ballnut; it can be a pain to remove the other way round.

[phill05]

Here you go

[CaptainBarnacles]

To be honest I'm not a fan of the open gantry design you are using with the profiles orientated in the vertical position which is there weakest orientation. Those same two profiles could make a much stronger gantry if you made it an L-shape and put the screw at the rear.

Do you reckon it would be stronger to use a single 40x160 rather than the 2 qty 80x80s (with some bracing across the back of them)?

I have 2 qty 80x80 and 2 qty 40x160. I was using the 40x160s as my Y axis rails but it occours to me that there's no reason I can't swap them out for the 80x80s and put a 40x160 on the gantry. Heck I suppose I could put 2 40x160s in the gantry, would that be overkill? The image in my head of two 40x160s bolted to make an L-shape, as you suggest, is scary big - it would be a behemoth - I like that but would the rest of the build cope with throwing all that mass around? I do also have a load of 40x80 so perhaps a 40x80 bolted to a 40x160 for a L-shaped gantry?

I'm going to take a look at it in Fusion and see how it looks.

[CaptainBarnacles]

Nothing wrong with the ballscrew being that length; its just that you're not going to use its entire travel, so if the ballscrew hadn't been purchased you could save some money by getting a smaller one.

I'd argue the easiest option is just to extend the plate.

Second option is to swap the rails and carriages (as I think Phil suggests) but its quite nice to be able to remove the spindle plate in one go with just four screws on the ballnut; it can be a pain to remove the other way round.

I did try it with the rails the other way around and I wasn't keen. I think that you're right, extending the plate is the easiest option.

[CaptainBarnacles]

I've been looking at different gantry arrangements that I can build using the material that I already have.



From left to right they are:

A: 3 off 40x80
B: 2 off 80x80, 1 off 40x40
C: 2 off 80x80 with 40x40 or 40x80 bracing
D: 1 off 40x160, 1 off 40x80 'L' arrangement
E: 1 off 40x160, 1 off 40x80 'L' arrangement with lower linear rail front mounted
F: 1 off 40x160, 1 off 40x80 'L' arrangement with greater gantry clearance
G: 1 off 40x160, 1 off 40x80 'T' arrangement

My original arrangement was 2 off 80x80, one above the other without any bracing. On the feedback I've had so far I think that any of these new arrangements should outperform my original. I like A, B and C as they allow the ballscrew to sit in the gap but I know that strength and stiffness are more important. D offers good spacing between the two linear rails but I think that it may be a step too far as it limits the material thickness too much. E is my current favourite. The only thing I don't like is that the Z axis will protrude out further from the gantry but I think I can live with it.

Of these arrangements which do you think offers the best performance?

[JAZZCNC]

My original arrangement was 2 off 80x80, one above the other without any bracing. On the feedback I've had so far I think that any of these new arrangements should outperform my original.

Your orginal would been ok if the profiles where bolted together without the gap. The gap wasn't required so bolted together the profiles are stronger.

I like A, B and C as they allow the ballscrew to sit in the gap but I know that strength and stiffness are more important.

The gap would just fill up with crap and shorten the screws life. Like wise being exposed to chips is why I don't like open gantry's along with being weaker. The L shape gantry helps protect the screw as it's behind and is also stiffer.

E: 1 off 40x160, 1 off 40x80 'L' arrangement with lower linear rail front mounted

E is my current favourite. The only thing I don't like is that the Z axis will protrude out further from the gantry but I think I can live with it.

This would be my choice with the profiles you have.

[Voicecoil]

How about a variation on "C", bring the 2 80x80s close together (ditch the crap collecting gap) and plate them front and back to make say a 90 something x 160 section? You could even slip a drop or 2 of epoxy where the extrusions meet if you were feeling keen

[AndyUK]

You could even slip a drop or 2 of epoxy where the extrusions meet if you were feeling keen

You sir are a brave, brave man.

[Voicecoil]

He who dares wins.