time to compute combineUnion

we are building a too for a Vinyl printing shop and we need to optmize a lot of text in a model.
few of our font have complicated geometry like below , and the text overlap, we are using "combineUnionfor" for every letter in the text , but its taking too long to get an output ,

so the Question is does combineUnion take this long to compute the path (very long about 20-30 seconds for the below code which can be tested in playgraound )

here is my code

var makerjs = require('makerjs');
var computeLayout = require('opentype-layout');
function DraftText(font, text, fontSize) `{`
        var textModel = { models: {} };
        var scale = 1 / font.unitsPerEm * fontSize;
        var layoutOptions = {
            lineHeight: 1 * font.unitsPerEm,
            width: 500 / scale
        };
        var layout = computeLayout(font, text, layoutOptions);
        layout.glyphs.forEach((glyph,i) => {
            var character = makerjs.models.Text.glyphToModel(glyph.data, fontSize);
            character.origin = makerjs.point.scale(glyph.position, scale);
            makerjs.model.simplify(character, { pointMatchingDistance: 0.001 });
            makerjs.model.combineUnion(textModel, character);
            makerjs.model.addModel(textModel, character, i);
         });
        return textModel;
    }
function Nameplate(font,font_scale, text,icon ) {
   var textModel = DraftText(font, text, font_scale);
   this.models = {
        text: textModel
   };
   makerjs.model.zero(this);
   this.units = makerjs.unitType.Millimeter;
}
Nameplate.metaParameters = [
    { title: "font", type: "font", value: '*' },
    { title: "font size", type: "range", min: 10, max: 200, value:  20},
    { title: "text", type: "text", value: 'Hello World! This box should start word-wrapping!' }
];
module.exports = Nameplate;

am i doing something wrong?

Reproduce the provided JavaScript example in the linked Maker.js playground, focusing on model.combineUnion and Text.glyphToModel for the supplied font and text. Profile the combineUnion calls to determine where the 20–30 second runtime comes from; done means a documented explanation of the behavior or a confirmed, measurable improvement.