Micro­cut Honing Sys­tem: Hig­hest pre­cisi­on, easy to control

The Micro­cut Honing Sys­tem deve­lo­ped spe­ci­fi­cal­ly for smal­ler bores (<8 mm) gua­ran­tees shape accu­ra­cy, sur­face qua­li­ty and dimen­sio­nal accu­ra­cy at the hig­hest level — even in seri­es production.

Check­list for Micro­cut Honing System

Micro­cut manu­fac­tures machi­nes, which are con­fi­gu­red to cus­to­mer requi­re­ments or can offer the ser­vice of con­tract honing.

Why does the Micro­cut Honing Sys­tem work so reliable?

Pro­cess and tool
The shape accu­ra­cy (cylin­der shape) is adjus­ted auto­ma­ti­cal­ly, depen­ding on the pro­cess, without mea­su­re­ment con­trol. The final dia­me­ter is deter­mi­ned by the one-pie­ce tool.
The one-pie­ce and thus maxi­mal­ly rigid tools with pre­cise­ly dres­sed dimen­si­ons defi­ne the final dia­me­ter prac­ti­cal­ly inde­pen­dent of the ambi­ent con­di­ti­ons, such as tem­pe­ra­tu­re. The­re can be no “evas­i­on” of the tool into the cross hole due to a chan­ge in the sur­face pres­su­re bet­ween the work pie­ce and the tool. The tool, which is stiff in dia­me­ter, can be “dri­ven” through the bore and extra­or­di­na­ri­ly good cylin­der shapes can be achie­ved. For inter­nal grin­ding and con­ven­tio­nal honing, the two-stro­ke rever­sal points have a signi­fi­cant influ­ence on the cylin­der shape. The­se must be per­ma­nent­ly moni­to­red and adjus­ted. A rela­tively lar­ge allo­wan­ce can also be remo­ved (coni­cal tool sec­tion) and the wear per part is mini­mal (cylind­ri­cal tool sec­tion). Due to the sin­gle-lay­er coated tool, no spon­ta­ne­ous chan­ges occur (e.g. grit breakage).

Machi­ne
The feed of the tool is for­ce-con­trol­led. This pre­vents, for examp­le, the elastic expan­si­on of a thin-wal­led com­po­nent. The tool is not under- or over­loa­ded and unpro­duc­ti­ve “air grin­ding” is avoided. Too small or too lar­ge raw bore dia­me­ters are detec­ted and can be inter­cep­ted and tool bre­aka­ge prevented.
The work pie­ce hol­der is an important com­po­nent. The work pie­ce must not be defor­med during fixing and the work pie­ce posi­ti­on is usual­ly deter­mi­ned by the tool axis.

Micro­cut Honing — Dis­tinc­tion from other methods

A cen­tral fea­ture of the Micro­cut Honing Sys­tem is the mini­mal disper­si­on of the machi­ning results, so that no parts are out of tole­ran­ce due to disper­si­on. In con­ven­tio­nal honing or inter­nal grin­ding, the shape must be per­ma­nent­ly con­trol­led by a mea­su­ring and con­trol loop through the stro­ke posi­ti­on and length and the dimen­si­on through the infeed of the tool. This com­pli­ca­tes a sta­ble pro­cess and is asso­cia­ted with gre­at tech­ni­cal effort and cos­ts. It is also important to note that the uncer­tain­ty of a mea­su­re­ment clo­se to the machi­ning pro­cess, espe­cial­ly of the form, is considerable. 

Down­load Machi­ne Capa­bi­li­ty Ana­ly­sis (MFU) now:

As shown sche­ma­ti­cal­ly abo­ve, the Micro­cut honing pro­cess is con­ti­nuous and not erra­tic, wit­hin a dia­me­ter tole­ran­ce of, for examp­le, +/-0.001 mm. The green cur­ve for the Micro­cut honing pro­cess shows a con­ti­nuous mini­mum wear of the tool and thus a smal­ler bore.

The wear of the tool and thus the num­ber of parts in the dia­me­ter tole­ran­ce of the Micro­cut Honing Sys­tem depends on the mate­ri­al to be machined, the bore length, the allo­wan­ce and the tool geo­me­try. This can vary from < 100 parts to several thousand parts with a tole­ran­ce win­dow of 1 µm. With a lar­ger tole­ran­ce win­dow, it can even be tens of thousands of parts. The Micro­cut machi­ning pro­cess is not tem­pe­ra­tu­re sen­si­ti­ve, i.e. even lar­ge tem­pe­ra­tu­re fluc­tua­tions or the start of pro­duc­tion have prac­ti­cal­ly no nega­ti­ve influ­ence on the dimen­sio­nal accu­ra­cy of the bore diameter.

The “cold” micro machi­ning pro­cess remo­ves dama­ged edge struc­tures (e.g. cau­sed by spark ero­si­on, har­de­ning) and addi­tio­nal­ly com­pres­ses the bore edge zone (resi­du­al com­pres­si­ve stres­ses). The sur­face struc­tu­re can be defi­ned and repro­du­ced as often as requi­red, typi­cal­ly a rough­ness value of Ra 0.1 µm (N3) is achie­ved with machi­ning tools with bond­ed grain. In hard mate­ri­als such as car­bi­de, a mir­ror-smooth sur­face can be pro­du­ced by using loo­se grits and spe­cial tools.

Some important points are sum­ma­ri­zed below:

 

  • No dres­sing cycle with cor­re­spon­ding irregularities
  • Pro­cess always for­ce-con­trol­led (essen­ti­al when machi­ning thin-wal­led work pieces)
  • Prac­ti­cal­ly no tem­pe­ra­tu­re drift; tem­pe­ra­tu­re fluc­tua­tions are not critical 

Micro­cut Honing Sys­tem and its advan­ta­ges with hydrau­lic con­trol valves

Spool slee­ves with cross bores have very high requi­re­ments for the cylin­der shape (round­ness and strai­ght­ness) of the bore and also on the sur­face in various indus­tries, such as avia­ti­on or automotive.

Spool slee­ve with cross bores and hig­hest accu­ra­cy requirements.

Form of a sli­de slee­ve with cross holes: cylind­ri­cal shape CYLt = 0.23 µm

As the Micro­cut Honing tools are one-pie­ce, 350 mm long and coated, the tool is in con­ta­ct with the hole and the full length of the hole. This results in the best pos­si­ble strai­ght­ness cor­rec­tion of the bore. In addi­ti­on, the advan­ta­ge is also visi­ble in the round­ness, as the sur­face pres­su­re bet­ween the tool and the bore wall is very homo­ge­ne­ous­ly dis­tri­bu­t­ed. In the case of a tool used for con­ven­tio­nal honing or inter­nal grin­ding (short honing tool or grin­ding pin), which is shor­ter than the length of the bore, the for­ces chan­ge much more due to the trans­ver­se bore, which is ulti­mate­ly reflec­ted in the shape (espe­cial­ly the strai­ght­ness of the bore wall) of the finis­hed bore.

Burr for­ma­ti­on
With hydrau­lic con­trol com­pon­ents, burr for­ma­ti­on in the cross bores is a rele­vant issue. The debur­ring pro­cess with brushes can be con­trol­led to a limi­ted extent and is cost-inten­si­ve due to brush wear. In con­trast to con­ven­tio­nal honing and grin­ding, the Micro­cut Honing Sys­tem does not gene­ra­te a typi­cal fla­ke burr, but a sym­metri­cal micro burr with a solid root, which usual­ly does not need to be removed.

Work pie­ce clam­ping technology
When machi­ning thin-wal­led work pie­ces (slee­ves), the work pie­ce clam­ping tech­no­lo­gy and the con­trol of the machi­ning for­ces are of par­ti­cu­lar impor­t­ance. Any defor­ma­ti­on of the work pie­ce during clam­ping has a direct effect on the shape of the machined bore.

For­ce-con­trol­led machi­ning process
If the feed of the tool is not for­ce-con­trol­led, the­re is a risk, depen­ding on the cut­ting abi­li­ty of the tool, of expan­ding the work pie­ce during machi­ning, so that the thin-wal­led slee­ve “con­tracts” again when the tool is not any­mo­re in the work­pie­ce and thus the dia­me­ter of the finis­hed machined bore does not fol­low the tool exactly.

 

Micro­cut sonic-honing©

Micro­cut sonic-honing© tech­no­lo­gy com­bi­nes pre­cisi­on with maxi­mum pro­duc­ti­vi­ty. It is pos­si­ble to achie­ve cycle times of 10 — 15 seconds for mate­ri­al remo­val in dia­me­ters of 0.02 — 0.04 mm.

If you want to know more about the Micro­cut sonic-honing© tech­no­lo­gy, plea­se con­ta­ct us.