V Groove change to linear rails

V Groove change to linear rails

Postby GJHall » Mon May 14, 2018 12:44 am

I have a DIY router table that I have built. The gantry came from a not so reputable company here in Canada.
I have V groove bearings on the Y axis and have too much movement in the Z axis. The attached photo shows the similar gantry. The suppoet plate that holds my router with the V wheels has flex in it. I have tried to adjust the bearings but still has flex.

I am wondering if using linear bearings and rail would help solve the problem? The plate would need to be replaced to allow for different spacing.

Any comments appreciated.

TIA

Gary
Attachments
IMG_8.jpg
Gantry Style
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Re: V Groove change to linear rails

Postby ger21 » Mon May 14, 2018 2:53 am

That gantry beam is really much too small. Even with linear bearings, I'd expect to see some flex.And I'm guessing that the Z axis itself probably has some flex in it.
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Re: V Groove change to linear rails

Postby AlanAndrews » Mon May 14, 2018 10:37 am

Yes I totally agree with the last comment here.

The X axis beam is going to flex in all directions.

This will provide additional flex to the Z axis. And potentially throw out any accuracy on the Y axis too.

If you know someone with some mechanics experience, he/she may be able to advise on some retrospective reinforcement action that will stiffen the beam plus the z axis mountings....I.e. is a simple 'mechanics' issue.

However you might need to invest in a complete replacement.

If you take a little time to look at other machines of a similar size, and of a capacity you require, then this will give you some ideas. There is a machine gallery in this forum as a starting point.
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Re: V Groove change to linear rails

Postby AlanAndrews » Mon May 14, 2018 10:44 am

I forgot to suggest that you post some additional photos.

Get some close-ups of the various axis with a rule in the photo.

This may help us to identify any quick fixes.

But ultimately you may need to invest further, to have a long term solution.
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Re: V Groove change to linear rails

Postby GJHall » Tue May 15, 2018 12:40 am

I have attached some pics as per your request.

Thanks

Gary
Attachments
IMG_0688.JPG
Beam width
IMG_0689.JPG
Beam hight
IMG_0693.JPG
Y axis plate
IMG_0694.JPG
Beam length is just over 5 ft long
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Re: V Groove change to linear rails

Postby Leo » Tue May 15, 2018 12:42 pm

On the 3rd pic (Y axis plate). This is going to be difficult using just words but here is my best shot at it.

There is a black steel plate with bearings top and bottom attached to the cross axis - I assume that is the "Y" axis. The bearings are a decent distance apart - OK for rigidity.

Mounted to that black steel plate is the "Z" axis. The bearings for the "Z" axis are NOT far apart. The bearings are close together. That is not good for ridigity. Additionally, the steel plate itself could flex a little. You may not "feel" it, but you could certainly measure it. It may be only a few thousandths at the plate, but at the cutting action is would be significantly more.

IF - you replaced the bearings at the same points there MAY be a very slight improvement but not really enough to matter.

IF you replaced the steel plate with something more robust, like a 1/2 thick aluminum plate - AND - spread the "Z" axis bearings much further apart - WITH - linear guides - THAT - would be significantly better -- BUT --- you would loose significant "Z" axis travel

I do not see any quick easy fix.
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Re: V Groove change to linear rails

Postby GJHall » Tue May 15, 2018 1:26 pm

Leo,
Thanks for your insight.

I agree with what you are saying. I think the best thing is find something better and get a real machine.

Thanks

Gary
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Re: V Groove change to linear rails

Postby Leo » Tue May 15, 2018 2:33 pm

I think you CAN enhance that machine and add value to it.

If you want to resell it, the added value may be worth the effort.

If you want to keep it, the added value may be worth the effort also.
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Re: V Groove change to linear rails

Postby AlanAndrews » Tue May 15, 2018 5:40 pm

As Leo has said, the main issue will be the rigidity of the z axis.

If you vertically extended the mounts at each end of the beam so that you can run a twin rail system, this will provide rigidity to both the beam and z axis. This will be a fairly simple retrospective modification that is very achievable.

The second beam needs to be of a similar material to that used already - I suggest a box beam, as this is inherently rigid and resists the torsional forces.

You might also consider adding some additional positive pressure from the z axis mount to act on each of the twin beams. This could be as simple as adding a roller onto a spring loaded pin. the spring should be very stiff i.e. car engine valve strings.
This will also allow you to adjust the present rollers to take up any slack.

Keep in touch with your thoughts and actions.
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Re: V Groove change to linear rails

Postby AlanAndrews » Tue May 15, 2018 6:30 pm

cnc mods.jpg
something like this
(15.64 KiB) Not downloaded yet
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Re: V Groove change to linear rails

Postby GJHall » Tue May 15, 2018 7:02 pm

Leo

I understand what you are saying about fixing this machine.
This would be a great plasma machine but, I have one now.

AlanAndrews

I like your ideas to fix it but I think it is time to consider a better built system.

Will definitely consider your ideas though.

Thanks for you valuable input. :D

Gary
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