Hold down ideas for machining dog tags and business cards on a CNC

[Crusarius]

Does anyone have any ideas for holding down dog tags on my CNC so I can machine them?

Right now I think the best cutter I have for making the dog tags is my 120 degree diamond drag cutter. When I can hold the tags in place it works great. Unfortunately, trying to hold a .036" thick dog tag in place with enough space to clear the drag tip has become very challenging.

Here is my furst fixture. I used a dovetail cutter to make the pockets giving me a 60 degree edge to hold the cards down. It worked ok, but in the MDF it did not last long with how small the pocket was.


 

Here is my second fixture where I used the 3d-printer to make the hold downs and some router work for the slots. The design is supposed to be universal for business cards and dog tags.


 

This one worked ok except I noticed in one of the videos I took that the card still moves and I had a probelm with the second card lifting and moving on me.

Now I realize I need to hold the card from all 4 edges much tighter and have a lip to keep the card from lifting.

I am just having a really hard time coming up with something simple and easy to change the cards out. I am hoping to machine 12 at a time so maybe alot of screws for changeout is not the end of the world.

The samples I have made take anywhere from 7-10 minutes each.

Here is an example

[Crusarius]

I keep thinking about a pocket, but with the pocket that means all of the blanks need to be the perfect size. The text is only 0.13" tall so any card movement is very noticeable.

The blank will also need to be fully supported.

[Ianab]

Would the design with the blue plastic work better if the bevel was steeper and the other way up? That would then slightly overlap the card and lock it down. Not sure of that will give the clearance need, but it should hold better.

[btulloh]

Vacuum

[Crusarius]

Ianab, I actually just went out to the shop and took the blue off the board and flipped it over. It seemed to work much better. That is definitely a path I am going to follow. The biggest issue is the clearance on theh 120 degree drag tip. I need every bit of space I can get to be able to list everything on the card.


btulloh, I think you're on to something. My wonder is though how big of a vacuum pump will I need to hold 12 of those down? That would solve alot of issues for sure. and could also help for future parts hold down fixtures. Now I just need to find a vacuum pump for almost nothing.

[btulloh]

It takes surprisingly little vacuum IF there's an efficient coupling to the work piece. For a    card, 2 orifice, rubber or similar. Maybe one orifice if it's not round.

A very cheap way to try it would be a venturi device you could run off your compressor. 20 bucks at HF or amazon.  I slso see a/c evacuation pumps on FB and CL for pretty cheap. These work if well with a small holding tank added. (I've been using a rig made with one of those, a couple little tanks made from 4" pvc and a vacuum switch for a long time.  (I Use it for vacuum bagging and vacuum clamping.)  A venturi works well, just noisy and keeps your compressor cycling, but cheap and quick.  (I use a venturi on my oil sucker I made from an old paint pot.)

Add: after some thought, the important thing would be to use small orifices for the cards and keep the vacuum at minimum so the cards wouldn't deform under vacuum and present a concave surface to be machined. 

[Crusarius]

I do have a couple reasonably powerful shop vacs. I wonder if that would be enough to hold the small dog tags. Dog tags are 1.125x2".

It sux that I will have to invest a ton of time into making a test piece...... wait. I wonder ??? the blue stuff in the pictures is 3d-printed ABS. I wonder if I can just 3d-print a test vacuum table? wonder how porous the ABS would be?

[btulloh]

A shop vac should work. The magic is going to be in getting the interface to the card right. 

I saw a thing where they lifted a car with a couple shop vacs. 

[Hilltop366]

How about drilling a couple of holes in a board and cutting a o-ring grove around them and duct tape a vac hose to the under side as a proof of concept. I would guess that you would want the o-ring just peeking out and enough room in the grove so the o-ring will flatten out a bit.

If it works out then try a larger multi piece with a double layer with a space in between to allow the vac to hold more than one.

[btulloh]

Vac cleaners will/may overheat if all the air is cutoff at the inlet as I'm sure you know.  With the high volume they use, leaks and such will be your friend. 

I really like Hilltop's suggestion. It's a quick way to experiment. And besides, any development process is improved with the use of duct tape.  That self-sealing silicone tape might come in handy along the way as well. (Now if we could just work in some high explosives! lol)

[btulloh]

Double sided tape?  Are we overlooking the obvious?

[Crusarius]

Pretty sure the double sided tape I possess will come off.

But yes, we are definitely skipping the dumbest easiest idea. I also wondered about hot glue.

[btulloh]

I'm not so sure the double sided tape would come off while machining. I would be worried about getting the card off without deforming or breaking it. 

[Old Greenhorn]

Ever hear of MiteeBite clamps? Maybe take a look at THESE. I have used hundreds of them over the years in various setup and fixture designs. On one job I had 50 on a fixture and would swap two fixtures and change parts on one fixture while the other was running. Ran almost 1/4 million parts on that job and got to the point I was making my own cam screws for the clamps.
 Handy little buggers in a setup like yours, good holding power too.

[Crusarius]

yea, thats what I meant. probably never come off the tag without damaging it.


OG, I never thought about something that simple. that could easily work.

[Crusarius]

So just for fun I ran out to the freezing cold shop in my slippers and tried something.



 

This is what we call a super ghetto vacuum table. 

The MDF was painted on both side so I could not just pull a vacuum through it. So I started with drilling 2 holes and slid the tag into position. 

The first tag held well, the second position it shifted. So I added a few more holes. I decided not to test until I make the programs for others that need to be done because I am burning through tags at an alarming rate.

I used a 2.5hp shop vac. I let the suction hold the hose in place.

with the extra holes it felt like it had a little more holding power. I wonder if adding a seal would make this work? I was able to move the tag pretty easily but I wonder if the drag tip is not as much side load as I thought it was?

[Crusarius]

hey tom, how do those things work? I see a cam bolt through the center but how do you tighten the bolt since it is the cam lock? How do they stay in place?

[Old Greenhorn]

The head of the screw is an offset cam. Tapped hole location is important  from the edge of the workpiece. Lay the clamp over the hole, put the screw in all the way down, back up 1/2-3/4 turn or so, put the work in place, and turn the screw, the cam locks the clamp against the workpiece.
 Gotta run off to work session 3 for today.

[JoshNZ]

We use 3m double sided foam tape for weird parts but it'd be a shame to go through so much of it if you're doing a bunch. It is strong though, the trick is to not use so much that you can't get it off again.

Have you tried adhesive spray? Line a bunch of them up spray the backs, flip over and stick in place on the MDF jig.

That idea coupled with a cam lock as above might work. Vacuum is easiest solution but you don't have much surface area for a vacuum to act on, compared to the side forces of dragging a tool

[Poquo]

Cut a pocket the size of the tag,  leave the depth shallow by a few thousandths, use a scrap piece to cover the tag as a clamp. Cut design thru scrap piece used to hold it down. With just engraving should be able to use that multiple times.

[Crusarius]

All good ideas. I think I might play with a cam idea like OG had. But I will just make my own. probably 3d-print an offset ring that I can just rotate into place then tighten the screw,

Stay tuned for the continuing saga

Still open to any ideas. 

Puquo, I was thinking a clamp mask like that. I never thought about machining through it to get to the tag. I think that is going to be the missing step to make it work.

[Larry]

I vacuum clamp stuff all the time and build my own clamps.  A few thoughts.  MDF is porous and air goes through it.  It can be sealed with sanding sealer, lacquer, or poly.  Some of my clamps use commercial vacuum tape.  Its just rubber tape that is sticky on one side.  It does have a special composition so it won't squirm.  For less demanding stuff, vinyl shelf paper glued down with contact cement works fine.  A few of my clamps have "O" ring gaskets.

Than there are commercial clamps called vacuum clamp pods with a "O" ring seal that can be re-positioned for different sizes.

My main vacuum is a high quality pump that will pull 24".  I have a couple of backup venturi pumps along with the Harbor Freight one.  The venturi pumps won't pull as high of vacuum.  A rule of thumb for holding power is divide inches of vacuum by 2.  Multiply this number times the surface area of your clamp.  This will be the amount of hold in PSI.  You won't get much holding power on your small pieces.  With my good pump I would get 21 pounds on your small piece.

If you can get enough holding power, vacuum clamps are great.  Flipping a switch to lock a part down is just cool.

[Crusarius]

Definitely agree with the koolness factor

Just putting the vacuum hose on the bottom side of the MDF was satisfying to see the part stay put. I do have a bigger shop vac I may try.

[Old Greenhorn]

Vacuum works well but you need to secure the part from sliding around, so you need ban edges or something. I lost a few parts because I didn't take the time to make those banking edges and it slid, just a bit under cutting.
Cru, do you have a lathe? If so, I can look up the screw dimensions I use and make you some sketches as well as the simple jig I made to turn the offset screw heads. I recall now, I was making my own screws because I designed a single clamp that would hold 2 parts because I think we were running 50 parts on a fixture and halving the clamps was a lot of time saved. With a lathe, those screws are really really easy to make, take a few seconds apiece, and cost pennies. I think I used a .050" offset, but I am remembering back over 25 years now, so my dimensional recall may be off. There is a VERY slight chance I may still have that little fixture in my toolbox. I can look tomorrow. I may even have a couple of the screws in there too.

 The trickiest part of the whole thing is to drill and tap the hold on your fixture in just the right place so the cam clamps with decent force, but does not slip by. You should be able to get some design info off that MitteeBite website.

[Ianab]

anab, I actually just went out to the shop and took the blue off the board and flipped it over. It seemed to work much better. That is definitely a path I am going to follow. The biggest issue is the clearance on theh 120 degree drag tip. I need every bit of space I can get to be able to list everything on the card

I can see the blue clamps as they are would overlap the work piece a bit, and so lose some area. But you could reprint them with a compound bevel. Angled inward at maybe 80 deg, just tall enough enough to get over the edge of the work piece. Then angle away at a shallow angle to give the thickness you need to secure them. 

Then the off-centre screw / cam idea could work to secure the moving corner. Put a flat on the outside corner off the moving clamp, and you could print a cam and arm gizmo to move the floating piece and lock it on place. The moving clamp would be held down by bolts, but able to slide when the cam is released. 

[Hilltop366]

If the tags are a consistent size you could combine the pocket idea with the vac clamp idea. the vac holds them down and the pocket stops them from sliding.

[Crusarius]

OG, I do have a lathe and I was laying awake last night designing them in my head.

Ianab, I tested by flipping the printed bottom clamp over and it did make a difference. I was thinking about trying exactly what you described.

Hilltop, I was also thinking about the pocket. I almost wondering about integrating the last 3 ideas. I would think that would give me a pretty solid setup. I am still trying to make the fixture to handle the dog tags and business cards but when all else fails I might just be better off making separate fixtures for each.

Thanks a ton guys, you have helped get my creative mojo moving again.

[Old Greenhorn]

OK, Thanks for the reminder. I just came in from morning chores (late start again) and forgot to look. When I go back out I'll pick through my old rollaway toolbox and see if I can find any remnants to reconstruct the numbers and try to make you a sketch later. This is so simple to make you will laugh at it. But as I said we ran hundreds of thousands of parts with them, and I just remembered another job I used them on, machining the jaws for the schrade multi-tool. I think we did near a million of those. Lot's of clamps  :D . I think we had 200 clamps on each of two fixture tombstones.

[21incher]

I have seen people do things like that using a Cameo 4 vinyl cutter with a scribe using the strong sticky mats not as deep a scribe thought. I am guessing Cricut can do the same. The mats are flexible so that peel fairly easy but don't slide.
Looks like you could also make a fixture using a diamond pin in the hole and sliding v clamp for the dogtags.

[Crusarius]

Ok, so I spent a bunch of time on this and think I finally have something that is going to work.

I took everyone's ideas squeezed them all together then simplified my original plan and here is what I came up with.



 

The fixture can accommodate a standard dogtag and an aluminum business card. All I have to do is move the hold down locations. Everything is drilled and ready to go.


The pockets are machined using a 1/2" dovetail cutter to 0.050" deep. The thickest card I have is 0.036" thick. This makes it so the card fits cleanly inside the angle of the dovetail. 



 

I lose a very small area around the outside but it is close enough to the edge I don't want to machine there anyhow.

The blue pieces you see are 3D-printed using ABS. the are oval shaped to give me the cam lock feature. I place the card into the pocket, the rotate the clamps till they touch the card and tighten them. They all tighten rotating towards the card. 



 

So far I have been happy with my 4 card test. The first image in this post is what I am running now. I am anxious to see the results.

It is going to be nice to be able to machine 16 cards at a time. Instead of having to babysit the machine and change cards every 10 minutes now I can just let it go.

Picture results anxiously waiting...

[Crusarius]

pictures as promised

This picture is the full layout and my first big test. Small tags are dog tags and then I have 2 business cards on there. I am using a 120 degree diamond drag tip. Loving the drag tip for this kind of stuff.


 

Action photo taken during machining. 



 

End result after a quick vacuum to get rid of the dust. Still need a rag wipe down to get them clean. Very happy with the results. 



 

Fixture is working great. The machine has been running for over 2 hours now and still going. nothing has moved!!!!

[btulloh]

Cool.  Nice solution and all done in house. It's a win.  smiley_hollywood_cool

Good score on snagging the Flintstone account too. The new tool is already paying dividends!

[Crusarius]

here are the three styles.

I belong to a four wheel drive club and we have been trying to figure out how to do emergency contacts forever. Everyone said we will just laminate a full members list and give everyone a copy. Needless to say that was not a very popular thing for a bunch of ppl. So this is my idea. Hopefully I can sell them on it and then get to engraving.

[Crusarius]

I did learn something very valuable. Since the business cards are thinner than the dog tags, I need to change the tool depth. I think I machined one blank card and half of another.

[Crusarius]

and a couple more....


I think I am starting to get pretty good at this CNC thing.



 



 

[Crusarius]

using carbide create to do the G-code. Definitely not my preferred software but its the only thing I can afford right now.

[21incher]

Here is a video about that dot peen machine I got doing the dog tags. Really fun tool  toy.
Vevor Electronic Dot Peen CNC Marker 300mm x 200mm Making Dog Tags - YouTube

[Crusarius]

How is it removing the film after its been engraved?

[Old Greenhorn]

I am very familiar with these machines, they are called 'dot peen' engravers or markers. In my previous life as an M/E I was given a project to mark model and s/n data on one line of our smaller hydraulic tools that we sold to the military. We did several models and I had programs for each. Some were steel and some were plastic shrouds that were engraved. I researched and tested a lot of machines before settling in on one particular company. The name escapes me (I think it was 'Pro-Pen') but it cost in the 5500-8k range and had the programming features we needed imbedded in the machine. (No computers needed.) I designed the fixtures to hold our tools and the operator only had to set or confirm his/her starting S/N and run the tools throu8gh, one at a time. We did thousands of them and I replicated the entire system, programs and all and sent it to our plant in MX. It came back two years later when they pulled the line out from that plant, it was a mess and missing most of the tooling I made. I fixed the machine up and put it to work for another dedicated purpose. Around the time I was retiring we had a similar project to mark bigger tools and it was given to one of the new guys. He was looking at smaller units that could be handheld in place on the tool to run the program. Those were bigger tools.

 As was said, simple tools, easy to program and run, and with a good setup work very consistently. That noise can get on your nerves after a while though. :D 21, did you mention it and I missed it, what does that unit go for? 

[21incher]

How is it removing the film after its been engraved?

Peels right off. It's funny how the film just seems to stretch. They scratch too easy if it's removed before hand. I bought some clear rubber rustoleum spray to try coating them with when it warms up outside


OGH I did mention in the description to prepare for a headache ;). This is just a crude knockoff of the machines you used. It's a fun tool toy that would be good for things like home use and craft shows. The software seems to be from years ago but works good after figuring it out.  I had a lot of fun with it. They were about $450 minus my 5% discount code a couple weeks ago but now have jumped to $495 minus the 5% if you use the code. Vevor seems to be the new Sears and Roebuck of Harbor Freight tools with pretty good quality. Most of this type of work is done with lasers today but I thought it would be fun to show different options.