Shopbot accuracy with welded steel table

[robinsoncr@naxs.net]

I'm still looking at the SB for my cabinet business. How many of you have checked your SB's accuracy cutting square panels? I know repeatability is a seperate issue, but I feel confident that the SB's repeatability is more than adequate.

I will employ a welded steel table to insure the upmost in rigidity.

Does anyone achieve an accuracy of .002" over 39.4"? (.05mm over 1000mm)

Thanks,

Chris

[wdyasq@yahoo.com]

Chris,

Do you have the tools to measure .0002:1 accuracy?

I will agree accuracy is very desirable. I will contend the accuracy of my OLD ShopBot is better than I can do with my $15,000 German rolling table saw and my 20" Italian Jointer. I know the ShopBot is the MOST accurate woodworking tool in my shop. And mine WAS cable driven at one time.

I think you will find your substrate will move more than your ShopBot (should you decide on one).

If you would like, I will pull out some engineering books and we can talk tempeature/expansion/weld/structure stability to the point of absurdity. After all of the analysis and measuring, the "proof is in the pudding". I know I make parts with my dial calipers in hand; calculating and entering cuts on the keyboard. When the parts don't fit, it is usually because I blew the math......

Can you commend a good book on the 32mm system?

Ron

[Gerald D]

Chris, I basically agree with Ron.

The squareness depends on how good you set it up - the SB comes in a kit form and you have to do the rest.

0.05mm resolution is completely unrealistic. The SB cannot achieve this and I doubt whether you can see or measure this in a cabinet shop.

[rgengrave@aol.com]

I just cut a 60" X 40" rectangle in foam and tried to messure it, I used my 8' metal ruler and check both corners for square, it came to about 64th off, the ruler only shows 1/16 and it is in there somewhere.

Ron V

[robinsoncr@naxs.net]

Yep, I understand what you are saying about thermal expansion and enviromental impacts on the tool and substrate. I was trying to get an idea of accuracy as compared to the published specs of a well know european sliding table saw.

I ask because I purchased a slider a month ago that ended up not being able to deliver acceptable accuracy for cabinet construction. It would only hold +/- .014" over 42", amoung other serious issues. Anyway, I was disappointed with it and sent it back after receiving minimal help from the seller.

I want to know whether or not if I use the SB to machine and cut out panels for my carcases, is it accurate enough to provide a tight joint.

Thanks for your help!

Chris

[wdyasq@yahoo.com]

Chris,

IMO, asjusted properly the SB will do the job you are asking. Bit selection; feed rate and other factors will influence the accuracy - as will something as mundane as the dust skirt filling with chips.

Brush up on your CAD skills and, if possible, visit someone with a ShopBot that can help you with the learning curve. I don't believe anyone who has one will say you can put a CNC machine to work in an instant. The knowlwdge of woodworking doesn't make a ShopBot run.

My Table saw is a Kirchfeld I purchased about a dozen years ago. It weighs 2700 lbs and I have had to adjust it once since the initial setup.

By chance did the name of the 'slider' you puchased start with a "V"?

Ron

[olivier]

In my experience, the shopbot is precise down to 0.2 mm. (o.oo8") ie : if I do vary the width of slots every 0,2 mm, you can feel the difference when you slide the corresponding piece into them. but there are other issues like vibrations, and steps losts which can interfere with this.

olivier

[robinsoncr@naxs.net]

Ron,

Nope, the saw was from Laguna Tools. Just as a side note, the local Altendorf salesman called today. The F92 slider (old F45 ver. now assembled in China) is $12k! I could buy TWO SB's!

As for the learning curve, I contacted my local Small Business Develop Center that is located in the local community college. They have been a tremendous help to us. Anyway, the director is working out some help/training with the cad/cnc instructor. SBDC's are well worth the tax dollars!

I'm in the process of scheduling a demo with SB so I can see it work at my application first hand.

Olivier, do you mean that if you cut a 19mm dado, when you insert the corresponding 19mm panel, you can feel slop, or on one end?

Thanks,
Chris

[olivier]

The way I use the precision of the shopbot is as follow.
To take you example : if I want to fit a 19 mm panel in a 19 mm dado. If I make the dado 19 or 19.2 it gets in fine but wobble a bit and you need a to cramp the assembly together.
At 19.6 it does not get in the dado
At 19.8 it slides in with a bit of forcing, perfect glue joint, no need of clamping, lots of time saved with a single programming setting.

That is why for me the practical precision of a shopbot is 0.2 mil.

Olivier