Lowrider with 1.9m x 2.8m bed area

Hello,

I was wondering if anyone has tried a longer x axis with the lowrider 2?

Stock boards here come in 1830mm x 2745mm so to get the extra 630mm I figured a thicker walled stainless steel tubing would work?
or is it the flex and strain on the printed parts that’s the limiting factor of the gantry distance?

 

Thanks for the help,

It would probably be alright. It might still flex a bit in the center though.

 

Keep in mind thicker tubes mean more weight, so you’d need to adjust your speeds.

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Extending the usable width from 48" to 72" will increase the deflection seen at the center by ~2.75x. To put this in perspective an 80" long, 1" diameter tube with .092" wall thickness will deflect an extra 1" at the center when loaded with 5lbs of weight (2m, 25.4mm, 2.35mm, 25mm for the metric types). And that is on top of whatever sag there is in the pipe just from its own weight. A thicker pipe will reduce the deflection from the router/carriage, but the extra weight will add to the sag so I don’t know if you will end up winning or losing if you make that trade.

The “proper” solution would be to move up to a larger tubing size. Increase the diameter from 1" to 2" (25mm to 50mm) would reduce the sag by 8x and only increase the weight by 2x but that would require a redesign of a lot of parts.

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There was a mondo build a while ago. There was significant sag in the middle, and he figured out Marlin’s mesh levelling, so if you were try to cut straight across, the Z would actually move up in the middle to keep it closer to level. It’s going to be tough at that size no matter what.

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FYI

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I still need to put together a test apparatus to prove/disprove my sag-combatting internal support scheme detailed in that thread. I have all the bits, just need the time/space…

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Thanks Jeff and Frosty,

Frosty, the correct way as you pointed out may be for a later point, but might be achievable with just doubling the scale of everything and sourcing some larger bearings. Not sure how the motors would cope with lifting that extra weight. I plan on building a few iterations including one with geared steppers so that could end up in one of them.

Jeff, mesh levelling does seem the way to go to be absolutely certain with the cuts, I’ll look into it once the other half of my end stops arrive, will certainly help me with the finer details in carving.

Frosty in your link inside the post Jeff mentions, there’s a bit of confirmation for 2 ideas of reducing sag that I was thinking of implementing after a walk around the workshop.

Firstly, inside the tube, epoxy a length of 2-3mm flat bar vertically to act like an I beam, eliminating Z axis sag without much weight gain and still allowing for cable runs.

Secondly, the aluminium angle used for the vacuum hose, printing a second pair of supports a second channel can be fitted to stiffen the x and y axis to some degree. I found an aluminium 50x50x3 extrusion in the workshop today with ridges to increase rigidity but also reduces weight comparatively, a test bend of the 3.0m ( just under 10’ ) long stock I had showed about at 5-8mm deflection on the edge/angle and nothing noticeable when bending from the sides.

any thoughts?

Sorry about all the metric I’d try convert to inches but I’m not sure what the standard fractions or equivalent stock is so the result would be laughably wrong no doubt.

Carving on a rig that size seems nearly impossible, even with mesh leveling. You don’t want to carve anything nearly that big, do you? That would take weeks.

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No I don’t intend to carve that large off the bat, main purpose of the machine is going to be cutting flatpacks as well as cutting the more involved joints in sets of hardwood.
Once I’ve got that up and running properly I figure it can’t hurt to try a few of the crazier ideas, though like you point out machine time (and with that, the bits potentially wearing down during the job) would be a major factor even if I could get the required accuracy.
The carving idea is just a bit of running before I’ve learnt to walk.

One more thing to keep in mind. Due to the sag, your endmill won’t be perpendicular to the bed, so your cuts are going to be a little wonky. It will always point a little bit to the closest side. Might not be enough to make a difference, but keep this in mind.

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The angle the z bit would have would be based on the sag at each end of the 611 plate. Since they are only 6" apart, there won’t be anywhere on the span where it would be that much different. Something like:

tan-1((sag(X)-sag(X+6"))/6)

To be off by 1 degree, you’d need 0.1" difference in sag over 6".

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Thanks Barry, will keep it in mind, hopefully the I-Beam will limit that sag enough for it to not be noticeable.

And thanks Jeff, I’ll run the numbers once I’ve got it built up, then I know what I’ll have to account for in my cuts.

 

Maybe I’ll offset any sag with some bracing on the 611 plate if it turns out significant enough, some aluminium angle offcuts should do the trick.

From the roughing you’ve made to get a 1 degree deviation I think I’d be still have to be fighting with the sag to be effected on any noticeable level.

But, even if the sag in the middle is 5", the difference between the middle and 6" from the middle won’t be 0.1".

I was arguing that it would be no big deal.

Hi Jeff, on that topic of sag on the CNC, how much weight is that allowing for on the router?

I see the DeWalt 611 is 4.6lb (+/- 2.1kg), the spindle I plan on using since I can’t get my hands on anything resembling a DeWalt here is a 1.5kW 80mm Spindle which weights around 8lb (3.6kg) which is the closest I could find in stock that’s going to reach similar rpm to the DeWalt.

Below is the link to the spindle and its specs,

https://neotronics.co.za/index.php?route=product/product&path=113_115&product_id=386

Also any idea on the weight limit of the Z axis? or issues on the X and Y with using a heavier spindle?

Motors I’m using for the Z axis are linked below, but basic specs are , 32oz/inch holding toque per motor, 1.33A.

Maybe I did something wrong here, but I checked and 6500 ZAR is $440 USD. I’m going to go out on a limb and say that is way too much spindle for a LR. You will not get close to needing a fancy spindle like that.

There must be some kind of trim router for woodworking in South Africa. The top speed of the dewalt isn’t really necessary. I would try to find one with a similar weight, diameter (in terms of the body of the router), and power, and at least 75% of the dewalt’s rpm. It’s your money, you can spend it on the fancy spindle if you like, but I think that’s a bit out of balance with the rest of the machine.

On the low rider, the coupler actually helps let the leadscrew stay aligned with the nut, since there can be a little bit of flex in the materials. I would recommend using a regular motor and a coupler over an integrated leadscrew motor. Also, those motors are very weak. The ones Ryan sells are 76oz-in. The E3D ones are 32oz-in. The bigger ones (70-90 oz-in) are pretty common, so you should be able to find some.

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Your conversion there is correct.
I was working off having to special order a 500W single speed 33000rpm handheld laminate trimmer as linked below, for about $250 locally, and figured for the extra cash I could get something that’s made for the job and have speed control.

https://ryobi.co.za/products/laminate-trimmer-500w-industrial-5yr/

Prices here aren’t really proportionate to ability and more on what they can move the most of, routers readily available are 11lb (5kg+) plunge routers (equivalent linked below) which come in at similar prices to the spindle.

 

I do get your point on it being overkill though, would a 600W spindle as linked below be more the Lowriders size? it comes in the same price as the Ryobi Laminate Trimmer above, my main concern with it was the rpm

https://neotronics.co.za/index.php?route=product/product&path=113_115&product_id=298

 

Oh I see, I’ll have to get replacements for those motors then before I scramble them. As long as they’re 72oz/inch and above they’ll be fine?I’ll try source some lead screws and couplers as well, didn’t realise it was a structural thing, I thought it was more a price saving thing.
I’d have ordered the whole kit direct from Ryan but the local postal system here is notorious for losing stuff or at best taking months to clear it and get it to you, so if its not sent by courier there’s no guarantees it’ll actually be received.

It must be really frustrating to have a postal system like that, and also see the same choices elsewhere.

The last link you posted isn’t going through for me. Maybe all of neotronics is down, ATM.

The other point about a regular router is that you’ll have to find a collet that works for you. The Ryobi one you posted doesn’t have a 1/8" collet.