Which shopbot for me?

[TopLine Mike]

Hello there. I am seriously looking at buying a shopbot to make a product I have designed. The product will be a plaque made out of wood, and is roughly 5" by 3". I may be dreaming, but I am hoping to make about 100 plaques a day. I have a 60X40 shop built already, which is just being used as storage right now. Space will not be a factor. I also have two buddies with wood shops who are encouraging me to get a shopbot so they can use it (or rent it). My question is, which size shopbot will get the job done most efficiently? Money is a factor, and I am trying to stay around 10 grand.

Thanks for your help.
Mike in the Madison, WI area.

[thewoodcrafter]

I wouldn't get anything smaller than a 96x48 to run full size sheets.
And wouldn't think of anything less than Alpha. Much faster machine.
Look for used machines with a spindle also.

[cabnet636]

with the 4x8 you will be for the most part unlimited in your goal, to profile 100 plaques in a day will be done and you will be able to nest cabinet parts for the "buddies" (make sure they pay) friends will be as enthused by your new machine as you are!

jim

[richards]

Because your product is only 5" X 3", you would be able to use even the smallest machine.

If I were doing that type of job, I would build a pallet system so that I could pre-mount 4 or more plaques to a pallet. Then, if you had a simple vacuum system and some All*Star gasket material, you could set the pallet on some register marks, turn on the vacuum and cut a set of plaques. While one set of plaques was being cut, you could prepare the next batch.

Spindles are nice, but for that particular type of work, you could easily encapsulate the machine inside a cabinet to keep the noise down and to control dust.

The small machine would quickly pay for itself and then you could add a larger machine to do routine work.

I have a 120X60 PRT-Alpha, but when I do plaques, I would rather use a small table-top machine, like the Tyro, that was dedicated just to making plaques.

[rcnewcomb]

At 100 per day that means a cycle time of 4:48 per plaque. (Load, cut, clear, clean).

Trying to do a glue-up of solid wood that would take advantage of the larger table would be a challenge. I'm fond of smaller glue-ups. If plaques are your primary work then a smaller machine like the Tyro might make better sense since, as volume picks up, you could buy additional small machines.

[michael_schwartz]

If your going to use your machine for production, and if you plan to make a certain quantity of parts, each day, get every last bit of machine that you can afford.

Consider how you will tool-path and cut your parts. How many bits will you use. How will you load/unload parts, and what hold down methods you will use.

Lets use 100 plaques a day, with 3 tools as an example. I see your parts are smaller than my example but this is just hypothetical.

On bench top machine with the capacity of a single part, you would have 300 bit changes, in addition to 100 load/unload cycles. 300 bit changes would of course be a nightmarish prospect, so you would need to make a jig to accurately zero(index) your parts, and run all the parts through for each tool. If your only engraving with a single tool this wouldn't really be a big deal.

This would lead to 3x as many load and unload cycles, but of course with vac jig, or other hold down that accurately positions your part is much more of a reasonable prospect than changing bits 300 times.

On the larger machine, if you could load perhaps 16 of the same part per cycle, you would have more time to work on other things. 3 bit changes per batch of 16 is also more reasonable. A tool changer would eliminate that consideration all together.

If your goal is production, make sure whatever machine you get will allow for a smooth workflow, and increased production if needed.

With that being said, if the space and budget permits I wouldn't go less than 4x8. Below that, 4X4 Would be the next benchmark, since you can cut 1/2 sheets of plywood.

For production, vac holdowns would be the next thing to consider. If you are making allot of parts that involve multiple tool changes, an ATC while expensive may be worth considering, if it would improve workflow.

Seeing how your budget is about 10 grand though obviously an ATC is out of the picture.

I am not sure if that figure includes tooling, additional software, dust collection hose/fittings, sheet goods for your table, etc... If those are not budgeted separately consider what additional expenses might come up.

If you can spend a bit more, it sounds like you have the space for a 4x8 machine. Otherwise figure out the smallest machine you can get that will allow for a smooth workflow, and and spend the left over funds on software.

[myxpykalix]

Michael seems to have hit the nail on the head here. I think you need at least a 4x8 machine in an alpha.
With certain programs you can do what is called plate production and i think that is where you can set up say 8 pieces on the table and it will do cut 1 on all pieces, change bit it will do cut 2 on all pieces, then cut 3 on all pieces. That seems to be a more efficient toolpathing and cutting strategy then one at a time with 3 tool chages per part.

I think it would be better to get a bigger used machine then a smaller newer one within your budget.

[TopLine Mike]

Thanks for the tips, gentlemen. I am a surveyor, and I use autocad on a regular basis, so I have a head start with the drawing end of it. I am posting a 3D look of the plaque, along with a 4x8 sheet with 128 plaques drawn on it. A guy from Albany, WI gave me a demo on his machine. He cut a few of the plaques out for me, and created the 3D drawing for me. Thanks, Ryan. I will need to change the bit once. I think I may need more space around each plaque so they stay in place while cutting. I witnessed the piece Ryan was cutting for me let loose with 2 clamps on the wood, although he was cutting at .4 inches at the time. Each board is 5.5 inches wide and 8 ft long in the drawing. Maybe if I went up to 8 inches wide it would be best?? So if I went with a 4x4 machine, I could cut 64 at a time, which sounds like it would work for me. OK, I just tried to load my pdf file from autocad, and it was too big. (Actually, it wasn't very big at all) I have 8 boards that are 5.5 inches wide, with a 1/2 inch gap between each board. I can fit 16 plaques on each board, with a 1/2 inch gap between each plaque.

My other option is to hire one of you guys for the job, so I can start selling these things. I will have 5 different options with the wood type. Oak, cherry, hickory, black walnut, and pine. If you may be interested in this, my email is toplinesurvey at centurytel. net

[rcnewcomb]

You might consider getting a second Z so you could have both the straight bit and the V bit mounted. This costs more but it saves you a bit change.

[thewoodcrafter]

Michael,
Two easy ways to hold small parts-
Tabs or onion skin.
It's all in the software.

[TopLine Mike]

My friend Ryan used tabs when he cut the two out for me. I'm concerned about the edge of the wood having no support when the final cut is made. But what do I know, i've never done this stuff before.

As far as getting a second Z, that one went right over my head. I have been reading this forum for the last month, trying to gain knowledge about the mighty shopbot. A lot to learn, that's for sure. What the heck does "&amp" mean??

[butch]

Michael
I do several items like this, although not at 100 per day. That would be a nice job.
I use different size boards and then use the nest function. I use 4 - .5wide x .25high tabs to hold the cutouts in place. I use a .25 down spiral bit with a .33 gap between the pieces. I usually cut these at 2in per second at 16000 rpm on a 2.2hp spindle. I clamp these in place with either clamps made from wood, or a piece of scrap screwed to the table. But I am moving more toward specialized clamps, and using a cam to hold piece in place. There were several posts reciently on this and I like this better than cutting a length of board. Boards are not exactly flat, so it leaves and uneven cut between pieces. Using the cam clamps you should be able to do 100 per day fairly easy. Also look at a vacuum pod, that would hold you part down without tabs.