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

[CaptainBarnacles]

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.

Rather than compromise my design to accomodate thick material do you think I would be better to design a machine to work thin material well and accept that I just won't be able to work thicker material. Being able to work thicker material was a bonus rather than a necessity.

[JAZZCNC]

Well, first I think you need to rethink your Z-axis design because that cannot possibly work how you have it shown now.?

Regards the Gantry height then it depends on what your cutting. All the machines I build have at least 100mm of Z travel and most have 150mm and will happily cut aluminum at full extension with a reasonable finish quality and accuracy using correct feeds n speeds. If you require a higher finish quality or deeper cuts or higher feeds then yes it's better, even necessary to have a lower machine or if not then a machine that is built much much stronger than your typical router needs.

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.

[CaptainBarnacles]

Well, first I think you need to rethink your Z-axis design because that cannot possibly work how you have it shown now.?

Regards the Gantry height then it depends on what your cutting. All the machines I build have at least 100mm of Z travel and most have 150mm and will happily cut aluminum at full extension with a reasonable finish quality and accuracy using correct feeds n speeds. If you require a higher finish quality or deeper cuts or higher feeds then yes it's better, even necessary to have a lower machine or if not then a machine that is built much much stronger than your typical router needs.

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.

OK, I've gone back to the drawing board with my Z Axis and had another stab at it.





With regards to the gantry, the profiles that I have are 80x80 heavy which I intend to brace across the back with perhaps 3mm aluminium sheet or some flat bar. I had thought that would be sufficiently strong for my needs (I'm cutting wood, MDF, ply, plastics and possibly the odd bit of aluminium), do I need to beef it up further?

Is it the case that you tune the machine's feed rates to the strength and stiffness of the machine?

I intend to use timing belts to drive 2010 ballscrews on my X and Y axes. Is it worth having two sets of pulleys and belts to gear it down for cutting harder materials?

[AndyUK]

I had assumed that your previous drawings with the spindle back-plate were making it shorter so we could see past it, but your latest drawings seem to continue the theme. Are you genuinely planning to have the top of the linear rails for the Z axis hanging in mid air like that? Seems like quite a flimsy design decision for the minimal cost of some extra aluminium plate.

I'd also doubt that the ballscrew needs to be that long - but I gather you've already purchased it?

[CaptainBarnacles]

I had assumed that your previous drawings with the spindle back-plate were making it shorter so we could see past it, but your latest drawings seem to continue the theme. Are you genuinely planning to have the top of the linear rails for the Z axis hanging in mid air like that? Seems like quite a flimsy design decision for the minimal cost of some extra aluminium plate.

I'd also doubt that the ballscrew needs to be that long - but I gather you've already purchased it?

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.

[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.

[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]

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.

[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