Multiple gas springs for extended stroke
 

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Jeopardy,

Do you use any parts of the MechMate on your Z axis? Same spider plate and Z slide perhaps? or it all had to be modified to fit both the gas springs? I am scratching my head thinking how to use 2 springs and get them to work together to be effective for the whole length.

My Z Slide Drawing
 

Francis,

As you can see from the attached drawing, my Z slide is different from Geralds. I designed my machine to handle a long slide (24+ inches). On my machine, the X & Y axis' also have wheels & rails on the top and bottom - so that the gantry does not rely on its weight to remain on track.

Also, because my Z is 24", I did not have a good solution for using a single gas spring. It worked perfectly when I restrict the Z movement to about 14 inches, but above that, a single gas spring was not practical. Therefore, I designed a "nested" gas spring - so I was able to get about 27" of travel in about 45". I also found that standard compression/extension springs (unbalance force) and constant force extension springs (too large to be practical) were not a good alternative for my application.

With regards to putting a gas spring on Gerald's spider, it should work. You still have a "sliding" plate and a "stationary" plate. The gas spring just needs to be attached between the two points. You may have to put an extension bracket on the spider (sliding plate) to make allowances for the height of your gas spring. When working with gas springs, make sure that you use one that will not "bottom out" when it is fully compressed.

Understanding the concept
 

Jeopardy

Thanks.

Let me see if I got this straight, here we go:

You grab 2 gas springs, join them, back to back :confused:. Fix one of the ends to the "stationary plate" (MechMate's spider plate) and the other end gets fixed to the "moving plate" (the MechMate Z slide. More precisely part# 10.40.372 or simply the Z strut bracket. or even ...Little bent sheetmetal part that serves as a flange to the rod of the gas spring:eek:")

Am I correct?

I tried to understand exactly how your machine works, looking at the drawing, but I got a bit confused. Have you got 4 springs in your drawing? 2 pairs back-to-back?


Francis

Z Slide Explanation
 

Francis,

I will do my best to explain with a series of drawings ...

Page 1 - This is my Z axis attached to the Y axis - without the gas springs. The Z axis has 2 parts - the sliding part is on the left side (Lower - left side), the fixed part (Upper - right side) is permanently attached to the Y axis.

Page 2 - This is the two main parts of the Z axis. I am also showing some additional brackets mounted to the moving portion of the Z. These brackets are used to mount two 3/4" x 36" steel shafts.

Page 3 - This shows the two 3/4" x 36" steel shafts permanently mounted to the moving portion of the Z axis.

Page 4 - This shows two steel tubes - .77 ID, 1" OD, about 14" long. These tubes move freely on the 36" steel shafts.

Page 5 - This shows a steel plate mounted to the tubes. This "Cylinder Plate" slides freely up and down the steel shafts.

Page 6 - This shows the two gas cylinders mounted to the sliding "Cylinder Plate". The gas springs are connected as follows:
Left Spring - Top is mounted to the top of the moving Z axis (Orange Plate)
Left Spring - Bottom is mounted to the bottom of the Cylinder Plate
Right Spring - Top is mounted to the top of the Cylinder Plate
Right Spring - Bottom is mounted to the bottom of the Fixed Z axis (to a bracket not shown on the drawing)

The only reason that I have 2 gas springs is because my Z axis travels about 25". The gas springs that are readily available (McMaster Carr) have a maximum travel distance of 16". If my Z axis traveled less than 16", then I would have used only one gas spring. I would have attached the top of the spring to the top of the moving Z axis (orange Plate) and the bottom of the spring to the bottom of the fixed Z axis (to a bracket not shown on the drawings) - and eliminated all of the shafts, tubes, sliding plates, etc shown on the drawings.

Again, this is how I did it on my machine. You will have to adapt the mounting points for the gas spring to the mechmate drawings - but the principal should be the same.

Hope this helps!

Jeopardy

Thanks again. Your explanation was quite good and I did understand your mechanism.

It does gives a solution that people can adapt to the mechmate.

Francis.

Hi,
Is it possible to connect two gas springs in serial?
Like screw one to the other one using rod coupler.
krod

Krod, Nothing of a personal attack, just a reminder, see this
Amicalement, Robert

Hi Krod. That is the theory, but the coupler wants to move sideways because the whole thing gets too long. You need to hold the coupler on a guide so that the coupler can only move up and down. And this is exactly the concept discussed in the posts above.

Robert,
I'm sorry if I made a mistake. I didn't have experience with forums. Maybe it's a silly question but I have no experience with gas springs. Anyway, I'm also trying to make MM with 24" travel and thinking of connecting two gas springs directly w/o sliding plate. I've researched about this but no result. I'd like to know if anyone has information.
Thank you.
krod

Thank you for the information.
krod

Hi Krod,

Check out this link. It may help answer your question with an alternative.

http://mechmate.com/forums/showthread.php?t=439

Hi Krod, don’t get me wrong, I’m one of those who firmly believe there is no such as a stupid / silly question. Like most of us, I too tend to ask before making further / in depth searching :o
Don’t be sorry for any single mistake I say to my sons, it’s an opportunity to improve, if no repeated :rolleyes:
Amicalement, Robert

Krod,
Sean posted an idea he had for weight balancing on a longer Z here. :)

http://www.mechmate.com/forums/showt...6&postcount=29