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Using 3-D printing for fixturing and setup

aerospace_eng

Plastic
Joined
Sep 26, 2017
I'm absolutely not well experienced in machining but I have been around it a bit.

I 'd like to hear of some experience anyone has 3D printing for fixturing or setup or if anyone thinks it can be done effectively.

Thanks in advance.
 
For plastic, metal? For what kind of tooling? For what kind of application? Metal printing is expensive- do you have a large order quantity that can justify it?

I've printed everything from rough hand gauge tooling to vise jaws for cutoff applications to hold welded assemblies in a specific orientation to even rudimentary form tooling for thin sheet metal with a hobbyist grade plastics printer. We've purchased 3D printed exotic alloy low quantity production tooling from companies as well- $$$$$$$.
 
The only fixturing I've printed was a block with a part nest on the front and several angled facets on the back for pressing bushings into a plastic part at various angles, and another block which would hold a part at a certain angle for video system inspection. My vise jaws need much greater precision, strength, and hardness than a plastic printer can provide.
 
I'd like to do it for welding, but mostly metal parts in 3 axis CNC mill. I have access to plastic printers with carbon fiber material that's extremely strong.
 
There's extremely strong and then there's extremely strong. When considering vise or clamping forces I don't know if that stuff would stand up.
 
I used this technique last weekend with some funky compound angles on a part. I wouldn't do it for anything that I needed to hold tight tolerances due to the fragile nature of printed plastic (FDM using PLA) but for the application it fit the bill and allowed me to get the part to the customer on time without having to machine the fixtures which would have taken much longer. Designed the parts in like 5 minutes using the cavity feature inside SolidWorks. Had the necessary fixtures in 45 minutes.
 
I'd like to do it for welding, but mostly metal parts in 3 axis CNC mill. I have access to plastic printers with carbon fiber material that's extremely strong.
MarkForged is pushing this application Big Time with a huge spam campaign. I wish there were more public examples of their printed product - it's pretty hard to find an actual user who will relate actual experiences. The printer costs about 7x what a decent pro-sumer 3D printer costs, so I'd hope the quality and strength of the printed product would reflect that - but again, pretty hard to come by independent confirmation. There was a brief thread over on the print forum where a guy bought one and said preliminary results weren't very good but no update.

Are you associated with MarkForged?

Another issue may be I can cut aluminum soft jaws about 10X faster than I can print them. Unless it was something really complex.
 
MarkForged is pushing this application Big Time with a huge spam campaign. I wish there were more public examples of their printed product - it's pretty hard to find an actual user who will relate actual experiences. The printer costs about 7x what a decent pro-sumer 3D printer costs, so I'd hope the quality and strength of the printed product would reflect that - but again, pretty hard to come by independent confirmation. There was a brief thread over on the print forum where a guy bought one and said preliminary results weren't very good but no update.

Are you associated with MarkForged?

Another issue may be I can cut aluminum soft jaws about 10X faster than I can print them. Unless it was something really complex.

I'm absolutely not associated with mark forged. We have one at my work though, the carbon fiber I'm talking about, but it has material get stuck in the lines pretty often and someone has to come out and fix it. The tight tolerances would be a concern for 3d printed fixtures. But some Stratasys printers can hit pretty close tolerances I believe.
 
Those are the kind of things that MarkForged seems to leave out of their slick marketing shtick. They have been accused of showing up on forums as a newly minted poster expounding the virtues - I don't know if that is true, but that's why I asked.

I have a cheap pro-sumer grade printer (Zortrax). The accuracy is around +/- 0.005, but the repeatability is perhaps +/- 0.002. I've not tried printing a workholding fixture with it, probably is possible for light machining using some of their harder materials.

I'd really like the MF printer to live up to the hype, if it provably did I'd buy one - but independent verification has been hard to find.
 
When it comes to 3d printed softjaws, I find they can be useable so long as tool pressure is VERY low. At best, you essentially have a light-density softjaw made from plastic. Alternately, at worst, the jaws won't hold anything and are worthless.

We do some production parts with 1/16" endmills using printed jaws, and it works pretty good considering the workpeices are extremely fragile. The tools are barely applying any force. The biggest issue here is accounting for the jaw squish. (see picture below)
IMG_0558.jpg

Naturally the type of printer and the jaws' orientation during printing will have a large affect on the final properties (accuracy, warpage, direction of layers, jaw resistance to squishing etc). Even when dealing with 100% solid jaws (""""solid"""") you will still have a lot of flexibility as if the jaws were made from a soft plastic like HDPE or UHMW (milkjug). Making jaws from PLA material would be risky due to how prone it is to crack and warp, and trying to save print time by using a partial fill would be asking for trouble unless you actually wanted some compression.

I don't have many pictures of the stuff we do, but here's another one from the opposite end of the coin. It was an ill-conceived attempt to mill out some lathe knobs using jaws with a 5/32" endmill. The workpiece moved around so much that the jaws quickly started to melt. At that point we let it keep going just to see what it would do, lol
20180217_142221.jpg

Really the programming will determine whether or not the part will survive via light cuts, but the programming is also in control of the elapsed machining time (which decides whether or not it was actually quicker to "do it the right way"). But hey that's always the fun part of prototype work....
 
The MF material is a carbon laced nylon, they claim stiffness and strength roughly the same as aluminum. There are two versions, one a plastic filled with short carbon fibers, another where continuous carbon filament is inlayed in the printed plastic. According to their literature, the properties are considerably different than the usual PLA or ABS print.

But again, there seems to be nobody independent of them to back up the claims.
 
I use the markforged stuff for robot grippers sometimes. It's great in that application, as you only need stiffness in the gripping direction and the continuous carbon fiber gives you that. The results are pretty impressive.

That said, I can have a set printed for $50-$100 and delivered to me in three days via 3dhubs, so there's absolutely no reason for me to buy the machine. Complex 3D parts go for about 2x the material cost. Unless I needed a new gripper daily the payback would be... Long.

So try it out via a service and see for yourself.
 
I machine a lot of soft jaws from 4142 prehard for holding 17-4 H900 surgical parts. I usually design in half an hour, program in half an hour, machine in half an hour. Even if there were a miracle printer that could print to .001" or better with steel hardness I doubt it would be faster.
 
I machine a lot of soft jaws from 4142 prehard for holding 17-4 H900 surgical parts. I usually design in half an hour, program in half an hour, machine in half an hour. Even if there were a miracle printer that could print to .001" or better with steel hardness I doubt it would be faster.

I have 3d printed lots of parts from stainless and inconel using EOS DMLS printers. They are pretty accurate. The down side (that I have noticed myself) is the experience of laying out the model to print could lead to unnecessary support material ( which is the base metal ) that has to be ground and finished, which can really hurt the tolerances. 0319181253.jpg (stainless part, lots of finishing)
 
I've used a plastic printer to make a few vacuum fixtures. Post-machined, but it works nice to create the general shape, flanges to bolt to the table, and all the vacuum passages.

Face the bottom side, bolt to table, then skim the contour and cut the o-ring grooves. If the part grows overnight it's almost free labor. :)

PM
 
I use the markforged stuff for robot grippers sometimes. It's great in that application, as you only need stiffness in the gripping direction and the continuous carbon fiber gives you that. The results are pretty impressive.

That said, I can have a set printed for $50-$100 and delivered to me in three days via 3dhubs, so there's absolutely no reason for me to buy the machine. Complex 3D parts go for about 2x the material cost. Unless I needed a new gripper daily the payback would be... Long.

So try it out via a service and see for yourself.
I will try that. One of the things I really like about having the printer on my desk is instant gratification, and quick iteration - not sure a service bureau can do that.
 








 
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