A modular profile (item) construction - tolerances?

[elinah34]

Hello,

This is the first time I draw a modular profile (item) construction. What type of tolerances (and values range) is acceptable and reasonable?
I guess that size tolerances are OK, but what about the required precision?
If I want profiles to be parallel to each other, can I require it and on the same time avoid "no bid" by manufacturers?
I am very experienced in machining and know what precisiona can be achieved, but in this case (assembled modular profiles) I am not sure what and how can be achieved.

I am adding pictures for illustration.

 

[elinah34]

Assuming that this is a screw jack of some sort, it would be fairly simple to mount an inverted jack to the underside of the green plate. It may be necessary to use a spacer plate. Without more information on the device it is hard to provide more assistance.

View attachment 5227

Thanks,
What is the difference between my jack and inverted like the one you presented?

 

[dvd]

I do not know anything about your jack, so cannot comment. The jack I showed is from a Duff-Norton catalog. Joyce-Dayton also offers similar products.

 

[mfgenggear]

OP
I mean it can get fancy ,
Cast Rectangular frame , top and bottom machined. Top mounted by dowels and socket head screws to the green . Both surfaces machined.
The bottom attaches to the green plate precision dowels and socket head screws.
Easily maintain 1 mm parallel

 

[elinah34]

OP
I mean it can get fancy ,
Cast Rectangular frame , top and bottom machined. Top mounted by dowels and socket head screws to the green . Both surfaces machined.
The bottom attaches to the green plate precision dowels and socket head screws.
Easily maintain 1 mm parallel

The big problem is that the one who needs to approve the design opposes to connect the mechanism directly to the green plate because "it makes the design complicated" and insists to keep connecting the mechanism to the purple plate and solve the unparallelism issues by means of some kind of joint.
I can show you a picture of it...please ignore the fact the bolt is short, I need to replace it.

 

[kjoiner]

One other factor to remember when using 8020 type extrusions is many of the fastener types for those extrusions rely on friction. If you are generating a vertical load, there may be a possibility of the joints slipping and throwing off your parallelism between the two plates.

 

[elinah34]

One other factor to remember when using 8020 type extrusions is many of the fastener types for those extrusions rely on friction. If you are generating a vertical load, there may be a possibility of the joints slipping and throwing off your parallelism between the two plates.

thank you' you are right.
I don't feel comfortable with the current design and I am really considering stopping and reconsider other consepts.
It's quite upsetting because I was about to start manufacturing.