[ataxy]

hi there people! a friend of mine recently contacted me to let me know that he might have some work for me doing prototype part and some drilling jig for the place he work for most of them a small work envelope job around 2"x4"x6" and since the are all job made of aluminium, mild steel and brass it wont require a big heavy duty machine, the place where i am not sure the small machine i am looking at would be deficient are in the precision departement, for example piece would need to be parallele inside 0.002" with some hole with tight precision of 0.0001" on the diameter, the general tolerance chart the use is the following
x.xx = +/- 0.005"
x.xxx = +/- 0.0001"

so my question is the following, since the SX3 is less costfull and offer a smaller work envelope but still is able to make part inside the work envelope i need i was wondering if with some fine tuning the tormach and syil are comparable precision wise? i know those two machine may have hard time holding precision of 0.0001" but these tolerance is only on hole diameter the positioning and dimension tolerance are mostly around +/- 0.002" and in some rare case slightly smaller around +/- 0.0015"
now why i am looking at if the sx3 would be capable of such precision is that since it would cost me less i could invest in a better boring head and tooling for it, also the the ipm feeding is of secondary importance for me as most most of the job i would have to do are like 2 or 3 small simple part but with slightly tight tolerance as stipulated before but most if not all the time i would have around 2 day to produce them the same goes for depth of cut since there would be no need for depth of cut in most situation over 0.05"

so what do you think? now this would only be in the short run if all goes well and they are satisfyed of my work the work load may grow and at that point i would plan on buying a bigger machine with faster capacity and would keep the small machine for what it is done for small job?

[philbur]

Hole diameter precision is mostly about procedure and tool runout and not really about CNC performance. You will not get 0.0001" with a boring head. Reaming may get it if you're good.

The positional tolerance on the holes will dictate CNC precision and repeatability requirement and the size of the hole will dictate the machine stiffness/size requirement.

The biggest problem with a low-end machine with regard to predicting performance is the variability between machines, no two come of the production line the same. Does the Syril come with a test cert. At least you would be able to return it if it doesn't meet expectations.

Just some thoughts from a novice.

Regards
Phil

hi there people! a friend of mine recently contacted me to let me know that he might have some work for me doing prototype part and some drilling jig for the place he work for most of them a small work envelope job around 2"x4"x6" and since the are all job made of aluminium, mild steel and brass it wont require a big heavy duty machine, the place where i am not sure the small machine i am looking at would be deficient are in the precision departement, for example piece would need to be parallele inside 0.002" with some hole with tight precision of 0.0001" on the diameter, the general tolerance chart the use is the following
x.xx = +/- 0.005"
x.xxx = +/- 0.0001"

so my question is the following, since the SX3 is less costfull and offer a smaller work envelope but still is able to make part inside the work envelope i need i was wondering if with some fine tuning the tormach and syil are comparable precision wise? i know those two machine may have hard time holding precision of 0.0001" but these tolerance is only on hole diameter the positioning and dimension tolerance are mostly around +/- 0.002" and in some rare case slightly smaller around +/- 0.0015"
now why i am looking at if the sx3 would be capable of such precision is that since it would cost me less i could invest in a better boring head and tooling for it, also the the ipm feeding is of secondary importance for me as most most of the job i would have to do are like 2 or 3 small simple part but with slightly tight tolerance as stipulated before but most if not all the time i would have around 2 day to produce them the same goes for depth of cut since there would be no need for depth of cut in most situation over 0.05"

so what do you think? now this would only be in the short run if all goes well and they are satisfyed of my work the work load may grow and at that point i would plan on buying a bigger machine with faster capacity and would keep the small machine for what it is done for small job?

[ataxy]

Hole diameter precision is mostly about procedure and tool runout and not really about CNC performance. You will not get 0.0001" with a boring head. Reaming may get it if you're good.

i said boring head as an example of the type of upgrade where i could put more money if i would go with a SX3 instead of a tormach but you are right that reamer would be better at this job or actualy honing in a way to finish in thight tolerance

The positional tolerance on the holes will dictate CNC precision and repeatability requirement and the size of the hole will dictate the machine stiffness/size requirement.

that would actualy be what i would want people point view on, i do understand that these machine tend to vary more from one another but in a overall point of view do you think i might be able to get pretty close to what i am looking for, i definitly should have precised more the size of the hole, i am talking of hole where the size would be between 1/8 and 5/8 and range from 1/4 to 3/4 inch deep, but i do understand that those machine are as tight as big machine, i am mostly looking if those machine have so far respected there advertised accuracy or if they have so far tend to be uterly off precision wise to what there advertised.

Just some thoughts from a novice.

Regards
Phil

thanx thats what i am asking and it helps me into my soon to be decision

[bucont]

x.xxx = +/- 0.0001"

This always makes me smile when i see it on a drawing.

[307startup]

Usually on a three place decimal for a dimensioned drawing, it calls for no more than +.001" on the OD or -.001" ID, or if they are really anal .0005". How much scrap will they tolerate? Are they providing material or are you? There will be scrap. Inattentiveness, inaccuracies in measuring, product damaged during/after handling, etc.

Asking to hold a tenth is basically asking for one-at-a-time production or piecemeal work, as most machines will constantly be over or under .0002" due to thermal growth. There is almost no way to anticipate the growth or shrinkage of a part at this tight of a tolerance without some really expensive machines (with built-in thermal compensation), even with adjusting offsets after every part. Of course this is also dependent on weather factors, amount of heat put into the part during/before/after the process, climate control inside the building, repeatability of measuring due to differences in operator styles and practices, measuring the part at room temperature with tools that are at the same temperature, etc. We had a part that could only be +.0003"/-.0000" and we could hold it, but we were running that part ONE at a time on a machine that was manually loaded, unloaded and operated, with a hard stop at the end of the program. We had to measure EACH part and adjust the offset up or down after EACH part. This special job was run on a 4 month old machine that ran production 16 hours a day, normally with an insert change every 250 parts and offset adjustments made every 10 parts, measuring every 5th part, using proven programs. Oh, by the way, this machine also cost the better part of $100,000 before barfeeder and tooling. This sounds like a tough job for someone using a hobby-type machine, regardless of brand. Not to spoil the party, just giving some feedback from the industrial side of CNC machining.

[in2steam]

I was going to leave this one alone because I thought that there was a misprint, but I agree with wyld. Someone drivnig there car into the drive way 2 doors down could knock you out of your tolerance range, with machines like the x3. The ball screw conversions from what i understand have aleast .002 slop. If you add that with the other axis you could be way out. Thats not to say you could not tighten it up, but you are looking for a dedicated machine not somehting you need to tightenup all the time or rebuilt out of the box. As for the hole tolerance sx3 has around 1 tho of walk, getting 10x more accurate may be a stretch even if reaming, thats assuming its placed correctly to being with.
chris

[ataxy]

so then you would be all more confident with the tormach

[philbur]

I think the others posters did not read your mail correctly.

Your 0.0001" on hole diameter is doable. Your positional tolerance of 0.002" or some times 0.0015 is doable. The Tormach will easily do the positional tolerance. A reamer will achieve the hole diameter tolerance, providing as I said, if you are good.

If the Syril does not come with a test cert this would imply that the manufacturer accepts that performance between machines has a wide variable, which means you would be taking a gamble on getting a good one. Most hobby users don't have specific tolerance criteria, they just want the best they can get for the money. Commerical users must and do look at the situation differently.

If this is about a commercial venture then buy the Tormach. If the venture falls through resell the Tormach and take a USD1,000 hit.

Some might consider me biased as I own a Tormach.

Regards
Phil

so then you would be all more confident with the tormach

[in2steam]

so then you would be all more confident with the tormach

Phil seems to be the resident Tormach expert I would take his advice.


chris

[MichaelHenry]

How big are the holes? Temperature of the part is going to affect that diameter measurement and it gets worse as the hole gets bigger.

I suspect that if you contact both Syil and Tormach you will find that neither is willing to guarantee that level of accuracy.

Mike

[ataxy]

How big are the holes? Temperature of the part is going to affect that diameter measurement and it gets worse as the hole gets bigger.

I suspect that if you contact both Syil and Tormach you will find that neither is willing to guarantee that level of accuracy.

Mike

check this post i give an idea of them there

here is an example of the part i would be required to do, the tolerance required for this part are easyer in this example
x.x= +/- 0.05 x.xx= +/- 0.005 x.xxx= +/- 0.002 and its made of 1010 steel

[bucont]

I think the others posters did not read your mail correctly.

Your 0.0001" on hole diameter is doable.

I am just wondering what you use to measure a hole tolerance like this?

[in2steam]

looks like this would almost be better done on a lathe, just my 2 cents.

chris

[bucont]

I am just wondering what you use to measure a hole tolerance like this?

Anyone?

[in2steam]

Easiest would be ground pins in a go- no go setup, otherwise really good mic's and or height gauges.

chris

[ataxy]

yeah i would go with the go no go solution

[307startup]

Just from my experience, regardless of machine type, there is variability in sizes of drills and reamers from the manufacturers...a .5" drill can easily be .498" and still be "good". Reamers may be +/- .0005. So holding a tenth on hole size will still be a crapshoot. And that is buying A1 quality tooling, unless you go for mega-bucks medical supplier tools.

[DareBee]

The best way to measure those holes and be truly accurate to .0001 is with bore gauges and setup masters (this is completely ignoring all environmental variables as well).
Quality gauges taht are certified this accurate will cost MANY MANY thousands of dollars.

As far are processing these to size with YOUR setup, I would bore them really close undersize (.0001 - .0005) and hone or lap them to finished size.
These holes would be easiest to size in a lathe, but setup would be a lot of work.

Otherwise - get a jig grinder.

[SyilAmerica]

A hot or cold day will throw that tolerance off.

[fast89]

hot or cold day, hehehe, 10* change can screw that tolerance.