Low volume welding with robots

[RobWard]

Hi.
As part of our process we need to weld together some fairly small assemblies in fairly low volumes - say 100 at a time.
These assemblies weigh up to about 5kgs, are made up of up to 7 mild steel parts and are currently mig welded on home made jigs by hand.
We are struggling to keep up with demand and wondered whether some automation might help.
I've Googled it and it seems to get talked about but I haven't found any examples of anyone doing so successfully.
Ideally we would make 100 of one type then swap over to make 100 of a second type, then on to a third etc.

Has anyone any knowledge of anyone doing something like this cost effectively or do people think we might be better sticking with human welding operatives?
We're only a small company (25 employees) so can't throw the resources at it that a large corporation might but if there was a reasonable ROI we would like to look at it.
(We only started with CNC machinery a few years ago and that has been more successful than we had hoped)

Alternatively does anyone know anywhere I can look for more information and importantly what search terms I should try?

Thanks,

Rob

"I love deadlines. I love the whooshing noise they make as they go past." Douglas Adams

 

[BrianPetersen]

Do you ever have repetition of those 100 batches of parts?

Is there similarity between this batch of 100 parts and the next batch of 100 parts? (i.e. are the various batches only small variations of each other, or are they apples-and-oranges different)?

If you've made fixtures, even if homemade, that would suggest that there is at least some level of similarity that would warrant the construction of those fixtures.

If there's enough similarity to build (and presumably, re-use) fixtures, there could very well be opportunity to automate.

The process doesn't have to be 100% automated. If you have (let's say) 3 parts that are always the same and 4 other variations of mounting brackets etc, you can have the robot do the repetitive part and do the non-recurring parts manually as you do now.

More info required ...

 

[RobWard]

Thanks for the reply.
The parts are generally quite similar.
They consist of a length of tube average 70mm long, 30mm od, 12mm id, and a piece of waterjet cut steel plate about 10mm thick.

The assembly would consist of two, three or four of these tubes arranged with the hollow axis vertically and then the steel plates, which have 30.5mm holes in them, placed horizontally over the tubes in laminations but with spacers between to hold them apart slightly. The plates are then welded to the tubes to form a rigid assembly.

Hopefully the attached picture will demonstrate what I'm trying to describe.

This is ongoing work - we would make 100 of one type, then 100 of the next, then 100 of the next etc then start over again. Currently we probably have 10 variations.
(These assemblies are parts which we mould polyurethane around and we need to be able to keep up with the moulding side which is proving difficult as production increases.)

We could certainly make more fixtures. I had wondered whether a Baxter type "combot" could load and unload fixtures and leave the welding to human operatives.
I keep seeing second hand robotic welding cells for sale very cheaply (caveat emptor!), but they look as though they are best suited to performing the same task 10's of thousands of times before reprogramming.

"I love deadlines. I love the whooshing noise they make as they go past." Douglas Adams

 

[BrianPetersen]

You could pretty easily make 10 fixtures on interchangeable base plates that can be clamped in place on a work table at the load station. When you change jobs, you change out the fixture, select the new robot program, and carry on. If you want to get fancy, there are ways for the fixture to tell the robot which program to use.

If the tube needs to be fully welded to each plate (hopefully only from one side!), you will probably have to load the tubes and the first plate, have the robot weld the tubes to the plate, then load the next plate and have the robot weld that, etc until it's done. Distortion during welding might be an issue but I'm operating on the assumption that this is the way you are welding them together now, and it won't be any different with a robot doing it.

There are lots of places that do robotic weld cell integration who could take a look at the job.

Beware of used robots. There is a safety standard that new robot cells are meant to conform to, and the latest version of that standard took effect in 2015, and if you go too far back in time (which is not all that far back), robots built back then don't meet today's standards, and "grandfathering" only works if it is an existing application, not a new one that you want to put an old robot into. There's a reason old robots are cheap.

 

[sreid]

Take a look at Epson Robots. Priced right, excellent quality, exceptional new customer service.

http://robots.epson.com/

 

[BrianPetersen]

Hmmm, I've never seen one of those in a MIG welding application. The original poster is welding together some pretty thick steel, so it's going to have to carry a serious MIG welding gun, and it's going to have to drag the wire feed and the hoses and cables for the weld gun along.

Fanuc, ABB, Yaskawa/Motoman, Kuka, Panasonic are the ones that I routinely see in industrial welding and material handling applications.

I'm thinking it will need something more like this ...

http://www.fanucrobotics.com/cmsmedia/datasheets/ARC Mate 120iC Series_8.pdf

 

[RobWard]

Thank you for the replies.
I shall do some reading on the links you have posted, and I shall certainly be careful now that you have mentioned the safety standards!

"I love deadlines. I love the whooshing noise they make as they go past." Douglas Adams

 

[Don56]

About 10 years ago we bought a Lincoln E-cell for welding small parts like these. One cell welded while the operator loaded/unloaded the other. Was the best investment we ever made. WE had batches typically of 100 - 1000 pieces per run. Once you have your tooling and programs set up you are goo to go.

 

[RobWard]

We're going to have to look very carefully at this.
Decent welding jigs will help but I've not found anyone who can design and make them. Our home made jigs are a bit fiddly to use -they give good access for welding but they are slow and I don't think a good design.

"I love deadlines. I love the whooshing noise they make as they go past." Douglas Adams