Is chatter in new PRSalpha a Promblem?

[largoles]

I am new to this forum. I like all the info on the forum. I am getting ready to purchase a PRSalpha. I have seen some previous posts that there has been a problem with chatter. Has this been fixed or is this still a problem?

I have looked at the Shop Sabre info and cost. Is the Shop Sabre worth the extra money? Has anyone wished they had gotten a Shop Sabre instaed of the ShopBot?

Last question. Is there anyone using a ShopBot in the Tampa Bay, FL area?
Thanks

[richards]

Les,
Take some time to visit the 'Virtual Show and Tell' part of the forum. You'll see some close-ups that are 'chatterless'. You might also contact Danny L. Ray II directly. He's been doing a lot of work with his PRS. If anyone can tell about the machine, he can.

The parts that Bill Young cut on a PRS-Alpha at the Jamboree in California earlier this year were chatter free. I personally picked up more than a dozen parts, carefully checked for chatter with my eyes and by running a finger along the edges. Those parts were as good as any that I've seen cut by any machine - and they had NO chatter.

[mthomas]

Maybe Les should have phrased his question differently... maybe he should have asked "Is QC a problem with the new PRS Alphas?" There are (at least from my reading) some experienced users having the problem.

Maybe it's all in the wording?

[Brady Watson]

Les et al,
The PRS Standard OR Alpha both cut exceptionally well. Some people are never happy and ask a lot from a value priced tool or simply don't have enough 'seat time' on a CNC to know where the problem really lies. The thing to keep in mind with a CNC tool is, you can hand 10 people the same part to cut on the same model machine and you will get very different results from each. There are many factors involved with the 'chatter' issue...Speed, RPM, the method in which the part is being held down, cutting direction, stepdown values, and the geometry of the cutting bit ALL make a tremendous difference in cut quality in some materials. Equally important is the number of hours one has spent fine-tuning their cutting strategy, altering feeds, speeds and hold-down methods in the name of quality. One guy gets 'chatter'...and another gets perfect cuts. Like anything else worth doing well, the R&D it takes to create perfect cuts pays off big time. Anybody can just turn on a machine & run it...a CNC Operator makes adjustments along the way and records his findings to make life easier in the future when it comes time to cut that same material again.

In my 6yrs of 'Botting' I have learned that 99% of the problems, quality issues or glitches have been 100% my fault. The percentage has gone up even more since I have been running a PRS Alpha powered tool, since it's fine resolution eliminates some of the edge quality issues on older PRT tools with 1/4 stepping motor drivers. I compete with big iron & use my tool to make a living. If it wasn't up to the tasks I threw at it, it would have been sold long ago.

-B

[richards]

I agree with Brady 100%. My PRT-Alpha, with one small modification - a 3:1 reducer for the steppers - and with more moderate feed rates and depths, has totally changed the way my machine cuts. I'm getting cuts equal to any that I've ever seen from any machine. But, as Brady said, it takes some testing and some experimenting and some practice before the cuts started working.

Three minor things have led to the increase in quality:

1. Vacuum holddown using Brady's all-in-one plenum /spoil board.

2. 3:1 belt driven transmission. The PRS-Alpha has a 7.2:1 gear reduction, making it much better than my Alpha.

3. Gabe Pari's method of climb cutting and then ending up with a conventional finishing pass.

Some parts take longer to cut than I would like, but the parts are good. It seems to be like everything else: you can do it fast or you can do it good. When 'good' is important, going slower works for me.

When I bought my Alpha in 2004, I thought that thirty years in the process computer arena would go a long way towards making it 'easy' to use a CNC router. I also thought that my years of experience using routers of every make and model had qualified me to 'jump right in'. Well, that experience didn't hurt, but it also didn't automatically make everything easy.

Years and years ago when I joined the High School track team, the coach gathered us all together and simply said: "A poor carpenter always blames his tools." At the time, I had no idea of how profound his statement was, but over the years, I've had dealings with a lot of 'poor carpenters' who found it easy to blame everyone but themselves. I've also had the priviledge of working with 'champions' who had worked and worked, practiced and practiced, studied and studied until they were masters at their craft. I'm beginning to believe that you can't buy excellence. You can buy excellent tools. You can buy excellent materials. You can buy excellent cutters. But you have to earn excellence slowly and carefully, just like every other master craftsman.

[largoles]

Thanks everyone for the input. I'll check out the info everyone suggested.

[dray]

I get chatter. But the option is either slow the cutting down or speed up the router. It is not a chatter from the gantry moving or vibrating, it is a chatter from the gantry moving faster than the spirals on my bits.

If I slow down or speed up the router there is no chatter at all.

I will put my machine up against a thermwood any day of the week.

Alot of it is in the build as well. I am a finish carpenter and when I set up my machine I was within a 64th" or so on my setup and have improved it since.

The Prs Alpha 4'X8' has a large sag in the middle of the table (approx 1/32") but the Xcar follows this so as you machine your spoil board it also follows the sag, so its not really a problem.

I do not look at my Shopbot as a value priced tool. I first went to Thermwood, then onto techno and a few others. I could have purchased the thermwood but there is a much larger "tinkerer" base with the shopbot which makes for many many different ways around any problem you may run into. I cant stand single solutions, there are always many ways around any problem.

I didnt have any luck with the Shopbot Tech support setting up my machine and to be honest I did not like working with them at all except Chris. The rest all seemed really cocky and lacked humility (just my opinion) I am not an engineer and they made me feel pretty dumb whilst setting up my machine so I just didnt call anymore.

But I got mine setup at the same time a few others were setting theirs up and we worked together over the phone and on the boards.

If you need any help dont hesitate to give me a call. It helps me to learn more by showing the little I know.

D.Ray

[Gary Campbell]

Les Sr.....
I too have just purchased a PRSalpha 5x8 with a spindle for our woodworking shop. We are a small but very high quality oriented operation similar to Danny Ray. I too had some difficulies with the setup, squaring, and running the machine. I feel that the tech support at SB was more than gracious for my needs. An old anal woodworker griping about 3/64ths out of square on a 5x8 rectangle. They took care of it! And the same goes for every call I have made to the whole group. I have called and recalled to Frank, Ryan and Scott and in the end, if I explaned the problem correctly and LISTENED, each and every issue has been taken care to my satifaction. These guys do not get enough credit for the job they do trying to make sense out of what us new owners question in our Bots. Hats off to them and welcome aboard and good luck to you.
Gary