Alternatives to Z lift design?


Alternatives to Z lift design?

Postby LeonS » Fri Dec 18, 2009 6:23 pm

I like the Z lift designs discussed in other posts and can certainly appreciate the engineering and craftsmanship being presented.

I'd like to present a couple of options to the design for discussion:

1) Use no adjustable table at all. This what full spectrum engineering does when it modifies a typical small Chinese laser. They remove the table lift assembly completely and support the cutting surface, or the material, with 123 blocks and printed circuit board shims for fine adjustments. This provides a bit more than 2.5 " of extra cutting area since the threaded rods are no longer blocking the use of 11 inch material. This is cheap and seems pretty flexible. It seems to me that most materials would fall into one of maybe 5 or 6 thicknesses for which you could have precisely the right length of risers and shims. Simple, cheap, larger cutting area with no bridges burnt if you want to go back to a lift assembly. Keeping the material square to the X-Y axes and having a repeatable positioning capability would want to be resolved but shouldn't be too hard.

2) Another way to increase the cutting area of a small Chinese laser might be to have the cutting platform supported by the ends of the threaded rods but not having them protruding through the platform. The nuts could be fastened to the case bottom and the screws could extend into an area created under the laser in a new box attached under the old laser case. This would be the equivalent of turning the current design on its head. The ends of the threaded rod would support the cutting platform but would screw down into the new addition to the case. I guess to work properly, the nuts would be attached to the case bottom in a way that the could be rotated by a belt and stepper.

As you can see number 2 is harder and not as well developed (at least in my mind). The advantage to either of these approaches is that larger stock can be passed through the laser without hitting the protruding threaded rods and for small Chinese lasers you can get a nice increase in cutting area. If I wanted to alter my Artcut jsm40 I would do number 1. For the new build, approach #2 may be more trouble than it is worth since I can control the size of the platform and the location of the screws as Bart has done in his design.

Any ideas on other puts and takes for either approach?

Sorry for rambling. This was written in between a dozen phone calls and conferences.

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Re: Alternatives to Z lift design?

Postby bdring » Fri Dec 18, 2009 7:30 pm

My method is similar to your #2. I have the mechanism mounted to the bottom of the enclosure and the "legs" are long enough to provide the room for it. The threaded shafts are not in the range of the laser head. The complaints about my system are , the chain and sprocket method is noisy and sounds lame, It cannot go very fast witout jamming, it is not very accesible for adjustments because I have it on a flat table..

Here are my thoughts

1) I like the motorized feature. It seems like I make a minor adjustment on nearly every cut. I have a gauge block that I hold on my laser head then raise the table until I touch the gauge. This might could be automated with a switch, but I probably won't bother.

2) I have way more adjustment than I have ever used. I have never cut anything thicker than about 2".

3) I think it would be nice to induce airflow though the platform. The smoke flow now often stains the material.
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Re: Alternatives to Z lift design?

Postby Robert Williams » Mon Dec 21, 2009 1:44 pm

Chain and sprocket... I'm about to change to belt and pulley by making the legs longer. Bad idea?
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Re: Alternatives to Z lift design?

Postby lasersafe1 » Mon Dec 21, 2009 2:04 pm

You might want to check my thread to see the timing pulleys that I bought. viewtopic.php?f=4&t=26
I didn't realize when I was buying them that they were so tall. I lost a good 3/8" ultimate depth on the Z drop because of the pulley set screw. If I could have purchased a press fit pulley with no set screw I would have my depth back.

I also looked very closely at the assembly before tearing it down to work on the Z. I realized that there was still a good 1/2" of clearance on all aspects of motion with regard to the lid of the M40 laser system. With that in mind, I will be putting it back together with 3/8" spacers under the laser tray and the rail assembly. This will at least get me back to my planned Z drop.
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Re: Alternatives to Z lift design?

Postby bdring » Mon Dec 21, 2009 9:35 pm

Are you saying you are going to use a belt and you plan to make the legs longer? If so I think that is a good plan. That way you get the benefits of the belt, the benefits of having the drive out of the way of the table by putting it below the table and you still have access to the belts if needed.
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Re: Alternatives to Z lift design?

Postby TLHarrell » Thu Jul 28, 2011 11:55 pm

I am considering a build in the semi-near future. I just recently got a FSE 40W unit to start with. I love it, but it has it's drawbacks. The new unit will take into consideration all the low points of the small Chinese laser.

For the Z-axis table, I'm considering another alternative to a linear system. The Sarrus Linkage.

I plan on having a 24"x48" laserable area, perhaps slightly more than that. Running timing belts all over the underside of the table to pick up something that large would be interesting if possible. My design I'm considering would place a Sarrus linkage in each of the four corners of the table, then a series of lever arms nearer the center of the table would crank it up and down similar to lifting a car. The stepper motor to drive this would be mounted partially out of the bottom of the case, and the levers would have their shaft sitting on the case floor and extend downward when the table is raised. Total travel would be +/- 8". Simple all-thread rod could be used to drive the levers.

For reworking the Chinese laser, a similar idea could be used but only using a single lever in the center of the table, or along one edge, driven by a stepper mounted hanging below the unit, and perhaps 2 Sarrus linkages in opposing corners due to the small size of the table.
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