Adding a scissor lift table.

[CNYDWW]

Wanted to run this by the forum. We're considering investing in a hydraulic lift table for the shop bot. The plan would be removing the bed on the PRT Alpha and dropping the front rails. With that adding extra triangulated supports on the x to maintain stability. The alpha is used primarily for surfacing large thick live edge slabs and reclaimed beams. It's already been raised 6". We use a shop made router jig nicknamed the "JoBot" so we can surface off stumps, large beams and the like. If we do the above and add a hydraulic scissor lift table in the center of the Alpha to gain more versatility, we can toss out the JoBot that doesn't do a very good job as is. Trick will be making sure the scissor lift stays on the same plane. Theoretically that type of lift would do so. I'm specifying a minimum capacity for the lift at 2 Ton for stability.

Cons? Thoughts?

Any would be appreciated.

Regards
Randy

[Brady Watson]

It's pretty tough to keep it level, repeatable and stable. Been there...done that...the only way to pull it off is with large screws that are synchronized & preloaded to eliminate uneven backlash, and beefy linear rails to keep it moving true and tight to the rest of the table. DeWalt DW735 comes to mind here...If you are doing 'hatchet work' on big slabs then accuracy might not make a whole lot of difference to you.

-B

[CNYDWW]

That's what i was afraid of. It really was hatchet work till i got there to tune it as is. My old machine is still sitting in the back corner in pieces. I would at least want to maintain a maximum variance of 1/16" in the 10ft length. Mainly the machine is used for the surfacing. Sometimes other things are milled but i'm going to try to limit that to my old Mach3 Bot.

Regards

[Brady Watson]

You can always jack up the X or Y car to gain more clearance, or just drop the table with some spacers to gain more clearance. The simplest is a pair of 1/4" plates welded together so they overlap an inch or so & bolt in place of the v-roller axles. Then transfer the v-rollers to the bottom plates. You can weld on some gussets onto the plates and bolt them to the X car Y-rail supports. When you want to lower it down again, just remove the plates.

-B

[CNYDWW]

Thanks Brady,

It already has a 6" High lift on the rails using the long bolt and pipe meathod. We need rapid adjustment or else the boss wont be happy. It might be a better idea to rebuild the JoBot out of better materials including better linear rails and bearings.

[danhamm]

I do a lot of rugged beams and heavy timbers on mine, I have the side cars adjustable from 6 inches to 14 inches, I just raise the gantry, am thinking of using linear rails on the vertical on the side cars, make the whole gantry a z-axis.

[Steve M]

You can build simple and precise height stops for a scissors lift to solve the consistency issue.
If you add linear encoders and a gear system that can be operated with an electric drill, you can have a very quick and very precise adjustment system.
There are other ways to attack this problem, but I don't want to break a nail from all the typing.

[CNYDWW]

A thought that came to me today would be permanent pads on four corners. Adding spacers and sitting the table back down on them depending on what i'd need.

[myxpykalix]

Heres how i might do it. Take a look at these pics. The height of the rails on the legacy is held by these cap screws that tighten on the slit on the leg.

What i would do is have a horizontal rail on both sides of the table that the cap screw and square nut could ride in a vertical rail.

You then have a house jack in the center under the table surface that you raise and lower as needed and then only have to tighten each corner.

To make sure it is level on all 4 corners when setting it up just lower you bit to the table surface desired level, raise the table till it meets the bit, repeat this on all 4 corners.
I can see how this wouldn't take 5 minutes to do a setup.

[CNYDWW]

Thanks for the advice jack but if it's more then too simple then it wont get done in this shop.

Regards
Randy

[Brady Watson]

There lies the problem, Randy...When you do something like this, it has a way of snowballing into a huge project in order to maintain versatility. It is hard to 'have it all' when you increase the machinable area/height too much, because you lose a lot of stiffness. If it were me, I would consider building a machine just for this purpose, if there is enough work/money in it to justify it.

-B

[CNYDWW]

There lies the problem, Randy...When you do something like this, it has a way of snowballing into a huge project in order to maintain versatility. It is hard to 'have it all' when you increase the machinable area/height too much, because you lose a lot of stiffness. If it were me, I would consider building a machine just for this purpose, if there is enough work/money in it to justify it.

-B

Really appreciate the advice from all.

Brady, I know exactly what you mean. A purpose build machine is really what we need. I don't think they'll let me build it nor do i have the time too. I'm going to switch gears and see if i can't rebuild the JoBot as they call it with some precision rails etc.

Regards