Work holding for non-vacuum tables

[Roehm]

We recently set up our SB Buddy and it's dedicated cyclone dust collector. The Buddy will be used by undergraduate and Graduate students in our Fine Arts program.

What we haven't done is decide on work holding for the various materials we will be cutting. We will have multiple departments with the School of Fine arts using the machine: Ceramics, Sculpture, Expanded Media, Graphic Design...etc. This means we will be cutting wood, acrylic, plaster, and foam. Everything BUT metal. Unfortunately, we do not have a vacuum table. To compound the matter we are not going to be using any metal fasteners as the faculty is concerned that students will cut them and break the tooling and/or hurt themselves. Not that a student has ever done something like that.;)

The vinyl nails SB recommends seem a little flimsy for work holding; has anyone had success with them? My experience is with manual and CNC mills, so I want to have a Kurt vise and some T-Bolts....which obviously isn't going to happen.

Festool's perforated table tops work great. I have one that was bought new when they were first released in NA. My thought was to replicate the design on an elevated spoil board to take advantage of the Z travel we have.

Any out-of-the-box ideas for work holding that have worked for you?

[Burkhardt]

Not sure if you mean the Raptor nails when you write "vinyl nails" but if so they are not flimsy at all and hold down well, don't break the bits and can be sheared/sanded off. Unfortunately the required Omer nail guns are very expensive.
I use these polymer nails rarely since I do have vacuum but once a while I have parts too small or complex for vacuum pods and then the Raptor nails come handy. At other time I use wood screws, aluminum clamps or whatever works. FWIW, 1/4" bits or bigger can survive a collision with aluminum clamps.

[mclimie]

We have a vacuum table, but I find we were using 23ga pins out of convenience (odd sizes, etc) - if the bit hits a pin, not the end of the world, and they are easy to pull.

However, I ran across this video that changed everything for me:

https://www.youtube.com/watch?v=ub6PsY4cgwg

To be clear, I have extensively used double sided masking tape a lot with some success, but some failure as well. And it's just too expensive. There is often no way to get really good "rub the adhesive into the part/table" contact on one side. You can beat the hell out of it with a mallet and hope you get good contact.

This changes everything, and I'm holding down things (without clamps) that I never would have attempted (see photo attached). That entire block is all of 3.5"x5.75". With the method in the video, you can really work the tape into both the part and the table, then use a medium or thick CA glue to secure the two. The glue makes up for any unevenness in the union where the double sided masking tape failed. And it's way way cheaper even with double the run of tape and a line of glue.

Once the part is done, it takes a rubber mallet to shear it from the table, but the tape just peels right off, no residue on the part or table. Or on larger parts, just use it in the corners, center, whatever.

Marc

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[knight_toolworks]

I use transfer tape over the regular tape as iti s much wider though I wish It stuck better. usually I throw the parts in a vacuum bag to make sure they are stuck together.

[curtiss]

I have a number of 17/64 holes that go through the table on 5 1/2 inch centers. For small signs I drill a few holes in the bottom of the work-piece at say 11 inches. Thread as desired.

I use a proper length lag bolt to "pull the piece" down. As long as you stay above or beside the bolts it is fine. Entire upper surface is free to cut. Beginners can use a nylon threaded bolt ...

[Ken Sully]

A friend told me about this and it works great! No more clamps,screws,naile or need of a vacuum. Take a look give it a try and let me know how it works for you


https://www.youtube.com/watch?v=3uTsQ3dYRrk

[Burkhardt]

I did experiment a bit with various adhesive methods, including the CA/masking tape idea. It did work well enough for larger parts but I can hold such parts much better and simpler with a vac pod.
For smaller and intricate parts neither the double sided carpet tape not he masking tape held up well unless using really small bits like 1/16". The other thing that bothers me is that the bit often curls up snots of the tape adhesive when cutting through and that it is often a pain to remove adhesive residue from the surfaces (have not tried transfer tape, though).
After all, I use a variety of methods, gave up on the adhesive tape and still don't have a real good solution for very small parts (say <1 square inch) other than tabs.

[scottp55]

G.
Had VERY good luck using the carpet tape shown(1.88" width essential)/ and the "No Residue" Duck tape on a surface like HDO(waxed) or lacquered/waxed wood.
"Bonnie" buttons were .75"D, and the Bloodwood "Trees" were cut Monday and no residue even though that Bloodwood has been stuck down 11 months(AND STAYED stuck FLAT) and were cut out using a .5" (.25"R)pointed round over bit.
The trick is to cut only into the no residue tape, and to make last pass less than .01".
I don't know, but works great for me.
scott

[joe]

Roehm

Thank you for posting.

This topic is usually about vacuum systems which I don't use. I for one have been routing detailed large signs for years and don't rely on stickey stuff or a vacuum. Vac systems are excellent in many application but for those of us who route uneven, rough surfaces a physical hold downs work well. Also when carving letters we screw our substrate down using bridges for the lettering. Small delicate dingbats and decorative detail work is also done with bridges.

When carving large 3D panels, which takes several hours and done overnight, sticky tapes or vacuums, we've found isn't the optimum way to go. Opening up the shop in the morning to find a panel has moved will start the day off wrong. Each of us has to find their best method. All of the above methods seem reasonable and fit the operators methods. I like screws and the Raptor plastic attachment method. But for the most part it's screws for me.

Joe Crumley
www.normansignco.com

[dlcw]

I use a 1" thick piece of MDO with slots milled for T-tracks (Rockler). Then I make the "clamps" from OAK or HICKORY for strength.

I'd like to attach pictures but no matter what I do this BBS won't let me upload the pictures. Used to be easy... :(

[kaetamer]

Roehm

When carving large 3D panels, which takes several hours and done overnight,
www.normansignco.com

I wonder how many of us actually do this - set-up a long carve, start the machine, and go to bed. I'd love to have that much confidence but I'm not sure I'd be able to sleep. Does anyone else routinely let an unattended machine do its thing?

My question is not meant to be criticism. If many do this, maybe I'll try it. My gut tells me many don't.

Whattaya think?
Scott

[Tim Lucas]

I wonder how many of us actually do this - set-up a long carve, start the machine, and go to bed. I'd love to have that much confidence but I'm not sure I'd be able to sleep. Does anyone else routinely let an unattended machine do its thing?

My question is not meant to be criticism. If many do this, maybe I'll try it. My gut tells me many don't.

Whattaya think?
Scott

I have had a cut out part come loose and the bit spinning in it created enough heat to start my mdf deck smoldering, and with the vac hold sys running if I had been sleeping and not checking the machine I would have most certainly burned my shop to the ground !! It was red hot and I had to use water to put it out.

So you can let yours run all night or day without watching it but I will not.

Just my 2 cents
Tim

[scottp55]

+2 cents added to Tim's.
Too much can go wrong, and shop is part of the house,and I'm not looking to join the homeless.
scott

[guitarwes]

I think way too much can go wrong to justify the time saved by running the machine unattended for hours (or even minutes for that matter). I'm always within about a 10' radius or closer from my machine while it's running.........just in case.

[joe]

Anyone running a loud, noisy router should NOT walk away. That could burn down a shop. Ear protectors are also necessary.

Joe

[joe]

Woops I didn't mean to down-play you router guys. Routers are excellent! They can do as good a job as a spindle and cost so much less. But these motors weren't intended for hour of non-stop continuous use. I'd never suggest the hobby folks or part timers spend extra for a spindle.

Joe

[willnewton]

I'd never suggest the hobby folks or part timers spend extra for a spindle.

Joe, I must respectfully disagree on that one. :) I love my Desktop with spindle. The main reason is how quiet it is vs. a router. The Shopvac is louder than the Shopbot and it is no problem to have it running while I do other stuff. Listening to a router scream for hours is not my idea of fun, even with earmuffs.

Also the spindle's high quality of cut and ability to handle occasional non-wood items, such as G-10, aluminum, and even hardened steel is a fantastic bonus. As someone that uses a SB primarily for hobby use, the increased capability keeps my machine from gathering dust.

I'll agree that not everyone NEEDS a spindle, but it is awfully nice. I have lots of woodworking, CNC, and machining experience vs. the average new owner and can definitely say that I work on advanced projects way beyond knocking out the occasional wooden part, so I needed more than what the router could deliver. Once you have one, you'll never go back. Other than the initial $ting at purchase time, I have had ZERO regrets since the first time I heard it power on.

[EricSchimel]

Joe is the guy you outsource your CNC work to running a router or a spindle? Also, do you have any examples of some of his mechanical hold downs? I've been doing some work lately that has warranted mechanical hold downs like this one:

30044

I've been making a fair amount of jigs like this one lately and I'd love to see some of those examples.

[joe]

Eric,

Let me apologize for my late response. One of my favorite mechanical hold-downs was made using Oak scraps. At one time we had a couple dozen in different sizes. The design was to look purposeful and not too mechanical. My inspiration came from looking at piano strikers.

Yes my former employee uses a 5hp Colombo. I met him during a period when he was bending neon. It runs in the family. His father was an old time Neon fellow. That was twenty years ago. After visiting my shop several times Ron indicated the interest in dimensional signage. From there we started working
together. He's a great guy.

http://www.talkshopbot.com/forum/attachment.php?attachmentid=30089&stc=1

[Roehm]

Thank you all for your replies and please accept my apology for neglecting this post for so long! We have been BUSY since the MFA and BFA shows at the end of the semester. I also have seven studios full of metal, wood, ceramic, and glass working equipment that needs servicing every chance we can get! (Man those students can run those machines HARD).

The spindle vs. router argument is a real one. Especially if you are primarily going to be cutting the same material. However, we will be cutting acrylic, ceramics, foam, and plaster in addition to wood products. The ability to ramp up the RPMS to 18K has me wanting to engrave everything I can. I ran an engraving project for my wedding on a FADAL that spun to 10K and wasn't happy with the time or finish. You can see that program run https://www.youtube.com/watch?v=8RwMAdg7eeI We have a dedicated 3 HP Grizzly cyclone dust collector for the Buddy which produces great velocity and volume, but, it's a *tad* loud in a room with concrete walls, floor and steel roll up door! Perfect way to make sure everyone is wearing their ears though!

The multitude of solutions has amazed me. I would never have though to use super glue to adhere masking tape together! Brilliant!

We have been getting by with hardwood blocks and screws for the familiarization projects we've been running so far. A vac system is absolutely out of the question due to cost. We have been using nylon 1/4"x20 bolts to secure the spoil board and they have actually impressed me quite a bit; I thought they were nothing but toys at first. I am drawn immediately to T-Slots and bolts. Simple, secure, and cheap. I also like the idea of using the accuracy of the machine to drill a matrix of undersized holes for lags to secure in. However, this wouldn't stand up to the almost industrial level use we will see at peek usage. Compounding the problem is that the footprint of a large percentage of jobs ran on the machine will be identical because the students will be working on similar projects throughout the academic calendar. I think that a spoil board with T-Slots would be a good balance of price and performance. The T-Slots would also help to control chips with vertical boards surround the work when we can't run the dust collector close enough to the tool.

Eric and joe: I really appreciate you sharing your solutions. Their simplicity and function is elegant. I also have all the materials to replicate them! It's looking like a hybrid of your clamps with T-Slots might be the ticket.

Our first "real" project (I'm not counting cutting foam ;) ) was cutting some molds for our glass department. They are for a 8" decanter which required a 4" deep pocket tapering up to a ~1.5" diameter neck and mouth of the decanter. All wooden glass molds have to be fruitwood and traditionally cherry. The density of the grain holds up to the stress of spending it's life submerged in water then subject to the heat of the molten glass. I had to use an extended 0.500" and 0.250" CBEM for the large pocket and standard length for the neck. I need to improve my V Carve skills as I could not get the finishing pass to follow the geometry of the roughing pass; the finishing tool had to travers the entire face of the mold when doing the finishing pass. I have been spoiled by MasterCam7 and need to study V Carve to make my programs more efficient.

30435


My only beef with the ShopBot is the software and lack of a Control Box on the machine. I know this isn't a CNC Mill, but, I'm used to a FANUC or FADAL controller. It can be frustrating not to be able to control the machine directly like one can with a proper CNC control box in regards to speeds/feeds and offsets. However, I can appreciate that the increase in price would be a huge percentage of the current cost of the machine. The thing that makes it frustrating is that our control software freezes every time I try to decrease or increase speeds with the keyboard shortcuts. I've just gone through and manually edited code which is something students WILL NOT be doing! I'm hoping this is just a computer issue. I know I have A LOT to learn between V Carve and the ShopBot language, so, I'm counting this complaint as user error.

This was my last machine after I moved out of the FADAL cell. That's if you don't count the monster Okuma that had a bad attitude: the spindle would randomly stop while the table was moving! :eek: We ran it for P.O.s for a specific part line for a energy company that starts with a "W" and ends with the name of an American car manufacturer. (Sorry, I had to pay the bills!)
30436

[rachelatrandolph]

I have a 36X24 desktop and work in an Innovation Center in a rural school in Vermont. I'm trying to come up with an easy and safe way for holding down material (wood exclusively at this point). The Shopbot came with some bolts and bits that fit in the t-rail but they seem too short to hold anything over 1/2 inch thick! Or I'm just really confused.

From your pictures it looks like you are using some kind of hold down jig. How does that all work? Where does the carpet tape/no residue tape go? I'm a real newbie and don't even understand most of the acronyms people are using on this site. HDO? MDO?

I've tried the super glue thing and it worked but seems expensive to go through that much glue. Any ideas/further explanation would be greatly appreciated!
Thanks!
Rachel



G.
Had VERY good luck using the carpet tape shown(1.88" width essential)/ and the "No Residue" Duck tape on a surface like HDO(waxed) or lacquered/waxed wood.
"Bonnie" buttons were .75"D, and the Bloodwood "Trees" were cut Monday and no residue even though that Bloodwood has been stuck down 11 months(AND STAYED stuck FLAT) and were cut out using a .5" (.25"R)pointed round over bit.
The trick is to cut only into the no residue tape, and to make last pass less than .01".
I don't know, but works great for me.
scott

[coryatjohn]

The art of hold down is a lot like the art of setting concrete forms. Too little and the project is ruined. Too much and the setup/teardown process is too arduous and time consuming. What you want is the goldilocks zone of hold down.

Before deciding on your hold down, you should understand the forces that the machine will exert on the workpiece. A good rule of thumb is that the bigger the end mill, the more forces are involved. So if you're using a 1/8" end mill, then your hold down is minimized.

Feeds and speeds impact the forces too, so if you're not in a hurry, using slower speeds will reduce the side loads and allow for less hold down.

The type of bit also influences the hold down requirements. An upcut end mill will try to pull the workpiece off the machine, while a downcut will push down on the piece. Cutting thin material without a vacuum would be a trick with an upcut. V-bit's have no pull or push on the piece so if you're using one of these, all you need to do is stop sideways movement.

For thick pieces, I typically will use an edge clamp on at least two places and then block the sides with scraps of wood. Block all sides. The key thing is to stop any movement from starting so if your hold down is weak in one direction and the piece starts moving, it won't stop until it's thrown off the table or the bit breaks. So keep your hold down jigs tight so there's not the slightest wiggle.

To tell if your piece is down tight, tap on the corners of the piece and listen for a hollow sound. That means the piece isn't firmly attached to the machine and will likely wiggle and break free.

Be wary of steel clamps and bolts that may be in the path of the endmill. While the bit can probably chew through the edge of your aluminum clamp, it will break the millisecond it touches steel. So steel is bad. Wood, plastic, aluminum good.

Hold down is a topic that's both wide and deep and the best way to learn is to try different methods.

[scottp55]

Sorry so long Rachel, but had a deadline for my Mom's 90th Bday party tomorrow and have been out Straight Making Tiny Harleys with that same rig.
Each 3D cut was a.25mm TBN followed by a 30* engraving bit for a total of over 4 hrs a Pair. So thin stock was on a minimum of 5 days. Worked Great for 30 pairs!
NOT sure it's a good setup for a school though(?), as I made it for thin stock cutting(buttons and key fobs .23" thick).
MDO(Medium Density Overlay) is resin coated ply, and most of our highway signs up here are made out of it.
HDO(High Density Overlay) is just ply with a thicker resin coat so I could wax it for easy removal of carpet tape that goes down first.
Then sanded to finish grit(600G) thin stock, is cleaned and Duck brand "No residue" tape applied to stock and both tapes are rolled down Tight.
Then Paper is pulled off carpet tape, stock carefully placed, and then firmly whacked down with a spacer block and a deadblow.
I think it's overkill for you, but we were making thousands of buttons with 7 HDO blanks, and bit was ZZeroed to spoilboard from surfacing to cutout,
so just change blanks, not bits...and sped things up a lot.
Worked great this last month on the project shown in pics.

The spoilboard is a combo of Bill Young's design on this thread;
http://www.talkshopbot.com/forum/showthread.php?19057-Desktop-Jigging-Pics
and the addition of threaded inserts has worked Great for 7 years!
It is easy with cam clamps to change out blanks and set up for a new material!

Lots of other members hold down methods are on this thread;
http://www.talkshopbot.com/forum/showthread.php?24660-Hold-down-techniques-and-jigs-please-share!
As John mentioned, there is not one "Perfect" hold down for all projects.

Bullet points from Ryan are worth looking at;
https://www.youtube.com/watch?v=o_KWFVefsQg

as are the Shopbot document;
https://www.shopbottools.com/ShopBotDocs/files/holdingdown.pdf

Read somewhere that some teachers and Makerspaces make their students put their material on ply or MDF, so mistakes don't screw up the Actual spoilboard,
but I've never been in a teaching/school environment.
Kyle Stapleton is a teacher who had a full size machine and a Desktop in his classroom...Hoping he'll chime in.

After tomorrow, ask any questions that stump you please....and you'll get faster responses:)
Have to go pack up the last of the BDay stuff now!
scott