Future User...Can I do this

[david_shaw]

I make archery grips for bows. I have been doing this with power and hand tools for the past two years. I use a table saw, two router tables, bandsaw, 48" belt sander, spindle sander, chop saw, 4 orbital sanders each with a different grit of paper and two buffing machines in various steps for each grip made. I have it down to where it takes 28 minutes to make one grip. BUT I am getting tired of doing all these steps for each grip since I do several thousand of these grips each year in my part time (every evening and all weekend). Also I have a couple of new bow manufactures that may be wanting grips. I am wondering if anyone is doing something similar on their CNC machine?

The grips are made from a block that is 1 1/8 x 2 1/4 x 5 inch in size. I quess my questions are...

Does this look like an application for a CNC?
How to hold the small stock.. Looks like clamping or tape
Length of time to 3d a profile of the grip.
Corners must be sharp, NO chipping.
Each grip has a slot in it that has an inside radius. Looks like I wood need an indexer/4th axis to cut that.
How smooth will the grip come off the CNC. I still plan on hand sanding from, 360 grit and up.

Any info that you might be able to throw this way would be much appreciated.


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7248

[henrik_o]

Does it need to be machined out of one blank, or would it be acceptable to machine two halves that were then glued together? While that is in itself an added step, since there is in any case a need to machine both sides of a half, you could machine pilot holes and use a simple glue jig to increase productivity.

As far as I can tell the latter method would lend itself to easier and faster machining. It should be possible to machine many handle halves out of one blank, and so on.

Besides the cnc issue, if you're hand sanding for finish sanding I think you should look into purchasing a brush sanding system. Put three brushes with sequentially finer grit on an axis run by a small lathe or similar machine, and sanding should be a snap.

[david_shaw]

When we first started making the grips we did use 3 pieces and epoxy together. But we had to many joint failures so we scrapped the multiple pieces and use a solid block. The Wood we use is Dymondwood and regular woodworking glue does not hold on it. We have tried Gorilla Glue, several types of epoxy and super glues. We did find an epoxy that works, it is an epoxy used for inlaying gun barrels in rifle stocks. Have not had any failures with it, but it is a step that adds alomost 1/2 hour to the production of the grip plus a 24 hour drying time. We use this process on one brand of grip we sell because we can't cut it in one piece with the tools we have now. That's another reason we are looking at a CNC.

We build and ship grips, usally on the same day that we receive the orders.

A little more info on the brush sanding system would be nice. Where to get it?

Thanks,
Dave

[Brady Watson]

David,
I have about a 1/2 dozen customers who send me their grips to be laser digitized & setup for toolpathing, and they cut them on their CNCs. So in a word, yes - it is definately doable. Some customers do bow grips, others gun grips, others rifle stocks and other assorted items. These customers cater to the big boys...with only one shop being 'Mom & Pop' - who are quickly on their way to the bigtime.

As far as how long it takes, this depends on how much post-machining cleanup you want to do. 3D simply takes time, but there are ways to streamline the process to have the tool do as much as it can quickly, and let you take it to the sander from there. Looking at your parts, I don't believe that a 4th axis is needed, and to be quite frank, you don't want to do production parts like this on an indexer. These are simple 2-sided parts that can be cut on any 3-axis machine.

Feel free to contact me after you get your CNC if you need help getting your parts into the computer and cutting on the CNC.

-B
www.ibild.com (http://www.ibild.com)

[wberminio]

Wood that contains alot of silica/oil-such as-
teak/rosewood can be glued by wiping the surface down with denatured alcohol just before applying
the adhesive.I wonder if you tried this in your situation.

Erminio

[david_shaw]

Brady,
The grips are one piece with a slot about 1/2 wide and 7/8" deep. The slot at one changes to a radius. Since this radius has a wall on each side of it, formed by the sides of the slot, the only way I see to cut this radius is by having the grip rotate as the slot is cut by the means of an indexer-4th axis.

Erminio,
Dymondwood is an extremely hard laminated wood formed under high pressure and heat. The resin they use is kind of like an epoxy that goes all through the wood. To finish the wood you sand and buff to the desired shine. They is hardly any moisture content and other materials do not absorb into it.

[zeykr]

David,

Here are pics from a previous shopbot camp showing bow grips made on a shopbot:

http://www.flickr.com/photos/campshopbot/page3/

[david_shaw]

Ken,
Thanks, I have already talked with Bob. He makes only sideplates on his machine. Sideplates, like most pistol grips are mirrored pieces, one piece for each side. I make a full grip, all one piece which is much more difficult to produce properly and make fit.

Dave

[Brady Watson]

OK David - I see that it is a 1pc now. It can still be produced on a 3-axis machine by manually indexing the material. You can use a 4th axis, but it is not required & my concern would be reliably holding the material, and part throughput, unless you were doing several out of one piece of material. Unless I am missing something, it only looks like it has to be machined from 2-sides, as your glue-up should take care of the dado in the center of the part - 3 sides if you want to machine the dado in using the CNC or router table.

Bob's grips are not mirrored sides of each other. Each side is a different geometry. They really aren't much different than your grips, aside from the separator laminated between the 2 sides, in terms of setting it up and cutting.

-B

[david_shaw]

Brady,
I only use glue up on one model of grip because I can't cut it in one piece with my present tools. Glue up is one of the things I want to get away from, it is very time consuming using epoxy and jigging it so every thing fits right.

I am looking to steamline my production, increase production and add new products to my grip line.

Dave

[Gary Campbell]

David..
can you post a pic of the side showing the dado?
Thanks, Gary

[ryan_slaback]

David,
Are the grips all the same dimensions or are they specific to an order? If they are the same I see no reason why you can't machine the outside profile (perhaps on each side if it is a countour) and then make a negative jig that the contoured shape fits down into and machine the slot. It would require manually indexing the part a couple times but it would be faster I think than 28 minutes.

[henrik_o]

Just a quick post here re:

quote:A little more info on the brush sanding system would be nice. Where to get it?

Since I am in Europe you probably have to find American suppliers, but if you feel like googling around to see some of what is offered here are some of the companies that make such products, that I'm familiar with

-Engis; still exists as a company but not sure if they make wood sanding systems anymore. They had a line that was a very basic (and afaik low cost) flap+brush deal (in flap+brush the brushes support flaps of sanding paper)

-Edruflex; makes flap+brush systems in many configurations. A pretty basic system, but they build to order and as an added item of interest have experience with cnc sanding (they market, amongst other things, a 5 axis cnc sander).

-NaxoFlex; makes flap+brush and brush systems. In my opinion, they have the best system on the market and prices are not that high. Since they make both flap+brush and brush systems they cover a wider range of sanding applications than Edruflex (in my understanding). We are discontinuing our older systems in favour of the NaxoFlex system, but I have yet to test run our built to order cores (yes, they build to order like Edruflex).

-Svenska Industriborstar; just brushes (no brush+flap), not a big selection of wood sanding systems, but I include them here because they have some interesting specialty brushes. For example, they make brushes that afaict pattern the material, such as creating faux "wood grain" in flooring products.

These are the ones I can think off the top of my head.

Overall, one needs to approach it as a whole system, not just a brush or two. But if you can make such a system, and the manufacturers will help you with this, you can achieve very good sanding very rapidly.

Edit: to give you an idea of prices, I think Edruflexes go for about $100/50mm (mm is width) in standard core sizes, while NaxoFlexes go for about $150/50mm. You can stack brushwheels side by side to build wider systems, and at least NaxoFlex also permits grading the grit sideways on the same core.